DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 211248
SWODY1
SPC AC 211246

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0646 AM CST SAT DEC 21 2013

VALID 211300Z - 221200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF THE LWR MS AND LWR
TN VLYS...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM E TX AND THE CNTRL GULF CST NE INTO THE OH VLY...

...SYNOPSIS...
AN OUTBREAK OF SVR TSTMS IS POSSIBLE TODAY INTO TNGT OVER THE LWR MS
AND LWR TN VLYS. THE POTENTIAL WILL EXIST FOR A FEW STRONG
TORNADOES...IN ADDITION TO SWATHS OF DMGG WINDS.

POTENT SHORTWAVE TROUGH NOW ENTERING W TX SHOULD PIVOT NE ACROSS THE
RED RVR VLY LATER TODAY/EARLY TNGT...AND ACCELERATE NE INTO IL EARLY
SUN...AS LARGE-SCALE/HIGH-AMPLITUDE TROUGH REMAINS CENTERED OVER THE
PLAINS. THE SHORTWAVE WILL ASSUME A SLIGHTLY NEGATIVE TILT BEFORE IT
BECOMES ABSORBED WITHIN DOWNSTREAM CONFLUENT FLOW OVER THE OH VLY
LATER SUN.

AHEAD OF THE IMPULSE...STRENGTHENING/DEEPENING SWLY FLOW WILL ALLOW
A SWATH OF SEASONABLY WARM/MOIST AIR TO SURGE NE ACROSS THE LWR MS
VLY INTO MUCH OF THE OH VLY TODAY THROUGH EARLY SUN. COUPLED WITH
THE VERY STRONG WIND FIELD ACCOMPANYING THE UPR IMPULSE...SETUP WILL
BE FAVORABLE FOR BANDS OF TSTMS/SUPERCELLS CAPABLE OF BOTH DMGG WIND
AND POTENTIALLY STRONG TORNADOES LATER TODAY INTO TNGT.

...WRN/CNTRL GULF CST INTO THE OH VLY TODAY/TNGT...
SFC OBS SHOW STRONG/BROAD CURRENT OF VERY MOIST AIR SURGING N FROM
THE WRN GULF OF MEXICO ATTM INTO THE LWR MS VLY...AHEAD OF
SLOWLY-PROGRESSIVE COLD FRONT ASSOCIATED WITH W TX SHORTWAVE TROUGH.
NUMEROUS BUOYS REPORT 30 KT SLY FLOW WITH DEWPOINTS AOA 70 F IN AREA
WITH PW AOA 1.50 INCHES. THE MOIST PLUME WILL SPREAD FARTHER NE
ACROSS THE OH VLY THROUGH EARLY SUN...AND LARGELY DELINEATE THE
NRN/ERN EXTENT OF SFC-BASED INSTABILITY ACROSS THE REGION. CLOUDS
WILL LIMIT DIURNAL STEEPENING OF LOW-LVL LAPSE RATES OVER MOST
AREAS. BUT QUALITY OF MOISTURE INFLOW AND PRESENCE OF RESIDUAL EML
LIKELY WILL YIELD SUFFICIENT BUOYANCY /MLCAPE OF 500-1000 J PER KG/
FOR SUSTAINED TSTMS...ESPECIALLY OVER THE LWR MS VLY/DEEP SOUTH.

WIDESPREAD SHOWERS/STORMS NOW OCCURRING ALONG AND W OF THE COLD
FRONT SHOULD GRADUALLY INCREASE IN STRENGTH/COVERAGE THROUGH LATER
THIS MORNING AS STRONGER FORCING FOR ASCENT ASSOCIATED WITH THE UPR
IMPULSE APPROACHES THE WARM SECTOR. TOGETHER WITH CONTINUED
MOISTENING OF CONFLUENT LWR TROPOSPHERIC FLOW...SETUP ALSO MAY
SUPPORT DEVELOPMENT OF BANDS/CLUSTERS OF STORMS AHEAD OF THE FRONT
OVER FAR E TX...LA...ERN AR...AND MS BY EARLY AFTN.

ALTHOUGH THE INTENSITY AND NEGATIVE-TILT NATURE OF THE SHORTWAVE
IMPULSE MAY RESULT IN WIND PROFILES WITH A SLIGHT VEER-BACK PATTERN
IN THE VERTICAL...STRENGTH OF THE WIND FIELD /WITH 60-70 KT 850-700
MB WINDS BENEATH 100 KT FLOW AT 250 MB/ WILL BE VERY FAVORABLE FOR
ROTATING UPDRAFTS. THE GREATEST RISK FOR DISCRETE OR SEMI-DISCRETE
STORMS WITH POTENTIAL FOR TORNADOES /SOME OF WHICH COULD BE
STRONG/...SHOULD EXIST OVER PARTS OF LA...AR...MS...AND WRN TN THIS
AFTN/EARLY TNGT.

CONTINUED NE MOTION OF THE SHORTWAVE IMPULSE SHOULD FOSTER
CONSOLIDATION OF THE FRONTAL AND PRE-FRONTAL STORMS INTO A FAIRLY
LENGTHY SQLN BY MID-LATE AFTN. ATTENDANT FAST-MOVING BOW/LEWP
STRUCTURES WILL MAINTAIN A RISK FOR SWATHS OF DMGG WIND...IN
ADDITION TO A FEW TORNADOES...INTO THE NIGHT FROM WRN/CNTRL KY SSW
THROUGH TN INTO MS...AL...AND LA. IN ADDITION...ALTHOUGH BUOYANCY
WILL DECREASE WITH NEWD EXTENT...THE STRONGEST LOW-LVL MASS
CONVERGENCE/WAA WILL FOCUS ON THE OH VLY BY LATE EVE. COUPLED WITH
THE INTENSITY OF THE WIND FIELD...AND THE LIKELIHOOD FOR MODEST SFC
DEVELOPMENT ALONG THAT PART OF THE FRONTAL ZONE STRADDLING THE OH
VLY...ISOLD TORNADOES AND DMGG WIND GUSTS MAY OCCUR AS FAR N AS
PARTS OF IND...OH...AND WV THROUGH SUN MORNING.

..CORFIDI/MOSIER.. 12/21/2013

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