Issued by NWS
000 ACUS02 KWNS 231731 SWODY2 SPC AC 231730 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1130 AM CST MON NOV 23 2009 VALID 241200Z - 251200Z ...NO SVR TSTM AREAS FORECAST... ...SYNOPSIS... SERIES OF PROGRESSIVE SHORTWAVES WILL HELP TO SHIFT SYNOPTIC TROUGHING EWD FROM HIGH PLAINS TOWARD MS VALLEY REGION THROUGH DAY-2 PERIOD. STG SHORTWAVE TROUGH -- NOW ANALYZED OVER FRONT/LARAMIE/BIG HORN RANGES OF CO/WY -- IS FCST TO STRENGTHEN WITH 500 MB CLOSED LOW DEVELOPING OVERNIGHT DAY-1 OVER KS. THIS LOW SHOULD MOVE ENEWD FROM NRN MO TOWARD SRN LM AND WEAKEN SOMEWHAT DAY-2...AS UPSTREAM PERTURBATION APCHS/INTENSIFIES. LATTER TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY APCHG BC COAST -- IS FCST TO MOVE THROUGH LARGE SCALE RIDGE POSITION OVER WRN CANADA DAY-1...THEN TURN SEWD ACROSS SWRN PORTIONS OF PRAIRIE PROVINCES AND NRN U.S. HIGH PLAINS DAY-2. BY 25/12Z...THIS FEATURE SHOULD EVOLVE INTO CLOSED CYCLONE WITHIN 500-300 MB LAYER...OVER ERN DAKOTAS AND WRN MN...WITH POSITIVELY TILTED TROUGH SWWD ACROSS NEB. AT SFC...LOW NOW EVIDENT OVER SWRN KS IS EXPECTED TO MOVE NEWD ALONG BAROCLINIC ZONE TO VICINITY STJ BY START OF PERIOD...THEN DEEPEN SLIGHTLY AND BECOME MORE CLOSELY COLLOCATED WITH LEADING MID-UPPER PERTURBATION INVOF SRN LM. TRAILING COLD FRONT WILL MOVE EWD ACROSS LOWER-MID MS VALLEY...AND SEWD FROM TX/LA ACROSS NWRN GULF. MEANWHILE...OLDER FRONTAL ZONE ACROSS CENTRAL/SRN FL PENINSULA IS EXPECTED TO DECELERATE...BECOMING MORE DIFFUSE WITH TIME THROUGHOUT PERIOD. ...S TX... ISOLATED TO WIDELY SCATTERED TSTMS ARE POSSIBLE...BEGINNING AT START OF PERIOD AS CARRY-OVER FROM POTENTIAL DISCUSSED IN DAY-1 OUTLOOK. REGIME SHOULD BE CHARACTERIZED BY STG LOW LEVEL WAA AND MOISTURE TRANSPORT...WHICH WILL COMBINE WITH POCKETS OF ENHANCED SFC HEATING TO DESTABILIZE PREFRONTAL BOUNDARY LAYER THROUGH MUCH OF AFTERNOON. AS PREFRONTAL SFC DEW POINTS UPPER 60S F BECOME MORE COMMON...MLCAPE MAY RISE INTO 2000-2500 J/KG RANGE IN AREAS OF RELATIVELY SUSTAINED CLOUD BREAKS. FRONTAL LIFT IMPINGING ON THIS ALREADY WEAKLY CAPPED AIR MASS SHOULD BOOST CONVECTIVE COVERAGE INTO SCATTERED-NUMEROUS RANGES AS FRONT MOVES SWD/SEWD OVER THIS REGION. MAJOR LIMITING FACTOR FOR ANY ORGANIZED SVR POTENTIAL WILL BE LACK OF SHEAR...WITH WEAK LOW-MID LEVEL WINDS LIMITING BOTH HODOGRAPH SIZE AND BULK WIND DIFFERENCE THROUGH DEEP-LAYER SAMPLES. ...NRN MO TO WI/IL BORDER REGION... WIDELY SCATTERED AND SHALLOW TSTMS ARE POSSIBLE IN ZONE OF STRONG DEEP-LAYER ASCENT...STEEPENING LOW-MID LEVEL LAPSE RATES SUFFICIENTLY TO SUPPORT RELATIVELY UNCAPPED AND MRGL BUOYANCY. MODIFIED FCST SOUNDINGS SUGGEST LOW LEVEL FRONTOGENETIC/CYCLOGENETIC FORCING AND WEAK CINH WILL SUPPORT MLCAPE UP TO ABOUT 250 J/KG AND MUCAPE APCHG 500 J/KG FOR REASONABLY PROGGED SFC TEMPS 50S F AND DEW POINTS UPPER 40S. LACK OF MORE ROBUST SHEAR...LOW LEVEL THETAE AND CAPE PRECLUDE SVR THREAT. ...CENTRAL/SRN FL... ISOLATED TO WIDELY SCATTERED TSTMS WILL BE POSSIBLE WITHIN LOW-LEVEL BAROCLINIC ZONE ACROSS THIS REGION...SUPPORTED BY WEAK FRONTAL ASCENT...DIURNAL HEATING...AND SFC DEW POINTS UPPER 60S/LOW 70S F. 50-80 KT UPPER-LEVEL WINDS BENEATH SRN FRINGE OF SUBTROPICAL JET BRANCH MAY AID IN STORM ORGANIZATION...ESPECIALLY INVOF E COAST WHERE SLY AND ELY FLOW COMPONENTS MAY AID IN SHEAR THROUGH CLOUD-BEARING LAYER. HOWEVER...SVR POTENTIAL APPEARS TOO MRGL/CONDITIONAL FOR AOA 5-PERCENT PROBABILITIES ATTM. ..EDWARDS.. 11/23/2009
