Severe Thunderstorm Warning 15, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
935 PM CDT MON MAY 1 2000

LOOKS LIKE AN OLD OUTFLOW BOUNDARY IN CONCERT WITH WEAK SFC TROF
MOVED IN FROM MEXICO INTO DEEP SOUTH TEXAS PROVIDED ISOLATED SEVERE
THUNDERSTORMS SOME WITH MODERATE TO STRONG ROTATION OVER THE MIDDLE
WEST PORTIONS OF DEEP SOUTH TEXAS. LOOKS LIKE THESE STORMS WILL BE
ON THE DECREASE AND WILL WEAKEN AS THEY DO HEAD NORTH IN AN HOUR OR
TWO.

ALTHOUGH THUNDERSTORMS WILL ABATE OVER DEEP SOUTH TEXAS IN A COUPLE
HOURS...THE GENESIS OF THUNDERSTORMS WILL AGAIN OCCUR OVER THE RIO GRANDE
VALLEY DURING THE OVERNIGHT HOURS AND EARLY TUESDAY. NEXT SHORT WAVE
TROUGH IS OVER EXTREME WEST TX PER WV LOOP AND THIS SHOULD BRING
ANOTHER ROUND OF CONVECTION THIS FAR SOUTH. THE ETA AT 12Z HAS GOOD
3H SPEED DIVERGENCE...STRONG PVA MIGRATING IN WITH MID LEVEL TROF...
GOOD 850-500 MB Q-VECTOR CONVERGENCE ALONG THIS FEATURE AND GOOD
UPWARD VERTICAL MOTION/OMEGA AND PRECIPITATION BETWEEN .50 AND .75
INCHES IN SOME SPOTS.

ETA INDICATES WE WILL GET COLD AIR ADVECTION FROM THE SFC TO 500 MB
WITH H8 TEMPS DROPPING FROM 20C TO 14 C BY TUESDAY MORNING. THIS
WILL EFFECTIVELY ERODE THE CAP AND STEEPEN LAPSE RATES. ETA
DEPICTION OF 12Z TUESDAY SOUNDING SHOWS CAPE OF 3128 J/KG OVER THE
LOWER VALLEY WITH 0-3 KM STORM RELATIVE HELICITY AT 204 M2/S2.
STILL ACCORDING TO THE HELICITY/CAPE SCATTER DIAGRAM FROM 8{8D
OPERATION COURSE...SOME THUNDERSTORMS COULD BE STRONG TO SEVERE WITH
THAT SOUNDING.

.WFO BRO INTERNET ADDRESS...
WWW.SRH.NOAA.GOV/BRO

SYNOPTIC...CORDERO (64)
MESO...JW (62)
HMT...VEGA

.BRO...NONE.

TXZ248>257-021600-

DEEP SOUTH TEXAS THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1148 PM CDT MON MAY 1 2000

THE NATIONAL WEATHER SERVICE IS MONITORING A POTENT UPPER LEVEL
STORM SYSTEM...MOVING ACROSS NORTH CENTRAL TEXAS. THIS SYSTEM WILL
AGAIN INCREASE THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS OVER DEEP
SOUTH TEXAS.  ANOTHER ROUND OF STORMS IS EXPECTED TO DEVELOP A FEW
HOURS BEFORE DAYBREAK THROUGH THE EARLY AFTERNOON HOURS TODAY...
AS THE UPPER LEVEL STORM SYSTEM TRACKS SOUTHWARD OVER THE LONE STAR
STATE.  ALTHOUGH THE MAIN THREAT WILL BE HEAVY RAIN...A FEW
THUNDERSTORMS MAY REACH SEVERE LIMITS WITH STRONG WINDS...HAIL AND
CONCEIVABLY ISOLATED TORNADOES.

SEVERE THUNDERSTORMS DID OCCUR OVER THE WEST-CENTRAL PART OF THE RIO
GRANDE VALLEY MONDAY EVENING. ALSO...A NORTH TO SOUTH SWATH OF 1 TO
2 INCHES OF RAINFALL FELL. THIS SWATH EXTENDED FROM RIO GRANDE CITY
TO LA GLORIA TO THE WESTERN PART OF BROOKS COUNTY. A RIO GRANDE CITY
WEATHER OBSERVER REPORTED 1.10 INCHES OF RAINFALL. IN ADDITION...A
FUNNEL CLOUD WAS REPORTED SOUTH OF LA GLORIA BY THE STARR COUNTY
SHERIFF MONDAY EVENING.

SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL IN DEEP SOUTH
TEXAS SHOULD BE ON THE ALERT FOR THE RE-DEVELOPMENT OF OMINOUS
WEATHER CONDITIONS. ALL RESIDENTS OF DEEP SOUTH TEXAS SHOULD KEEP
UPDATED ON THE WEATHER TUESDAY THROUGH LOCAL RADIO...TELEVISION...OR
CABLE SOURCES...AND NOAA WEATHER RADIO.

CORDERO