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Dec 20, 2013 0600 UTC Day 1 Convective Outlook

December 20, 2013

Dec 20, 2013 0600 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1127 PM CST THU DEC 19 2013

VALID 201200Z – 211200Z

…THERE IS A SLGT RISK OF SVR TSTMS FOR PARTS OF THE ARKLATEX EARLY SAT…

…SYNOPSIS…
A VIGOROUS SHORTWAVE TROUGH NEAR THE SRN CA/BAJA CA BORDER WILL PROGRESS EWD AND SHOULD APPROACH THE TX BIG BEND BY EARLY SAT. A COLD FRONT INITIALLY FROM THE LOWER MO VALLEY TO THE SRN HIGH PLAINS SHOULD REACH THE LOWER OH VALLEY TO S-CNTRL TX. THIS BOUNDARY WILL STALL IN RESPONSE TO THE UPSTREAM TROUGH WITH MODEST CYCLOGENESIS OCCURRING ALONG THE TX PORTION OF THE FRONT LATE IN THE PERIOD.

…CNTRL TX TO THE MID-SOUTH…
LOW-LEVEL MOISTURE WILL CONTINUE TO INCREASE FROM THE WRN GULF BENEATH A PROMINENT CAPPING INVERSION/EML NOTED IN REGIONAL RAOBS ON THU EVENING. LOWER TO MIDDLE 60S SURFACE DEW POINTS WILL BECOME PREVALENT NEAR THE CONFLUENCE OF THE OH/MS RIVERS S/SWWD ACROSS SRN/ERN TX AHEAD OF THE FRONT BY FRI EVENING.

FORCING FOR ASCENT SHOULD REMAIN LIMITED DURING THE DIURNAL HEATING CYCLE WITH NEAR-NEUTRAL MID-LEVEL HEIGHT CHANGE. WITH STOUT CAPPING…SURFACE-BASED INITIATION APPEARS UNLIKELY DURING THE FIRST HALF OF THE PERIOD. HOWEVER…AS MID-LEVEL HEIGHT FALLS OVERSPREAD THE QUASI-STATIONARY FRONT AND LOW-LEVEL WAA STRENGTHENS ATOP THE FRONTAL ZONE…ASCENT WILL INCREASE SUBSTANTIALLY FRI NIGHT WITH TSTMS BECOMING WIDESPREAD BY EARLY SAT. MOST CONVECTION WILL DEVELOP ON THE COOL SIDE OF THE SURFACE FRONT WITHIN A SLIGHTLY ANAFRONTAL DEEP-LAYER FLOW REGIME. ELEVATED UPDRAFTS SHOULD POSE A RISK FOR LOCALIZED SEVERE HAIL AMIDST WEAK BUOYANCY BUT STRONG EFFECTIVE SHEAR.

OF GREATER CONCERN IS THE POTENTIAL FOR WARM SECTOR TSTMS NEAR THE END OF THE PERIOD WITH THE LIKELIHOOD OF A 60-70 KT LLJ ACROSS ERN TX TOWARDS THE MID-SOUTH. THE STRENGTHENING LARGE-SCALE ASCENT MAY AID IN SUFFICIENT WEAKENING OF THE CAPPING INVERSION BETWEEN 09-12Z. IF TSTMS BECOME SUSTAINED IN THE WARM SECTOR…LARGE LOW-LEVEL HODOGRAPHS WOULD BE FAVORABLE FOR SUPERCELLS PRODUCING SEVERE WINDS AND TORNADOES. ALTHOUGH THIS APPEARS MUCH MORE PROBABLE TO OCCUR IN THE D2 PERIOD…A CONDITIONAL SLIGHT RISK SEEMS APPROPRIATE TO DELINEATE FOR LATE D1.

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From → Weather Blog

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