700 ACUS11 KWNS 140005 SWOMCD SPC MCD 140005 ILZ000-IAZ000-MOZ000-140130- MESOSCALE DISCUSSION 0819 NWS STORM PREDICTION CENTER NORMAN OK 0705 PM CDT WED MAY 13 2009 AREAS AFFECTED...NERN MO/SERN IA/W CENTRAL IL CONCERNING...TORNADO WATCH 293... VALID 140005Z - 140130Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 293 CONTINUES. SEVERE/TORNADO THREAT CONTINUES AS STORMS CONTINUE MOVING EWD ACROSS THE ERN HALF OF THE WW. STRONG/SEVERE STORMS CONTINUE...WITH A LARGE/PERSISTENTLY-ROTATING SUPERCELL CROSSING THE KNOX/CLARK/LEWIS COUNTY AREAS ATTM. THIS STORM HAS A HISTORY OF PRODUCING A DAMAGING TORNADO...AND CONTINUES TO EXHIBIT STRONG ROTATION. MODERATE INSTABILITY/AROUND 2000 J/KG MIXED-LAYER CAPE/ REMAINS IN PLACE AHEAD OF THE CONVECTIVE BAND...WHICH WILL FUEL ONGOING CONVECTION AND ASSOCIATED THREAT FOR HAIL AND DAMAGING WINDS. ADDITIONALLY...WITH LOCALLY-BACKED/SLY SURFACE FLOW INVOF THE WNW-ESE WARM FRONT /STRETCHING FROM NERN MO TO SWRN INDIANA/...THREAT FOR TORNADOES WILL PERSIST OVER THE NEXT COUPLE OF HOURS. ..GOSS.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...ILX...LSX...DVN...EAX... LAT...LON 39179231 39649300 40489196 41359221 42029069 41428973 39298982 39179231  953 ACUS01 KWNS 140103 SWODY1 SPC AC 140100 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0800 PM CDT WED MAY 13 2009 VALID 140100Z - 141200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM CNTRL THROUGH NERN OK...SERN KS...SRN AND CNTRL MO AND SRN AND CNTRL IL... ...THERE IS A SLGT RISK OF SVR TSTMS FROM OK THROUGH THE LOWER MS VALLEY INTO THE GREAT LAKES... ...OK THROUGH SERN KS... EARLY THIS EVENING A COLD FRONT EXTENDS FROM A SURFACE LOW IN SERN IA SWWD THROUGH NW MO...SERN KS...NWRN OK INTO THE TX PANHANDLE. A WARM FRONT EXTENDS EWD AND SEWD FROM THE LOW THROUGH CNTRL IL INTO SRN IND. A RESERVOIR OF 2500-3500 MLCAPE EXISTS FROM NWRN TX...OK INTO SERN KS AND SWRN MO WHERE PLUME OF STEEP MID LEVEL LAPSE RATES HAVE OVERSPREAD AXIS OF MID-UPPER 60S DEWPOINTS...AND WHERE SURFACE TEMPERATURES HAVE WARMED INTO THE 80S. EWD ADVECTION OF THE EML HAS CONTRIBUTED TO AN INVERSION BETWEEN 850 AND 700 MB IN MUCH OF WARM SECTOR. THIS SUGGESTS IT WILL PROBABLY REMAIN DIFFICULT TO INITIATE STORMS AWAY FROM ZONE OF LINEAR FORCING ALONG COLD FRONT...ESPECIALLY WITH ONSET OF NOCTURNAL COOLING. INCREASING POST FRONTAL NLY BOUNDARY LAYER FLOW IN WAKE OF SHORTWAVE TROUGH MOVING EWD THROUGH NRN PLAINS COINCIDENT WITH STRENGTHENING NOCTURNAL LOW LEVEL JET WILL RESULT IN AN INCREASE IN FRONTOGENETIC FORCING ALONG THE FRONT AS IT CONTINUES SEWD THROUGH THE SRN PLAINS. STORMS WILL LIKELY CONTINUE DEVELOPING ALONG THIS BOUNDARY THROUGH THE EVENING INTO THE OVERNIGHT. STORMS MAY REMAIN DISCRETE IN NATURE NEXT COUPLE HOURS. FLOW ALOFT IS NOT PARTICULARLY STRONG...BUT BULK SHEAR OF 30-35 KT AND STRONG INSTABILITY ARE SUPPORTING SUPERCELL STRUCTURES WITH VERY LARGE HAIL AND ISOLATED TORNADOES POSSIBLE. THE STRONG LINEAR FORCING MIGHT EVENTUALLY RESULT IN AN UPSCALE LINEAR GROWTH LATER TONIGHT WITH AN INCREASING THREAT OF DAMAGING WIND. ...LOWER AND MID MS VALLEY REGIONS... AXIS OF MODERATE INSTABILITY WITH MLCAPE FROM 2500 J/KG OVER SWRN MO TO NEAR 1000 J/KG OVER NRN IL EXISTS IN PRE-FRONTAL WARM SECTOR. THE SWLY LOW-LEVEL JET WILL STRENGTHEN NEWD THROUGH MID MS VALLEY AND GREAT LAKES THIS EVENING DOWNSTREAM FROM EWD ADVANCING SHORTWAVE TROUGH AND ITS ATTENDANT MID LEVEL JET. THE COUPLED JET STRUCTURE WILL MAINTAIN STRONG BULK SHEAR AND HODOGRAPHS FAVORABLE FOR ORGANIZED STORMS. PRIMARY ZONE OF THUNDERSTORM DEVELOPMENT SHOULD REMAIN ALONG ESEWD ADVANCING COLD FRONT...BUT A FEW STORMS COULD DEVELOP AND INTENSIFY AHEAD OF THE FRONT. MIXED MODES WITH BOTH DISCRETE CELLS AND LINE SEGMENTS PERSIST WITH STORMS ALONG THE FRONT. DOMINANT MODE IS EXPECTED TO TRANSITION TO LINEAR LATER THIS EVENING...BUT THREAT OF EMBEDDED SUPERCELLS WILL CONTINUE INTO THE NIGHT. LARGE LOW LEVEL HODOGRAPHS ALONG STRENGTHENING LOW LEVEL JET AXIS WILL SUPPORT A THREAT OF TORNADOES...ESPECIALLY DURING THE EVENING. HOWEVER...THE THREAT FOR DAMAGING WIND MAY INCREASE LATER TONIGHT AS DOMINANT MODE TRANSITIONS TO LINEAR. ..DIAL.. 05/14/2009  715 ACUS11 KWNS 140122 SWOMCD SPC MCD 140122 MOZ000-ARZ000-OKZ000-KSZ000-140215- MESOSCALE DISCUSSION 0820 NWS STORM PREDICTION CENTER NORMAN OK 0822 PM CDT WED MAY 13 2009 AREAS AFFECTED...CNTRL/SWRN MO...NWRN AR...MUCH OF OK...FAR SERN KS CONCERNING...SEVERE THUNDERSTORM WATCH 295...296... VALID 140122Z - 140215Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 295...296...CONTINUES. ADDITIONAL WW/S WILL LIKELY BE ISSUED PRIOR TO 03Z DOWNSTREAM OF WW/S 295/296. SEVERAL LINE SEGMENTS WITH EMBEDDED/SEMI-DISCRETE SUPERCELLS CONTINUE TO EVOLVE ALONG COLD FRONT BOUNDARY THAT EXTENDED ROUGHLY FROM 20 E IRK TO 20 E CSM AS OF 01Z. LARGE HAIL AND BRIEF TORNADOES HAVE BEEN THE PRIMARY THREATS THUS FAR. WHILE TRANSITION TO AN ELONGATED QLCS HAS APPEARED TO BE DELAYED TO SOME EXTENT...STORM INTERACTIONS AND CONVERGENCE ALONG THE FRONT/OUTFLOW BOUNDARIES SHOULD BE SUFFICIENT FOR ADDITIONAL DEVELOPMENT IN BETWEEN ONGOING CLUSTERS. AMBIENT WARM SECTOR AIR MASS REMAINS VERY UNSTABLE BASED ON MODIFIED 00Z OUN/SGF RAOBS WITH LARGE LOW-LEVEL HODOGRAPHS. THIS SUGGEST OVERALL STORM INTENSITY WILL BE MAINTAINED AS ACTIVITY SHIFTS S/EWD THIS EVENING...WITH ADDITIONAL WW/S LIKELY BEING NEEDED FOR DOWNSTREAM OF WW/S 295/296. DAMAGING WINDS WITH EMBEDDED BOWING SEGMENTS SHOULD BECOME THE MAIN THREAT AS COLD POOL DEVELOPMENT LIKELY OCCURS. ..GRAMS.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LSX...LZK...SGF...EAX...TSA...ICT...OUN... LAT...LON 34779916 35339873 36569675 38129453 39129295 38629219 38279142 37599162 36619235 35129421 34329618 34199784 34409896 34779916  814 ACUS11 KWNS 140135 SWOMCD SPC MCD 140135 ILZ000-WIZ000-IAZ000-MOZ000-140300- MESOSCALE DISCUSSION 0821 NWS STORM PREDICTION CENTER NORMAN OK 0835 PM CDT WED MAY 13 2009 AREAS AFFECTED...NERN MO/NRN AND CENTRAL IL CONCERNING...TORNADO WATCH 293... VALID 140135Z - 140300Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 293 CONTINUES. SEVERE/ISOLATED TORNADO THREAT CONTINUES. RADAR LOOP REVEALS BROKEN BANDS OF STORMS PROGRESSING EWD AHEAD OF THE ADVANCING COLD FRONT...WHERE 500 TO 1500 J/KG MIXED-LAYER CAPE PERSISTS PER OBJECTIVE ANALYSES. AN OVERALL/SLOW WEAKENING TREND APPEARS TO HAVE BEGUN IN CONJUNCTION WITH SOME DIURNAL STABILIZATION...BUT EXPECT ISOLATED STRONG/SEVERE STORMS TO CONTINUE. STORMS MAY LINGER ACROSS WW 293 BEYOND THE SCHEDULED 14/03Z EXPIRATION -- WHICH COULD REQUIRE A LOCAL EXTENTION OF THE WATCH...OTHERWISE MUCH OF THE CONVECTION WILL CONTINUE SHIFTING INTO WW 294 OVER THE NEXT 1-2 HOURS. ..GOSS.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LOT...ILX...MKX...LSX...DVN...EAX... LAT...LON 39359282 39739295 40849119 42608987 42568769 40148761 39459006 39359282  448 ACUS11 KWNS 140318 SWOMCD SPC MCD 140317 MIZ000-INZ000-ILZ000-WIZ000-140415- MESOSCALE DISCUSSION 0822 NWS STORM PREDICTION CENTER NORMAN OK 1017 PM CDT WED MAY 13 2009 AREAS AFFECTED...CENTRAL AND NERN IL/W CENTRAL AND NWRN INDIANA/SWRN LOWER MI CONCERNING...TORNADO WATCH 297... VALID 140317Z - 140415Z THE SEVERE WEATHER THREAT FOR TORNADO WATCH 297 CONTINUES. SEVERE/ISOLATED TORNADO THREAT CONTINUES ACROSS PARTS OF WW 297...WHILE SOME INCREASE IN SEVERE POTENTIAL WITH TIME EWD INTO SWRN LOWER MI/NWRN INDIANA MAY WARRANT ADDITIONAL WW ISSUANCE. STORMS CONTINUE MOVING EWD ACROSS NWRN IL AND THE LK MI AREA ATTM...AHEAD OF THE ADVANCING COLD FRONT. STORMS HAVE WEAKENED SLOWLY OVER THE PAST COUPLE OF HOURS...AS AIRMASS HAS BEGUN SLOWLY STABILIZING WITH THE LOSS OF DAYTIME HEATING. HOWEVER...WITH AMPLE INSTABILITY TO SUPPORT A CONTINUATION OF CONVECTION E/NE OF WW 297...EXPECT STORMS TO CONTINUE SPREADING ACROSS NERN IL/NWRN INDIANA/SWRN LOWER MI OVER THE NEXT FEW HOURS. WHILE INSTABILITY WILL REMAIN LIMITED...STRONG SHEAR MAY ALLOW A FEW STRONGER/ORGANIZED STORMS TO PRODUCE LOCALLY-DAMAGING GUSTS AND/OR MARGINAL HAIL -- OR EVEN AN ISOLATED/BRIEF TORNADO. DEGREE OF THREAT -- WHILE LIKELY TO REMAIN LIMITED E OF WW 297 -- COULD REQUIRE NEW WW ISSUANCE...PARTICULARLY WITH WW 297 SCHEDULED TO EXPIRE AT THE TOP OF THE HOUR. ..GOSS.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...IWX...GRR...IND...LOT...ILX...MKX...DVN... LAT...LON 39638967 40718995 42168900 42538760 42778658 43998586 43638487 42118484 39548684 39638967  925 ACUS11 KWNS 140428 SWOMCD SPC MCD 140427 INZ000-KYZ000-ILZ000-TNZ000-MOZ000-ARZ000-OKZ000-KSZ000-TXZ000-140600- MESOSCALE DISCUSSION 0823 NWS STORM PREDICTION CENTER NORMAN OK 1127 PM CDT WED MAY 13 2009 AREAS AFFECTED...SRN AND ERN MO/SRN IL/SRN IN/WRN KY/NWRN TN/CENTRAL AND ERN OK/MUCH OF AR CONCERNING...SEVERE THUNDERSTORM WATCH 298...299... VALID 140427Z - 140600Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 298...299...CONTINUES. BROKEN BAND OF STORMS -- WITH EMBEDDED SUPERCELLS -- CONTINUES MOVING EWD ACROSS PARTS OF IL/MO/OK/NWRN AR. NEW CONVECTION INCREASING ACROSS ERN PORTIONS OF THE TWO WATCHES -- OVER SRN IL/SERN MO/NWRN AR -- MAY REQUIRE NW WW ISSUANCE. BAND OF WIDESPREAD STRONG/SEVERE STORMS CONTINUES SHIFTING SLOWLY SEWD ACROSS WW 298 AND 299 ATTM...ALONG AND AHEAD OF THE MAIN COLD FRONT. OTHER STORMS CONTINUE TO INCREASE E OF THE MAIN CONVECTIVE LINE...LIKELY IN RESPONSE TO AN INCREASE /60 KT/ SWLY LOW-LEVEL JET. WITH MODERATE INSTABILITY PERSISTING IN THE WARM SECTOR...THESE STORMS SHOULD CONTINUE TO SLOWLY INCREASE -- WITH DEGREE OF THREAT POSSIBLY REQUIRING AN ADDITIONAL WW E OF THE CURRENT WATCHES. OTHERWISE...EXPECT A CONTINUED THREAT FOR LARGE HAIL...DAMAGING WINDS...AND AN ISOLATED TORNADO WITH THE MAIN CONVECTIVE BAND AS IT SLOWLY PROGRESSES ACROSS WW 298/299. ..GOSS.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...LMK...IND...PAH...ILX...MEG...LSX...LZK...SGF... SHV...TSA...OUN... LAT...LON 33999828 34809832 37659342 39479038 39528539 37898609 34009287 33999828  604 ACUS02 KWNS 140544 SWODY2 SPC AC 140541 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1241 AM CDT THU MAY 14 2009 VALID 151200Z - 161200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN PLAINS...CNTRL PLAINS...MID TO UPPER MS VALLEY AND OH VALLEY... ...SRN PLAINS/MID-MO VALLEY... A BROAD UPPER-LEVEL TROUGH IS FORECAST TO MOVE INTO THE GREAT PLAINS FRIDAY. AT THE SFC...A COLD FRONT SHOULD ADVANCE SEWD ACROSS THE CNTRL PLAINS. BY AFTERNOON...THE BOUNDARY IS PROJECTED FROM THE ERN TX PANHANDLE NEWD ACROSS SRN AND ERN KS. THUNDERSTORMS SHOULD INITIATE ALONG THE BOUNDARY AS SFC TEMPS WARM AND THE CAPPING INVERSION WEAKENS. FORECAST SOUNDINGS ALONG THIS CORRIDOR SHOW SFC DEWPOINTS IN THE MID 60S F...MLCAPE VALUES IN THE 2500 TO 3500 J/KG RANGE AND 0-6 KM SHEAR VALUES GENERALLY IN THE 30 TO 40 KT RANGE. THIS SHOULD BE SUFFICIENT FOR A SEVERE THREAT AS CONVECTION INCREASES IN COVERAGE LATE FRIDAY AFTERNOON INTO THE EVENING. SUBSTANTIAL DIRECTIONAL SHEAR IN THE LOWER TO MID-LEVELS COMBINED WITH THE MOIST AND VERY UNSTABLE ENVIRONMENT MAY PROMOTE SLOW MOVING STORMS WITH HAIL AND/OR AN ISOLATED TORNADO THREAT. IF A COLD POOL CAN DEVELOP DRIVING AN MCS SWD ACROSS THE SLIGHT RISK AREA...THEN AN ENHANCED WIND DAMAGE THREAT COULD ALSO EXIST FRIDAY EVENING. ...MID TO UPPER MS VALLEY/WRN OH VALLEY... WEST SOUTHWEST FLOW IS FORECAST OVER THE MID-MS AND OH VALLEYS FRIDAY WITH A QUASI-STATIONARY FRONT POSITIONED FROM NRN MO INTO NRN IL AND NRN IND. AS SFC TEMPS WARM UP FRIDAY...SFC DEWPOINTS IN THE MID TO UPPER 60S F SHOULD RESULT IN MODERATE INSTABILITY ALONG AND SOUTH OF THE BOUNDARY. THUNDERSTORMS APPEAR LIKELY TO INITIATE NEAR THE BOUNDARY AND INCREASE IN COVERAGE ENEWD DURING THE LATE AFTERNOON AND EARLY EVENING. FORECAST SOUNDINGS AT 00Z SATURDAY SHOW MODERATE VERTICAL SHEAR PROFILES WITH 20 TO 30 KT OF FLOW AT 850 MB. THIS SHOULD FAVOR DAMAGING WIND GUSTS AS A LINEAR MCS ORGANIZES BY EARLY EVENING. AN ISOLATED TORNADO THREAT MAY ALSO EXIST DUE TO THE LOW-LEVEL SHEAR IF A FEW SUPERCELLS CAN DEVELOP ACROSS THE REGION. ..BROYLES.. 05/14/2009  154 ACUS01 KWNS 140600 SWODY1 SPC AC 140558 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1258 AM CDT THU MAY 14 2009 VALID 141200Z - 151200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF SWRN TX... ...SYNOPSIS... UPPER TROUGH CURRENTLY MOVING THROUGH THE UPPER MS VALLEY WILL EJECT NEWD THROUGH THE GREAT LAKES...REACHING SRN QUEBEC THIS AFTERNOON. THIS FEATURE WILL PROVIDE IMPETUS FOR A COLD FRONT TO ADVANCE THROUGH THE OH VALLEY. TRAILING PORTIONS OF FRONT WILL STALL ACROSS THE SRN PLAINS. BY THURSDAY EVENING THIS BOUNDARY SHOULD EXTEND FROM SWRN TX NEWD THROUGH NRN AR...INTO PA. TRAILING PORTION OF FRONT WILL BEGIN TO RETREAT NWD THURSDAY NIGHT AS LEE TROUGH DEVELOPS OVER THE HIGH PLAINS. ...SRN HIGH PLAINS AREA... MODEST HEIGHT RISES IN WAKE OF LEAD SHORTWAVE TROUGH WILL RESULT IN FURTHER WEAKENING OF MID-UPPER FLOW OVER THE SRN PLAINS WITH 15-25 KT AT 500 MB. FRONT SHOULD STALL FROM SOUTH OF MIDLAND NEWD THROUGH SERN OK. RICH BOUNDARY LAYER MOISTURE WILL RESIDE IN WARM SECTOR BENEATH STEEP MID-LEVEL LAPSE RATES RESULTING IN MODERATE INSTABILITY DURING THE AFTERNOON...BUT REMNANT EML WILL LIKELY CONTRIBUTE TO A CAPPING INVERSION OVER MUCH OF THIS REGION. SOME POTENTIAL WILL EXIST FOR ISOLATED-WIDELY SCATTERED STORMS TO DEVELOP OVER SWRN TX ALONG TRAILING END OF FRONT AS THE BOUNDARY LAYER MIXES AND DESTABILIZES DURING THE AFTERNOON. DESPITE THE MODEST MID LEVEL FLOW...SUFFICIENT DIRECTIONAL SHEAR WITH SELY BOUNDARY LAYER FLOW VEERING TO WLY 25 KT AT 500 MB WILL SUPPORT THREAT OF UPDRAFT ROTATION...ESPECIALLY GIVEN EXPECTED 2500-3000 MLCAPE. A BETTER CHANCE FOR STORM INITIATION MAY OCCUR OVERNIGHT OVER WRN TX AS THE LOW LEVEL JET INCREASES AND AUGMENTS LIFT ALONG AND NORTH OF THE FRONT. LARGE HAIL WILL BE THE PRIMARY THREAT WITH THIS ACTIVITY. STORMS CURRENTLY MOVING THROUGH SERN OK INTO WRN AR COULD STILL BE IN PROGRESS FROM NERN TX INTO SWRN AR THURSDAY MORNING...BUT A WEAKENING TREND IS EXPECTED AS ACTIVITY CONTINUES SWD INTO A MORE STRONGLY CAPPED ENVIRONMENT. DIABATIC HEATING WILL DESTABILIZE THE BOUNDARY LAYER OVER NERN TX...AND STORMS COULD REDEVELOP ALONG RESIDUAL OUTFLOW BOUNDARY DURING THE AFTERNOON. WEAK FLOW ALOFT WILL SUPPORT MULTICELL STORMS...BUT THE THERMODYNAMIC ENVIRONMENT MAY BECOME SUFFICIENT FOR A THREAT OF ISOLATED DAMAGING WIND AND HAIL. ...OH VALLEY THROUGH NERN STATES... AN AXIS OF UPPER 50S TO LOW 60S DEWPOINTS WILL ADVECT NEWD THROUGH PRE-FRONTAL WARM SECTOR...BUT INSTABILITY WILL REMAIN LIMITED DUE TO WEAK LAPSE RATES AND WIDESPREAD CLOUDS. STORMS WILL BE ONGOING ALONG AND AHEAD OF FRONT OVER THE TN AND OH VALLEYS EARLY THURSDAY. ACTIVITY WILL BE EMBEDDED WITHIN STRONG SWLY LOW-MID LEVEL FLOW AND COULD POSE A MODEST THREAT FOR ISOLATED WIND DAMAGE. HOWEVER...TENDENCY WILL BE FOR THE BOUNDARY LAYER FLOW TO WEAKEN AS LOW LEVEL JET SHIFTS RAPIDLY NEWD IN ASSOCIATION WITH SHORTWAVE TROUGH EJECTING INTO SERN CANADA. THIS ALONG WITH LOW DESTABILIZATION POTENTIAL SHOULD SERVE AS LIMITING FACTORS FOR A MORE ROBUST THREAT. ...ERN KS...SERN NEB...SRN IA THROUGH WRN MO... STRENGTHENING NOCTURNAL LOW LEVEL JET EAST OF DEVELOPING LEE TROUGH WILL CONTRIBUTE TO THETA-E ADVECTION AND LIFT FROM CNTRL AND ERN KS INTO WRN MO NORTH OF RETREATING FRONTAL BOUNDARY. ELEVATED STORMS ARE EXPECTED TO DEVELOP IN THIS REGION THURSDAY NIGHT. MODERATE MUCAPE AND 7-7.5 C/KM MID LEVEL LAPSE RATES WILL SUPPORT A THREAT OF HAIL WITH THE STRONGER CORES. ...SERN STATES... SCATTERED MULTICELL STORMS WILL LIKELY ONCE AGAIN DEVELOP IN THIS REGION AS THE ATMOSPHERE DESTABILIZES DURING THE AFTERNOON. THE STRONGER STORMS COULD PRODUCE ISOLATED DOWNBURSTS AND MARGINALLY SEVERE HAIL. ..DIAL.. 05/14/2009  112 ACUS01 KWNS 140609 SWODY1 SPC AC 140607 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0107 AM CDT THU MAY 14 2009 VALID 141200Z - 151200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER A PORTION OF SWRN TX... ...SYNOPSIS... UPPER TROUGH CURRENTLY MOVING THROUGH THE UPPER MS VALLEY WILL EJECT NEWD THROUGH THE GREAT LAKES...REACHING SRN QUEBEC THIS AFTERNOON. THIS FEATURE WILL PROVIDE IMPETUS FOR A COLD FRONT TO ADVANCE THROUGH THE OH VALLEY. TRAILING PORTIONS OF FRONT WILL STALL ACROSS THE SRN PLAINS. BY THURSDAY EVENING THIS BOUNDARY SHOULD EXTEND FROM SWRN TX NEWD THROUGH NRN AR...INTO PA. TRAILING PORTION OF FRONT WILL BEGIN TO RETREAT NWD THURSDAY NIGHT AS LEE TROUGH DEVELOPS OVER THE HIGH PLAINS. ...SRN HIGH PLAINS AREA... MODEST HEIGHT RISES IN WAKE OF LEAD SHORTWAVE TROUGH WILL RESULT IN FURTHER WEAKENING OF MID-UPPER FLOW OVER THE SRN PLAINS WITH 15-25 KT AT 500 MB. FRONT SHOULD STALL FROM SOUTH OF MIDLAND NEWD THROUGH SERN OK. RICH BOUNDARY LAYER MOISTURE WILL RESIDE IN WARM SECTOR BENEATH STEEP MID-LEVEL LAPSE RATES RESULTING IN MODERATE INSTABILITY DURING THE AFTERNOON...BUT REMNANT EML WILL LIKELY CONTRIBUTE TO A CAPPING INVERSION OVER MUCH OF THIS REGION. SOME POTENTIAL WILL EXIST FOR ISOLATED-WIDELY SCATTERED STORMS TO DEVELOP OVER SWRN TX ALONG TRAILING END OF FRONT AS THE BOUNDARY LAYER MIXES AND DESTABILIZES DURING THE AFTERNOON. DESPITE THE MODEST MID LEVEL FLOW...SUFFICIENT DIRECTIONAL SHEAR WITH SELY BOUNDARY LAYER FLOW VEERING TO WLY 25 KT AT 500 MB WILL SUPPORT THREAT OF UPDRAFT ROTATION...ESPECIALLY GIVEN EXPECTED 2500-3000 MLCAPE. A BETTER CHANCE FOR STORM INITIATION MAY OCCUR OVERNIGHT OVER WRN TX AS THE LOW LEVEL JET INCREASES AND AUGMENTS LIFT ALONG AND NORTH OF THE FRONT. LARGE HAIL WILL BE THE PRIMARY THREAT WITH THIS ACTIVITY. STORMS CURRENTLY MOVING THROUGH SERN OK INTO WRN AR COULD STILL BE IN PROGRESS FROM NERN TX INTO SWRN AR THURSDAY MORNING...BUT A WEAKENING TREND IS EXPECTED AS ACTIVITY CONTINUES SWD INTO A MORE STRONGLY CAPPED ENVIRONMENT. DIABATIC HEATING WILL DESTABILIZE THE BOUNDARY LAYER OVER NERN TX...AND STORMS COULD REDEVELOP ALONG RESIDUAL OUTFLOW BOUNDARY DURING THE AFTERNOON. WEAK FLOW ALOFT WILL SUPPORT MULTICELL STORMS...BUT THE THERMODYNAMIC ENVIRONMENT MAY BECOME SUFFICIENT FOR A THREAT OF ISOLATED DAMAGING WIND AND HAIL. ...OH VALLEY THROUGH NERN STATES... AN AXIS OF UPPER 50S TO LOW 60S DEWPOINTS WILL ADVECT NEWD THROUGH PRE-FRONTAL WARM SECTOR...BUT INSTABILITY WILL REMAIN LIMITED DUE TO WEAK LAPSE RATES AND WIDESPREAD CLOUDS. STORMS WILL BE ONGOING ALONG AND AHEAD OF FRONT OVER THE TN AND OH VALLEYS EARLY THURSDAY. ACTIVITY WILL BE EMBEDDED WITHIN STRONG SWLY LOW-MID LEVEL FLOW AND COULD POSE A MODEST THREAT FOR ISOLATED WIND DAMAGE. HOWEVER...TENDENCY WILL BE FOR THE BOUNDARY LAYER FLOW TO WEAKEN AS LOW LEVEL JET SHIFTS RAPIDLY NEWD IN ASSOCIATION WITH SHORTWAVE TROUGH EJECTING INTO SERN CANADA. THIS ALONG WITH LOW DESTABILIZATION POTENTIAL SHOULD SERVE AS LIMITING FACTORS FOR A MORE ROBUST THREAT. ...ERN KS...SERN NEB...SRN IA THROUGH WRN MO... STRENGTHENING NOCTURNAL LOW LEVEL JET EAST OF DEVELOPING LEE TROUGH WILL CONTRIBUTE TO THETA-E ADVECTION AND LIFT FROM CNTRL AND ERN KS INTO WRN MO NORTH OF RETREATING FRONTAL BOUNDARY. ELEVATED STORMS ARE EXPECTED TO DEVELOP IN THIS REGION THURSDAY NIGHT. MODERATE MUCAPE AND 7-7.5 C/KM MID LEVEL LAPSE RATES WILL SUPPORT A THREAT OF HAIL WITH THE STRONGER CORES. ...SERN STATES... SCATTERED MULTICELL STORMS WILL LIKELY ONCE AGAIN DEVELOP IN THIS REGION AS THE ATMOSPHERE DESTABILIZES DURING THE AFTERNOON. THE STRONGER STORMS COULD PRODUCE ISOLATED DOWNBURSTS AND MARGINALLY SEVERE HAIL. ..DIAL/GRAMS.. 05/14/2009  324 ACUS03 KWNS 140731 SWODY3 SPC AC 140728 DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0228 AM CDT THU MAY 14 2009 VALID 161200Z - 171200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MID-ATLANTIC... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS... ...MID-ATLANTIC/UPPER OH VALLEY/TN VALLEY... AN UPPER-LEVEL TROUGH AND WELL-DEFINED MID-LEVEL JET IS FORECAST TO MOVE ACROSS THE GREAT LAKES SATURDAY. AHEAD OF THIS SYSTEM...MODEL FORECAST SHOW AN INSTABILITY AXIS LOCATED FROM THE CNTRL APPALACHIAN MTNS NNEWD INTO ERN PA AND ERN NY. THUNDERSTORMS SHOULD BE ONGOING SATURDAY MORNING ALONG A COLD FRONT AND INCREASE IN COVERAGE EWD ACROSS THE MID-ATLANTIC DURING THE AFTERNOON. FORECAST SOUNDINGS ALONG THIS CORRIDOR AT 21Z SATURDAY SHOW MODERATE VERTICAL SHEAR PROFILES SUGGESTING AN ISOLATED SEVERE THREAT WILL EXIST. ALTHOUGH STORM MODE IS NOT YET CLEAR...SUPERCELLS WILL BE POSSIBLE ESPECIALLY IF MODERATE INSTABILITY CAN DEVELOP LATE SATURDAY AFTERNOON. IN ADDITION...FORECAST SOUNDINGS SHOW 25 TO 35 KT OF LOW-LEVEL FLOW SUGGESTING LINE-SEGMENTS SHOULD BE EASILY CAPABLE OF PRODUCING WIND DAMAGE. FURTHER SOUTHWEST ALONG THE COLD FRONT INTO WV...KY AND TN...FORECAST SOUNDINGS SHOW MODERATE INSTABILITY BY SATURDAY AFTERNOON. AS INSTABILITY AND CONVERGENCE INCREASE ALONG THE FRONT...THUNDERSTORMS SHOULD DEVELOP. IN SPITE OF THE INSTABILITY...VERTICAL SHEAR SHOULD BE MARGINAL FOR A SEVERE THREAT. IF A FEW SEVERE STORMS DUE DEVELOP...THE MOST LIKELY THREAT WOULD BE STRONG WIND GUSTS AS LOW-LEVEL LAPSE RATES STEEPEN IN THE LATE AFTERNOON. ...SRN PLAINS... A WNW FLOW PATTERN WILL BE IN PLACE ACROSS THE SRN PLAINS AS A BROAD UPPER-LEVEL TROUGH EXITS EWD INTO THE MID-MS VALLEY. AT THE SFC...A COLD FRONT IS FORECAST TO MOVE SWD ACROSS NRN AND CNTRL TX SATURDAY. THUNDERSTORMS SHOULD BE ONGOING ALONG THIS BOUNDARY SATURDAY MORNING AND SEVERAL MODELS INCREASE STORM COVERAGE DURING THE AFTERNOON SWD ACROSS WEST TX AND THE HILL COUNTRY. FORECAST SOUNDINGS IN THIS AREA SHOW MODERATE TO STRONG INSTABILITY AND ENOUGH VERTICAL SHEAR FOR A SEVERE THREAT. STEEP MID-LEVEL LAPSE RATES COULD FAVOR A THREAT FOR HAIL. IF AN MCS CAN ORGANIZE AS SEVERAL MODELS SUGGEST...THEN A WIND DAMAGE THREAT COULD ALSO DEVELOP AND PERSIST INTO THE EARLY EVENING. ..BROYLES.. 05/14/2009  696 ACUS48 KWNS 140852 SWOD48 SPC AC 140851 DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0351 AM CDT THU MAY 14 2009 VALID 171200Z - 221200Z THE MEDIUM RANGE MODELS MOVE A BROAD UPPER-LEVEL TROUGH EWD INTO THE ERN SEABOARD SUNDAY/DAY 4 AS A COLD FRONT ADVANCES SEWD ACROSS THE GULF COAST STATES. THUNDERSTORMS SHOULD DEVELOP SUNDAY AFTERNOON IN RESPONSE TO SFC HEATING ALONG THE BOUNDARY. RELATIVELY WEAK VERTICAL SHEAR PROFILES OVER THE WARM SECTOR SHOULD KEEP THE SEVERE THREAT LOCALIZED. BEYOND DAY 4...THE MEDIUM RANGE MODELS DEVELOP A PERSISTENT UPPER-LEVEL RIDGE OVER THE CNTRL U.S. THIS SHOULD IMPEDE MOISTURE RETURN FROM THE GULF OF MEXICO UNTIL LATE IN THE DAY 4 TO 8 PERIOD. FOR THIS REASON...AN EXTENSIVE REGIONAL SEVERE THREAT IS NOT EXPECTED THROUGH MOST OF NEXT WEEK. ..BROYLES.. 05/14/2009  738 ACUS11 KWNS 140856 SWOMCD SPC MCD 140856 TNZ000-KYZ000-MSZ000-MOZ000-ARZ000-141000- MESOSCALE DISCUSSION 0824 NWS STORM PREDICTION CENTER NORMAN OK 0356 AM CDT THU MAY 14 2009 AREAS AFFECTED...NERN AR...NWRN MS...WRN TN...WRN KY CONCERNING...SEVERE THUNDERSTORM WATCH 302... VALID 140856Z - 141000Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 302 CONTINUES. SQUALL LINE IS PROGRESSING SOUTHEAST AT ROUGHLY 30KT ACROSS NERN AR/SERN MO. AS A RESULT...THIS ACTIVITY SHOULD EXIT THE WATCH AROUND 10Z. LATEST RADAR DATA SUGGESTS GUST FRONT IS RACING ABOUT 5-10 MI AHEAD OF SQUALL LINE AND IS LIKELY PRODUCING STRONG/SEVERE WIND GUSTS. LOCAL WATCH EXTENSION MAY BE REQUIRED JUST DOWNSTREAM FROM NWRN MS INTO WRN TN AND WRN KY TO ACCOUNT FOR THESE TRENDS. ..DARROW.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...OHX...PAH...MEG...LZK... LAT...LON 35129137 36798869 36168807 34728972 34579112 35129137  603 ACUS11 KWNS 140938 SWOMCD SPC MCD 140937 OHZ000-KYZ000-INZ000-141030- MESOSCALE DISCUSSION 0825 NWS STORM PREDICTION CENTER NORMAN OK 0437 AM CDT THU MAY 14 2009 AREAS AFFECTED...OH CONCERNING...SEVERE THUNDERSTORM WATCH 301... VALID 140937Z - 141030Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 301 CONTINUES. LEADING EDGE OF SQUALL LINE WILL SOON MOVE EAST OF WW301. A GENERAL DECREASING TREND HAS BEEN NOTED OVER THE LAST FEW HOURS AS THIS CONVECTION SPREADS INTO INCREASINGLY STABLE AIR OVER OH. EVEN SO IT APPEARS GUSTY WINDS MAY ACCOMPANY THE STRONGEST STORMS FOR THE NEXT FEW HOURS AS THEY SPREAD EAST. UNLESS SQUALL LINE INTENSIFIES SIGNIFICANTLY NEW WW WILL NOT BE ISSUED DOWNSTREAM. ..DARROW.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...CLE...ILN...LMK...IND... LAT...LON 38848554 40328388 41658293 41198217 39638271 38708395 38848554  998 ACUS11 KWNS 141027 SWOMCD SPC MCD 141026 LAZ000-ARZ000-TXZ000-141130- MESOSCALE DISCUSSION 0826 NWS STORM PREDICTION CENTER NORMAN OK 0526 AM CDT THU MAY 14 2009 AREAS AFFECTED...SRN AR...NERN TX...NRN LA CONCERNING...SEVERE THUNDERSTORM WATCH 303... VALID 141026Z - 141130Z THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 303 CONTINUES. OUTFLOW FROM ARKLATEX CONVECTION IS SURGING WELL AHEAD OF PRECIPITATION AS IT SPREADS TOWARDS NWRN LA. A WELL DEFINED WIND SHIFT NOW EXTENDS ACROSS SRN AR INTO NERN TX...ROUGHLY 10 MI AHEAD OF STRONGEST PORTIONS OF THE SQUALL LINE. GUSTY WINDS WILL LIKELY ACCOMPANY THIS ACTIVITY AS IT SPREADS TOWARD SHV. AT THIS TIME DO NOT ANTICIPATE ANOTHER WW DOWNSTREAM. ..DARROW.. 05/14/2009 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...JAN...LZK...SHV... LAT...LON 32569556 33569357 33129182 32129249 31869462 32569556  220 ACUS01 KWNS 141226 SWODY1 SPC AC 141223 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0723 AM CDT THU MAY 14 2009 VALID 141300Z - 151200Z ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SOUTHWEST TX... A POTENT UPPER TROUGH IS ROTATING ACROSS THE GREAT LAKES REGION TODAY...WHILE THE ASSOCIATED COLD FRONT SWEEPS EASTWARD ACROSS THE UPPER OH VALLEY...TN VALLEY...AND LOWER MS VALLEY. TODAY IS EXPECTED TO BE MUCH LESS CONVECTIVELY ACTIVE THAN WEDNESDAY...BUT MAY STILL SEE POCKETS OF STRONG TO SEVERE STORMS THIS AFTERNOON AND EVENING. ...SOUTHWEST TX... A MOIST AND VERY UNSTABLE AIRMASS WILL ONCE AGAIN BE PRESENT THIS AFTERNOON OVER PARTS OF CENTRAL AND SOUTHWEST TX WITH DEWPOINTS IN THE 60S AND MLCAPE VALUES OF 2000-3000 J/KG. WEAK FLOW...RIDGING...AND SOME CAPPING ALOFT WILL LIMIT THE AREAL COVERAGE OF CONVECTION THROUGH MOST OF THE DAY. HOWEVER...IT APPEARS LIKELY THAT AT LEAST ISOLATED CELLS WILL DEVELOP BY LATE AFTERNOON ALONG THE DRYLINE FROM NEAR ABI SOUTHWARD. STORMS THAT FORM WILL LIKELY BE ORGANIZED MULTICELLS OR SUPERCELLS WITH A RISK OF HAIL AND DAMAGING WINDS THROUGH THE EVENING. ...PA/WV/KY... REMNANT CONVECTIVE LINE CONTINUES TO TRACK EASTWARD ACROSS THE UPPER OH VALLEY THIS MORNING. TRENDS IN RADAR AND LIGHTNING DATA INDICATE THAT THE LINE HAS WEAKENED CONSIDERABLY AND IS NO LONGER SEVERE. HOWEVER...LOW AND MID LEVEL WIND FIELDS ARE QUITE STRONG AND MORNING RAOBS SUGGEST MARGINAL INSTABILITY IS PRESENT. A FEW HOURS OF DAYTIME HEATING MAY BE SUFFICIENT TO REJUVENATE STORMS AND POSE A RISK OF LOCALLY GUSTY/DAMAGING WINDS EARLY THIS AFTERNOON. ...CENTRAL GULF COAST STATES INTO FL... A MOIST AND MODERATELY UNSTABLE AIRMASS IS IN PLACE TODAY OVER THE SOUTHEAST STATES...WITH DEWPOINTS IN THE 60S TO LOWER 70S AND THE POTENTIAL FOR STRONG DAYTIME HEATING. COOL TEMPERATURES ALOFT /-9 TO -11C AT 500MB/ WILL HELP TO YIELD SUFFICIENT AFTERNOON CAPE FOR A RISK OF A FEW RATHER DISORGANIZED THUNDERSTORM CLUSTERS CAPABLE OF DAMAGING WINDS AND HAIL. ...OK/KS/MO OVERNIGHT... A SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY OVER THE PACIFIC NORTHWEST WILL CROSS THE ROCKIES AND APPROACH THE CENTRAL PLAINS BY LATE TONIGHT. STRONG SOUTHERLY LOW LEVEL WINDS WILL TRANSPORT MOISTURE NORTHWARD AND RESULT IN ELEVATED INSTABILITY OVER MUCH OF OK/KS/MO BY THE END OF THE FORECAST PERIOD. IT APPEARS LIKELY THE SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THIS REGION WITH A RISK OF HAIL IN THE STRONGER CORES. ..HART/HURLBUT.. 05/14/2009  960 ACUS01 KWNS 141618 SWODY1 SPC AC 141614 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1114 AM CDT THU MAY 14 2009 VALID 141630Z - 151200Z ...THERE IS A SLGT RISK OF SVR TSTMS PARTS OF WEST AND NORTHWEST TEXAS... ...SYNOPSIS... VIGOROUS TROUGH GREAT LAKES LIFTS QUICKLY INTO SERN CANADA TODAY AS ANOTHER WEAKER S/WV TROUGH PAC NW CROSSES NRN ROCKIES TONIGHT. ASSOCIATED PORTIONS OF COLD FRONT THRU GREAT LAKES INTO OH VALLEY CONTINUES EWD TO ACROSS NEW ENGLAND TONIGHT WHILE TRAILING PORTION STALLS ACROSS SRN PLAINS WITH RETURN FLOW DEVELOPING LATER TODAY/TONIGHT. ...WESTERN TX... WHILE OVERNIGHT CONVECTION HAS PUSHED SURFACE BOUNDARY SWD INTO CENTRAL TX THIS AM...THE ACTUAL FRONT HAS OR WILL STALL BACK NEAR RED RIVER AND WITH WRN PORTION BEGINNING TO RETURN NWD TONIGHT AS LEE TROUGH DEVELOPS AHEAD OF NEXT SYSTEM. WHILE DEEP LAYER SHEAR WILL NOT BE VERY STRONG...GENERALLY 20KT...THE AIR MASS IS EXPECTED TO BECOME VERY UNSTABLE ON WRN PERIPHERY OF THE LOW LEVEL MOISTURE WHERE HEATING WILL RAISE MLCAPES TO NEAR 3000 J/KG BY LATE AFTERNOON. HAVE EXTENDED THE RISK OF THE MOSTLY ISOLATED COVERAGE OF SEVERE THUNDERSTORMS NWD INTO PARTS OF NWRN TX WHERE FRONTAL ZONE WILL BE RESIDING THROUGH THE AFTERNOON. PRIMARY CONCERN IS FOR SLOW MOVING TRANSIENT SUPERCELL STRUCTURES...WITH LARGE HAIL PRIMARY THREAT. ANY TORNADO THREAT WILL BE AT BEST ISOLATED AND BRIEF. ..PA/WV/KY... REMNANT CONVECTIVE LINE CONTINUES TO TRACK EASTWARD CURRENTLY LOCATED FROM SCENTRAL PA TO ERN KY. ACTUAL COLD FRONT STILL BACK IN OH AND SRN MO AND WILL BE THE FOCUS FOR A FEW STRONG LOW TOPPED THUNDERSTORMS LATER THIS AFTERNOON AS IT MOVES EWD ACROSS APPALACHIANS . POOR LAPSE RATES GENERALLY AROUND 6C/KM COMBINED WITH EXPECTED WEAK INSTABILITY...MLCAPES GENERALLY LESS THAN 500 J/KG...WILL LEAD TO A LOW END SEVERE THREAT. PRIMARY CONCERN WILL BE STRONG WINDS AS SHEAR ENVIRONMENT THE STORMS WILL BE FORMING IN WILL BE CHARACTERIZED WITH 40-50 KT OF BULK SHEAR. A FEW GUSTS COULD BE BRIEFLY SEVERE FROM MID AFTERNOON UNTIL SUNSET WHEN THE BOUNDARY LAYER SHOULD STABILIZE SUFFICIENTLY AND SHUT DOWN WHAT THREAT THERE IS. ...CENTRAL GULF COAST STATES INTO FL... A MOIST AND MODERATELY UNSTABLE AIRMASS IS IN PLACE TODAY OVER THE SOUTHEAST STATES...WITH DEWPOINTS IN THE 60S TO LOWER 70S AND THE POTENTIAL FOR STRONG DAYTIME HEATING. COOL TEMPERATURES ALOFT /-9 TO -11C AT 500MB/ WILL HELP TO YIELD SUFFICIENT AFTERNOON CAPE FOR A RISK OF A FEW RATHER DISORGANIZED THUNDERSTORM CLUSTERS CAPABLE OF DAMAGING WINDS AND HAIL. ...OK/KS/MO OVERNIGHT... THE PAC NW SHORTWAVE TROUGH WILL CROSS THE ROCKIES AND APPROACH THE CENTRAL PLAINS BY LATE TONIGHT. WITH DEVELOPMENT OF THE LEE TROUGH STRONG SOUTHERLY LOW LEVEL WINDS WILL TRANSPORT MOISTURE NORTHWARD AND RESULT IN ELEVATED INSTABILITY OVER MUCH OF OK/KS/MO BY THE END OF THE FORECAST PERIOD. IT APPEARS LIKELY THE SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THIS REGION WITH A RISK OF HAIL IN THE STRONGER CORES. ..HALES/SMITH.. 05/14/2009  963 ACUS02 KWNS 141724 SWODY2 SPC AC 141722 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1222 PM CDT THU MAY 14 2009 VALID 151200Z - 161200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE OH VALLEY AND UPPER MIDWEST SWWD INTO THE SRN HIGH PLAINS... ...SYNOPSIS... MAIN FEATURE OF INTEREST DURING THE DAY TWO PERIOD IS MIDLEVEL TROUGH WHICH WILL INTENSIFY CONSIDERABLY WHILE TRANSLATING GENERALLY EWD FROM THE CANADIAN PRAIRIES AND NRN HIGH PLAINS INTO THE UPPER GREAT LAKES. IN THE LOW LEVELS...PRIMARY SURFACE CYCLONE WILL UNDERGO OCCLUSION WHILE DEVELOPING FROM ERN ND ENEWD INTO CNTRL ONTARIO. TRAILING COLD FRONT INITIALLY FROM THE CNTRL DAKOTAS SWWD INTO THE CNTRL HIGH PLAINS WILL PUSH EWD/SEWD...EXTENDING FROM LOWER MI SWWD THROUGH THE MID MS VALLEY INTO SRN HIGH PLAINS BY 16/12Z. MEANWHILE...WARM FRONT FROM THE MID MO VALLEY ESEWD TO ALONG THE OH RIVER WILL RETREAT SLOWLY NWD IN ADVANCE OF EWD-MOVING COLD FRONT WITH SECONDARY CYCLONE DEVELOPMENT OCCURRING AT THE INTERSECTION OF THESE TWO BOUNDARIES. ...LOWER MO INTO OH VALLEYS... NEWD MIGRATION OF SWLY LLJ WILL MAINTAIN A MOIST LOW-LEVEL AIR MASS INVOF SURFACE WARM FRONT WITH DEWPOINTS OF 65-70 F. THIS MOISTURE WILL COMBINE WITH ERN EXTENSION OF EML/STEEP LAPSE RATE PLUME TO SUPPORT A MODERATE TO POTENTIALLY STRONGLY UNSTABLE AIR MASS WITH MLCAPE APPROACHING 2000-3000 J/KG BY MID TO LATE AFTERNOON. TSTMS ARE EXPECTED TO BE ONGOING FRI MORNING FROM PORTIONS OF ERN KS INTO THE LOWER MO VALLEY ALONG ERN EDGE OF EML/CAP AND WITHIN EXIT REGION OF LLJ WHERE MOIST AND WARM THERMAL ADVECTIONS WILL BE ENHANCED. THIS ACTIVITY WILL GRADUALLY INCREASE IN BOTH COVERAGE AND INTENSITY THROUGH THE DAY ALONG/N OF RETREATING WARM FRONT AS LOW-LEVEL FORCING ALONG NOSE OF MIGRATORY LLJ IS AUGMENTED BY DEEP-LAYER ASCENT IN ADVANCE OF APPROACHING MIDLEVEL TROUGH. WHILE HAIL WILL BE THE PRIMARY THREAT WITH SLIGHTLY ELEVATED STORMS N OF WARM FRONT...ENVIRONMENT ACROSS NRN MO INTO CNTRL IL WILL BECOME INCREASINGLY SUPPORTIVE OF INTENSE STORMS CAPABLE OF LARGE HAIL...DAMAGING WINDS AND TORNADOES. HERE...THE COMBINATION OF THE MODERATE TO STRONG INSTABILITY...40-45 KT OF DEEP-LAYER SHEAR AND LOCALLY ENHANCED LOW-LEVEL SHEAR FROM SECONDARY SURFACE LOW EWD ALONG WARM FRONT WILL FAVOR SUSTAINED SUPERCELL AND/OR BOWING STRUCTURES THROUGH THE AFTERNOON AND EVENING HOURS. EXPECT THE SEVERE WEATHER THREAT TO CONTINUE FRI NIGHT EWD/NEWD INTO PORTIONS OF IND AND SRN LOWER MI FROM VICINITY OF SECONDARY SURFACE LOW SWWD ALONG TRAILING COLD FRONT. ...CNTRL/SRN PLAINS... VERY STEEP MIDLEVEL LAPSE RATES /8-9 C PER KM/ ASSOCIATED WITH EML COUPLED WITH BOUNDARY LAYER DEWPOINTS IN THE 60S WILL CONTRIBUTE TO A STRONGLY UNSTABLE AIR MASS BY AFTERNOON WITH MLCAPE APPROACHING 2500-3500 J/KG. WHILE REGION WILL RESIDE TO THE S/SW OF ANY APPRECIABLE HEIGHT FALLS/DYNAMIC FORCING ASSOCIATED WITH ABOVE-MENTIONED SHORT WAVE TROUGH...THE COMBINATION OF STRONG DIURNAL HEATING AND FRONTAL ASCENT SHOULD FOSTER TSTM DEVELOPMENT FRI AFTERNOON AND EVENING SWWD ALONG COLD FRONT. ADDITIONAL... MORE ISOLATED STORMS WILL BE POSSIBLE SWD ALONG DRYLINE INTO WRN TX. VERTICAL SHEAR WILL REMAIN ON THE MARGINS OF THAT SUPPORTIVE OF SUSTAINED UPDRAFT ROTATION /I.E. AROUND 30 KT THROUGH 6 KM/. BUT THE PRESENCE OF THE STRONG INSTABILITY WILL SERVE TO ENHANCE STORM ORGANIZATION WITH THE POTENTIAL FOR VERY LARGE HAIL IN ADDITION TO DAMAGING WINDS AND PERHAPS A BRIEF TORNADO OR TWO. ACTIVITY SHOULD GROW UPSCALE INTO AN MCS WITH A WIND/HAIL THREAT CONTINUING INTO FRI NIGHT ACROSS OK. ...UPPER MS VALLEY... WHILE BOUNDARY LAYER IS NOT FORECAST TO BECOME AS WARM/MOIST AS LOCATIONS TO THE S...CONSIDERABLE DYNAMIC COOLING IN THE MIDLEVELS WILL CONTRIBUTE TO A NARROW AXIS OF WEAK CONVECTIVE INSTABILITY ALONG COLD FRONT DURING THE AFTERNOON. SCATTERED...DIURNAL TSTMS ARE EXPECTED TO DEVELOP AS STRONG FORCING FOR ASCENT ASSOCIATED WITH MIDLEVEL TROUGH OVERSPREADS FRONTAL ZONE. SOME OF THE MORE INTENSE STORMS WILL BE CAPABLE OF MARGINALLY SEVERE HAIL INTO THE EVENING HOURS. ..MEAD.. 05/14/2009  071 ACUS01 KWNS 142001 SWODY1 SPC AC 141958 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0258 PM CDT THU MAY 14 2009 VALID 142000Z - 151200Z ...THERE IS A SLGT RISK OF SVR TSTMS THROUGH THIS EVENING OVER PARTS OF WRN AND NRN TX... ...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT OVER PARTS OF CNTRL/ERN KS... ...SRN PLAINS THROUGH THIS EVENING... PRESSURE FALLS OVER THE HIGH PLAINS HAVE ALLOWED FOR THE SLOW NWD RETREAT OF SURFACE WARM FRONT THIS AFTERNOON WITH BOUNDARY EXTENDING FROM CNTRL OK SWWD TO LOW PRESSURE NEAR MAF. AIR MASS ALONG AND S OF THIS BOUNDARY REMAINS RELATIVELY MOIST WITH DEWPOINTS IN THE 60S. WHEN COUPLED WITH STEEP MIDLEVEL LAPSE RATES...ENVIRONMENT HAS BECOME MODERATELY UNSTABLE WITH MLCAPE OF 1500-2500 J/KG AND A WEAKENING CAP. GIVEN THE ABSENCE OF ANY DISCERNIBLE FORCING MECHANISM /I.E. MIDLEVEL SHORT WAVE TROUGH/...DIABATIC HEATING...CONVERGENCE ALONG THE SURFACE BOUNDARY AND PERHAPS TERRAIN WILL BE THE PRIMARY FOCI FOR STORM INITIATION. RATHER WEAK VERTICAL SHEAR WILL LIMIT THE DEGREE OF STORM ORGANIZATION/SUSTENANCE. NONETHELESS...THE STRONGER STORMS WILL BE CAPABLE OF HAIL AND DAMAGING WIND GUSTS THROUGH THE EVENING HOURS. ...CNTRL PLAINS INTO LOWER MO VALLEY TONIGHT... NOCTURNAL LLJ WILL INTENSIFY OVERNIGHT FROM WRN TX INTO THE MID/LOWER MO VALLEY IN RESPONSE TO NEXT UPSTREAM SYSTEM MOVING INTO THE NRN HIGH PLAINS. THIS FEATURE WILL SERVE TO ENHANCE LOW-LEVEL MOISTURE FLUX BENEATH ERN EXTENSION OF EML/STEEP LAPSE RATE PLUME WITH ENVIRONMENT BECOMING MODERATELY UNSTABLE WITH MUCAPE INCREASING TO 1000-2000 J/KG. GIVEN 30-35 KT OF EFFECTIVE BULK SHEAR...ENVIRONMENT WILL BE SUPPORTIVE OF A FEW SEVERE STORMS CAPABLE OF HAIL. AS SUCH...HIGHER HAIL PROBABILITIES AND A CATEGORICAL SLIGHT RISK HAVE BEEN INCLUDED. ...LOWER GREAT LAKES INTO CUMBERLAND PLATEAU THROUGH THIS EVENING... AFTERNOON VISIBLE SATELLITE AND RADAR IMAGERY INDICATE DEEPENING MOIST CUMULUS CONVECTION OCCURRING ALONG COLD FRONT FROM PORTIONS OF CNTRL PA SWWD INTO CNTRL/ERN KY. THIS ACTIVITY IS ASSOCIATED WITH THE SRN FRINGE OF STRONGER FORCING FOR ASCENT ASSOCIATED WITH STRONG SHORT WAVE TROUGH LIFTING NEWD THROUGH SRN ONTARIO INTO WRN QUEBEC. CONSIDERABLE CLOUDINESS AND MARGINAL BOUNDARY LAYER MOISTURE WILL CONTINUE TO LIMIT DESTABILIZATION WITHIN PRE-FRONTAL AIR MASS WITH MLCAPE AOB 500 J/KG WITHIN REGION OF STRONGER SHEAR OVER PA/WV...TO 500-1000 J/KG ACROSS KY/TN WHERE VERTICAL SHEAR IS NOTABLY WEAKER. AS SUCH...POTENTIAL WILL EXIST FOR ISOLATED STRONG TO MARGINALLY SEVERE STORMS THROUGH THIS EVENING. LOCALLY STRONG WIND GUSTS AND PERHAPS SOME HAIL WILL BE POSSIBLE WITH THE STRONGER STORMS. ..MEAD.. 05/14/2009 .PREV DISCUSSION... /ISSUED 1114 AM CDT THU MAY 14 2009/ ...SYNOPSIS... VIGOROUS TROUGH GREAT LAKES LIFTS QUICKLY INTO SERN CANADA TODAY AS ANOTHER WEAKER S/WV TROUGH PAC NW CROSSES NRN ROCKIES TONIGHT. ASSOCIATED PORTIONS OF COLD FRONT THRU GREAT LAKES INTO OH VALLEY CONTINUES EWD TO ACROSS NEW ENGLAND TONIGHT WHILE TRAILING PORTION STALLS ACROSS SRN PLAINS WITH RETURN FLOW DEVELOPING LATER TODAY/TONIGHT. ...WESTERN TX... WHILE OVERNIGHT CONVECTION HAS PUSHED SURFACE BOUNDARY SWD INTO CENTRAL TX THIS AM...THE ACTUAL FRONT HAS OR WILL STALL BACK NEAR RED RIVER AND WITH WRN PORTION BEGINNING TO RETURN NWD TONIGHT AS LEE TROUGH DEVELOPS AHEAD OF NEXT SYSTEM. WHILE DEEP LAYER SHEAR WILL NOT BE VERY STRONG...GENERALLY 20KT...THE AIR MASS IS EXPECTED TO BECOME VERY UNSTABLE ON WRN PERIPHERY OF THE LOW LEVEL MOISTURE WHERE HEATING WILL RAISE MLCAPES TO NEAR 3000 J/KG BY LATE AFTERNOON. HAVE EXTENDED THE RISK OF THE MOSTLY ISOLATED COVERAGE OF SEVERE THUNDERSTORMS NWD INTO PARTS OF NWRN TX WHERE FRONTAL ZONE WILL BE RESIDING THROUGH THE AFTERNOON. PRIMARY CONCERN IS FOR SLOW MOVING TRANSIENT SUPERCELL STRUCTURES...WITH LARGE HAIL PRIMARY THREAT. ANY TORNADO THREAT WILL BE AT BEST ISOLATED AND BRIEF. ..PA/WV/KY... REMNANT CONVECTIVE LINE CONTINUES TO TRACK EASTWARD CURRENTLY LOCATED FROM SCENTRAL PA TO ERN KY. ACTUAL COLD FRONT STILL BACK IN OH AND SRN MO AND WILL BE THE FOCUS FOR A FEW STRONG LOW TOPPED THUNDERSTORMS LATER THIS AFTERNOON AS IT MOVES EWD ACROSS APPALACHIANS . POOR LAPSE RATES GENERALLY AROUND 6C/KM COMBINED WITH EXPECTED WEAK INSTABILITY...MLCAPES GENERALLY LESS THAN 500 J/KG...WILL LEAD TO A LOW END SEVERE THREAT. PRIMARY CONCERN WILL BE STRONG WINDS AS SHEAR ENVIRONMENT THE STORMS WILL BE FORMING IN WILL BE CHARACTERIZED WITH 40-50 KT OF BULK SHEAR. A FEW GUSTS COULD BE BRIEFLY SEVERE FROM MID AFTERNOON UNTIL SUNSET WHEN THE BOUNDARY LAYER SHOULD STABILIZE SUFFICIENTLY AND SHUT DOWN WHAT THREAT THERE IS. ...CENTRAL GULF COAST STATES INTO FL... A MOIST AND MODERATELY UNSTABLE AIRMASS IS IN PLACE TODAY OVER THE SOUTHEAST STATES...WITH DEWPOINTS IN THE 60S TO LOWER 70S AND THE POTENTIAL FOR STRONG DAYTIME HEATING. COOL TEMPERATURES ALOFT /-9 TO -11C AT 500MB/ WILL HELP TO YIELD SUFFICIENT AFTERNOON CAPE FOR A RISK OF A FEW RATHER DISORGANIZED THUNDERSTORM CLUSTERS CAPABLE OF DAMAGING WINDS AND HAIL. ...OK/KS/MO OVERNIGHT... THE PAC NW SHORTWAVE TROUGH WILL CROSS THE ROCKIES AND APPROACH THE CENTRAL PLAINS BY LATE TONIGHT. WITH DEVELOPMENT OF THE LEE TROUGH STRONG SOUTHERLY LOW LEVEL WINDS WILL TRANSPORT MOISTURE NORTHWARD AND RESULT IN ELEVATED INSTABILITY OVER MUCH OF OK/KS/MO BY THE END OF THE FORECAST PERIOD. IT APPEARS LIKELY THE SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THIS REGION WITH A RISK OF HAIL IN THE STRONGER CORES.