DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1130 AM CDT THU MAY 24 2012 VALID 241630Z - 251200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER NERN IA...EXTREME SERN MN...AND MUCH OF WI... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE LOWER MO VALLEY INTO THE CENTRAL PLAINS... ...NERN IA/EXTREME SERN MN/MUCH OF WI... WATER VAPOR IMAGERY INDICATES A STRONG UPPER SHORT WAVE TROUGH MOVING NEWD OVER ERN NEB. THIS SYSTEM IS EXPECTED TO PROGRESS INTO THE UPPER MS VALLEY BY THIS EVENING AND CONTINUE ACROSS THE UPPER GREAT LAKES TONIGHT AS AN UPSTREAM LOW DEVELOPS SWD ALONG THE NRN PACIFIC COASTAL REGION. THIS TROUGH WILL BECOME MORE NEGATIVELY TILTED WITH TIME AS IT LIFTS NEWD...PROVIDING INCREASING DIVERGENCE ALOFT. THIS WILL RESULT IN THE SURFACE LOW CURRENTLY NEAR OMA TO DEEPEN AS IT MOVES NNEWD...REACHING WRN LAKE SUPERIOR THIS EVENING AND CONTINUING INTO ONTARIO TONIGHT. A SURFACE COLD FRONT EXTENDING SWD FROM THE LOW WILL ACCELERATE INTO THE UPPER MS VALLEY THIS AFTERNOON BEFORE REACHING LOWER MI LATE TONIGHT. VERY STRONG WINDS ALOFT ARE ASSOCIATED WITH THE MIDWEST TROUGH...WITH A 50 KT LOW LEVEL JET OVER THE LOWER MO VALLEY FORECAST TO STRENGTHEN AS IT MOVES NWD INTO WI THIS AFTERNOON...WHILE AN 80-90 KT MID LEVEL JET STREAK CURRENTLY OVER THE CENTRAL ROCKIES/HIGH PLAINS LIFTS NEWD TOWARD THE UPPER MS VALLEY. THIS WILL CREATE VERY STRONG LOW/MID LEVEL SHEAR OVER THE WARM SECTOR AHEAD OF THE COLD FRONT SUPPORTIVE OF SEVERE STORMS. THE PRIMARY LIMITING FACTOR REMAINS LOW LEVEL MOISTURE WITH SURFACE DEW POINTS LIKELY REACHING THE 55-60F RANGE PRIOR TO FRONTAL PASSAGE. A PLUME OF MODERATELY STEEP MID LEVEL LAPSE RATES ALSO EXTENDS OVER THE WARM SECTOR AND IS CONTRIBUTING TO GREATER INSTABILITY GIVEN THE SOMEWHAT LIMITED LOW LEVEL MOISTURE. ENHANCED DIABATIC HEATING AHEAD OF THE CLOUD SHIELD OVER THE UPPER MS VALLEY WILL AID IN FURTHER DESTABILIZATION WITH MLCAPE REACHING 1000-1500 J/KG THIS AFTERNOON. CURRENT ELEVATED STORMS OVER NWRN WI ARE EXPECTED TO MOVE RAPIDLY NEWD AND POSE A RISK OF HAIL INTO EARLY AFTERNOON. THESE STORMS WILL ALSO BE MONITORED FOR THE POTENTIAL TO BECOME SURFACE BASED THIS AFTERNOON...WHICH WOULD INCREASE THE LIKELIHOOD OF STRONG WIND GUSTS. ADDITIONAL STORMS ARE EXPECTED TO DEVELOP NEAR THE COLD FRONT FROM NERN IA INTO WRN WI BY MID AFTERNOON. THE FAVORABLE WIND SHEAR WILL PROMOTE DEVELOPMENT OF FAST MOVING SUPERCELLS AND BOW ECHO STRUCTURES CAPABLE OF PRODUCING DAMAGING WIND GUSTS...LARGE HAIL...AND TORNADOES. THE STORMS ARE LIKELY TO DEVELOP INTO ONE OR MORE BOWING LINE SEGMENTS BY LATER AFTERNOON OR EVENING...WITH THE SEVERE THREAT TRANSITIONING INTO PRIMARILY A WIND DAMAGE SCENARIO AS BOWING SEGMENTS MOVE RAPIDLY NEWD THROUGH THE EVENING HOURS. THE ACTIVITY IS EXPECTED TO SLOWLY DIMINISH IN INTENSITY AFTER 03-6Z. ...CENTRAL PLAINS LATE TONIGHT... SSWLY LLJ WILL STRENGTHEN OVER MUCH OF KS AND WRN MO LATE TNGT IN RESPONSE TO DIURNAL INFLUENCES AND TO THE CONTINUED ESE ADVANCE OF UPR LOW INTO NRN CA AND THE NRN GREAT BASIN. THIS STRENGTHENING WILL OCCUR ATOP TRAILING...SW END OF SAME FRONTAL ZONE THAT WILL CROSS THE UPR MS VLY LATER TODAY. COUPLED WITH THE ARRIVAL OF FAIRLY SUBSTANTIAL MOISTURE RETURN /P.W. AOA 1.25 INCHES/ AND WITH THE CONTINUED PRESENCE OF 40-50 KT WSWLY SHEAR ABOVE THE FRONTAL SFC...SETUP MAY SUPPORT ELEVATED TSTMS AFTER 06-09Z WITH HAIL AND PERHAPS LOCALLY STRONG WIND GUSTS. ...CNTRL/S FL... SCTD TSTMS EXPECTED THIS AFTN IN ZONE OF STRONG HEATING...HIGH PW...AND UPR DIVERGENCE BENEATH SWLY HIGH LVL JET STREAK. THESE MAY YIELD A FEW INSTANCES OF SVR WIND/HAIL...MAINLY ALONG SEA BREEZE BOUNDARY INTERSECTIONS. ...MID ATLANTIC INTO PARTS OF CAROLINAS... TROPICAL MOISTURE SPREADING NWD/CONVERGING BENEATH RESIDUAL AXIS OF RELATIVELY COOL MID LVL TEMPS MAY SUPPORT A FEW DIURNAL STORMS/STORM CLUSTERS WITH LOCALLY SVR WIND/MARGINALLY SVR HAIL. CONVECTION WILL BE ENHANCED BY WEAK UPPER VORTICITY MAX MOVING NNEWD OVER THE WRN CAROLINAS. ..WEISS/GARNER.. 05/24/2012
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1630.html
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