SPC AC 251943
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT SUN OCT 25 2009
VALID 252000Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SE OK...NORTH
TX AND THE TX HILL COUNTRY...
ONE CHANGE TO THE OUTLOOK FOR THE 20Z ISSUANCE IS TO DROP THE 5
PERCENT HAIL PROBABILITY OUT OF SE KS. THE THUNDERSTORMS NEAR THE
KS-MO STATE-LINE ARE MOVING AWAY FROM THIS AREA SUGGESTING THE
THREAT HAS ENDED THERE. ANOTHER CHANGE IS TO EXTEND THE THUNDER LINE
NEWD INTO WRN IL FOR THE CONVECTION IN NCNTRL MO WHICH SHOULD MOVE
INTO WRN IL LATE THIS AFTERNOON. FURTHER SOUTHWEST ACROSS THE SLIGHT
RISK AREA...CONDITIONS WILL BECOME INCREASINGLY FAVORABLE FOR SEVERE
STORMS AS MOISTURE ADVECTS NWD ACROSS CNTRL AND NORTH TX THIS
AFTERNOON. THE MODELS ARE IN AGREEMENT...INITIATING NUMEROUS STORMS
THIS EVENING FROM NEAR THE RED RIVER IN SE OK SSWWD INTO THE WRN TX
HILL COUNTRY. FORECAST SOUNDINGS AT 03Z ALONG THIS CORRIDOR SHOW
MUCAPE VALUES APPROACHING 2000 J/KG WITH STRONG DIRECTIONAL SHEAR IN
THE BOUNDARY LAYER AND 0-6 KM SHEAR VALUES OF 40-50 KT. THIS SHOULD
BE SUFFICIENT FOR SUPERCELLS. LARGE HAIL AND ISOLATED WIND DAMAGE
WILL BE POSSIBLE WITH THE MORE INTENSE STORMS. AS STORMS INCREASE IN
COVERAGE...THE MORE DOMINANT THREAT COULD BECOME WIND DAMAGE
ESPECIALLY IF A SQUALL-LINE DEVELOPS ACROSS CNTRL AND NORTH TX.
FURTHER SOUTH ACROSS THE MIDDLE TX COAST...WILL MAINTAIN LOW-END
PROBABILITIES FOR MARGINALLY SEVERE THUNDERSTORMS ONGOING ALONG THE
MOIST AXIS.
..BROYLES.. 10/25/2009
.PREV DISCUSSION... /ISSUED 1130 AM CDT SUN OCT 25 2009/
...SYNOPSIS...
A SERIES OF EMBEDDED SHORTWAVE TROUGHS WILL CONTINUE TO DIG SEWD
FROM THE NRN/CENTRAL ROCKIES TO THE CENTRAL/SRN HIGH PLAINS THROUGH
THE PERIOD...AS MID LEVEL RIDGING IS MAINTAINED OVER THE PACIFIC AND
ATLANTIC COASTS. THE AMPLIFYING PLAINS TROUGH IS ACCOMPANIED BY A
REINFORCING SURGE OF COOL CONTINENTAL AIR...WITH THE SURFACE FRONT
NOW LOCATED ALONG THE I-35 CORRIDOR IN KS AND I-44 IN OK. THIS
BOUNDARY WILL CONTINUE TO MOVE SEWD ACROSS OK/TX AS A REMNANT LEE
CYCLONE OVER NW TX DEVELOPS SWD TO THE DRT AREA. THIS FRONT WILL
SERVE AS THE PRIMARY FOCUS FOR THUNDERSTORM DEVELOPMENT THROUGH
TONIGHT.
...SRN PLAINS THROUGH TONIGHT...
BOUNDARY LAYER DEWPOINTS NEAR 70F ARE SPREADING NWD FROM S TX INTO
CENTRAL TX IN THE WAKE OF THE PREVIOUS FRONTAL INTRUSION. THIS
MOISTURE AND A PLUME OF 7 C/KM MID LEVEL LAPSE RATES WILL CONTRIBUTE
TO MLCAPE VALUES OF 1000-2000 J/KG. SOME INITIAL ELEVATED
CONVECTION HAS DEVELOPED ACROSS SE KS NEAR THE FRONT AND IN THE ZONE
OF MID LEVEL ASCENT IN ADVANCE OF THE AMPLIFYING MID LEVEL TROUGH.
HERE...ELEVATED INSTABILITY COULD BE SUFFICIENT FOR STORMS WITH
MARGINALLY SEVERE HAIL THIS AFTERNOON. FARTHER S AND LATER THIS
AFTERNOON/EVENING...THE INCREASING MOISTURE AND INSTABILITY OVER TX
WILL ENCOUNTER THE DEVELOPING BAND OF LOW-MID LEVEL ASCENT ALONG THE
FRONT...WHICH WILL PROMOTE THUNDERSTORM DEVELOPMENT IN THE 00-03Z
TIME FRAME FROM SE OK INTO N CENTRAL TX. THE SEWD MOTION OF THE
FRONT AND NE-SW ORIENTATION OF THE BOUNDARY SUGGESTS THAT CONVECTION
WILL TEND TO BECOME UNDERCUT BY THE COOL AIR RATHER EARLY IN THE
STORM EVOLUTION...LEAVING ONLY A NARROW WINDOW OF OPPORTUNITY FOR
SURFACE-BASED STORMS ALONG THE FRONT. OTHER STORMS COULD FORM
FARTHER S IN THE WARM SECTOR ACROSS S CENTRAL TX LATE THIS
AFTERNOON/EVENING...THOUGH THESE STORMS SHOULD REMAIN ISOLATED GIVEN
NO CLEAR FOCUS FOR INITIATION.
FORECAST HODOGRAPHS NEAR AND S OF THE FRONT THIS EVENING INTO
TONIGHT SHOW PROFILES WITH VEERING LOW-LEVEL WINDS AND MODEST
SRH...A PRONOUNCED WEAKNESS IN THE 700-500 MB LAYER FLOW...AND THEN
BACKING/STRENGTHENING FLOW ALOFT. THESE HODOGRAPH STRUCTURES MAY
SUPPORT SOME SUPERCELL STRUCTURES EARLY IN THE STORM EVOLUTION...BUT
A RATHER QUICK TRANSITION TO A MORE LINEAR/ANAFRONTAL CONVECTIVE
MODE IS EXPECTED BY EARLY TONIGHT. AS SUCH...IT APPEARS THAT LARGE
HAIL AND DAMAGING WINDS SHOULD BE THE MAIN SEVERE THREATS.
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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