DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 231240
SWODY1
SPC AC 231238

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0638 AM CST SUN DEC 23 2012

VALID 231300Z - 241200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...

AN INITIALLY QUASI-ZONAL FLOW REGIME WILL UNDERGO AMPLIFICATION
DURING THE D1 PERIOD AS AN UPPER-LEVEL JET STREAK OVER THE ERN
PACIFIC DIGS SEWD TOWARD THE LOWER CO VALLEY. THIS FEATURE WILL
GRADUALLY MERGE WITH A SUBTROPICAL JET STREAK ALONG THE GULF
COAST...RESULTING IN A HIGH-MOMENTUM AIR STREAM ACROSS THE SRN TIER
OF STATES. WITHIN THIS BROAD-SCALE PATTERN...A WEAK SHORTWAVE
TROUGH OVER THE RED RIVER VALLEY OF OK/TX THIS MORNING WILL WEAKEN
TODAY WHILE MOVING ACROSS THE GULF COAST STATES. MEANWHILE...A
STRONGER...UPSTREAM PERTURBATION NOW OVER THE LOWER CO VALLEY WILL
TRANSLATE EWD...REACHING THE LOWER MS VALLEY BY 24/12Z. THIS SYSTEM
WILL PRECEDE THE ABOVE-MENTIONED...DIGGING JET STREAK AND ASSOCIATED
VORTICITY MAXIMUM WHICH WILL APPROACH THE LOWER CO VALLEY BY THE END
OF THE D1 PERIOD.

IN THE LOW LEVELS...WEAK CYCLOGENESIS IS ANTICIPATED TODAY INVOF THE
RED RIVER W OF TXK. THIS SURFACE LOW WILL SUBSEQUENTLY DEVELOP NEWD
THROUGH CNTRL AR TONIGHT...REACHING WRN TN BY 24/12Z. MEANWHILE...A
TRAILING COLD FRONT WILL SETTLE SWD/SEWD THROUGH NRN/CNTRL
TX...AR...AND NRN LA BY THE END OF THE PERIOD.

...ERN TX INTO THE LOWER MS VALLEY...

SATELLITE-DERIVED PW IMAGERY AND SURFACE/BUOY OBSERVATIONS INDICATE
THAT THE COLD FRONT ASSOCIATED WITH THE STRONG SYNOPTIC SYSTEM
DEPARTING THE NERN CONUS HAS PUSHED WELL SOUTH INTO THE CARIBBEAN
BASIN WITH A NARROW RIBBON OF MODIFIED CP AIR RETURNING NWD THROUGH
THE FAR WRN GOM AND SRN TX. THE ABOVE-MENTIONED WAVE TRAIN IN THE
SUBTROPICAL AIR STREAM WILL MAINTAIN A SWLY LLJ THROUGH THE PERIOD
FROM ERN TX INTO THE TN VALLEY...ENHANCING THE NEWD FLUX OF THE
MODIFIED CP AIR MASS ACROSS THE REGION.

CAPPING OBSERVED BY 12Z CRP/LCH SOUNDINGS IS EXPECTED TO INHIBIT
TSTM DEVELOPMENT THROUGH THIS AFTERNOON WITHIN PRE-FRONTAL WARM
SECTOR. BY TONIGHT...SUFFICIENT LOW-LEVEL MOISTENING WILL COMBINE
WITH STRENGTHENING WAA/ISENTROPIC ASCENT AND DCVA ATTENDANT TO THE
VORTICITY MAXIMUM APPROACHING THE LOWER MS VALLEY TO FOSTER WIDELY
SCATTERED TSTMS ELEVATED ABOVE A STABLE NEAR-SURFACE LAYER. WHILE
SOME HAIL APPROACHING SEVERE LEVELS WILL BE POSSIBLE WITH THE
STRONGEST STORMS...GENERALLY POOR MIDLEVEL LAPSE RATES AND MUCAPE
LESS THAN 1000 J/KG ARE EXPECTED TO PRECLUDE A MORE ROBUST SEVERE
WEATHER THREAT. THEREFORE...THE 5 PERCENT HAIL PROBABILITIES HAVE
BEEN REMOVED WITH THIS FORECAST UPDATE.

..MEAD/LEITMAN.. 12/23/2012

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