DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 050540
SWODY1
SPC AC 050539

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1139 PM CST FRI JAN 04 2013

VALID 051200Z - 061200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
AN AMPLIFIED UPPER TROUGH IS IN THE PROCESS OF SPLITTING AS IT
APPROACHES THE PACIFIC COAST. WHILE THE NORTHERN IMPULSE PROGRESSES
INLAND ACROSS BRITISH COLUMBIA AND THE PACIFIC NORTHWEST...THE
SOUTHERN IMPULSE IS FORECAST TO DIG INTO THE CALIFORNIA COAST BY 12Z
SUNDAY. AS THIS OCCURS...A COUPLE OF SIGNIFICANT DOWNSTREAM
IMPULSES ARE EXPECTED TO REMAIN PROGRESSIVE WITHIN THEIR RESPECTIVE
NORTHERN AND SOUTHERN STREAMS TO THE LEE OF THE ROCKIES...MERGING
INTO THE LINGERING CONFLUENT REGIME ENCOMPASSING MUCH OF THE EASTERN
U.S...BETWEEN A BROAD/DEEP NORTHEASTERN CANADIAN VORTEX AND A STRONG
SUBTROPICAL HIGH CENTERED OVER THE SOUTHWESTERN ATLANTIC. IN
ASSOCIATION WITH THE SOUTHERN STREAM FEATURE...MID/UPPER FLOW IS
FORECAST TO INTENSIFY ON THE NORTHWESTERN PERIPHERY OF THE UPPER
HIGH...ACROSS PORTIONS OF THE LOWER MISSISSIPPI AND TENNESSEE
VALLEYS. FORCING FOR UPWARD VERTICAL MOTION IN THE RIGHT ENTRANCE
REGION OF THIS JET MAY CONTRIBUTE TO WEAK FRONTAL WAVE DEVELOPMENT
OVER THE GULF OF MEXICO.

...WESTERN GULF COAST...
BOUNDARY LAYER DESTABILIZATION IN THE WARM SECTOR OF THE FRONTAL
WAVE...COUPLED WITH LARGE SCALE ASCENT NEAR THE DEVELOPING LOW AND
ALONG/NORTH OF THE FRONT TO ITS EAST...PROBABLY WILL FOCUS THE
PRIMARY RISK FOR THUNDERSTORM ACTIVITY ACROSS PARTS OF THE WESTERN
AND CENTRAL GULF OF MEXICO DURING THIS FORECAST PERIOD.
HOWEVER...WITH SOME VARIABILITY...MODELS DO INDICATE A BROAD ZONE OF
LOWER/MID TROPOSPHERIC THERMAL AND MOISTURE ADVECTION EXTENDING
ACROSS TEXAS...AND PERHAPS PORTIONS OF LOUISIANA...COASTAL AREAS
THROUGH AT LEAST THE FIRST HALF OF THE PERIOD. WHILE FORCING FOR
UPWARD VERTICAL MOTION IS MORE UNCLEAR ACROSS THESE AREAS...MODELS
SUGGEST THAT THERMODYNAMIC PROFILES WILL BE CONVECTIVELY
UNSTABLE...WITH WEAK CAPE ALSO EVIDENT FOR PARCELS EMANATING FROM A
MOIST LAYER BASED BETWEEN 850-700 MB. THIS SEEMS TO SUPPORT THE
RISK FOR THUNDERSTORM ACTIVITY...THOUGH PROBABILITIES MAY BE
GENERALLY NEAR THE MINIMUM 10 PERCENT THRESHOLD FOR A CATEGORICAL
THUNDERSTORM OUTLOOK.

...CALIFORNIA...
WITH A MID-LEVEL COLD CORE CHARACTERIZED BY 500 MB TEMPERATURES NEAR
-30C...SCATTERED CONVECTIVE DEVELOPMENT WILL PROBABLY ACCOMPANY THE
UPPER LOW/TROUGH DIGGING INTO THE REGION LATE IN THE
PERIOD...PARTICULARLY ALONG COASTAL AREAS BETWEEN POINT CONCEPTION
AND MONTEREY. HOWEVER...IT IS NOT YET CLEAR WHETHER DESTABILIZATION
WILL BECOME SUFFICIENT FOR VERTICAL DEVELOPMENT THROUGH THE MIXED
PHASE LAYER FAVORABLE FOR CHARGE SEPARATION AND THE PRODUCTION OF
LIGHTNING. AT THE PRESENT TIME...PROBABILITIES FOR THUNDERSTORMS
STILL SEEM BELOW THE MINIMUM 10 PERCENT THRESHOLD FOR A CATEGORICAL
THUNDERSTORM OUTLOOK.

..KERR/DISPIGNA.. 01/05/2013

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