SWODY1
SPC AC 181637
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 AM CDT SUN MAR 18 2012
VALID 181630Z - 191200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTERNOON THROUGH
TONIGHT FROM W TX TO WRN KS...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON FOR PARTS OF ERN
INDIANA...NRN KY...AND SW OH...
...SYNOPSIS...
HIGHLY AMPLIFIED PATTERN WILL PERSIST OVER THE CONUS THROUGH
TOMORROW WITH A DEEP TROUGH OVER THE GREAT BASIN/ROCKIES AND A
DOWNSTREAM RIDGE JUST W OF THE APPALACHIANS. WITHIN THE BROADER
FLOW REGIME...AN EMBEDDED SPEED MAX OVER SE AZ THIS MORNING WILL
MOVE NNEWD TO THE CENTRAL/NRN HIGH PLAINS BY MONDAY MORNING...WHILE
THE PRIMARY TROUGH AXIS REMAINS JUST W OF THE FOUR CORNERS. AT THE
SURFACE...A BROAD WARM SECTOR COVERS THE MAJORITY OF THE CONUS E OF
THE ROCKIES. BOUNDARY LAYER DEWPOINTS OF 55-60 F HAVE SPREAD AS FAR
N AS THE MN/MB BORDER...AND AS FAR NE AS THE LOWER GREAT LAKES.
THIS MOISTURE...ALONG WITH AN EML PLUME OVER THE PLAINS...WILL
SUPPORT A LARGE REGION OF WEAK-MODERATE INSTABILITY FROM THE MS/OH
VALLEYS WWD INTO THE PLAINS THROUGH TONIGHT.
...SRN HIGH PLAINS LATE THIS AFTERNOON THROUGH TONIGHT...
REGIONAL 12Z SOUNDINGS CONTINUED TO SHOW BOUNDARY LAYER DEWPOINTS
AOA 60 F BENEATH A PLUME OF MIDLEVEL LAPSE RATES AOA 8 C/KM. A
PRONOUNCED CAP ACCOMPANIES THE EML FROM TX NWD ACROSS THE CENTRAL
PLAINS...WITH THE RICHEST MOISTURE AND RELATIVELY WEAKER CAP
EXPECTED THIS AFTERNOON ALONG THE TX/OK PORTION OF THE DRYLINE.
THUS...EXPECT CONVECTIVE INITIATION PRIMARILY NEAR AND S OF THE
KS/OK BORDER LATE THIS AFTERNOON/EVENING AS SURFACE TEMPERATURES
WARM TO 78-80 F IN A NARROW ZONE OF SURFACE HEATING BETWEEN BANDS OF
HIGH CLOUDS. FORCING FOR ASCENT WILL BE CONFINED TO THE DRYLINE
CIRCULATION THIS AFTERNOON SINCE THE MAJORITY OF THE LARGE SCALE
ASCENT WILL REMAIN FARTHER TO THE W. OF NOTE IS THE PERSISTENT
CONVECTIVE PRECIPITATION SIGNAL THIS AFTERNOON ALONG THE I-35
CORRIDOR IN TX...PER A MAJORITY OF SREF RSM AND ARW MEMBERS. SUCH
WIDESPREAD CONVECTION APPEARS UNLIKELY GIVEN THE CAP OBSERVED ACROSS
TX...AND COULD BE RELATED TO MIDLEVEL MOISTENING FROM ABOVE AND ITS
IMPACTS ON THE CONVECTIVE SCHEMES. EXPECT ANY WARM SECTOR
CONVECTION FROM CENTRAL TX NEWD INTO OK TO REMAIN RATHER ISOLATED
TODAY AND BASED ABOVE THE CAP...BUT WILL MAINTAIN LOW SEVERE
PROBABILITIES TO REFLECT THE SMALL CHANCE OF SURFACE-BASED
CONVECTION.
ISOLATED-WIDELY SCATTERED STORM DEVELOPMENT IS EXPECTED BY 22-00Z
ALONG THE DRYLINE FROM W TX NWD INTO THE ERN TX PANHANDLE. THE
STORM ENVIRONMENT WILL BE CHARACTERIZED BY MLCAPE VALUES OF
2000-2500 J/KG AND FAVORABLE DEEP-LAYER VERTICAL SHEAR FOR
SUPERCELLS...WITH VERY LARGE HAIL THE MAIN SEVERE CONCERN THIS
EVENING. ADDITIONALLY...SUFFICIENT LOW-LEVEL MOISTURE AND AN
INCREASE IN LOW-LEVEL SHEAR THROUGH THE EVENING WILL SUPPORT THE
RISK FOR A FEW TORNADOES...THOUGH THE WINDOW OF OPPORTUNITY COULD BE
JUST A FEW HOURS BEFORE CONVECTIVE INHIBITION INCREASES AND THE
DIURNAL STORMS WEAKEN. OVERNIGHT...THE PACIFIC COLD FRONT WILL
OVERTAKE THE DRYLINE AND MORE WIDESPREAD THUNDERSTORM DEVELOPMENT
WILL BE POSSIBLE DURING THE EARLY MORNING HOURS MONDAY. THIS
ACTIVITY WILL POSE A RISK FOR LARGE HAIL AND DAMAGING WINDS.
...ERN INDIANA/NRN KY/SW OH THIS AFTERNOON...
A REMNANT MIDLEVEL VORT MAX IS DRIFTING EWD OVER NE INDIANA AS OF
LATE MORNING. STRONG SURFACE HEATING AND SOME MOISTURE ADVECTION
WILL BOOST AFTERNOON MLCAPE VALUES TO 1000-1500 J/KG INVOF THE
SRN/SWRN FLANK OF THIS VORT MAX...WHERE ADDITIONAL THUNDERSTORM
DEVELOPMENT IS EXPECTED THIS AFTERNOON. THE COMBINATION OF MODERATE
INSTABILITY AND A BELT OF ENHANCED /AOA 30 KT/ WNWLY MIDLEVEL FLOW
COULD SUPPORT A FEW ORGANIZED MULTICELL CLUSTERS AND/OR MARGINAL
SUPERCELL STRUCTURES WITH AN ATTENDANT RISK FOR LARGE HAIL AND
DAMAGING WINDS.
..THOMPSON/LEITMAN.. 03/18/2012
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