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May 12, 2014 1630 UTC Day 1 Convective Outlook

May 12, 2014

May 12, 2014 1630 UTC Day 1 Convective Outlook

day1otlk

day1probotlk_wind

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1111 AM CDT MON MAY 12 2014

VALID 121630Z – 131200Z

…THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER GREAT LAKES TO TX…

…SUMMARY…
CLUSTERS OF STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE TODAY FROM WISCONSIN AND LOWER MICHIGAN SOUTHWARD ACROSS PARTS OF THE MID-MISSISSIPPI VALLEY INTO THE SOUTHERN PLAINS.

…SYNOPSIS…

A HIGH-AMPLITUDE AND ONLY SLIGHTLY PROGRESSIVE PATTERN WILL PERSIST OVER NORTH AMERICA THROUGH THE DAY ONE PERIOD WITH THE PRIMARY FEATURE OF INTEREST BEING A FULL-LATITUDE TROUGH WHICH WILL EDGE EWD FROM THE ROCKIES INTO GREAT PLAINS. WITHIN THIS LARGE-SCALE PATTERN…A 70-80 KT MIDLEVEL JET STREAK OBSERVED OVER THE CNTRL/SRN PLAINS THIS MORNING WILL PROGRESS NEWD INTO THE UPPER MS VALLEY BY TONIGHT.

AT THE SURFACE…LOW PRESSURE OVER CNTRL IA WILL DEEPEN SLIGHTLY PRIOR TO UNDERGOING OCCLUSION AS IT DEVELOPS NNEWD INTO WRN ONTARIO. AN ASSOCIATED COLD FRONT WILL ADVANCE EWD INTO THE UPPER GREAT LAKES AND MID MS VALLEY WITH THE SRN EXTENSION OF THIS BOUNDARY MOVING SEWD THROUGH THE OZARK PLATEAU AND MUCH OF THE SRN PLAINS. THIS COLD FRONT WILL SERVE AS THE PRIMARY FOCUS FOR STRONG TO SEVERE TSTM
DEVELOPMENT THIS AFTERNOON INTO TONIGHT.

…UPPER GREAT LAKES INTO MIDWEST/OH VALLEY THIS AFTERNOON/EVENING…

MULTIPLE CLUSTERS OF TSTMS ARE ONGOING AS OF MID MORNING FROM ERN IA INTO WI/LOWER MI/OH…AIDED BY CONVECTIVELY GENERATED VORTICITY MAXIMA AND A BROAD ZONE OF WAA WITHIN THE EXIT REGION OF A NOCTURNAL LLJ. A SUBSET OF THESE EARLY-DAY STORMS WILL LIKELY CONTINUE INTO AFTERNOON WITH ADDITIONAL STORMS FORMING ALONG THE SYNOPTIC COLD FRONT AND RESIDUAL OUTFLOW BOUNDARIES. 12Z OBSERVED SOUNDINGS INDICATE THAT THE WARM SECTOR AIR MASS HAS BECOME QUITE MOIST WITH LOWEST 100-MB MEAN-MIXING RATIOS AS HIGH AS 13-14 G/KG. THIS MOISTURE WILL COMBINE WITH DAYTIME HEATING AND STEEPENING MIDLEVEL LAPSE RATES TO YIELD AFTERNOON MLCAPE VALUES APPROACHING 1500-2500 J/KG.

THE STRONGEST VERTICAL SHEAR WILL RESIDE ACROSS MN/IA INTO WI/NRN IL WHERE A NWD-MIGRATING 30-40 KT SLY LLJ WILL ALIGN WITH THE MIDLEVEL JET STREAK PROGRESSING NEWD FROM THE CNTRL PLAINS. WHERE STRONGER HEATING/DESTABILIZATION CAN OCCUR…THE ENVIRONMENT WILL SUPPORT BOWING AND SUPERCELL STRUCTURES WITH A RISK FOR DAMAGING WINDS…LARGE HAIL AND PERHAPS A COUPLE OF TORNADOES.

FARTHER TO THE E INTO LOWER MI AND THE OH VALLEY…VERTICAL SHEAR WILL DECREASE OWING TO THE PROXIMITY OF THE MIDLEVEL RIDGE AXIS. HOWEVER…GIVEN AT LEAST MODESTLY STRONG DEEP SWLY FLOW AND THE POTENTIAL FOR MODERATE AFTERNOON INSTABILITY…SOME ORGANIZED LINE SEGMENTS AND/OR MULTICELL CLUSTERS APPEARS POSSIBLE WITH DAMAGING WINDS AND LARGE HAIL BEING THE PRIMARY HAZARDS.

…OZARK PLATEAU TO TX THIS AFTERNOON/EVENING…

WHILE LARGE-SCALE FORCING FOR ASCENT WILL REMAIN MINIMAL ACROSS THE REGION…LOW-LEVEL UPLIFT ALONG THE SYNOPTIC COLD FRONT AND A PROMINENT GRAVITY WAVE PROPAGATING THROUGH AR AND CNTRL/ERN TX WILL FOSTER SCATTERED TSTM DEVELOPMENT. THE AREA WILL REMAIN ON THE SERN/ERN PERIPHERY OF STRONGER MID AND HIGH-LEVEL FLOW ATTENDANT TO THE CNTRL U.S. TROUGH…EFFECTIVELY LIMITING THE POTENTIAL FOR HIGHER-ORDER STORM MODES. NONETHELESS…THE CO-LOCATION OF ABUNDANT BOUNDARY-LAYER MOISTURE AND STEEP MIDLEVEL LAPSE RATES /AND RESULTING IN MLCAPE OF 1500-3000+ J PER KG/ WILL PROMOTE STRONG-SEVERE STORMS WITH THE POTENTIAL FOR UPSCALE GROWTH INTO A BROKEN BAND WITH AN ATTENDANT RISK FOR DAMAGING WIND GUSTS AND HAIL.

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