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May 11, 2014 0600 UTC Day 1 Convective Outlook

May 11, 2014

May 11, 2014 0600 UTC Day 1 Convective Outlook

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DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT SUN MAY 11 2014

VALID 111200Z – 121200Z

…THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE CENTRAL PLAINS AND MID-MS VALLEY…

…THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM THE SRN HIGH PLAINS TO THE OH VALLEY…

…SUMMARY…
SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS PORTIONS OF THE CENTRAL PLAINS TO THE OHIO VALLEY. GREATEST CONCENTRATION OF SEVERE SHOULD EXTEND FROM NORTHERN KANSAS INTO SOUTHEASTERN NEBRASKA AND MUCH OF IOWA. VERY LARGE HAIL AND TORNADOES ARE POSSIBLE.

…CENTRAL PLAINS/MID-MS VALLEY…

WEAK HEIGHT RISES ARE EXPECTED TO DOMINATE MUCH OF THE MID-WEST AND OH VALLEY DURING THE DAY1 PERIOD AS PRIMARY TROUGH DIGS INTO THE 4-CORNERS REGION. AS A RESULT…LOW LEVEL WARM ADVECTION WILL LIKELY PROVE INSTRUMENTAL IN EARLY-DAY CONVECTION ACROSS THE CNTRL PLAINS/MID-MS VALLEY. LATEST THINKING IS ELEVATED CONVECTION SHOULD BE ONGOING AT SUNRISE ACROSS ERN NEBRASKA ALONG NOSE OF LLJ. THIS ACTIVITY SHOULD PROPAGATE ALONG WARM FRONT ACROSS IA DURING THE DAY INTO NRN IL BY AFTERNOON WHEN BOUNDARY LAYER HEATING SHOULD CONTRIBUTE TO PRE-STORM BUOYANCY. IT/S NOT ENTIRELY CLEAR HOW EARLY-DAY CONVECTION WILL UNFOLD AS VERTICAL SHEAR PROFILES STRONGLY FAVOR SUPERCELL STRUCTURES. IF AN MCS EVOLVES FROM SUNRISE CONVECTION THEN STORM MODE WILL FAVOR MORE WIND/HAIL ACROSS IA DURING THE DAY. HOWEVER…IF DISCRETE SUPERCELLS EVOLVE THEN TORNADO THREAT WILL BE ENHANCED ALONG THE WARM FRONT AS FORECAST SOUNDINGS STRONGLY SUPPORT ORGANIZED DEEP ROTATING UPDRAFTS AND SUPERCELLS. GIVEN THE PROXIMITY OF HIGHER BOUNDARY LAYER MOISTURE…JUST SOUTH OF I-70 ACROSS MO ATTM…IT APPEARS LEGITIMATE MID 60S SFC DEW POINTS WILL ADVANCE INTO IA AHEAD OF CONVECTION LATER TODAY.

IN THE WAKE OF THIS EARLY TSTM ACTIVITY…MUCH OF THE PLAINS WILL REMAIN CONVECTIVE-FREE THROUGH MID AFTERNOON. STRONG CAPPING ACROSS KS/OK/TX SHOULD PREVENT THUNDERSTORM DEVELOPMENT PRIOR TO 21Z. HOWEVER…FRONTAL CONVERGENCE SHOULD AID CONVECTIVE DEVELOPMENT ACROSS NEBRASKA/KS BY 21Z. WITH SFC TEMPERATURES WARMING TO NEAR 90 ACROSS KS THIS ACTIVITY WILL INITIALLY BE HIGH BASED. HOWEVER…WARM SECTOR ACROSS NEBRASKA SHOULD HAVE TEMPERATURES RISE ONLY INTO THE 80S AND CLOUD BASES SHOULD REFLECT A MORE MOIST ENVIRONMENT. FOR THIS REASON IT APPEARS THE GREATEST RISK FOR TORNADOES IS ACROSS NEBRASKA/IA…ESPECIALLY IF DISCRETE SUPERCELLS CAN EMERGE WITHIN AN AIRMASS THAT SHOULD BE CHARACTERIZED BY SBCAPE IN EXCESS OF 3000 J/KG. MID-LEVEL FLOW IN EXCESS OF 50KT SHOULD EASILY VENT/SHEAR DEVELOPING UPDRAFTS POTENTIALLY SUPPORTING LONG-LIVED SUPERCELLS. IN ADDITION TO VERY LARGE HAIL A FEW STRONG TORNADOES COULD FORM IF SUPERCELLS CAN ADVANCE INTO MOIST WARM SECTOR AHEAD OF COLD FRONT.

STORM MERGERS/FRONTAL ASCENT SHOULD ENCOURAGE AN EXPANDING CORRIDOR OF STRONG/SEVERE THUNDERSTORMS TO ADVANCE TOWARD IA/NWRN MO BY DAYBREAK MONDAY MORNING.

…SOUTHERN PLAINS…

STRONG HEATING IS EXPECTED ACROSS THE HIGH PLAINS OF OK/TX SUNDAY. TEMPERATURES SHOULD WARM INTO THE LOWER 90S ALONG THE DRYLINE…SUFFICIENT FOR PARCELS TO REACH THEIR CONVECTIVE TEMPERATURE BY 22-23Z. WHILE LATEST NAM GUIDANCE…AND A FEW OTHER HIGH-RES MODELS…DO NOT DEVELOP MUCH CONVECTION ALONG THE DRYLINE IT WOULD APPEAR AT LEAST ISOLATED SUPERCELLS SHOULD FORM. VERY LARGE HAIL AND GUSTY WINDS ARE THE GREATEST THREATS WITH THIS RELATIVELY HIGH-BASED ACTIVITY.

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