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Apr 27, 2014 0600 UTC Day 1 Convective Outlook

April 27, 2014

Apr 27, 2014 0600 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0106 AM CDT SUN APR 27 2014

VALID 271200Z – 281200Z

…THERE IS A MDT RISK OF SVR TSTMS FROM EXTREME ERN KS…ERN OK…MUCH OF MO…AR…EXTREME NERN TX…WRN TN AND NWRN MS…

…THERE IS A SLGT RISK OF SVR TSTMS OVER ERN PORTIONS OF THE CNTRL AND SRN PLAINS THROUGH MUCH OF THE LOWER-MID MS VALLEY AND WRN TN VALLEY…

CORRECTED FOR TEXT IN LAST PARAGRAPH

…SUMMARY…
NUMEROUS SEVERE STORMS WITH POTENTIAL FOR STRONG TORNADOES…VERY LARGE HAIL AND DAMAGING WIND ARE LIKELY ACROSS MUCH OF THE MISSISSIPPI RIVER VALLEY…WITH THE GREATEST THREAT FROM THE ARK-LA-TEX INTO ARKANSAS…WESTERN TENNESSEE AND WESTERN AND CENTRAL MISSOURI AND ERN KS. A SECONDARY THREAT AREA WILL BE FROM EASTERN NEBRASKA INTO IOWA…AND STORMS DEVELOPING IN THIS REGION DURING THE DAY WILL ALSO LIKELY PRODUCE LARGE HAIL AND SEVERAL TORNADOES.

…SYNOPSIS…

VIGOROUS SHORTWAVE TROUGH WILL BE LOCATED ACROSS ERN WRN KS BY 12Z SUNDAY AND LIFT NEWD INTO NEB BY LATE SUNDAY AFTERNOON AND EVENING. A SECONDARY IMPULSE/JET MAX WILL ADVANCE THROUGH THE BASE OF THE UPPER TROUGH AND THROUGH THE SRN PLAINS…REACHING THE LOWER MS VALLEY REGION SUNDAY EVENING. AT THE SFC AN AREA OF LOW PRESSURE WILL DEEPEN AND LIFT NWD INTO NEB IN ASSOCIATION WITH THE PRIMARY SHORTWAVE TROUGH…WHILE A PACIFIC FRONT/DRYLINE SURGES EWD THROUGH THE CNTRL AND SRN PLAINS…REACHING THE MID MS VALLEY REGION BY EVENING. A WARM FRONT WILL EXTEND EWD FROM THE LOW AND LIFT NWD THROUGH NEB AND IA.

…EXTREME ERN PORTIONS OF CNTRL/SRN PLAINS THROUGH LOWER-MID MS AND TN VALLEYS…

IT STILL APPEARS THAT MID-LEVEL CONVECTION MAY DEVELOP ABOVE THE CAP EARLY IN THE PERIOD ACROSS PORTIONS OF THE SRN PLAINS AND LOWER-MID MS VALLEY AREA. HOWEVER…THIS ACTIVITY IS EXPECTED TO SHIFT NEWD ALLOWING FOR UPSTREAM DESTABILIZATION. RICH GULF MOISTURE CURRENTLY RESIDES ACROSS ERN TX INTO LA AND WILL ADVECT NWD THROUGH THE LOWER-MID MS VALLEY WARM SECTOR WITH UPPER 60S DEWPOINTS AS FAR NORTH AS ARKANSAS AND MID 60S INTO MO BENEATH PLUME OF STEEP MID-LEVEL LAPSE RATES. THIS PROCESS WILL CONTRIBUTE TO AN AXIS OF MODERATE INSTABILITY WITH 1500-2000 J/KG MLCAPE EXPECTED BY MID AFTERNOON. HOWEVER…WIDESPREAD MULTILAYER CLOUDS SHOULD TEMPER BOUNDARY LAYER WARMING AND DESTABILIZATION TO SOME DEGREE.

TWO AREAS OF SURFACE BASED THUNDERSTORM INITIATION APPEAR LIKELY INCLUDING ALONG THE DRYLINE/PACIFIC FRONT FROM ERN OK/ERN KS AS WELL AS FARTHER SOUTH WITHIN PRE-FRONTAL CONFLUENCE ZONE BY MID AFTERNOON…AS THE DIFFLUENT UPPER JET EXIT REGION OVERTAKES THE WARM SECTOR. DEEP LAYER WIND PROFILES WILL BECOME VERY FAVORABLE FOR SUPERCELLS WITH 0-6 KM SHEAR IN EXCESS OF 50 KT AND 0-1 KM STORM RELATIVE HELICITY FROM 200-300 J/KG. INITIAL STORMS ALONG THE DRYLINE AS WELL AS PRE-FRONTAL CONFLUENCE ZONE WILL LIKELY BE DISCRETE AND POSE A THREAT FOR VERY LARGE HAIL AND TORNADOES…A FEW OF WHICH COULD BE STRONG. SOME STORMS MAY EVENTUALLY CONSOLIDATE INTO ONE OR MORE MCSS DURING THE EVENING BUT WITH A CONTINUED THREAT FOR DAMAGING WIND…TORNADOES AND LARGE HAIL AS ACTIVITY DEVELOPS TOWARD THE TN VALLEY. A PORTION OF THE LOWER MS VALLEY MAY NEED TO BE INCLUDED IN A HIGH RISK IN LATER UPDATES.

…NEB AND IA…

COOL TEMPERATURES ALOFT…STEEP LAPSE RATES AND MODEST LOW LEVEL MOISTURE WILL SUPPORT A NARROW AXIS OF MODERATE SURFACE BASED INSTABILITY IN VICINITY OF WARM FRONT ACROSS NEB INTO IA. FORCING FOR ASCENT ASSOCIATED WITH THE EJECTING SHORTWAVE TROUGH WILL INCREASE BY LATE MORNING SUPPORTING AN ARC OF STORMS IN VICINITY OF WARM FRONT. VEERING LOW-LEVEL WINDS WITH LARGE 0-2 KM HODOGRAPHS AND 50 KT EFFECTIVE SHEAR WILL SUPPORT SUPERCELLS WITH TORNADOES AND LARGE HAIL AS ACTIVITY DEVELOPS NWD. MODERATE RISK MIGHT BE EXPANDED FARTHER NW TO INCLUDE A PORTION OF THIS AREA ON NEXT UPDATE.

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