Flash Flood and Hail in Texas, September 20, 2001

SOUTH PLAINS AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LUBBOCK TX
200 PM CDT THU SEP 20 2001

AN MCS LOOKING MORE PROBABLE LATE TODAY AND TONIGHT OVER THE EASTERN
COUNTIES. HIGH DEWPOINTS HAVE POOLED ACROSS THE ROLLING PLAINS NORTH
INTO THE SOUTHEASTERN PANHANDLE. THIS COMBINED WITH COLD
TEMPERATURES ALOFT HAS RESULTED IN HIGH INSTABILITY ACROSS THE AREA
TODAY WITH CAPES AS HIGH AS 3500 J/KG. SURFACE TROUGH OF LOW
PRESSURE NOTED FROM THE CENTRAL OK PANHANDLE SOUTHWEST INTO
SOUTHEASTERN NM. SHORTWAVE NOTED ON WV IMAGERY MOVING INTO SW NM.
THIS WAVE COMBINED WITH A WEAK WAVE INTO COLORADO WILL COMBINE TO
PRODUCE INCREASING SYNOPTIC SCALE MOTION AND FURTHER STEEPEN LAPSE
RATES LATE TODAY. THUNDERSTORMS COULD DEVELOP ALMOST ANYWHERE IN CWA
BUT INITIAL GUESS IS THAT THEY WILL BE FOCUSED ALONG SURFACE TROUGH
NORTHWEST...PERHAPS ISOLATED TO WIDELY SCATTERED...WITH BETTER
COVERAGE OVER THE EAST WHERE INSTABILITY WILL BE MAXIMIZED LATER
THIS EVENING AS BOUNDARY FORCING INCREASES BENEATH INCREASING
VERTICAL MOTION FIELD ALOFT. MID LEVEL FLOW LOOKS WEAK TO SUPPORT
SUSTAINED SUPERCELLS...BUT STRONG MULTICELL STORMS WITH HAIL AND
GUSTY WINDS LOOKS LIKELY..AGAIN MORE NUMEROUS EAST.

THIS ACTIVITY SHOULD MOVE EAST INITIALLY...AND THEN BEGIN TO
PROPAGATE SOUTHEAST AND SOUTH AS MESOSCALE COMPLEX DEVELOPS OVER THE
EASTERN PANHANDLE/WESTERN OK AND PERHAPS INTO THE ROLLING PLAINS
TONIGHT. SYSTEM WILL FEED ON 20 TO 30 KNOT SOUTHERLY 850 MB JET.
WITH VERY HIGH PRECIPITABLE WATER VALUES...LOCALLY HEAVY RAIN WILL
BE POSSIBLE.

THIS SYSTEM LOOKS AS IT WILL PROPAGATE SOUTHEAST TOWARD THE BIG
COUNTRY TOWARD MORNING...WITH OUTFLOW BOUNDARY/FRONT BRIDGING
SOUTHWARD INTO CENTRAL AND SOUTHWEST TEXAS WITH EASTERLY BOUNDARY
FLOW OVER THE SOUTH PLAINS FOR SATURDAY. AIRMASS SAT OVER THE
EASTERN ZONES WILL DRY CONSIDERABLY ON SATURDAY WITH HIGH CENTERED
OVER NW OK. COULD SEE ADDITIONAL DEVELOPMENT OVER THE WESTERN
COUNTIES INTO EASTERN NM WITH UPSLOPE FLOW AND STILL FAIRLY HIGH
DEWPOINTS NORTH OF THE BOUNDARY. WITH NW FLOW ALOFT...SOME OF THESE
STORMS MAY MOVE INTO THE SOUTH PLAINS SO WILL MAINTAIN CHANCE POPS
SAT AND SAT NIGHT.

STRONG STORM COMING ASHORE ALONG THE PACIFIC NORTHWEST COAST LATE
SATURDAY WILL RESULT IN SHARPLY AMPLIFYING UPPER PATTERN OVER THE
CONUS SUNDAY. TROUGH MOVING THROUGH THE MIDWEST WILL PUSH FRONT
ACROSS THE AREA ON SUNDAY WILL COOLER TEMPS AND A CHANCE OF
SHOWERS/THUNDERSTORMS. BLOCKING HIGH PRESSURE PATTERN TOWARD MID
WEEK...WITH MAIN WESTERLIES HAVING RETREATED NORTHWARD ALONG
CANADIAN BORDER. STILL LOOKS COOLER THAN NORMAL WITH SLIGHT CHANCE
OF RAIN THROUGH EXTENDED. PRELIM NUMBERS FOLLOW.

FRIONA     59/82/58/83   4433   TULIA       60/83/59/84   5333
CHILDRESS  65/85/63/87   7432   BROWNFIELD  63/85/61/87   4433
LUBBOCK    62/84/60/86   5433   ASPERMONT   68/87/65/88   6533

.LUB...NONE.

JAMES

TXZ021>044-202300-

AREA THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE LUBBOCK TX
1135 AM CDT THU SEP 20 2001

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS ALL OF THE
SOUTH PLAINS...EXTREME SOUTHERN PANHANDLE AND ROLLING PLAINS THIS
AFTERNOON AND TONIGHT. THE BEST CHANCE FOR SEVERE THUNDERSTORM
DEVELOPMENT IS GENERALLY ALONG AND EAST OF A LINE FROM TULIA TO
SHALLOWATER TO ODONNELL...INCLUDING THE CITY OF LUBBOCK. ALTHOUGH
THE BETTER THUNDERSTORM CHANCES WILL REMAIN ACROSS THE CENTRAL SOUTH
PLAINS...SOUTHEAST TEXAS PANHANDLE AND THE ROLLING PLAINS...AN
ISOLATED SEVERE THUNDERSTORM IS POSSIBLE FOR AREAS WELL WEST OF
LUBBOCK TO THE NEW MEXICO BORDER.

A STRONG UPPER LEVEL DISTURBANCE MOVING ACROSS SOUTHWEST NEW MEXICO
LATE THIS MORNING WILL MOVE RAPIDLY EAST AND ENTER THE SOUTH PLAINS
REGION LATER THIS EVENING. AHEAD OF THIS SYSTEM THE ATMOSPHERE
ACROSS THE SOUTH PLAINS WILL BECOME INCREASING UNSTABLE WHILE A
SURFACE TROUGH OF LOW PRESSURE MOVES SOUTHEAST INTO THE AREA. THE
COMBINATION OF THIS TROUGH...A MOIST AND UNSTABLE ATMOSPHERE AND
THE APPROACH OF THE UPPER LEVEL DISTURBANCE WILL FAVOR THE
DEVELOPMENT OF SCATTERED THUNDERSTORMS BY LATE AFTERNOON. A FEW OF
THE STORMS WILL HAVE TO POTENTIAL TO BECOME RAPIDLY SEVERE WITH
LARGE HAIL AND DAMAGING WINDS BEING THE MAIN THREATS. THERE IS
ALSO A POTENTIAL FOR LOCALLY HEAVY RAINFALL WHICH COULD PRODUCE
AREAS OF FLASH FLOODING.

LAW ENFORCEMENT AGENCIES...EMERGENCY MANAGEMENT OFFICIALS AND SPOTTER
GROUPS SHOULD MONITOR THE LATEST WEATHER CONDITIONS AND BE PREPARED
FOR POSSIBLE ACTIVATION.

STAY TUNED TO NOAA WEATHER RADIO...TV OR YOUR LOCAL NEWS SOURCE FOR
THE LATEST WEATHER INFORMATION FROM THE NATIONAL WEATHER SERVICE.

ST