DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171945
SWODY1
SPC AC 171943

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT SUN MAR 17 2013

VALID 172000Z - 181200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM FAR NERN TX INTO WRN TN
AND KY...

...TX PANHANDLE INTO ERN NM...
SHOWERS ALONG A STRONG COLD FRONT WILL CONTINUE TO PUSH EWD OUT OF
NM AND INTO TX WHERE HEATING PERSISTS. NEAR SEVERE WIND GUSTS WERE
MEASURED IN NM...SUGGESTING STRONG TO NEAR SEVERE WIND GUSTS MAY
OCCUR DOWNSTREAM. FOR MORE INFORMATION SEE MCD 271.

...ARKLATEX...
HIGH RESOLUTION MODELS GENERALLY AGREE WITH DEVELOPING ISOLATED
CONVECTION OVER EXTREME NERN TX OR SWRN AR IN THE 00-03Z TIME FRAME.
MEANWHILE...SURFACE OBSERVATIONS INDICATE COLD AIR HAS MOVED SWWD
THROUGH PBF. THIS HAS LEFT A RELATIVELY SMALL AREA FOR SURFACE BASED
THUNDERSTORMS AND ANY WIND OR TORNADO THREAT. AS A WEAK SURFACE LOW
DEVELOP NEWD ALONG THIS BOUNDARY THIS EVENING...A NARROW CORRIDOR OF
SEVERE WILL BE POSSIBLE. ONCE STORMS BECOME ELEVATED N OF THE
FRONT...ONLY MARGINAL HAIL WILL BE POSSIBLE.

..JEWELL.. 03/17/2013

.PREV DISCUSSION... /ISSUED 1129 AM CDT SUN MAR 17 2013/

...NERN TX INTO THE MID-SOUTH...
12Z UPPER AIR DATA AND WATER VAPOR IMAGERY SHOW A SHORT WAVE TROUGH
MOVING EWD INTO CENTRAL/SRN HIGH PLAINS...IN ADVANCE OF A STRONGER
TROUGH DIGGING INTO THE INTERMOUNTAIN REGION. THE PLAINS TROUGH IS
FORECAST TO TURN ENEWD TOWARD THE MID MS VALLEY THROUGH TONIGHT AND
SLOWLY WEAKEN AS THE MAJOR TROUGH PROGRESSES INTO THE NRN/CENTRAL
PLAINS BY THE END OF THE PERIOD. AT THE SURFACE...THE PRIMARY FRONT
EXTENDS FROM NEAR DRT NEWD INTO EXTREME SERN OK THEN EWD ACROSS
CENTRAL AR AND SRN TN. A WEAK LOW OVER CENTRAL TX IS FORECAST TO
MOVE NEWD ALONG THE FRONT TOWARD THE ARKLATEX BY THIS EVENING...THEN
CONTINUE MOVING NEWD TOWARD SERN MO/SRN IL BY 18/12Z.

BROAD SOUTHERLY LOW LEVEL WINDS HAVE DEVELOPED ACROSS THE
WRN/CENTRAL GULF COAST INTO SRN/ERN TX AND THE LOWER MS
VALLEY...RESULTING IN A GRADUAL INCREASE IN MOISTURE WITH SURFACE
DEW POINTS NOW IN THE LOW 60S AS FAR NORTH AS NERN TX/NWRN LA.
ALTHOUGH EXTENSIVE CLOUDS ARE EVIDENT IN VISIBLE SATELLITE
IMAGERY...OCCASIONAL BREAKS IN THE CLOUD COVER WILL PERMIT LOCALIZED
AREAS OF STRONGER DIABATIC HEATING THIS AFTERNOON WITH MLCAPE
REACHING NEAR 1000 J/KG FROM NERN TX INTO SRN AR.

12Z RAOBS AT FWD AND SHV SHOW A STRONG CAPPING INVERSION AROUND 800
MB WHICH WILL LIKELY INHIBIT SURFACE-BASED CONVECTION DEVELOPING IN
THE WARM SECTOR THROUGH MUCH OF THE AFTERNOON. HOWEVER...PERSISTENT
LARGE SCALE ASCENT COUPLED WITH LOW LEVEL CONVERGENCE NEAR THE
SURFACE LOW AND WARM FRONT AND MODEST HEATING IS EXPECTED TO
GRADUALLY WEAKEN THE CAP...WITH CONVECTION DEVELOPING LATE THIS
AFTERNOON AND EVENING FROM NERN TX INTO SWRN LA. STRONG DEEP LAYER
VERTICAL SHEAR WILL ENHANCE STORM ORGANIZATION AND INTENSITY WITH
POTENTIAL FOR ISOLATED SUPERCELLS TO DEVELOP. STRONG/SEVERE STORMS
ARE LIKELY TO SPREAD NEWD TONIGHT FROM NERN TX TOWARD THE MID-SOUTH
WITH A THREAT FOR LARGE HAIL...DAMAGING WINDS...AND POSSIBLY A FEW
TORNADOES. AS ACTIVITY MOVES FARTHER NEWD THROUGH THE OVERNIGHT
HOURS...THE STORMS ARE EXPECTED TO BECOME INCREASINGLY ROOTED ABOVE
THE BOUNDARY LAYER WITH NWD EXTENT AND HAIL WILL BECOME THE PRIMARY
THREAT TOWARD THE LOWER OH VALLEY.

...NORTH CENTRAL/NERN TX INTO SOUTH CENTRAL/SERN OK LATE TONIGHT...
THE NAM APPEARS TO SPURIOUSLY DEVELOP LARGE VALUES OF MUCAPE
EXCEEDING 2000 J/KG LATE TONIGHT OVER THIS REGION. EXAMINATION OF
NAM FORECAST SOUNDINGS INDICATE DEVELOPMENT OF WHAT APPEARS TO BE AN
UNREALISTIC SATURATED MOISTURE PROFILE TO THE INVERSION LEVEL.
ALTHOUGH THERE WILL BE A POSSIBILITY OF ADDITIONAL CONVECTION
DEVELOPING LATE TONIGHT IN ASSOCIATION WITH A DEVELOPING SURFACE LOW
ALONG THE TRAILING FRONT...MORE MODEST INSTABILITY IS EXPECTED WITH
ISOLATED STRONGER CELLS CAPABLE OF PRODUCING MARGINAL HAIL.

...TX PANHANDLE...
FORECAST MODEL GUIDANCE INDICATES ISOLATED TSTMS MAY DEVELOP OVER
THE TX PANHANDLE ALONG A LEE SFC TROUGH AS A WEAK UPPER IMPULSE
APPROACHES. DESPITE SCANT LOW-LEVEL MOISTURE...DEEP BOUNDARY LAYER
MIXING AND STEEP MID-LEVEL LAPSE RATES WILL BE SUFFICIENT TO YIELD
AROUND 100-300 J/KG OF MLCAPE. WITH APPROXIMATELY 30 KT OF 0-3 KM
AGL WLY FLOW...THE POTENTIAL FOR EVAPORATIVELY COOLED DOWNDRAFTS
EMANATING FROM HIGH-BASED TSTMS TO PRODUCE A FEW STRONG TO
MARGINALLY SVR WIND GUSTS CANNOT BE RULED OUT.

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