DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 021229
SWODY1
SPC AC 021227

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0727 AM CDT TUE APR 02 2013

VALID 021300Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO TONIGHT ACROSS PARTS
OF CENTRAL AND SOUTHERN TEXAS...

...SYNOPSIS...
WITHIN THE PREVAILING SPLIT MID-LATITUDE WESTERLIES...MODELS
INDICATE THAT THE MAIN SHORT WAVE IMPULSE...WITHIN THE PROMINENT
NORTHERN BRANCH TROUGH OVER THE EASTERN U.S...WILL SLOWLY PROGRESS
EASTWARD INTO AND THROUGH THE CANADIAN MARITIMES DURING THIS
FORECAST PERIOD. AS THIS OCCURS...THE TRAILING EDGE OF CYCLONIC
NORTHERN STREAM FLOW IS EXPECTED TO SHIFT EAST OF THE MID/UPPER
MISSISSIPPI VALLEY. AT THE SAME TIME...THE TRAILING SOUTHERN BRANCH
CLOSED LOW/TROUGH IS FORECAST TO SLOWLY DIG THROUGH THE FOUR CORNERS
STATES...AS UPPER RIDGING BUILDS INTO CALIFORNIA...AHEAD OF THE NEXT
SIGNIFICANT SOUTHERN STREAM IMPULSE ADVANCING ACROSS THE EASTERN
PACIFIC. TO THE SOUTH AND EAST OF THE FOUR CORNERS TROUGH...BROADLY
CYCLONIC FLOW IS EXPECTED TO PERSIST ACROSS THE MEXICAN
PLATEAU...WHILE DEVELOPING EASTWARD ACROSS THE LOWER RIO GRANDE
VALLEY INTO THE WESTERN GULF COAST REGION.

SEVERAL WEAK/SMALLER SCALE IMPULSES WITHIN THIS LATTER REGIME MAY
CONTRIBUTE TO CONVECTIVE POTENTIAL TODAY ACROSS PARTS OF THE CENTRAL
AND SOUTHERN PLAINS...WHERE LOWER LEVELS REMAIN RELATIVELY
MOIST...AND MID-LEVEL LAPSE RATES REMAIN RELATIVELY STEEP. SEVERE
WEATHER POTENTIAL...HOWEVER...WILL BE COMPLICATED BY A DEEPENING
COLD INTRUSION ACROSS THE CENTRAL INTO SOUTHERN HIGH PLAINS. THIS
AIR IS ASSOCIATED WITH MUCH MORE EXPANSIVE SURFACE RIDGING EXTENDING
SOUTHEASTWARD OUT OF CENTRAL CANADA THROUGH THE EASTERN GULF OF
MEXICO...AND SOUTH ATLANTIC COASTAL AREAS...IN THE WAKE OF THE
NORTHERN BRANCH TROUGH.

...CENTRAL/SOUTHERN PLAINS...
NEAR/NORTH OF THE SURFACE FRONTAL ZONE...LOW POTENTIAL FOR
THUNDERSTORMS CAPABLE OF PRODUCING SEVERE HAIL MAY LINGER AS FAR
NORTH AS THE RED RIVER VALLEY AND PARTS OF NORTH CENTRAL TEXAS THIS
MORNING. MID-TROPOSPHERIC WARM ADVECTION DOWNSTREAM OF THE DIGGING
SOUTHERN BRANCH TROUGH MAY ALSO CONTRIBUTE TO STORMS CAPABLE OF
PRODUCING SOME HAIL LATER TONIGHT ACROSS PARTS OF THE TEXAS
PANHANDLE AND SOUTH PLAINS. HOWEVER...AS THE DEPTH OF THE COLDER
AND DRIER SURFACE-BASED LAYER INCREASES...CAPE IS CURRENTLY EXPECTED
TO DECREASE ENOUGH THAT THE RISK FOR SEVERE HAIL WILL REMAIN BELOW
SLIGHT RISK PROBABILITIES.

FARTHER SOUTH...GUIDANCE IS SUGGESTIVE THAT A WEAK IMPULSE MAY
CONTRIBUTE TO CONVECTIVE DEVELOPMENT DURING THE DAY TODAY WITHIN A
BROAD WARM FRONTAL ZONE NEAR MID/UPPER TEXAS COASTAL AREAS. THE
BOUNDARY LAYER ACROSS THIS REGION IS INCREASINGLY MOIST...WITH MID
TO UPPER 60S SURFACE DEW POINTS CONTRIBUTING TO SIZABLE CAPE. AS
MODEST SOUTHERLY 850 MB FLOW STRENGTHENING TAKES PLACE BENEATH 30+
KT WEST SOUTHWESTERLY 500 MB FLOW...VERTICAL SHEAR PROFILES MAY
BECOME SUFFICIENT FOR A FEW SEVERE STORMS...INCLUDING ISOLATED
SUPERCELLS.

OTHERWISE...FORCING FOR CONVECTION TO THE WEST REMAINS
UNCLEAR...EXCEPT FOR THE MOIST UPSLOPE REGIME ACROSS THE HIGHER
TERRAIN WEST OF THE RIO GRANDE RIVER INTO THE DAVIS MOUNTAINS AREA
OF SOUTHWEST TEXAS. THE ENVIRONMENT ACROSS THIS REGION APPEARS
CONDUCIVE TO SUPERCELLS...WHICH MAY TEND TO PROPAGATE EAST
SOUTHEASTWARD OFF THE HIGHER TERRAIN INTO TEXAS. THERE IS SOME
SIGNAL AMONG THE MODEL DATA THAT LARGE-SCALE FORCING FOR UPWARD
VERTICAL MOTION COULD CONTRIBUTE TO THE UPSCALE CONVECTIVE GROWTH OF
A MESOSCALE CONVECTIVE SYSTEM ACROSS PARTS OF SOUTH CENTRAL TEXAS
LATE THIS EVENING. IF THIS OCCURS...THE ENVIRONMENT SHOULD BE
CONDUCIVE TO THE RISK FOR DAMAGING WIND GUSTS AND LARGE HAIL.

..KERR/LEITMAN.. 04/02/2013

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