SWODY2
SPC AC 180504
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1204 AM CDT THU MAR 18 2010
VALID 191200Z - 201200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
ONE VIGOROUS SHORT WAVE TROUGH LIFTING TOWARD THE BRITISH COLUMBIA
COAST...AND ANOTHER DIGGING OUT OF THE CANADIAN NORTHWEST
TERRITORIES...COULD BEGIN TO WEAKEN SHARP RIDGING ALONG THE PACIFIC
COAST. HOWEVER...MODELS CONTINUE TO INDICATE THAT THIS AMPLIFIED
REGIME WILL REMAIN STRONG THROUGH AT LEAST MUCH OF THIS FORECAST
PERIOD. AND A STRONG DOWNSTREAM SHORT WAVE TROUGH APPEARS LIKELY TO
DIG SOUTH SOUTHEASTWARD OR SOUTHWARD ACROSS THE CENTRAL ROCKIES INTO
THE SOUTHERN HIGH PLAINS BY 12Z SATURDAY. THIS IS EXPECTED TO BE
ACCOMPANIED BY A SIGNIFICANT COLD INTRUSION TO THE LEE THE
ROCKIES...THE LEADING EDGE OF WHICH MAY PROVIDE THE FOCUS FOR ONE OR
MORE SURFACE FRONTAL WAVES.
MODELS APPEAR TO BE TRENDING A BIT WEAKER WITH THE WAVE DEVELOPMENT
AND FASTER WITH THE COLD FRONT INTO AND THROUGH THE SOUTHERN PLAINS
FRIDAY. BUT...A BELT OF MODESTLY STRONG SOUTHERLY LOW-LEVEL FLOW
STILL SEEMS LIKELY TO DEVELOP OFF THE GULF OF MEXICO THROUGH MUCH OF
THE CENTRAL/SOUTHERN PLAINS AND LOWER HALF OF THE MISSISSIPPI
VALLEY. HOWEVER...IN THE WAKE OF RECENT DRYING...SUBSTANTIVE
BOUNDARY LAYER MOISTENING OVER THE GULF OF MEXICO WILL BE SLOW TO
OCCUR. WHILE THE LATEST SREF GUIDANCE SEEMS TO SUGGEST THAT THIS
MAY PROCEED A BIT MORE RAPIDLY THAN EARLIER ANTICIPATED...IT STILL
APPEARS PROBABLE THAT MID 50S SURFACE DEW POINTS WILL NOT ADVECT
MUCH FARTHER NORTH THAN THE TEXAS COASTAL PLAINS BY THE END OF THE
PERIOD. THIS WILL LIMIT THE CONVECTIVE POTENTIAL...BUT THE RISK FOR
THUNDERSTORM ACTIVITY SHOULD INCREASE ACROSS THE SOUTH CENTRAL
STATES BY FRIDAY EVENING...AND PROBABILITIES FOR SEVERE STORMS MAY
NOT BE COMPLETELY NEGLIGIBLE.
...SOUTH CENTRAL PLAINS...
A NARROW PRE-FRONTAL CORRIDOR OF STRONGER SURFACE HEATING... BENEATH
AN ELEVATED MIXED LAYER ADVECTING NORTHEASTWARD FROM THE TEXAS SOUTH
PLAINS THROUGH WESTERN/CENTRAL OKLAHOMA...IS STILL EXPECTED TO
CONTRIBUTE TO AN AXIS OF WEAK CONDITIONAL AND CONVECTIVE INSTABILITY
BY LATE FRIDAY AFTERNOON. EVEN WITH PRIMARY MID-LEVEL COOLING/LIFT
STILL LAGGING TO THE NORTH AND WEST...WEAK LOW-LEVEL MOISTENING AND
FRONTAL FORCING PROBABLY WILL CONTRIBUTE TO THE INITIATION OF STORMS
PRIOR TO 20/00Z. IN THE PRESENCE OF MODEST SHEAR...MARGINALLY
SEVERE HAIL MAY NOT BE OUT OF THE QUESTION. BUT...POTENTIALLY
DAMAGING WIND GUSTS ARE THE PRIMARY SEVERE CONCERN...AS SIZABLE
LOWER/MID TROPOSPHERIC TEMPERATURE/DEW POINT SPREADS ENHANCE
EVAPORATIVE COOLING IN DOWNDRAFTS WITHIN AN EVOLVING NARROW SQUALL
LINE. THIS THREAT MAY CONTINUE EASTWARD ACROSS PARTS OF
CENTRAL/EASTERN OKLAHOMA AND NORTH CENTRAL TEXAS...BEFORE
DIMINISHING DURING THE EVENING AS THE FRONT UNDERCUTS CONVECTION AND
MOISTURE RETURN.
...PARTS OF CENTRAL/NORTHEAST TEXAS...
A SEPARATE AREA OF VIGOROUS CONVECTIVE DEVELOPMENT STILL SEEMS
POSSIBLE PRIOR TO 12Z SATURDAY...WITHIN A STRENGTHENING ELEVATED
WARM ADVECTION REGIME...AS STRONGER MID/UPPER FORCING FINALLY BEGINS
TO SURGE EASTWARD INTO THE SOUTHERN PLAINS. THIS MAY BE AIDED BY A
SOMEWHAT STRONGER INFLUX OF GULF MOISTURE ON THE STRENGTHENING
SOUTHERLY LOW-LEVEL JET. INCREASING INSTABILITY COUPLED WITH
STRENGTHENING DEEP LAYER SHEAR COULD CONTRIBUTE TO A RISK FOR LARGE
HAIL.
..KERR.. 03/18/2010
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