DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 030557
SWODY1
SPC AC 030555

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CDT WED APR 03 2013

VALID 031200Z - 041200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
SPLIT UPPER UPPER FLOW REGIME WILL REMAIN OVER THE U.S. THROUGH
THIS FORECAST PERIOD. PRIMARY FEATURE OF INTEREST IS THE CUTOFF
UPPER LOW CENTERED NEAR THE 4-CORNERS REGION PER 03/00Z RAOB
ANALYSIS. THIS SYSTEM...INITIALLY POSITIVELY TILTED...SHOULD BECOME
NEAR NEUTRAL ORIENTATION BY 12Z THU AS IT REACHES THE SRN PLAINS.
AT THE SURFACE...A FRONT WILL STRETCH FROM THE SERN U.S. W/SWWD INTO
DEEP S TX AT 12Z TODAY.

AN ONGOING MCS MOVING EWD ACROSS CENTRAL/SOUTH CENTRAL TX PRIOR TO
THE START OF DAY 1 SHOULD BE OFFSHORE THE TX COAST INTO THE NWRN
GULF BY 12Z. THIS SCENARIO IS SUPPORTED BY THE 00Z 4 KM WRF-NMM AND
SHOWS THE EFFECTIVE COLD FRONT MOVING THROUGH DEEP S TX THIS
MORNING. MEANWHILE...FARTHER EAST...THE FRONT WILL LIKELY STALL OR
LIFT NWD TO NEAR THE LA COAST LATE IN THE FORECAST PERIOD...AS A
SURFACE WAVE DEVELOPS ALONG THIS BOUNDARY IN RESPONSE TO FORCING
ASSOCIATED WITH THE APPROACHING UPPER TROUGH.

...PARTS OF NRN AND CENTRAL TX...
FORECAST SOUNDINGS INDICATED COOLING MIDLEVEL TEMPERATURES AND
STEEPENING MIDLEVEL LAPSE RATES WILL AID IN DESTABILIZATION AS
HEIGHT FALLS/FORCING FOR ASCENT SPREAD ACROSS THIS REGION AHEAD OF
THE APPROACHING FOUR CORNERS TROUGH. THIS WILL SUPPORT MAINLY
ELEVATED CONVECTION...LIKELY ROOTED BETWEEN 850-700 MB...ATOP A
STABLE POST FRONTAL BOUNDARY LAYER. MUCAPE OF 250 TO AROUND 500
J/KG AND EFFECTIVE BULK SHEAR OF 25-40 KT WILL SUPPORT HAIL IN THE
STRONGER STORMS. A FEW HAILSTONES COULD APPROACH 1 INCH
DIAMETER...AND THUS THIS OUTLOOK HAS INTRODUCED A LOW PROBABILITY
FOR SEVERE HAIL. AT THIS TIME...FORECAST CONFIDENCE SUGGESTS MOST
HAIL WILL BE SUB-SEVERE.

...COASTAL REGIONS OF FAR SERN LA/SWRN AL AND WRN FL PANHANDLE...
MODELS DIFFER WITH THE TRACK OF THE SURFACE LOW DEVELOPING OVER THE
NWRN GULF AFTER 04/00Z...WITH THIS FEATURE POSSIBLY MOVING INLAND
ALONG THE FAR SERN LA COAST TO THE FAR WRN FL PANHANDLE THIS EVENING
THROUGH 12Z THU. AN EXTENSIVE AREA OF TSTMS IS EXPECTED TO BE
ONGOING ACROSS SRN LA/SRN MS AND SWD INTO THE ADJACENT NWRN AND NRN
GULF OF MEXICO AT 12Z TODAY...WHILE THE CURRENT MCS LOCATED IN SOUTH
CENTRAL TX SHOULD BE IN THE NWRN GULF AT THE START OF DAY 1. ALL OF
THIS CONVECTION IS EXPECTED TO MAINTAIN ANY WARM SECTOR OFFSHORE
THROUGH THIS AFTERNOON...AND THUS LIMIT ANY SEVERE WEATHER THREAT
UNTIL THE LATTER HALF OF THE PERIOD. IF THE SURFACE LOW CAN REACH
COASTAL SECTIONS OF SERN LA TO SWRN AL/WRN FL PANHANDLE THIS
EVENING/OVERNIGHT...THEN AN INCREASE IN LOW LEVEL MOISTURE /SURFACE
DEW POINTS INTO THE MID 60S/...STRENGTHENING BULK SHEAR AND LOW
LEVEL SHEAR WOULD SUPPORT LOW PROBABILITIES FOR A FEW DAMAGING WINDS
AND/OR A TORNADO.

..PETERS/GRAMS.. 04/03/2013

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