Sunday, December 25, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 251914
SWODY1
SPC AC 251912

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0112 PM CST SUN DEC 25 2011

VALID 252000Z - 261200Z

...NO SVR TSTM AREAS FORECAST...

...ERN PORTIONS OF THE SRN PLAINS AND INTO THE LOWER MS VALLEY...
GOING FORECAST REMAINS ON TRACK ATTM...WITH GREATEST POTENTIAL FOR
ELEVATED THUNDERSTORMS TO OCCUR THIS EVENING/OVERNIGHT FROM ERN
TX/ERN OK EWD TO THE LOWER MS VALLEY. HERE...INCREASING LOW-LEVEL
ISENTROPIC LIFT/WARM ADVECTION SHOULD SUPPORT SHOWERS AND STORMS
ATOP THE LOW-LEVEL STABLE LAYER.

..GOSS.. 12/25/2011

.PREV DISCUSSION... /ISSUED 1017 AM CST SUN DEC 25 2011/

...NW GULF COAST TODAY TO THE ARKLATEX/ERN OK TONIGHT...
UPPER CLOSED LOW CENTERED OVER W TX IS ACCOMPANIED BY POSITIVE TILT
TROUGH TRAILING SWWD INTO NRN MEXICO THIS MORNING. DOWNSTREAM MOIST
S-SWLY FLOW IS SITUATED ATOP A STABLE NEAR SURFACE AIRMASS OVER THE
SRN MS VALLEY/NW GULF COAST REGION. MODEST ELEVATED INSTABILITY
ROOTED AT 850 MB IS AIDING IN SHOWERS AND ISOLATED LIGHTNING STRIKES
THROUGH 16Z...BUT SHOULD WANE SOMEWHAT AS LLJ CONTINUES TO VEER
DURING THE AFTERNOON. BY EVENING INTO THE OVERNIGHT...MIDLEVEL
SHORTWAVE TROUGH WILL APPROACH THE BIG BEND AREA...LEADING TO
STRENGTHENING UPPER-LEVEL DIVERGENCE AND LOW-LEVEL ISENTROPIC
UPGLIDE FROM THE SABINE RIVER VALLEY ACROSS THE ARKLATEX INTO ERN
OK. THIS WILL FAVOR AN INCREASE IN SHOWERS OVER THE REGION...WITH
ISOLATED TO SCATTERED ELEVATED THUNDERSTORMS BECOMING PROBABLE GIVEN
THE PRESENCE OF SEVERAL HUNDRED J/KG OF MUCAPE ROOTED BETWEEN THE
850-700 MB LAYER.

...RIO GRANDE VALLEY INTO PORTIONS OF S-CNTRL TX...
LATE IN THE FORECAST PERIOD /NEAR 12Z/...COMBINATION OF INCREASING
ASCENT AHEAD OF APPROACHING MIDLEVEL SHORTWAVE TROUGH...AND WEAK
ELEVATED INSTABILITY...MAY FAVOR ISOLATED THUNDERSTORM DEVELOPMENT
FROM THE RIO GRANDE VALLEY INTO PORTIONS OF S-CNTRL TX.
HOWEVER...COVERAGE IS EXPECTED TO BE BELOW 10 PERCENT ATTM...WHICH
WILL PRECLUDE ISSUANCE OF A CATEGORICAL THUNDER LINE.

...SRN NEW ENGLAND COAST...
SHORTWAVE TROUGH WILL MOVE ACROSS NEW ENGLAND TONIGHT. LAPSE RATES
WILL STEEPEN AS THIS TAKES PLACE...WHICH COULD AID IN ISOLATED
THUNDERSTORM DEVELOPMENT NEAR THE SRN NEW ENGLAND COAST.
HOWEVER...GREATER PROBABILITY FOR LIGHTNING WILL BE OFFSHORE ACROSS
THE ATLANTIC AS COLD MIDLEVEL AIRMASS SPREADS ACROSS WARMER OCEAN
WATERS.

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