DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200600
SWODY1
SPC AC 200558

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1158 PM CST WED FEB 19 2014

VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OH AND TN VALLEY
REGIONS TO CENTRAL GULF COAST...

...SYNOPSIS...
PROGRESSIVE UPPER-AIR PATTERN IS FCST ACROSS CONUS THIS
PERIOD...FEATURING INITIALLY DISTINCT SHORTWAVE TROUGHS NOW ANALYZED
OVER WRN DAKOTAS AND SRN CO/NRN NM REGION. SRN PORTION OF
MID-UPPER-LEVEL VORTICITY FIELD ASSOCIATED WITH NRN-PLAINS
PERTURBATION IS EXPECTED TO LINK WITH AMPLIFYING SRN-ROCKIES SYSTEM
WHILE MOVING EWD ACROSS MAINLY CENTRAL/NRN PLAINS. COMBINED TROUGH
SHOULD REACH FROM OZARKS TO UPPER MS VALLEY BY 21/06Z. BY THAT
TIME...ACCOMPANYING/CLOSED 500-MB LOW SHOULD FORM OVER WI. BY END
OF PERIOD...500-MB LOW SHOULD DEEPEN AND MOVE NEWD TO NNEWD ACROSS
CENTRAL/WRN UPPER MI...WITH TROUGH ARCHING SEWD OVER WRN LOWER MI
AND INDIANA THEN SSWWD ACROSS WRN TN. 250-MB JET OF 110-120 KT WAS
ANALYZED AT 21/00Z OVER CO/NM...AND THIS SPEED MAX SHOULD
EXPAND/ELONGATE AHEAD OF COMBINED PERTURBATION THROUGH
PERIOD...WHILE GRADUALLY BECOMING MORE MERIDIONAL.

AT SFC...CYCLONE NOW NEAR CO/KS BORDER SHOULD CONTINUE TO DEEPEN AS
IT TRAVELS FROM ERN KS TO SWRN WI DURING 20/12-21/00Z TIME FRAME.
AT THAT TIME...COLD FRONT SHOULD EXTEND IN ARC FROM LOW ACROSS
CENTRAL-ERN IL...EXTREME WRN KY...SERN AR...AND MIDDLE-UPPER COASTAL
PLAIN OF TX.

...OH AND TN VALLEY REGIONS TO CENTRAL GULF COAST...
SCATTERED-NUMEROUS TSTMS IN BANDS SHOULD POSE PRIMARY THREAT OF
DAMAGING GUSTS...A FEW OF WHICH MAY REACH 65-KT/SIGNIFICANT-SVR
CRITERIA. TORNADO RISK EXISTS BUT IS SECONDARY TO DAMAGING TSTM
WIND IN TERMS OF COVERAGE...DURATION AND NUMBER OF EVENTS PROBABLE.
ALTHOUGH LOW-LEVEL AND DEEP SHEAR EACH WILL BE FAVORABLE FOR
SUPERCELLS...LIKELY DOMINANCE OF LINEAR STORM MODE INDICATES
PREDOMINANT SOURCE OF TORNADO RISK WILL BE QLCS-TYPE SPINUPS AND
EMBEDDED MESOCIRCULATIONS ASSOCIATED WITH LEWPS AND SMALL BOWS.
TORNADOES WITH SUCH REGIMES TEND BE RELATIVELY SHORT-LIVED AND
SMALL...BUT ALSO...FAST-MOVING AND RAIN-WRAPPED.

THIN BAND OF CONVECTION MAY DEVELOP DURING AFTN IN ZONE OF STRONG
FORCING ALONG SFC COLD FRONT...HOWEVER PRIMARY SVR-PRODUCING SWATH
IS LIKELY TO ARISE IN SW-NE ORIENTED/PREFRONTAL CONVERGENCE ZONE
FROM LATE AFTN INTO EARLY OVERNIGHT HOURS. 50-60 KT EFFECTIVE SHEAR
MAGNITUDES WILL BE COMMON WHEREVER SFC-BASED INFLOW EXISTS WITH MAIN
SQUALL LINE. 60S SFC DEW POINTS MAY REACH TO NEAR OH RIVER IN
NARROW CORRIDOR PRIOR TO TSTMS...BUT RICHEST MOISTURE SHOULD RESIDE
FROM TN SWD. MLCAPE SHOULD REMAIN BELOW 1000 J/KG OVER MOST OF
OUTLOOK AREA BECAUSE OF WEAK LAPSE RATES ALOFT...THOUGH POCKETS OF
PRECONVECTIVE DIABATIC HEATING OVER GULF COAST STATES CAN BOOST
VALUES HIGHER ON MESOBETA SCALE.

AS TSTM REGIME MOVES EWD ACROSS KY/TN/AL OVERNIGHT...IT WILL OUTPACE
FAVORABLE DESTABILIZATION/WAA FROM N-S...AND MOVE INTO PROGRESSIVELY
LOWER-CAPE AIR WITH EWD EXTENT. NET RESULT SHOULD BE DECREASE IN
OVERALL SVR POTENTIAL FROM NW-SE AND WITH TIME. HOWEVER...BECAUSE
OF GREATER MOISTURE PREVALENT CLOSER TO GULF COAST...SVR RISK MAY
LAST FOR MUCH OF OVERNIGHT HOURS AS CONVECTION CROSSES TN VALLEY AND
GULF-COAST STATES.

FARTHER N OVER NRN PORTIONS INDIANA/OH AND LOWER MI...SVR WIND
POTENTIAL DIMINISHES DUE TO PROGRESSIVELY WEAKER BUOYANCY.
ALSO...LOSS OF SFC-BASED PARCELS IS EXPECTED IN RELATION TO
PROGRESSIVELY DEEPER STABLE LAYER WITH NWD EXTENT...ATOP SNOW PACK.
MEANWHILE...EVEN FOR THOSE STG/NEAR-SVR GUSTS THAT CAN PENETRATE TO
SFC...SUBSTANTIAL TREE DAMAGE/TOPPLING ALSO BECOMES LESS PROBABLE
WITH NWD EXTENT DUE TO FROZEN GROUND AND LACK OF LEAVES.

...MO-IA-IL REGION...MORNING...
EXTENSION OF STG LOW-LEVEL WAA REGIME FROM PRIOR PERIOD WILL SUPPORT
CARRY-OVER POTENTIAL FOR SCATTERED TSTMS IN CLUSTERS ACROSS THIS
REGION. ACTIVITY WILL BE SUPPORTED BY ISENTROPIC LIFT TO
LFC...AMIDST ELEVATED MUCAPE 500-800 J/KG AND 35-45 KT EFFECTIVE
SHEAR MAGNITUDES FROM ASSORTED FCST SOUNDINGS. ISOLATED SVR HAIL
MAY OCCUR WITH THIS ACTIVITY DURING FIRST FEW HOURS OF PERIOD BEFORE
IT MOVES NNEWD AWAY FROM MOST FAVORABLE ELEVATED INSTABILITY.

..EDWARDS/GUYER.. 02/20/2014

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