Severe Thunderstorm Warning 80, NWS Lubbock, TX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LUBBOCK TX
240 PM CDT SUN APR 30 2000

NEED TO RUSH DISCUSSION TODAY...SINCE OFFICE WILL MOST LIKELY GO
INTO SEVERE WEATHER MODE THIS AFTERNOON.

12Z ANALYSIS SHOWS A 500MB CLOSED UPPER LEVEL LOW OVER NORTHERN NM
WITH A 50KT JET MAX ROUNDING THE BASE OF THE TROUGH INTO WEST TX.
VERY STEEP LAPSE RATES WERE NOTED OVER WESTERN AND CENTRAL TX...AS
DELTA T'S (700MB TEMP-500MB TEMP) RANGED FROM 22 TO 24 DEGREES.  AT
850 MB DEW POINTS GREATER THAN TEN DEGREES EXTENDED FROM BRO
NORTHWEST TO AMARILLO TO OKLAHOMA CITY...OK...SOUTHEAST TO
GALVESTON...TX. THE DEEPER MOISTURE IS ALREADY IN PLACE EAST OF THE
850MB TROUGH.

THE 17Z SURFACE ANALYSIS SHOWS DENSITY CURRENT/BARRIER JET MOVING
SOUTH THROUGH EASTERN NM AND WESTERN TX PNHDL. A SURFACE LOW WAS
LOCATED JUST NORTH OF LUBBOCK. THE SURFACE DRYLINE EXTENDED
SOUTHEAST FROM THE THE TRIPLE POINT WEST OF AMARILLO TO JUST EAST OF
LUBBOCK SOUTHWARD BETWEEN MIDLAND AND SAN ANGELO. AN OUTFLOW
BOUNDARY EXTENDED ALONG THE RED RIVER VALLEY NORTHWEST ACROSS THE
NORTHEASTERN COUNTIES OF THE FORECAST AREA INTO THE CENTRAL TX
PANHANDLE WHERE IT INTERSECTED THE SURFACE DRYLINE.

ETA MODEL SHOWS THE UPPER LEVEL TROUGH MOVING EAST INTO THE N.W. TX
PNHDL BY THIS EVENING.  THE SURFACE LOW IS FORECASTED TO TRACK
SOUTHEAST TODAY AS DRYLINE PUSHES EAST OFF THE CAPROCK ESCARPMENT
THROUGH THE AFTERNOON HOURS. LOOKS AS IF INTERSECTION OF OUTFLOW
BOUNDARY AND DRYLINE WILL BE OVER THE EASTERN COUNTIES. ETA IS
FORECASTING MID 60 DEWPOINTS TO ADVECT TO THE NORTHWEST ALONG AND
NORTH OF THE OUT FLOW BOUNDARY.  SURFACE WINDS WILL BE BACKED ALONG
AND NORTH OF THE OUTFLOW BOUNDARY OVER PORTIONS OF NORTH TX/SOUTHWEST
OK AND THE EASTERN SECTION OF THE FORECAST AREA. THE VERTICAL WIND
SHEAR PROFILE WILL SUPPORT SUPERCELLULAR CONVECTION TO DEVELOP EAST
OF THE DRYLINE AND ALONG AND NORTH OF THE OUTFLOW BOUNDARY THIS
AFTERNOON. ATMOSPHERE IS QUITE UNSTABLE GIVEN STEEP LAPSE
RATES...MID 60S DEWPOINTS...LOW TO MID 80 TEMPERATURES AND -15
DEGREES AT 500MB.  I ESTIMATED CAPES TO BE AT OR ABOVE 3000 J/KG
WHICH WILL SUPPORT INTENSE UPDRAFT.  THE PRIMARY THREAT WITH THESE
SUPERCELL THUNDERSTORMS WILL BE LARGE HAIL...HOWEVER ALONG AND NORTH
OF THE OUTFLOW BOUNDARY WHERE SURFACE WINDS ARE BACKED AND LOWER
TEMPERATURE/DEWPOINT TEMPERATURE DEPRESSIONS WILL EXIST A FEW
TORNADOES MAY BE POSSIBLE. DURING THE LATE EVENING HOURS THE
ISOLATED THUNDERSTORMS WILL PROBABLY MERGE INTO A COMPLEX OF STORMS
AND MOVE EAST OUT OF THE FORECAST AREA.

TONIGHT THE COLD FRONT WILL MOVE SOUTHWARD ACROSS THE REGION.  THERE
MAY BE SOME WEAK ISENTROPIC LIFT OVER EASTERN SECTION OF THE
FORECAST AREA...OVER THE WESTERN HALF OF THE FORECAST AREA THE COLD
AIR ADVECTION WILL BE TOO INTENSE FOR MUCH PRECIPITATION...BUT I
WILL GO WITH A SLIGHT CHANCE IN CASE OF DRIZZLE OR LIGHT SHOWERS.

ON MONDAY THE ETA MODEL SHOWS THE UPPER LOW MOVING RIGHT OVER THE
REGION...SO WITH COLDER AIR ALOFT ALONG ENOUGH RESIDUAL MOISTURE...
THERE MAY BE A CHANCE OF SHOWERS AND THUNDERSTORMS DEVELOPING DURING
THE AFTERNOON HOURS.

EXTENDED OUTLOOK...BOTH THE CANADIAN AND MRF MODELS CONTINUE TO SHOW
THE UPPER LOW OVER THE REGION...SO I WILL CONTINUE THE CHANCES OF
AFTERNOON SHOWERS AND THUNDERSTORMS ON TUESDAY AFTERNOON.  CANADIAN
AND ECMWF SHOW UPPER LOW SLOWLY MOVING TOWARDS SOUTHEAST TX AND A
SOUTHERN STREAM RIDGE BUILDING OVER THE REGION TOWARDS THE END OF
THE WEEK.  EXPECT DRY CONDITIONS AND WARMER TEMPERATURES FROM
WEDNESDAY THROUGH FRIDAY.

I WILL ISSUE A FLASH FLOOD WATCH TONIGHT OVER THE NORTHEAST FOUR
COUNTIES OF THE CWFA. THIS IS DUE TO REPEATED HEAVY RAINFALL LAST
NIGHT AND TROUGH THE MORNING HOURS OVER COTTLE AND CHILDRESS
COUNTIES....WHERE STORM TOTALS HAVE BEEN NEARLY 5 INCHES.  THE
POTENTIAL EXIST FOR WIDE SPREAD HEAVY RAINFALL THIS AFTERNOON AND
THROUGH THE EVENING HOURS. THE WATCH WILL BE IN EFFECT UNTIL THE
NEXT ZONE ISSUANCE AT 430 AM.

FRIONA     45/62/42/70 22-2        BROWNFIELD  47/67/45/74 22-2
TULIA      45/63/43/72 33-3        LUBBOCK     47/66/45/74 22-2
CHILDRESS  50/67/47/70 63-3        ASPERMONT   53/72/50/74 53-3

.LBB...

TORNADO WATCH UNTIL 8PM CDT TXZ 025-026>031-032>037-038>043-044

FLASH FLOOD WATCH UNTIL 430AM CDT TXZ 025-026>031-032

TXZ025-026-031-032-037-038-043-044-302350-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LUBBOCK TX
620 PM CDT SUN APR 30 2000

THE TORNADO WATCH IN EFFECT UNTIL 8 PM THIS EVENING HAS BEEN CANCELED
FOR THE FOLLOWING COUNTIES...

HALL...CHILDRESS...MOTLEY...COTTLE...DICKENS...KING...KENT AND
STONEWALL

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

VALDEZ