Significant Severe Outbreak Today Upper MS Valley
Posted by JAC on 4/10/2011, 6:34 am
 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0104 AM CDT SUN APR 10 2011 VALID 101200Z - 111200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS SOUTHEAST MN/EASTERN IA TO MUCH OF WI/WESTERN U.P. OF MI AND NORTHERN IL... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE UPPER MIDWEST/GREAT LAKES REGION TO ARKLATEX... ...UPPER MS VALLEY/UPPER GREAT LAKES/MIDWEST TO ARKLATEX... A POTENTIALLY SIGNIFICANT SEVERE EPISODE...INCLUDING FAST MOVING SUPERCELLS AND THE POSSIBILITY OF STRONG TORNADOES...WILL EXIST FROM MID AFTERNOON THROUGH EVENING ACROSS THE UPPER MS VALLEY...ESPECIALLY INCLUDING PORTIONS OF EASTERN MN INTO WI. UPPER TROUGH OVER THE ROCKIES EARLY THIS MORNING WILL SHIFT GENERALLY EASTWARD TOWARD THE PLAINS TODAY...WITH A LEAD/NORTHERN PIECE OF THIS TROUGH SHIFTING EASTWARD OVER THE UPPER MIDWEST THIS AFTERNOON/TONIGHT. AIDED BY THE LEFT EXIT REGION OF 100+ KT UPPER JET STREAK...THE PRIMARY SURFACE LOW IS EXPECTED TO GRADUALLY DEEPEN/ADVANCE NORTHEASTWARD ACROSS SOUTHERN MN INTO NORTHWEST WI/U.P. OF MI AND LAKE SUPERIOR TONIGHT...ALL WHILE A WARM FRONT RETREATS NORTHWARD ACROSS SOUTHERN/EASTERN MN AND WI AS WELL AS LOWER MI. SOUTH OF THE SURFACE LOW...ASSOCIATED COLD FRONT WILL SPREAD EAST-SOUTHEASTWARD FROM THE CENTRAL/SOUTHERN PLAINS AND MIDWEST TOWARD THE MS VALLEY VICINITY. INITIALLY...ON THE NOSE OF A STRONG/VEERING LOW LEVEL JET...EARLY DAY ELEVATED TSTMS MAY POSE A SEVERE HAIL THREAT FROM PORTIONS OF MN INTO WI/NORTHERN MI. SUCH A SEVERE THREAT COULD CONTINUE WELL THROUGH THE MORNING. OTHERWISE...TIED TO THE NORTHWARD ADVANCING WARM FRONT /PERHAPS AUGMENTED TO A DEGREE BY EARLY DAY ONGOING CONVECTION/...SEASONALLY HIGH MOISTURE CONTENT WILL QUICKLY DEVELOP NORTHEASTWARD DURING THE DAY WITHIN THE WARM SECTOR...WITH LOWER 60S F SURFACE DEWPOINTS BECOMING ESTABLISHED ACROSS THE MAJORITY OF THE UPPER MS VALLEY WARM SECTOR. BENEATH A SOUTHERN ROCKIES/PLAINS EMANATING ELEVATED MIXED LAYER...MLCAPE FROM 1500 J/KG TO UPWARDS OF 2000-2500 J/KG WILL LIKELY BE IN PLACE BY AFTERNOON ESPECIALLY ACROSS THE UPPER MS VALLEY. IT IS PROBABLE THAT THE EML/CAP SHOULD LIMIT SURFACE BASED TSTM DEVELOPMENT THROUGH EARLY/PERHAPS MID AFTERNOON...WHILE OTHERWISE CREATING UNCERTAINTY IN THE COVERAGE/EXTENT OF DEEP CONVECTIVE DEVELOPMENT DIURNALLY /SOUTH OF THE UPPER JET AXIS/ ACROSS AREAS SUCH AS EASTERN IA/NORTHERN IL AND ADJACENT PORTIONS OF THE MIDDLE MS VALLEY. THAT SAID...THE MOST LIKELY/HIGHEST CONFIDENCE SCENARIO WOULD BE FOR VIGOROUS DEEP CONVECTIVE DEVELOPMENT AHEAD OF THE ADVANCING SURFACE LOW AND NEAR THE WARM FRONT/ADJACENT WARM SECTOR. ACCORDINGLY...CURRENT EXPECTATIONS ARE FOR SEVERE TSTMS TO ERUPT BY MID/LATE AFTERNOON...INITIALLY ACROSS PORTIONS OF SOUTHEAST MN/FAR WESTERN WI/NORTHEAST IA. THIS SCENARIO IS WELL SUPPORTED BY MOST 00Z DETERMINISTIC NUMERICAL GUIDANCE...AS WELL AS THE 00Z RUNS OF THE WRF-NMM/WRF-NSSL. AMID A ROBUST LOW/MID TROPOSPHERIC WIND FIELD /HIGHLIGHTED BY 90-100 KT SOUTHWESTERLY FLOW IN MID LEVELS/...SUPERCELLS...SOME SPLITTING...WILL DEVELOP/LIKELY RACE NORTHEASTWARD AT UPWARDS OF 45-50 KT. EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WILL BE HIGHLY FAVORABLE WELL-ORGANIZED/SUSTAINED STORMS INCLUDING SUPERCELLS...AND PERHAPS EVENTUAL BOWS ECHOS BY MID/LATE EVENING. THE GREATEST RISK FOR TORNADOES...INCLUDING THE POTENTIAL FOR STRONG/LONG TRACK TORNADOES...WILL EXIST ACROSS FAR SOUTHEAST MN/FAR NORTHEAST IA INTO WI...WITH LARGE HAIL A LIKELIHOOD AS WELL. FARTHER SOUTH/SOUTHWEST...OTHER STRONG/SEVERE TSTM DEVELOPMENT IS PROBABLE TOWARD/AFTER DARK ALONG THE DRYLINE/OVERTAKING COLD FRONT FROM THE MIDDLE MS VALLEY/OZARKS TO THE ARKLATEX. SEVERE HAIL/DAMAGING WINDS AND A TORNADO OR TWO WILL BE POSSIBLE AS STORMS INCREASE/ADVANCE EAST-SOUTHEASTWARD THROUGH THE NIGHT. ...LOWER GREAT LAKES REGION... SURFACE WARM FRONT IS EXPECTED TO RETREAT NORTHEASTWARD TOWARD THE REGION THROUGH THE DAY...WITH MODEST BOUNDARY LAYER MOISTENING/INCREASING PW ATTENDANT TO THE WARM FRONT. AMID MARKEDLY STRENGTHENING NORTHWESTERLY FLOW ALOFT...CONVECTION COULD CREST THE UPPER RIDGE AND CROSS SOUTHERN ONTARIO/LAKE ERIE VICINITY INTO NY AND PERHAPS ADJACENT PORTIONS OF PA/WESTERN NEW ENGLAND DURING THE AFTERNOON...OR MORE LIKELY THIS EVENING/TONIGHT. THIS COULD RESULT IN A MARGINAL WIND/HAIL THREAT. ..GUYER/HURLBUT.. 04/10/2011 |
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In this thread:
- Watch coming up - JAC, 4/10/2011, 2:57 pm
- Chicago STP but NWS says capped. Severe event may be more WI and MN. - JAC, 4/10/2011, 6:43 am
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