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Mar 27, 2014 0600 UTC Day 1 Convective Outlook

March 27, 2014

Mar 27, 2014 0600 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT THU MAR 27 2014

VALID 271200Z – 281200Z

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF ERN OK…ERN KS…NRN/CNTRL/WRN AR…MO…WRN IL…FAR SRN IA…

…SYNOPSIS…
A MID-LEVEL SHORTWAVE TROUGH CURRENTLY CROSSING THE FOUR-CORNERS REGION PER WATER VAPOR IMAGERY WILL TRACK EWD/NEWD THROUGH TONIGHT. AN ASSOCIATED SFC CYCLONE WILL CONSOLIDATE OVER THE CNTRL PLAINS AND DEVELOP NEWD INTO THE UPPER GREAT LAKES REGION…WHILE A COLD FRONT TRAILS SW OF THE CYCLONE. A N/S-ORIENTED DRYLINE WILL PROGRESS EWD THROUGH THE DAY AS THE MIXING PROCESS COUPLES WITH LARGE-SCALE WLY MOMENTUM. THE DRYLINE WILL REACH ERN PORTIONS OF KS…OK…AND TX BY MID AFTERNOON. THE COLD FRONT WILL OVERTAKE THE DRYLINE ACROSS PORTIONS OF THE CNTRL PLAINS THROUGH THE DAY…WHILE STRONG POLEWARD MASS FLUXES ENCOURAGE LOW-LEVEL MOISTURE RETURN FROM ERN PORTIONS OF THE CNTRL/SRN PLAINS TO THE LOWER/MIDDLE MS VALLEY.

…ERN PORTIONS OF THE CNTRL/SRN PLAINS TO THE LOWER/MIDDLE MS VALLEY THIS AFTERNOON INTO TONIGHT…
ASCENT INVOF THE MERGING FRONT/DRYLINE WILL BE THE FOCUS FOR SCATTERED THUNDERSTORM DEVELOPMENT ACROSS PARTS OF THE LOWER MO VALLEY BY MID AFTERNOON…WHICH WILL BE ENHANCED AROUND THE SFC CYCLONE AND DOWNSTREAM OF THE SHORTWAVE TROUGH. FARTHER S ALONG THE DRYLINE…MORE ISOLATED THUNDERSTORM DEVELOPMENT IS ANTICIPATED INTO ERN OK AND WRN AR THROUGH LATE AFTERNOON WHERE DEEP FORCING FOR ASCENT WILL BE MORE MODEST.

WITH CURRENT SFC OBSERVATIONS INDICATING 60S SFC DEWPOINTS ONLY HAVING RETURNED TO S TX THUS FAR…GIVEN 30S-40S SFC DEWPOINTS CURRENTLY IN PLACE ACROSS MUCH OF THE SLIGHT-RISK AREA…AND GIVEN THE PROPENSITY FOR THE SFC CYCLONE AND ACCOMPANYING SHORTWAVE TROUGH TO LIFT AWAY FROM RICHER MOISTURE OVER THE W GULF…SUBSTANTIAL BOUNDARY-LAYER MOISTENING WELL INLAND IS DOUBTFUL. FURTHERMORE…STRONG ELEVATED MOISTURE TRANSPORT ALONG A LLJ MAINTAINED BY THE TIGHT LARGE-SCALE HEIGHT GRADIENT ON THE WRN FLANK OF SWRN N ATLANTIC RIDGING SHOULD SUPPORT WIDESPREAD STRATUS THROUGH THE DAY TO STUNT DIABATIC SFC HEATING. THESE FACTORS WILL TEMPER THE DEGREE OF DIURNALLY ENHANCED BUOYANCY AND THE SPATIAL EXTENT OF SUBSTANTIVE INSTABILITY.

BY MID AFTERNOON…INSOLATION ON THE WRN FRINGES OF 50S SFC DEWPOINTS WILL SUPPORT AROUND 500-2000 J/KG OF MLCAPE AIDED BY STEEP MID-LEVEL LAPSE RATES ACROSS FAR ERN KS/OK AND WRN MO/AR…YIELDING SFC-BASED CONVECTIVE INITIATION. STRONG DEEP SHEAR OFFERED BY 60-80 KT OF H5 FLOW WILL PROMOTE ORGANIZED CONVECTION. THE GREATEST POTENTIAL FOR DISCRETE CONVECTION/SUPERCELLS WILL BE ACROSS ERN OK AND WRN AR. CONVECTION FARTHER NORTH INTO THE LOWER MO VALLEY WILL HAVE A TENDENCY TO DEVELOP INTO BROKEN QUASI-LINEAR SEGMENTS IN CLOSER PROXIMITY TO STRONGER DEEP FORCING FOR ASCENT. SVR WIND/HAIL WILL BE THE MAIN CONCERNS WITH THESE STORMS. SOME POTENTIAL FOR SIGNIFICANT HAIL CANNOT BE COMPLETELY RULED OUT WITH THE MORE DISCRETE CONVECTION. HOWEVER…THE LIMITED MOISTURE…WITH PW GENERALLY AOB 1 INCH…AND LIMITED SPATIAL EXTENT OF STRONGER BUOYANCY CAST SUBSTANTIAL DOUBT ON SUCH POTENTIAL. SIMILAR MITIGATING FACTORS SHOULD ALSO TEMPER THE OVERALL TORNADO POTENTIAL…IN ADDITION TO THE TENDENCY FOR LOW-LEVEL FLOW TO VEER IN RESPONSE TO THE NEWD TRACK OF THE CYCLONE. REGARDLESS…FORECAST HODOGRAPHS EXHIBIT SUFFICIENT LOW-LEVEL CURVATURE/LENGTH TO SUPPORT SOME TORNADO POTENTIAL…PARTICULARLY FROM E-CNTRL OK INTO W-CNTRL AR AND NWD INTO CNTRL MO WHERE UPDRAFTS MAY REMAIN AT LEAST SOMEWHAT SEPARATED. STRONG-SEVERE CONVECTION WILL SPREAD EWD INTO THE EVENING HOURS TOWARD THE MS RIVER BEFORE OUTPACING STRONGER BUOYANCY AND WEAKENING OVERNIGHT TONIGHT.

THE LOW-AMPLITUDE NATURE OF THE AFOREMENTIONED SHORTWAVE TROUGH AND OVERLAPPING ZONE OF BUOYANCY WILL LARGELY CONFINE THE MOST LIKELY AREA OF SEVERE CONVECTION FROM N OF THE ARKLATEX TO THE IA/MO BORDER. S OF THE SLIGHT-RISK AREA FROM PARTS OF E TX INTO THE LOWER MS VALLEY…THE SVR THREAT IS NOT ENTIRELY NEGLIGIBLE GIVEN RICHER LOW-LEVEL MOISTURE AND AT LEAST MODERATE INSTABILITY/DEEP SHEAR. HOWEVER…RELATIVELY WEAKER LOW-LEVEL/DEEP FORCING FOR ASCENT SHOULD LIMIT THE OVERALL FOCUS FOR GREATER SVR COVERAGE. REGARDLESS…SPORADIC DMGG WINDS/HAIL CANNOT BE RULED OUT THROUGH TONIGHT.

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