DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 041958
SWODY1
SPC AC 041956

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0156 PM CST TUE DEC 04 2012

VALID 042000Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF LOWER TO MIDDLE
TX COAST...

A COUPLE OF CHANGES HAVE BEEN MADE TO THE OUTLOOK FOR THIS ISSUANCE.
THE FIRST CHANGE IS TO REMOVE PART OF THE SLIGHT RISK AREA IN THE
HOUSTON AREA WHERE NUMEROUS THUNDERSTORMS ARE ONGOING. THE AIRMASS
IS IN THE PROCESS OF BEING TURNED OVER IN SOUTHEAST TX AND THE
SEVERE THREAT MAY BE REDUCED LATER THIS AFTERNOON AS INSTABILITY
DECREASES DUE TO THUNDERSTORM OUTFLOW. THE SECOND CHANGE TO THE
OUTLOOK IS TO ADD A 5 PERCENT WIND DAMAGE PROBABILITY NEWD INTO
NCNTRL MS WHERE CONVECTION IS ONGOING. IN ADDITION...REMOVED THUNDER
ACROSS PARTS OF THE OZARKS. OTHERWISE...THE OUTLOOK APPEARS TO BE ON
TRACK.

..BROYLES.. 12/04/2012

.PREV DISCUSSION... /ISSUED 1011 AM CST TUE DEC 04 2012/

...SYNOPSIS...

THE PRIMARY FEATURE OF INTEREST THIS PERIOD IS A LOW-LATITUDE
SHORTWAVE TROUGH WHICH WILL TRANSLATE SEWD FROM THE OZARK PLATEAU
AND SRN PLAINS INTO THE LOWER MS VALLEY AND NRN GULF OF MEXICO.
EMBEDDED WITHIN THIS BROADER-SCALE FEATURE...A VORTICITY MAXIMUM
OVER ERN OK AS OF MID MORNING WILL WEAKEN TODAY IN RESPONSE TO THE
SEWD PROGRESSION AND AMPLIFICATION OF A SECONDARY VORTICITY MAXIMUM
AND ASSOCIATED MIDLEVEL JET STREAK FROM WRN TX INTO THE NWRN GULF OF
MEXICO. MEANWHILE...AN ACCOMPANYING SURFACE COLD FRONT ANALYZED
FROM NEAR THE CONFLUENCE OF THE MS AND OH RIVERS SWWD INTO THE TX
HILL COUNTRY AS OF 15Z WILL CONTINUE SEWD TOWARD THE TX COAST AND
INTO THE LOWER MS VALLEY...SERVING AS THE FOCUS FOR TSTM
DEVELOPMENT.

...MIDDLE TX COAST INTO DEEP S TX THIS AFTERNOON AND EVENING...

12Z REGIONAL SOUNDINGS SHOWED THE PRESENCE OF A MOIST AIR MASS /I.E.
LOWEST 100-MB MEAN-MIXING RATIOS OF 12-14 G PER KG/ BENEATH MODESTLY
STEEP MIDLEVEL LAPSE RATES OF AROUND 7 C/KM. WHEN COMBINED WITH
LOCAL CLOUD BREAKS...THE POTENTIAL WILL EXIST FOR CORRIDORS OF
MODERATE AFTERNOON INSTABILITY WITH MLCAPE VALUES APPROACHING
1000-2000 J/KG. LOW-LEVEL UPLIFT ALONG THE COLD FRONT AND
DEVELOPING SEA-BREEZE WILL COMBINE WITH INCREASING HEIGHT FALLS/DCVA
ATTENDANT TO W TX VORTICITY MAXIMUM TO FOSTER WIDELY SCATTERED TO
SCATTERED TSTMS BY MID/LATE AFTERNOON. THE SEWD PROGRESSION OF THE
MIDLEVEL JET STREAK ATTENDING THE VORTICITY MAXIMUM WILL LEAD TO A
CORRESPONDING INCREASE IN VERTICAL SHEAR WITH THE KINEMATIC
ENVIRONMENT BECOMING SUPPORTIVE OF SUPERCELLS AND ORGANIZED LINE
SEGMENTS WITH AN ASSOCIATED RISK FOR DAMAGING WINDS AND LARGE HAIL
THROUGH THIS EVENING.

...LOWER MS VALLEY THIS AFTERNOON AND EVENING...

CONSISTENT WITH CURRENT RADAR OBSERVATIONS...LATEST MODEL GUIDANCE
SUGGESTS A GENERAL INCREASE IN TSTM COVERAGE TODAY BOTH ALONG THE
SYNOPTIC COLD FRONT AS WELL AS WITHIN THE OPEN WARM SECTOR WHERE
LOW-LEVEL CONFLUENCE IS ENHANCED. WHILE THE THERMODYNAMIC
ENVIRONMENT WILL BE COMPARABLE TO THAT ACROSS TX /I.E. MLCAPE OF
1000-2000 J PER KG/...VERTICAL SHEAR WILL BE NOTABLY WEAKER. THIS
WILL RESULT IN LESS ORGANIZED AND OUTFLOW-DOMINANT STORMS CAPABLE OF
LOCALLY STRONG WIND GUSTS AND PERHAPS SOME HAIL.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.