Severe Thunderstorm Warning 55, NWS Brownsville, TX

DEEP SOUTH TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
310 PM CDT SUN JUL 1 2001

OVERALL...IT LOOKS AS IF MOST AREAS IN DEEP SOUTH TEXAS WILL HAVE A
DECENT CHANCE OF SEEING RAIN AT SOME POINT THROUGH THE MIDDLE OF THE
WEEK.  MID-AFTERNOON WATER VAPOR SATELLITE IMAGERY SHOWS A STRONG
UPPER LOW MOVING ACROSS THE GREAT LAKES AND INTO THE NORTHEAST U.S.
WITH A LARGE UPPER RIDGE OVER THE SOUTHWEST.  THIS FLOW PATTERN IS
FORCING THE UPPER-LEVEL WAVE OVER SOUTHERN ARKANSAS TO BECOME MORE
ELONGATED.  THIS FEATURE WILL EVENTUALLY MERGE WITH THE UPPER TROUGH
OVER THE WESTERN GULF OF MEXICO.  01/12Z RUNS OF THE ETA AND MESOETA
SHOW A POCKET OF COLDER 500 MB TEMPERATURES LOCATED IMMEDIATELY OVER
THE VALLEY ON MONDAY...WHICH WILL HELP TO MAINTAIN OR EVEN INCREASE
CURRENT INSTABILITY VALUES.  LOW AND MID LEVEL MOISTURE SHOULD BE
PLENTIFUL...AS PRECIPITABLE WATER VALUES (CURRENTLY AT 1.70 IN ON
12Z KBRO RAOB) ARE PROGGED BY THE ETA TO INCREASE WITH TIME...AND
PEAK LATE TUESDAY EVENING NEAR 1.95 INCHES.  MOISTURE WILL ALSO BE
ADVECTED INLAND FROM THE GULF...AS LOW LEVEL SOUTHEAST FLOW BACKS TO
THE EAST WITH TIME IN RESPONSE TO A WEAK SURFACE HIGH MOVING SOUTH
DOWN THE TEXAS COAST.  FORCING FOR UPWARD VERTICAL MOTION...IN THE
FORM OF POSITIVE VORTICITY ADVECTION ON WESTERN SIDE OF 500 MB
INVERTED TROUGH...SHOULD BE PRESENT PERIODICALLY THROUGHOUT THE
SHORT-TERM PERIOD.  AT THIS TIME...UPPER LEVEL FORCING APPEARS TO BE
STRONGEST ON MONDAY NIGHT/TUESDAY MORNING...WHICH WOULD NORMALLY
TEND TO BE AT A TIME OF HIGH STATIC STABILITY.  THE ONLY INHIBITING
FACTOR MAY BE AVAILABILITY OF LOW-LEVEL FORCING...BUT SEA-BREEZE
BOUNDARY WILL MOST LIKELY BE SUFFICIENT.  WILL GENERALLY TREND POPS
TOWARD 40 DURING THE DAYS AND 30 DURING THE NIGHTS FOR ALL
AREAS...WITH THE EXCEPTION OF 40 POPS FOR MONDAY NIGHT.

LATEST RUN OF THE AVN MODEL CONTINUES TO ADVERTISE PERIODIC CHANCES
OF PRECIPITATION THROUGH THE END OF THE WEEK...AS UPPER LEVEL
TROFFING REMAINS IN THE VICINITY OF DEEP SOUTH TEXAS.
HOWEVER...UPPER LEVEL TROUGH AXIS (AND HIGHEST PRECIPITATION
CHANCES) WILL SHIFT WEST WITH TIME...AS TROUGH RETROGRADES AROUND THE
SOUTHERN PERIPHERY OF WESTERN U.S. UPPER RIDGE.  BY FRIDAY...UPPER
RIDGE WILL BE CLOSE ENOUGH TO AREA TO SAFELY GO WITH A DRY
FORECAST.

MARINE...CURRENT OBS FORM BUOY020 INDICATE GENERALLY EAST WIND NEAR
10 KNOTS...PRODUCING 3-4 FOOT SEAS.  SHOWERS AND THUNDERSTORMS WILL
BE POSSIBLE THROUGH THE END OF THE WEEK.  LOCALLY HIGHER WIND GUSTS
AND SEAS WILL BE POSSIBLE AROUND THUNDERSTORMS...ALTHOUGH SCA IS NOT
ANTICIPATED.  SOUTHEAST WINDS WILL BACK TO THE EAST BY LATE
MONDAY...AS HIGH PRESSURE BUILDS SOUTH TOWARD THE AREA.

PRELIMINARY NUMBERS:
BRO EE 077/090 076/089 076 34443
HRL EE 076/091 075/090 075 34443
MFE EE 077/092 076/091 076 34443
RGC EE 076/094 075/093 075 34443
SPI EE 079/085 078/085 078 34443

SYNOPTIC...DD (65) / AVIATION-MARINE...SC (64) / MESO...SM

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

.BRO...NONE.