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Mar 27, 2014 1630 UTC Day 1 Convective Outlook

March 27, 2014

Mar 27, 2014 1630 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
ISSUED BY 15TH OWS SCOTT AIR FORCE BASE IL
1107 AM CDT THU MAR 27 2014

VALID 271630Z – 281200Z

…THERE IS A SLGT RISK OF SVR TSTMS ERN PARTS OF KS AND OK INTO MID MS VALLEY AND OZARK PLATEAU…

…SYNOPSIS…

A PROGRESSIVE…LOW-AMPLITUDE PATTERN WILL EXIST OVER THE CONUS THROUGH THE D1 PERIOD. WITHIN THIS REGIME…A POLAR-BRANCH SHORT-WAVE TROUGH AND ASSOCIATED 70-80 KT MIDLEVEL JET STREAK WILL TRANSLATE FROM THE CNTRL/SRN PLAINS ENEWD INTO THE GREAT LAKES AND OH VALLEY BY 28/12Z. THIS SYSTEM WILL BE ATTENDED BY A BROAD 50-60+ KT SWLY LLJ WHICH WILL CORRESPONDINGLY MIGRATE FROM LOWER ELEVATIONS OF THE GREAT PLAINS AND OZARKS TO UPPER OH VALLEY AND NERN U.S. BY THE END OF THE PERIOD.

AT THE SURFACE…LOW PRESSURE OVER N-CNTRL KS WILL UNDERGO GRADUAL WEAKENING WHILE DEVELOPING NEWD TO ERN IA BY 28/00Z…PRIOR TO REACHING NRN LOWER MI BY DAYBREAK FRIDAY. A DRYLINE EXTENDING SWD FROM THIS LOW WILL MIX EWD INTO ERN PARTS OF KS/OK BY AFTERNOON WHILE BEING GRADUALLY OVERTAKEN FROM THE N BY A COLD FRONT ADVANCING SEWD THROUGH THE CNTRL INTO SRN PLAINS. THE SRN EXTENSION OF THE DRYLINE WILL LIKELY REACH THE I-35 CORRIDOR OF TX BEFORE STALLING IN RESPONSE TO CYCLOGENESIS OVER N-CNTRL TX TONIGHT.

…ERN PARTS OF KS/OK INTO THE MID MS VALLEY AND OZARK PLATEAU THIS AFTERNOON INTO TONIGHT…

THE POLEWARD FLUX OF HEAT AND MOISTURE WILL BE MAINTAINED TODAY ALONG THE ABOVE-MENTIONED LLJ AXIS WITH WARM SECTOR DEWPOINTS RISING INTO THE 50S OVER ERN KS/WRN MO…AND UPPER 50S TO LOWER 60S ACROSS PARTS OF ERN OK AND AR. THIS MOISTURE INCREASE WILL BE SURMOUNTED BY A WELL-DEFINED EML WITH AFTERNOON MLCAPE VALUES APPROACHING 500-1200 J/KG WITHIN THE NWD-EXPANDING WARM SECTOR.

CLEARING SKIES IN CENTRAL AND EASTERN KS ALLOWING FOR FURTHER DESTABILIZATION IN LOW LEVEL…SURFACE-BASED STORM DEVELOPMENT WILL BECOME INCREASINGLY LIKELY IN THE 18-21Z TIME FRAME FROM THE VICINITY OF THE SURFACE LOW OVER SWRN IA OR NWRN MO SWWD ALONG THE COLD FRONT-DRYLINE OCCLUSION INTO ERN KS AND SW MO. THIS COUPLED WITH STRONG SHORTWAVE WILL ALLOW THE LINEAR NATURE OF LOW-LEVEL FORCING MECHANISM AND ITS ALIGNMENT TO THE DEEP-LAYER SHEAR VECTOR WOULD INDICATE THAT STORMS SHOULD EVOLVE INTO LINE SEGMENTS OR A CONTINUOUS BAND WITH HAIL AND DAMAGING WINDS BEING THE PRIMARY HAZARDS. AS THESE STORMS SPREAD EWD/SEWD INTO THE MID MS VALLEY AND OZARK PLATEAU OVERNIGHT…EXPECT THE SEVERE WEATHER THREAT TO GRADUALLY DIMINISH OWING TO THE COOLING AND RESULTANT STABILIZATION OF THE BOUNDARY LAYER.

DIURNAL STORM DEVELOPMENT SWD ALONG THE DRYLINE INTO ERN OK/WRN AR REMAINS MORE UNCERTAIN GIVEN THE TENDENCY FOR THE HEIGHT FALLS/FORCING FOR ASCENT ASSOCIATED WITH THE MIDLEVEL TROUGH TO SHIFT AWAY FROM THE REGION DURING THE TIME OF PEAK HEATING. AS SUCH…INITIATION WILL BE HEAVILY RELIANT ON BOUNDARY LAYER HEATING ALONG AND WEST OF THE DRYLINE. SHOULD SURFACE-BASED STORMS FORM AND BECOME SUSTAINED…THE COMBINATION OF MODERATE INSTABILITY…50-60 KT OF DEEP-LAYER SHEAR ORIENTED NORMAL TO THE DRYLINE AND MODERATELY STRONG LOW-LEVEL SHEAR WILL BE SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL AND A FEW TORNADOES.

…ERN TX INTO THE LOWER MS VALLEY THIS AFTERNOON THROUGH TONIGHT…

BOTH CONVECTION-ALLOWING AND PARAMETRIZED MODEL GUIDANCE INDICATE AN INCREASE IN TSTMS TODAY WITHIN THE OPEN WARM SECTOR FROM ERN TX INTO THE LOWER MS VALLEY. HERE…LOW-LEVEL CONFLUENT FLOW WILL BE AUGMENTED BY A DEEPER CIRCULATION TIED TO THE COUPLING OF POLAR AND SUB-TROPICAL-BRANCH JET STREAKS. WHILE THE BOUNDARY LAYER WILL UNDERGO CONTINUED WARMING AND MOISTENING THROUGH THE PEAK OF THE DIURNAL HEATING CYCLE…A CONSIDERABLE CAP AT THE BASE OF AN EML /REFERENCE 12Z SOUNDINGS/ CASTS UNCERTAINTY AS TO WHETHER ANY OF THESE STORMS WILL TRULY BECOME SURFACE BASED. AS SUCH…THE EXISTING LOW SEVERE PROBABILITIES WILL BE MAINTAINED IN THIS FORECAST.

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