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000
FXUS64 KBRO 150535
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1235 AM CDT WED MAY 15 2013

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

&&

.AVIATION...KBRO RADAR SHOWS MAINLY ISOLATED LIGHT RAIN SHOWERS
ACROSS THE VALLEY WITH MORE DEVELOPING UPSTREAM INTO NORTHERN
MEXICO AS ANOTHER PERTURBATION MOVES ACROSS THAT AREA. THERE ARE MVFR
LOW CLOUDS SNEAKING AROUND UNDERNEATH MID LEVEL DECK WITH HEIGHTS
AROUND 025. SHOWERS SHOULD CONTINUE TO DEVELOP AND MOVE ACROSS
THIS MORNING THEN ANOTHER SHOT OF SHOWERS WEDNESDAY AFTERNOON
BEFORE UPPER LEVEL LOW DEPARTS THE AREA. WINDS WILL INCREASE
TODAY AS LOW PRESSURE DEVELOPS OVER THE HIGH PLAINS WITH GUSTS TO
25 KNOTS POSSIBLE THROUGH THE DAY.

&&

.PREV DISCUSSION... /ISSUED 633 PM CDT TUE MAY 14 2013/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...DUAL CLOUDS DECKS CONTINUE ACROSS SOUTH TEXAS...WITH
LOWER DECK FROM 3000 TO 4000 FEET DRIFTING TO THE NW AND MIDLEVEL
DECK RACING OFF TO THE NE. CLOUD DECK WILL REMAIN THROUGH THE
NIGHT...WITH LOWER DECK SLOWLY LOWERING TO AROUND 2000 BY MORNING.
PROB30 RAIN CHANCES STARTING AT MIDNIGHT AS THE NEXT SYSTEM MOVES
INTO THE REGION...WITH SHOWERS ALREADY SHOWING UP ON RADAR TO THE
SW. OCCASIONAL RAINFALL WILL CONTINUE TOMORROW...MAINLY BEFORE
NOON. RAIN WILL REMAIN LIGHT...WITH ISOLATED LIGHTNING STRIKES
POSSIBLE.

PREV DISCUSSION... /ISSUED 155 PM CDT TUE MAY 14 2013/

SHORT TERM.../TONIGHT THROUGH WEDNESDAY NIGHT/...EVEN THOUGH THE
LATEST RUC13 MODEL RUNS CONTINUE TO SHOW SHOWERS DEVELOPING
ACROSS THE CWA THIS AFTERNOON...RADAR AND SATELLITE IMAGES INDICATE
NOT MUCH IN THE WAY OF RAIN DEVELOPING AS OF YET. SURFACE
INSTABILITY IS MARGINAL ACROSS THE RIO GRANDE VALLEY AND THE CLOUD
COVER MAY BE INHIBITING THE INSTABILITY. IN ADDITION...WATER VAPOR
SAT IMAGES AND NAM80 500MB VORTICITY ANALYSIS INDICATE NEGATIVE VORT
CENTER JUST TO THE WEST OF THE AREA. CURRENT FORECAST THINKING IS
THAT AS THE 500MB LOW ACROSS NORTHWEST MEXICO IS KICKED EASTWARD
WITH THE SHORTWAVE TROUGH MOVING INTO SOUTHERN CALIFORNIA...SHOWERS
AND THUNDERSTORMS WILL DEVELOP LATER THIS AFTERNOON INTO THIS
EVENING ACROSS THE MEXICAN PLATEAU AND MOVE EASTWARD INTO THE
WESTERN PORTIONS OF THE CWA TONIGHT INTO EARLY WEDNESDAY. WITH THAT
SAID...WILL ADJUST TIMING OF POPS TONIGHT INTO WED NIGHT AND KEEP AT
LEAST A CHANCE OF RAIN ACROSS MOST OF THE AREA THROUGH WED
AFTERNOON. RAIN CHANCES SHOULD DIMINISH WED AFTERNOON INTO WED
EVENING AS SUBSIDENCE WILL INCREASE ACROSS SOUTHWEST TX AS THE UPPER
LEVEL LOW MOVES ACROSS NORTHWEST TX WEDNESDAY.

LONG TERM.../THURSDAY THROUGH TUESDAY NIGHT/...
LOW PRESSURE SYSTEM OVER BAJA CA WILL QUICKLY MOVE ACROSS SOUTH
CENTRAL TEXAS WED INTO THU WITH SURFACE HIGH PRESSURE TO THE EAST
MOVING SOUTHWARD OVER THE GULF WATERS AS IT INTERACTS WITH THE LOW
PRESSURE OVER WEST TEXAS. AS THIS SYSTEM LIFTS TO THE NORTHEAST...
THE SURFACE WINDS WILL RETURN TO THE SOUTHEAST ACROSS SOUTH TEXAS
AND THE GRADIENT IN RETURN WILL STRENGTHEN. EXPECT BREEZE CONDITIONS
BETWEEN 20 TO 25 MPH THURSDAY AFTERNOON. MOST OF THE MOISTURE SEEN
IN THE LAST FEW DAYS WILL DROP DRAMATICALLY ACROSS THE AREA WITH THE
BUFF SOUNDING NEAR KBRO SHOWING THE INFILTRATION OF THE DRIER AIR IN
THE UPPER AND MID LEVEL OF THE ATMOSPHERE AND A DROP IN THE PWAT
VALUES TO 1.34 INCHES AND INTO 1.10 INCHES TOWARDS THE WEST. THE
DRIER AIR MASS FROM THE RIDGE BUILDING ACROSS THE WESTERN PLAINS
WILL SET UP THAT DRIER AND WARM PATTERN FOR MOST OF THE LONG TERM
FORECAST. HIGH TEMPERATURES THURSDAY THROUGH SUNDAY WILL BE WARM AND
HUMID REACHING THE MID TO UPPER 90S THROUGH THE WEEK. ANOTHER TROUGH
DIGS SOUTHWARD ALONG BAJA CALIFORNIA AND SWING NORTHEASTWARD INTO
THE CENTRAL PLAINS SATURDAY AND SUNDAY. THE MAIN IMPACT WITH THIS
SYSTEM FOR SOUTH TEXAS WILL BE THE SE WINDS AND THE ABUNDANT WARM
TEMPERATURES ACROSS THE CWA WITH NO CONVECTION AS THE SYSTEM REMAINS
NORTH OF THE CWA. EXPECT SURFACE GRADIENT TO INCREASE WITH BREEZE TO
CONDITIONS THIS WEEKEND.

NEXT WEEK...THE TROUGH WILL CONTINUE TO MOVE NORTHEAST AND STRENGTHEN
ITS SURFACE TROUGH OVER NORTH CENTRAL PLAINS. THIS WILL CONTINUE TO
KEEP THE AREA UNDER SOUTHEAST WINDS ACROSS THE CWA. BY TUESDAY...THE
HIGH PRESSURE ALOFT BUILDS FROM THE SOUTH AND A VERY WEAK GRADIENT
AT THE SURFACE RETURNS. LOW TEMPERATURES FOR MUCH OF THE LONG TERM
FORECAST REMAIN IN THE MID 70S ACROSS THE AREA.

MARINE...TONIGHT THROUGH WEDNESDAY NIGHT...SEAS WERE NEAR 4 FEET WITH
SOUTHEAST WINDS NEAR 10 KNOTS AT BUOY020 EARLY THIS AFTERNOON. WINDS
WILL INCREASE ACROSS THE COASTAL WATERS TONIGHT AS THE PRESSURE
GRADIENT INCREASES ACROSS THE WESTERN GULF OF MEXICO. MODERATE TO
STRONG SOUTHEAST WINDS WILL PREVAIL TONIGHT WITH SCEC CONDITIONS
LIKELY OFFSHORE. THE SCEC CONDITIONS WILL PERSIST WEDNESDAY INTO WED
NIGHT...ESPECIALLY OFFSHORE...AS THE PRESSURE GRADIENT REMAINS
STRONG ACROSS THE LOWER TEXAS COAST.

THURSDAY THROUGH TUESDAY...
THE UPPER LEVEL SYSTEM OVER THE BAJA CA WILL FINALLY BEGIN TO MOVE
NORTHEAST WEDNESDAY INTO THURSDAY LIMITING THE AREA OF ANY
CONVECTION. THE SURFACE HIGH PRESSURE OVER THE SOUTHEAST PLAINS WILL
BEGIN TO SHIFT SOUTH OVER THE GULF WATERS SHIFTING WINDS ACROSS THE
GULF TOWARDS THE SE. WINDS WILL INCREASE THURSDAY AFTERNOON WITH
POSSIBLE SCA FOR MUCH OF THE DAY AND EARLY EVENING AS WINDS INCREASE.
THIS SE FLOW WILL PREVAIL FOR MUCH OF THE LONG TERM FORECAST BUT WILL
WEAKEN BY NEXT WEEK. SEAS WILL BE BETWEEN 4 TO 5 FEET OVER THE GULF
WATERS AS THERE WILL BE A LONG DURATION FETCH OVER THE GULF. THE UPPER
AND LOWER FLOW WILL WEAKEN AND KEEP THE WAVE HEIGHT 5 FEET OR LESS.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

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