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Apr 3, 2014 1300 UTC Day 1 Convective Outlook

April 3, 2014

Apr 3, 2014 1300 UTC Day 1 Convective Outlook

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DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT THU APR 03 2014

VALID 031300Z – 041200Z

…THERE IS A MDT RISK OF SVR TSTMS PORTIONS AR…NRN LA…NWRN MS…SRN/ERN MO…WRN TN…SRN IL…WRN KY…EXTREME SWRN INDIANA…

…THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM LOWER MO/OH VALLEY REGIONS TO E TX…TN VALLEY AND PARTS OF MS DELTA REGION…

MULTIPLE ROUNDS OF SEVERE TSTMS WITH LARGE HAIL…DAMAGING GUSTS AND A FEW STG TORNADOES ARE POSSIBLE IN AND NEAR MDT-RISK AREA TODAY AND TONIGHT.

…SYNOPSIS…
MAIN UPPER-AIR FEATURE INFLUENCING THIS OUTLOOK IS HIGH-AMPLITUDE…POSITIVELY TILTED SHORTWAVE TROUGH NOW LOCATED OVER CENTRAL/SRN ROCKIES. NRN AND MIDDLE SEGMENTS OF THIS TROUGH WILL ASSUME MORE NEGATIVE TILT WITH TIME…AS TROUGH EJECTS NEWD. EMBEDDED 500-MB LOW SHOULD FORM OVER SERN NEB OR OMA AREA BETWEEN 00-06Z. BY 00Z…TROUGH SHOULD ARC FROM SRN NEB OVER CENTRAL KS…TX PANHANDLE AND ERN NM. BY 12Z…EXPECT COMPACT 500-MB CYCLONE CENTERED OVER NERN IA…WITH MAIN VORTICITY LOBE SEWD OVER WRN IL THEN SWWD ACROSS SRN MO. SUBTLE VORTICITY LOBE IS EVIDENT IN MOISTURE-CHANNEL IMAGERY MOVING NEWD ACROSS PORTIONS NW TX INTO SRN OK.

ASSOCIATED SFC LOW — ANALYZED AT 11Z OVER SERN KS — IS FCST TO DEEPEN AND MOVE TO N-CENTRAL/NERN MO BY 00Z…WITH COLD FRONT SWWD ACROSS SWRN MO….NERN/CENTRAL OK…AND SRN TX PANHANDLE. BY THEN…CONVECTIVELY REINFORCED WARM FRONT SHOULD EXTEND EWD OR ESEWD FROM LOW ACROSS S-CENTRAL IL. BY 12Z…SFC LOW SHOULD BECOME OCCLUDED OVER SRN WI…WHILE COLD FRONT CROSSES PORTIONS INDIANA…WRN TN…NWRN MS…AND UPPER TX COAST. DRYLINE WAS DRAWN AT 11Z OVER EXTREME SWRN OK AND W-CENTRAL TX…AND SHOULD MIX/ADVECT EWD TO ERN OK AND N-CENTRAL/CENTRAL TX BY 00Z.

…NEAR-TERM CONCERNS…
INITIAL MCS OVER SRN IL AND ERN MO MAY POSE SHORT-TERM RISK OF DAMAGING GUSTS…AND ANOTHER BRIEF/SMALL QLCS-TYPE TORNADO CANNOT BE RULED OUT AS LEADING EDGE ROLLS DOWN VORTICITY-ENHANCED WARM FRONT. REF SPC MESOSCALE DISCUSSION 255 FOR DETAILS. COLD POOL MAY SUPPORT ADDITIONAL CONVECTIVE DEVELOPMENT FARTHER E ALONG WARM FRONT THIS MORNING OVER PORTIONS LOWER OH VALLEY REGION…WITH AT LEAST MRGL WIND-DAMAGE RISK.

ADDITIONAL CONVECTION HAS DEVELOPED FARTHER SW…OVER PORTIONS N-CENTRAL TX. ACTIVITY INITIALLY APPEARED ROOTED IN LAYER OF ELEVATED INFLOW BELOW VERY STEEP EML-SUPPLIED/DCVA-ENHANCED LAPSE RATES AHEAD OF AFOREMENTIONED SRN-STREAM PERTURBATION. THIS ACTIVITY WILL OFFER RISK OF LARGE HAIL AND MAY INCREASE IN COVERAGE THROUGH MID-LATE MORNING. REF SPC MESOSCALE DISCUSSION 256 FOR MORE DETAILS. AS THIS ACTIVITY MOVES INTO WEAKER-CINH REGIME DESCRIBED BELOW…IT MAY ERODE CAPPING FROM ABOVE WHILE FOREGOING/INCREASINGLY MOIST AIR MASS HEATS DIABATICALLY.

…MIDWEST TO NRN/ERN TX AND MS DELTA REGIONS…AFTN ONWARD…
MAIN EVENT SHOULD OCCUR IN TWO PHASES THAT MAY OVERLAP SPATIALLY–
1. THIS AFTN INTO TONIGHT INVOF COLD FRONT/DRYLINE COMBO…OVER WRN/NRN PORTIONS OF OUTLOOK AREA…PERHAPS BACKBUILDING SWD THROUGH MID-SOUTH REGION AND AR…
2. SEPARATE BAND OF TSTMS FIRING ON CONFLUENCE AXIS E OF EML-CINH REGIME…OVERNIGHT FROM PARTS OF MID-SOUTH AREA SWWD TOWARD WRN GULF COAST…SHIFTING EWD OVER DELTA REGION INTO MS.

OUTFLOW/COLD-POOL BOUNDARY FROM MO/IL MCS WILL REINFORCE EFFECTIVE WARM FRONT ACROSS MO…WHICH MAY LIFT SLIGHTLY NWD OVER LOWER MO RIVER VALLEY PRIOR TO PASSAGE OF SFC CYCLONE AND COLD FRONT. THIS BOUNDARY WILL SERVE AS NRN BOUND FOR MORE ROBUST SVR THREAT TO DEVELOP THIS AFTN. TIMING/LOCATION OF MOST SIGNIFICANT DEVELOPMENT ALONG COLD FRONT AND DRYLINE IS STILL UNCERTAIN…THOUGH 12Z RAOBS OFFER SOME IMPORTANT CLUES. CAPPING WAS VERY STG AT FWD…STG AT SHV…WEAKER AT OUN…ALMOST NONEXISTENT AT LZK…WITH WEAK STABLE LAYER EVIDENT AT SGF. AS SUCH…SGF MAY HAVE FORTUITOUSLY SAMPLED ERN EDGE OF STRONGEST SBCINH THAT SHOULD EXTEND SSWWD ACROSS ERN OK THEN SEWD OVER ARKLATEX. SUBSTANTIAL DCVA/COOLING ALOFT MAY NEVER GET SUBSTANTIALLY PAST SFC COLD FRONT…INDICATING ONLY WEAK ADJUSTMENTS IN EML CONFIGURATION PRIOR TO FROPA.

DRYLINE AND LATER FRONTAL FORCING SHOULD INTENSIFY AS BOUNDARIES IMPINGE ON FAVORABLY MOIST AND HEATED AIR MASS THIS AFTN. THIS INITIAL ROUND OF CONVECTION SHOULD CROSS OZARKS REGION IN REGIME OF LARGE LOW-LEVEL HODOGRAPHS…EVEN AFTER SOME VEERING OF SFC WINDS OCCURS THIS EVENING. SUPERCELLS INITIALLY WILL BE POSSIBLE WITH EVENTUAL COALESCENCE AND UPSCALE GROWTH INTO QUASI-LINEAR TSTM REGIME WITH BOWS/LEWPS. AS THAT OCCURS…DOMINANT HAIL THREAT WILL TRANSITION TO DAMAGING WIND…WITH TORNADOES OF BOTH SUPERCELLULAR AND QLCS ORIGIN POSSIBLE.

FARTHER S…E OF EML-RELATED CAPPING CONCERNS…PROGS REASONABLY SUGGEST NOCTURNAL DEVELOPMENT OF PERSISTENT CONFLUENT/CONVERGENT ZONE IN BOUNDARY LAYER FROM NRN LA ACROSS PARTS OF SWRN AR/NWRN MS. SCATTERED TO NUMEROUS TSTMS MAY EVOLVE FROM THIS IN REGIME OF RICH LOW-LEVEL MOISTURE…LOW LCL…AND FAVORABLY LARGE HODOGRAPHS. DAMAGING WIND AND TORNADO RISKS ARE APPARENT AS ACTIVITY SHIFTS EWD OVER SRN PORTIONS OUTLOOK AREA.

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