Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 250824
SWODY3
SPC AC 250823

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0223 AM CST THU DEC 25 2014

VALID 271200Z - 281200Z

...THERE IS A MRGL RISK OF SVR TSTMS FOR SERN TX AND PARTS OF THE
LOWER MS VALLEY...

...SUMMARY...
SCATTERED THUNDERSTORMS ARE FORECAST ON SATURDAY FROM EASTERN
PORTIONS OF TEXAS INTO THE LOWER MISSISSIPPI VALLEY.  A FEW OF THE
STRONGER STORMS MAY POSE AN ISOLATED STRONG TO SEVERE THREAT.

...SYNOPSIS...
A LARGE-SCALE TROUGH SITUATED OVER THE N-CNTRL U.S. AND SRN ROCKIES
WILL SLOWLY MOVE EWD.  THE NRN PORTION OF THE TROUGH SHOULD MINOR
OUT OVER THE UPPER MIDWEST WHILE AN AMPLIFYING SHORTWAVE TROUGH
ROUNDS THE BASE OVER NRN MEXICO.  DOWNSTREAM OF THIS FEATURE...A
NEUTRAL MID-LEVEL HEIGHT CHANGE FIELD IS FORECAST THROUGHOUT THE DAY
AND THROUGH MOST OF SATURDAY NIGHT ACROSS THE LOWER MS VALLEY.  IN
THE LOW LEVELS...A COLD FRONT EXTENDING FROM THE GREAT LAKES SWWD
INTO TX WILL CONTINUE TO PROGRESS SEWD AND INTO PORTIONS OF THE
LOWER MS VALLEY.

...SERN TX AND LOWER MS VALLEY...
APPRECIABLE ISENTROPIC ASCENT ACCOMPANYING SLY LOW-LEVEL FLOW ATOP A
MODIFYING CP AIRMASS WILL LIKELY PROMOTE SHOWERS AND THUNDERSTORM
ACTIVITY EARLY IN THE DAY ACROSS ERN PORTIONS OF TX AND LA.  AN
EFFECTIVE WARM FRONT IS FORECAST TO REACH SERN TX AND PORTIONS OF
SRN LA COINCIDENT WITH BOUNDARY-LAYER DEWPOINTS RISING INTO THE
MID-UPPER 60S.  SOME MODELS SHOW A WEAKENING AND VEERING IN H85 FLOW
DURING THE DAY WITH ONLY WEAK LOW PRESSURE DEVELOPMENT INVOF THE
INVERTED TROUGH -- CASTING CONSIDERABLE DOUBT IN THE INLAND
PENETRATION OF A MODIFIED MARITIME AIRMASS BEYOND THE IMMEDIATE
COASTAL PLAIN.  ALTHOUGH SOME DIURNAL HEATING WILL OCCUR...MARGINAL
LAPSE RATES WILL TEND TO TEMPER OVERALL CONVECTIVE VIGOR.
ADDITIONALLY...THE ANAFRONTAL CHARACTER OF THE FRONT MAY SERVE TO
UNDERCUT AND WEAKEN CONVECTION ALONG THE FRONT.
NONETHELESS...EPISODIC PERIODS OF SHOWER/THUNDERSTORM ACTIVITY ARE
FORECAST AND A FEW OF THE STRONGER STORMS MAY ORGANIZE --GIVEN A
STRONG WIND PROFILE-- AND POSE AN ISOLD STRONG TO SEVERE STORM
THREAT.

..SMITH.. 12/25/2014



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