SWODY3
SPC AC 170713
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0213 AM CDT WED MAR 17 2010
VALID 191200Z - 201200Z
...SYNOPSIS...
ALTHOUGH ONE STRONG SHORT WAVE TROUGH LIFTING TOWARD THE BRITISH
COLUMBIA COAST...AND ANOTHER DIGGING OUT OF THE NORTHWEST
TERRITORIES...MAY CONTRIBUTE TO WEAKENING...MODELS SUGGEST THAT
AMPLIFIED RIDGING WILL PERSIST ALONG THE PACIFIC COAST THROUGH THIS
PERIOD. AND A STRONG DOWNSTREAM SHORT WAVE TROUGH APPEARS LIKELY TO
CONTINUE DIGGING SOUTH SOUTHEASTWARD FROM THE GREAT BASIN THROUGH
THE SOUTHERN PLAINS BY 12Z SATURDAY. THIS FEATURE IS PROGGED TO BE
ACCOMPANIED BY A STRONG COLD INTRUSION TO THE LEE OF THE
ROCKIES...THE LEADING EDGE OF WHICH IS EXPECTED TO PROVIDE THE FOCUS
FOR A DEVELOPING SURFACE LOW ACROSS THE RED RIVER VALLEY INTO THE
OZARK PLATEAU FRIDAY NIGHT.
A FAIRLY DEEP INITIAL SURFACE LOW IS PROGGED TO MIGRATE SOUTH
SOUTHEASTWARD THROUGH THE SOUTH CENTRAL HIGH PLAINS DURING THE DAY
FRIDAY...AS DOWNSTREAM SURFACE RIDGING RETREATS EASTWARD TOWARD THE
WESTERN ATLANTIC. AS THIS OCCURS...A BROADENING BELT OF MODESTLY
STRONG SOUTHERLY FLOW WILL DEVELOP OFF THE GULF OF MEXICO THROUGH
MUCH OF THE SOUTH CENTRAL STATES. HOWEVER...AN INITIALLY RELATIVELY
DRY BOUNDARY LAYER OVER THE GULF OF MEXICO WILL TAKE TIME TO
MODIFY...AND SREF GUIDANCE SUGGESTS THAT SURFACE DEW POINTS OF 55F
MAY NOT REACH MUCH BEYOND TEXAS COASTAL AREAS BY THE END OF THE
PERIOD...WITH DEW POINTS GENERALLY IN THE MID 50S TO LOWER 60S
ACROSS THE NORTHWEST GULF.
THE LACK OF A SUBSTANTIVE RETURN FLOW STILL APPEARS LIKELY TO LIMIT
THE CONVECTIVE POTENTIAL WITHIN AN EVOLVING LARGE-SCALE PATTERN THAT
MIGHT MORE TYPICALLY BE ASSOCIATED WITH A MORE SIGNIFICANT SEVERE
WEATHER THREAT. BUT...THE RISK FOR SEVERE STORMS MAY NOT BE
COMPLETELY NEGLIGIBLE.
...SOUTH CENTRAL PLAINS...
IF THE SURFACE COLD FRONT DOES NOT ADVANCE SOUTHWARD TOO MUCH FASTER
THAN CURRENTLY SUGGESTED BY THE MODELS...AN AXIS OF STRONGER SURFACE
HEATING /TO AROUND 70F/ APPEARS LIKELY BENEATH A NORTHEASTWARD
ADVECTING ELEVATED MIXED LAYER...FROM THE TEXAS SOUTH PLAINS THROUGH
WESTERN OKLAHOMA...PERHAPS SOUTH CENTRAL KANSAS...BY LATE FRIDAY
AFTERNOON. COUPLED WITH A NARROW WEAK TONGUE OF MOISTENING
/PRECIPITABLE WATER OF .5 TO .75 INCHES...SFC DEW POINTS NEAR
50F/...CONDITIONAL AND CONVECTIVE INSTABILITY EVIDENT IN FORECAST
SOUNDINGS APPEARS SUFFICIENT FOR VIGOROUS CONVECTIVE DEVELOPMENT.
THE PRIMARY MID-LEVEL COOLING MAY STILL LAG TO THE NORTH AND
WEST...BUT WEAKENING INHIBITION IN THE PEAK HEATING COMBINED WITH
FRONTAL FORCING PROBABLY WILL CONTRIBUTE TO THE INITIATION OF
CONVECTIVE DEVELOPMENT.
SOME STORMS MAY BE CAPABLE OF PRODUCING MARGINALLY SEVERE HAIL.
HOWEVER...THE PRIMARY SEVERE CONCERN MAY BE POTENTIALLY DAMAGING
WIND GUSTS...AS SIZABLE LOWER/MID TROPOSPHERIC TEMPERATURE/DEW POINT
SPREADS ENHANCE EVAPORATIVE COOLING IN DOWNDRAFTS WITHIN A NARROW
EVOLVING SQUALL LINE. AS ACTIVITY DEVELOPS EASTWARD...THE SEVERE
THREAT MAY CONTINUE INTO THE EVENING HOURS...BEFORE THE FRONT
PERHAPS UNDERCUTS THE CONVECTION AND/OR ACTIVITY BEGINS TO SPREAD
EAST OF THE MOIST AXIS...INGESTING DRIER AIR.
...PARTS OF NORTH CENTRAL/EASTERN TEXAS...
A SEPARATE AREA OF VIGOROUS CONVECTIVE DEVELOPMENT SEEMS POSSIBLE
ACROSS THE REGION PRIOR TO 12Z SATURDAY...WITHIN A STRENGTHENING
ELEVATED WARM ADVECTION REGIME...AS STRONGER MID/UPPER FORCING
FINALLY BEGINS TO SURGE EASTWARD ACROSS THE SOUTHERN PLAINS. THIS
MAY BE AIDED BY A SOMEWHAT BETTER INFLUX OF GULF MOISTURE ON THE
STRENGTHENING LOW-LEVEL JET...AND INSTABILITY COUPLED WITH
STRENGTHENING DEEP LAYER SHEAR MAY CONTRIBUTE TO A RISK FOR LARGE
HAIL.
..KERR.. 03/17/2010
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