SWODY1
SPC AC 190537
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 PM CST SUN DEC 18 2011
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS CNTRL AND EAST TX...
...CNTRL AND EAST TX...
AN UPPER-LEVEL LOW IN SE AZ WILL MOVE QUICKLY EAST TO NEWD ACROSS
WEST TX TODAY. TO THE EAST OF THE SYSTEM...A 45 TO 60 KT LOW-LEVEL
JET WILL STRENGTHEN...RAPIDLY TRANSPORTING MOISTURE NWD INTO CNTRL
TX THIS AFTERNOON. SFC-BASED THUNDERSTORM DEVELOPMENT IS FORECAST
THIS AFTERNOON ALONG THE WRN EDGE OF THE MOIST AXIS WHERE A LINE OF
THUNDERSTORMS IS LIKELY TO ORGANIZE AND MOVE EWD ACROSS THE I-35
CORRIDOR FROM NEAR DALLAS/FORTH WORTH SWD TO NEAR BRIAN-COLLEGE
STATION. THIS LINE SHOULD PERSIST EWD ACROSS THE SLIGHT RISK AREA
EVENTUALLY AFFECTING THE HOUSTON AREA DURING THE EVENING.
AS THE UPPER-LEVEL LOW MOVES OUT INTO THE SRN PLAINS...A 65 TO 80 KT
MID-LEVEL JET IN THE BASE OF THE TROUGH WILL CREATE STRONG DEEP
LAYER SHEAR PROFILES ACROSS THE SLIGHT RISK AREA. FORECAST SOUNDINGS
ALONG THE I-35 CORRIDOR AT 00Z SHOW 0-6 KM SHEAR VALUES IN THE 55 TO
65 KT RANGE. IN ADDITION...SFC DEWPOINTS MAY REACH THE LOWER 60S F
AS FAR NORTH AS DALLAS WITH UPPER 60S F LOCATED ALONG THE MIDDLE TX
COAST WHERE MODERATE INSTABILITY IS FORECAST. THIS ENVIRONMENT
SHOULD SUPPORT SEVERE STORMS WITH THE GREATEST POTENTIAL ACROSS THE
NRN HALF OF THE SLIGHT RISK AREA WHERE THUNDERSTORM DEVELOPMENT IS
MOST CERTAIN. AS THUNDERSTORMS INITIATE...SUPERCELL DEVELOPMENT WILL
BE POSSIBLE ACROSS THE WRN PART OF THE SLIGHT RISK AREA WHILE THE
CONVECTION REMAINS DISCRETE. AS STORMS INCREASE IN COVERAGE AND A
LINE ORGANIZES...A WIND DAMAGE THREAT MAY DEVELOP WITH THE GREATEST
POTENTIAL ACROSS THE CNTRL AND ERN PART OF THE SLIGHT RISK AREA. THE
MAGNITUDE OF THE SEVERE THREAT SHOULD DEPEND ON UPON HOW MUCH
DESTABILIZATION TAKES PLACE IN CNTRL AND EAST TX THIS AFTERNOON.
ALTHOUGH THE SRN END OF THE LINE SHOULD AFFECT THE HOUSTON AREA THIS
EVENING...LARGE-SCALE ASCENT WILL BE QUITE WEAK IN SE TX SUGGESTING
THE SEVERE THREAT COULD BE MORE ISOLATED THERE.
...NW TX/SW OK...
SCATTERED THUNDERSTORMS SHOULD BE ONGOING ACROSS WEST AND NORTHWEST
TX AT DAYBREAK. THIS ACTIVITY SHOULD BE FOCUSED ALONG THE NWRN EDGE
OF THE LOW-LEVEL JET AND ALONG THE LEADING EDGE OF LARGE-SCALE
ASCENT ASSOCIATED WITH AN APPROACHING UPPER-LEVEL LOW. FORECAST
SOUNDINGS ACROSS WEST AND NORTHWEST TX THIS MORNING SHOW SOME CAPE
IN THE 700 TO 500 MB LAYER WITH INSTABILITY INCREASING AS THE
AIRMASS WARMS THIS AFTERNOON. THIS ALONG WITH STEEP MID-LEVEL LAPSE
RATES SHOULD BE ENOUGH FOR AN ISOLATED HAIL THREAT AS CONVECTION
INITIATES JUST AHEAD OF THE UPPER-LEVEL LOW. THE HAIL THREAT APPEARS
MOST LIKELY TO AFFECT NW TX AND SW OK AS STORMS MOVE NEWD ACROSS THE
REGION LATE THIS AFTERNOON. THE POTENTIAL FOR HAIL IS EXPECTED TO
REMAIN MARGINAL WITH A 5 PERCENT HAIL PROBABILITY SUFFICIENT TO
COVER THE THREAT.
..BROYLES/DEAN.. 12/19/2011
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