062 ACUS11 KWNS 130022 SWOMCD SPC MCD 130022 MIZ000-130615- MESOSCALE DISCUSSION 0022 NWS STORM PREDICTION CENTER NORMAN OK 0622 PM CST SUN JAN 12 2003 AREAS AFFECTED...U.P. OF MI AND NRN LOWER MI CONCERNING...HEAVY SNOW VALID 130022Z - 130615Z LAKE EFFECT SNOW EVENT EXPECTED TO DEVELOP AND INTENSIFY OVERNIGHT DOWNWIND FROM LAKE SUPERIOR AND LAKE MICHIGAN. SNOWFALL RATES MAY EXCEED 1 IN/HR OVER PORTIONS OF THE UPPER MI AND NRN LOWER MI OVER THE NEXT 3-6 HOURS. ARCTIC FROPA EXPECTED TO PROGRESS SEWD ACROSS ERN UPPER PENINSULA OF MI AND INTO NRN LOWER MI OVER THE NEXT 3 HOURS WITH DRAMATIC COOLING BEHIND THE FRONT AND EXTREME LAPSE RATES DEVELOPING FROM LAKE SURFACE THROUGH 850MB. FAVORABLE LARGE SCALE FORCING FOR ASCENT WITHIN DIVERGENT LEFT EXIT REGION OF MID/UPPER JET STREAK WILL COMBINE WITH RESULTANT INSTABILITY AND RISING INVERSION HEIGHTS TO PROMOTE THE DEVELOPMENT OF INTENSE LAKE EFFECT SNOW BANDS...FIRST OFF CNTRL AND SRN LAKE SUPERIOR...AND THEN LATER OFF NRN PART OF LAKE MI. ORGANIZATION AND INTENSITY OF THE SNOW BANDS SHOULD INCREASE WITH TIME AS DIRECTIONAL SHEAR IN THE CLOUD BEARING LAYER GRADUALLY LESSENS THROUGH 06Z. ..CARBIN/NADEN.. 01/13/2003 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... 46369031 46609046 46849011 47128925 47428833 47388765 46878761 46708658 46798611 46808564 46728503 46308465 45648439 44898443 44168558 43878625 44418746 45298774 46068895 46128943  987 ACUS01 KWNS 130107 SWODY1 SPC AC 130103 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 130100Z - 131200Z NO TSTM AREAS FCST. --- SYNOPSIS --- UPPER AIR PATTERN FEATURES LARGE/DEEP CYCLONE OVER NERN PACIFIC WITH SEVERAL EMBEDDED VORTICITY MAXIMA ORBITING COMMON CENTER NEAR 45N140W. DOWNSTREAM LONGWAVE RIDGE DOMINATES WRN CONUS...WITH LONGWAVE TROUGH FROM HUDSON BAY TO WRN GULF OF MEXICO. SHORTWAVE TROUGH IS NOW EVIDENT ON MOISTURE CHANNEL IMAGERY OVER SRN PLAINS -- AND IS EXPECTED TO MOVE EWD ACROSS TX AND ACROSS OK INTO AR BY END OF PERIOD. AT SURFACE...STRONG CONTINENTAL HIGH CENTERED OVER LOWER MS VALLEY WHILE INTENSE COLD FRONT SURGES SSEWD ACROSS NRN PLAINS AND UPPER MIDWEST. --- WRN GULF COAST REGION --- POCKET OF MARGINAL/ELEVATED INSTABILITY AHEAD OF TX TROUGH SHOULD COMBINE WITH PARTIALLY MODIFIED GULF AIR MASS -- ISENTROPICALLY LIFTED TO LFC -- TO YIELD TSTM RISK OVER PORTIONS NWRN GULF. BRO/CRP RAOBS YIELD 100-500 J/KG ELEVATED MUCAPE...WHICH WILL DIMINISH OVER LAND AS TROUGH PASSES AND LARGE SCALE SUBSIDENCE OCCURS NEXT SEVERAL HOURS. MOST CONVECTIVELY FAVORABLE PORTION WAA REGIME SHOULD REMAIN S OF LA COAST. PRIND THUNDER POTENTIAL OVER TX COAST HAS DIMINISHED AND MOVED OFFSHORE ENOUGH THAT GEN TSTM FCST NOT NECESSARY. ..EDWARDS.. 01/13/03  666 ACUS01 KWNS 130650 SWODY1 SPC AC 130552 RTD STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 131200Z - 141200Z GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM BLI SEA 35 NNW PDX 25 ENE ONP 40 N OTH. --- SYNOPSIS --- PROGRESSIVE SHORTWAVE PATTERN IS FORECAST ACROSS MUCH OF CONUS...WITHIN BROADER REGIME OF WRN CONUS LONGWAVE RIDGE AND ERN TROUGH. PRONOUNCED PERTURBATION NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER SRN/ERN TX IS EXPECTED TO MOVE EWD ACROSS SERN CONUS AND MUCH OF NRN/WRN GULF THROUGH PERIOD...REINFORCING CONTINENTAL LOW LEVEL ANTICYCLONE NOW OVER SERN STATES. THIS SHOULD KEEP LOW LEVEL AIR MASSES MOIST/UNSTABLE ENOUGH FOR TSTMS OFFSHORE. MEANWHILE...SEVERAL RELATIVELY MINOR SHORTWAVE TROUGHS ARE FORECAST TO MOVE ONSHORE PACIFIC NW AND INTO MEAN RIDGE POSITION. --- COASTAL WA/NWRN ORE --- COLDEST AIR ALOFT AND STEEPEST LAPSE RATES SHOULD ACCOMPANY DPVA FIELD PRECEDING SHORTWAVE TROUGH FORECAST TO PASS OVER AREA AROUND 14/00Z. ISOLATED THUNDER MAY ACCOMPANY SERN EDGE OF FIELD OF MARINE CB NOW EVIDENT WELL OFFSHORE...WHICH HAS INCLUDED TSTMS ACCORDING TO ONLINE AWC LIGHTNING DETECTION PRODUCTS. ADDITIONALLY...SHALLOW TSTMS MAY DEVELOP IN BRIEF EPISODES THROUGHOUT MUCH OF PERIOD...IN ZONE OF NEAR-SHORE CONVERGENCE. ..EDWARDS.. 01/13/03  206 ACUS02 KWNS 130808 SWODY2 SPC AC 130804 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 2 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWI47 KWNS. VALID 141200Z - 151200Z NO SVR TSTM AREAS FCST. NO TSTM AREAS FCST. ...SYNOPSIS/FORECAST... LITTLE LARGE SCALE CHANGE EXPECTED THIS PERIOD. NRN STREAM JET WILL CONTINUE TO FAVOR LOW LEVEL COLD ADVECTION OVER THE CNTRL AND ERN U.S...WHILE SRN BRANCH PERSISTS FROM THE PACIFIC NW TO THE CNTRL PLNS. RELATIVELY DRY AIR AT LOWER LEVELS OVER MOST OF THE NATION...AND THE ABSENCE OF ELEVATED INSTABILITY IN ELSEWHERE... EXPECTED TO MINIMIZE ANY THREAT FOR THUNDERSTORMS. ..CORFIDI.. 01/13/03  088 ACUS03 KWNS 131031 SWODY3 SPC AC 130921 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 3 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWK48 KWNS. VALID 151200-161200 LESS THAN A SLIGHT RISK. ...SYNOPSIS/FORECAST... LARGE SCALE PATTERN WITH ABOVE NORMAL HEIGHTS IN WRN CANADA AND TROUGHING ACROSS ERN CANADA AND THE NERN U.S. WILL PERSIST ON WEDNESDAY. PART OF SRN BRANCH TROUGH NOW NEAR 140W WILL REFORM SEWD ACROSS THE GREAT BASIN AND CNTRL RCKYS...INDUCING SURFACE CYCLOGENESIS OVER THE CNTRL PLNS. CONSIDERABLE UNCERTAINTY EXISTS ATTM REGARDING TRACK/INTENSITY OF THIS DEVELOPMENT...WITH BOTH THE GFS AND ECMWF SHOWING RUN-TO-RUN INCONSISTENCIES. AT ANY RATE... GIVEN CURRENT CONDITIONS IN THE WRN GULF...AND WEAK COLD ADVECTION THAT WILL OCCUR OVER THE REGION THROUGH THE NEXT 48 HRS...IT APPEARS UNLIKELY THAT SUFFICIENT MOISTURE WILL HAVE RETURNED TO THE CNTRL/SRN PLNS TO SUPPORT STRONG THUNDERSTORM DEVELOPMENT... DESPITE EXPECTED STRENGTHENING OF LARGE SCALE FORCING WITH SURFACE LOW/UPPER TROUGH. ..CORFIDI.. 01/13/03  469 ACUS01 KWNS 131247 SWODY1 SPC AC 131245 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 131300Z - 141200Z NO SVR TSTM AREAS FCST. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM BLI SEA 35 NNW PDX 25 ENE ONP 40 N OTH. ...SYNOPSIS/FORECAST... VERY LITTLE CHANGE IN THE OVERALL UPPER FLOW PATTERN EXPECTED THIS PERIOD. DEEP COLD LOW OVER SERN CANADA/GREAT LAKES REGION WILL MOVE SEWD ACROSS THE NERN PARTS OF AMERICA...REINFORCING THE DRY/STABLE CP AIR MASS IN PLACE OVER THE ERN TWO-THIRDS OF THE NATION. MEANWHILE...IMPULSE APPROACHING THE PAC NW WILL MOVE ASHORE OVERNIGHT. AVIATION WEATHER CENTER EXPERIMENTAL LIGHTNING DATA SUGGESTS LIGHTNING NEARING 130 WEST AND A FEW LOW TOPPED TSTMS ARE POSSIBLE OVERNIGHT IN POST-FRONTAL SHOWERY REGIME ACROSS COASTAL WA/ORE. ELSEWHERE...TSTMS ARE NOT ANTICIPATED. ..RACY.. 01/13/03  276 ACUS01 KWNS 131600 SWODY1 SPC AC 131559 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 131630Z - 141200Z NO TSTM AREAS FCST. THE ONLY CONCERN FOR THUNDERSTORMS IN THE CONUS IS PAC NW COAST. HOWEVER THE OBSERVED LIGHTNING WITH SYSTEM W OF 130W NOW EXPECTED TO NOT REACH THE COAST AS THE ASSOCIATED SURFACE WAVE AND TROUGH WILL TRACK NNEWD INTO BRITISH COLUMBIA. THUS HAVE DROPPED EARLIER THUNDER FORECASTED FOR NWRN COAST. ..HALES.. 01/13/03  713 ACUS02 KWNS 131708 SWODY2 SPC AC 131704 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 2 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWI47 KWNS. VALID 141200Z - 151200Z NO TSTM AREAS FCST. BROAD UPPER TROUGH EXPECTED TO CONTINUE OVER THE ERN U.S. WITH AN UPPER RIDGE NEAR THE WEST COAST AND A SHORTWAVE TROUGH DIGGING SEWD THROUGH THE GREAT BASIN AND ROCKIES. A SURFACE LOW WILL DEVELOP IN THE LEE OF THE ROCKIES AS THE SHORTWAVE TROUGH APPROACHES. HOWEVER...RETURN FLOW OF LOW LEVEL MOISTURE FROM THE GULF OF MEXICO IS EXPECTED TO BE MINIMAL ON DY2. THEREFORE...THE LACK OF SUFFICIENT POTENTIAL POSITIVE BUOYANCY SHOULD PRECLUDE THUNDERSTORM DEVELOPMENT ACROSS THE NATION. ..JOHNS/HALES.. 01/13/03  864 ACUS01 KWNS 131945 SWODY1 SPC AC 131943 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 132000Z - 141200Z NO TSTM AREAS FCST. STABLE AIR IS EXPECTED TO PREVAIL ACROSS THE NATION DURING THE REMAINDER OF THE DY1 PERIOD...INHIBITING THUNDERSTORM DEVELOPMENT. ..JOHNS/HALES.. 01/13/03  467 ACUS01 KWNS 132007 SWODY1 SPC AC 132006 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 132000Z - 141200Z NO TSTM AREAS FCST. STABLE AIR IS EXPECTED TO PREVAIL ACROSS THE NATION DURING THE REMAINDER OF THE DY1 PERIOD...INHIBITING THUNDERSTORM DEVELOPMENT. ..JOHNS/HALES.. 01/13/03