11:28am update from the SPC outlook. Another one will come out at 3:00 and I will post that also. As of now the SPC has the entire area under a Slight Risk for Severe Weather with the biggest threat damaging winds with some areas under a 30% threat. An Isolated Tornado or two cant be ruled out along with some Hail. Still expecting a possible squall line in the late afternoon/evening. DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1128 AM CDT WED SEP 10 2014 VALID 101630Z - 111200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM LWR MI AND THE LWR OH VLY SWWD INTO THE OZARKS... ...SUMMARY... THUNDERSTORMS...SOME SEVERE...ARE EXPECTED TO DEVELOP NEAR A COLD FRONT FROM THE SOUTHERN GREAT LAKES SOUTHWESTWARD THROUGH THE LOWER OHIO AND MID-MISSISSIPPI VALLEYS INTO THE OZARKS. DAMAGING WINDS WILL BE THE PRIMARY THREAT THIS AFTERNOON THROUGH EARLY TONIGHT. ...SYNOPTIC SETUP... SEASONABLY STRONG WSW FLOW WILL PREVAIL FROM THE SRN PLNS TO THE LWR GRT LKS THROUGH THU...DOWNSTREAM FROM POTENT SHORTWAVE TROUGH AMPLIFYING SE FROM BC/AB INTO THE NRN RCKYS. WITHIN THE WSW FLOW...SHORTWAVE IMPULSE NOW OVER THE MID MS VLY SHOULD SHEAR NE ACROSS MI LATER TODAY...AND INTO WRN QUE EARLY THU...WHILE TRAILING DISTURBANCE NOW OVER ERN CO REACHES IA THIS EVE AND SRN MI/NW OH EARLY THU. AT THE SFC...LOW NOW OVER CNTRL WI SHOULD FURTHER DEEPEN AS IT CONTINUES ENE TO NRN LWR MI THIS EVE AND INTO SW QUE BY 12Z THU. COLD FRONT TRAILING SW FROM THE LOW WILL ACCELERATE S/SE ACROSS THE SRN PLNS/OZARKS/MID-MS VLY/LWR OH VLYS...EVENTUALLY OVERTAKING OUTFLOW FROM PRE-FRONTAL CONVECTION/SQLN. ...SRN GRT LKS SW INTO OZARKS/SRN PLNS... LEAD UPR MS VLY UPR IMPULSE WILL ENHANCE ASCENT OVER COLD FRONTAL ZONE CROSSING ERN IL/IND/LWR MI/WRN-NRN OH THROUGH EARLY-MID AFTN. MID-LVL LAPSE RATES ACROSS REGION WILL REMAIN WEAK PER MORNING 500 MB ANALYSIS. BUT GIVEN EXPECTED GRADUAL WARMING OF INCREASINGLY MOIST BOUNDARY LAYER /REF MCD 1707/...SETUP COULD PROMOTE SOME INTENSIFICATION OF SCTD STRONGER UPDRAFTS WITHIN EXISTING BROKEN...PRE-FRONTAL CONVECTIVE BANDS. 700-500 MB WSW FLOW WILL REMAIN AROUND 50 KTS...WITH LOW-LVL HODOGRAPHS ENLARGED BY BELT OF ENHANCED 925-850 MB FLOW ASSOCIATED WITH DEEPENING SFC LOW. THUS...SOME RISK WILL EXIST FOR ISOLD TORNADOES IN ADDITION TO LOCALLY DMGG WIND THROUGH LATE AFTN FROM ERN IL ENE INTO PARTS OF OH/LWR MI. LATER TODAY...ADDITIONAL STORM DEVELOPMENT APPEARS POSSIBLE FROM CNTRL/SRN IL SWWD THROUGH ERN/SRN MO INTO NRN AR AS SFC HEATING DESTABILIZES LWR LVLS ALONG IMMEDIATE COLD FRONT. PRE-FRONTAL CONVECTION IS INCREASINGLY LIMITED WITH SW EXTENT ALONG THIS CORRIDOR...ALLOWING FOR MORE SUBSTANTIAL LOW-LVL WARMING IN WAKE OF MORNING STORMS RELATIVE TO POINTS FARTHER NE. ALTHOUGH MID-LVL LAPSE RATES WILL REMAIN WEAK...SOME INCREASE IN FORCING FOR ASCENT LIKELY WILL OCCUR AS CO UPR IMPULSE CROSSES THE CNTRL PLNS. HIGH PW /AOA 2 INCHES/ COUPLED WITH 30-40 UNIDIRECTIONAL WSWLY 700-500 MB FLOW COULD YIELD SHORT LINES/SMALL CLUSTERS OF STORMS WITH A RISK FOR LOCALLY DMGG WIND AND PERHAPS A SPOT OR TWO OF HAIL. A TORNADO CANNOT BE RULED OUT IN IL/ERN MO GIVEN GREATER PROXIMITY TO FASTER FLOW ALOFT AND STRONGER FORCING FOR ASCENT. ...SRN PLNS LATE THIS AFTN/EVE... CAPPING ASSOCIATED WITH RESIDUAL EML SHOULD DELAY DIURNAL CONVECTIVE DEVELOPMENT...DESPITE STRONG SFC HEATING...ALONG COLD FRONT AND EWD-DISPLACED LEE TROUGH OVER SRN/ERN OK AND N TX LATER TODAY. COMBINATION OF WEAK CONVERGENCE ALONG THE FRONT/TROUGH AND DEEPLY-MIXED ENVIRONMENT MAY YIELD SCTD LATE AFTN/EVE STORMS WITH LOCALLY DMGG GUSTS.
Posted on: Wed, 10 Sep 2014 19:30:43 +0000
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