SWODY2
SPC AC 140551
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1151 PM CST WED FEB 13 2008
VALID 151200Z - 161200Z
..THERE IS A SLGT RISK OF SVR TSTMS FRI EVE ACROSS PARTS OF
CNTRL/SE TEXAS....
..SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT AMPLIFICATION WILL OCCUR WITHIN THE
MAIN BELT OF POLAR WESTERLIES...ACROSS THE NORTHEAST PACIFIC INTO
THE LEE OF THE CANADIAN/NORTHERN U.S. ROCKIES. AS AN UPPER RIDGE
GRADUALLY BUILDS JUST TO THE WEST OF THE BRITISH COLUMBIA/ PACIFIC
NORTHWEST COAST...A DOWNSTREAM SHORT WAVE TROUGH IS PROGGED TO BEGIN
TO DIG TO THE LEE OF THE ROCKIES. THIS MAY CONTRIBUTE TO AN
EASTWARD ACCELERATION OF THE COLD UPPER VORTEX THROUGH MUCH OF THE
REMAINDER OF THE EASTERN CANADIAN PROVINCES. HOWEVER...A STRONG
LOW-LEVEL COLD INTRUSION WILL CONTINUE THROUGH MUCH OF THE
CENTRAL/EASTERN U.S...AS A SIGNIFICANT SHORT WAVE IMPULSE PROGRESSES
THROUGH THE SOUTHERN PERIPHERY OF THE UPPER CIRCULATION...IN PHASE
WITH AN IMPULSE WITHIN THE MAIN POLAR STREAM.
THE INFLUENCE OF THE AFOREMENTIONED DEVELOPMENTS ON THE CLOSED
LOW...LIKELY BECOMING INCREASINGLY DETACHED FROM THE STRONGER
WESTERLIES ACROSS THE SOUTHWEST BY 12Z FRIDAY...IS STILL UNCERTAIN.
BUT...WHILE THE 14/00Z OPERATIONAL GFS VARIES SLIGHTLY...THE 14/00Z
NAM...13/21Z SREF AND 13/12Z MREF ARE ALL SIMILAR IN SUGGESTING THAT
THE CLOSED LOW WILL CONTINUE TO DIG INTO THE NORTHWESTERN MEXICAN
PLATEAU FRIDAY/FRIDAY NIGHT...WITHIN A WEAK BUT AMPLIFIED STREAM
EMANATING FROM THE SUBTROPICAL PACIFIC.
..SOUTHERN PLAINS INTO WESTERN/CENTRAL GULF STATES...
AT LEAST A SHALLOW SURFACE COLD FRONT IS STILL ANTICIPATED TO
PROGRESS INTO WESTERN/CENTRAL GULF COASTAL AREAS EARLY IN THE
PERIOD. THIS WILL STABILIZE THE BOUNDARY LAYER...BUT A SOUTHERLY
RETURN FLOW OF MOISTURE WILL CONTINUE ABOVE THE FRONTAL INVERSION
THROUGH MUCH OF TEXAS AND PORTIONS OF THE LOWER MISSISSIPPI VALLEY.
MODELS ARE SUGGESTIVE THAT THIS WILL OCCUR BENEATH A RESIDUAL
ELEVATED MIXED LAYER NOW IN THE PROCESS OF ADVECTING OFF THE HIGHER
TERRAIN TO THE WEST. AND...CONFIDENCE IS GROWING THAT A SHALLOWER
COLD SURGE INTO THE SOUTHERN PLAINS WILL ERODE THIS ELEVATED MIXED
LAYER LESS THAN PREVIOUSLY EXPECTED. THUS...A BROADER AREA OF
CONDITIONAL/CONVECTIVE INSTABILITY IS EXPECTED TO DEVELOP
FRIDAY/FRIDAY NIGHT ACROSS THE SOUTHERN PLAINS INTO WESTERN/CENTRAL
GULF COASTAL AREAS.
WEAK IMPULSES MIGRATING OUT OF THE BASE OF THE UPSTREAM TROUGH...
AHEAD OF THE CLOSED LOW...STILL APPEAR LIKELY TO PROVIDE THE PRIMARY
FORCING FOR ONE OR MORE CONVECTIVE CLUSTERS. THESE COULD BECOME
ORGANIZED IN THE PRESENCE OF AT LEAST WEAK INSTABILITY AND MODERATE
TO STRONG CLOUD BEARING LAYER SHEAR...WHICH COULD PROMOTE HAIL IN
STRONGER CELLS. AND...THERMODYNAMIC PROFILES SUGGEST POTENTIAL THAT
DOWNDRAFTS COULD PENETRATE THE COLD SURFACE LAYER ...ACCOMPANIED BY
GUSTY SURFACE WINDS.
ONE OF THESE CLUSTERS APPEARS POSSIBLE NEAR UPPER TEXAS/LOUISIANA
COASTAL AREA DURING THE DAY. BUT...POTENTIAL FOR MORE VIGOROUS
CONVECTIVE DEVELOPMENT...INCLUDING A FEW SEVERE STORMS...IS EXPECTED
TO INCREASE INLAND OF THE COASTAL PLAIN...ACROSS CENTRAL
TEXAS...FRIDAY EVENING. THIS IS WHERE LOW-LEVEL CONVERGENCE AND
DESTABILIZATION ARE EXPECTED TO BECOME MAXIMIZED ON THE NOSE OF A
STRENGTHENING SOUTHERLY LOW-LEVEL JET...BENEATH INCREASINGLY
DIFLUENT UPPER FLOW DOWNSTREAM OF THE CLOSED LOW. AND...SOME OF
THE HAIL COULD BECOME FAIRLY SIZABLE AS MOST UNSTABLE CAPE INCREASES
TO 500-1000 J/KG.
.KERR.. 02/14/2008
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