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000
FXUS64 KBRO 160519 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1219 AM CDT WED APR 16 2014

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

.AVIATION...VFR WILL CONTINUE THROUGH THE NEXT 24 HOURS WITH
SURFACE HIGH PRESSURE IN CONTROL. LIGHT WINDS OVERNIGHT WILL
VEER AND INCREASE TO MODERATE LEVELS TOMORROW BEFORE BEGINNING
TO DIMINISH IN THE EARLY EVENING HOURS.
&&

.PREV DISCUSSION... /ISSUED 719 PM CDT TUE APR 15 2014/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE A
FEW HIGH CLOUDS ACROSS THE SOUTHERN PORTIONS OF THE CWA EARLY THIS
EVENING. EXPECT VFR CONDITIONS TO PREVAIL ACROSS THE RIO GRANDE
VALLEY TONIGHT INTO WEDNESDAY AS HIGH PRESSURE ACROSS SOUTH TEXAS
CONTINUES TO PROVIDE SUBSIDENCE ACROSS THE AREA.

PREV DISCUSSION... /ISSUED 135 PM CDT TUE APR 15 2014/
SHORT TERM /NOW THROUGH WEDNESDAY NIGHT/...HIGH TEMPERATURES
MAINLY IN THE 60S TODAY WILL SINK INTO THE 40S TO NEAR 50 ACROSS
THE AREA TONIGHT...15 TO 20 DEGREES BELOW NORMAL. HIGH CIRRUS IS
LIKELY TO REMAIN IN PLAY ABOVE PORTIONS OF THE CWA AS THE
SUBTROPICAL JET ALOFT UNDULATES BETWEEN NORTH AND SOUTH. WINDS
WILL VEER SOUTHEAST ON WEDNESDAY AS HIGH PRESSURE CENTERED
OVERHEAD SHIFTS NORTHEAST AND BROAD MID LEVEL TROUGHING OVER THE
PLAINS SUPPORTS TRANSITING AREAS OF PRESSURE FALLS THERE. HIGH
TEMPS LOCALLY WILL RECOVER INTO THE 70S ON WEDNESDAY UNDER MOSTLY
SUNNY SKIES. VERY ISOLATED STREAMER SHOWERS WILL BE POSSIBLE
WEDNESDAY NIGHT IN RETURN FLOW...WITH LOW TEMPS REBOUNDING INTO
THE 60S.

LONG TERM /THURSDAY THROUGH TUESDAY/...
UPPER TROUGH WILL PASS NORTH AND EAST OF THE AREA THURSDAY MORNING
INTO THE AFTERNOON KEEPING THE REGION IN A SUBSIDENT UPPER LEVEL
PATTERN. LOW LEVEL MOISTURE WILL BE ADVECTING IN ON WEAK EAST AND
SOUTHEASTERLY LOW LAYER WINDS BUT TERRAIN AND SUBSIDENCE INDUCED
CAPPING SHOULD PREVENT MUCH IN THE WAY OF PRECIP DURING THE DAY.
TEMPERATURES WILL BE WARM BUT MODERATED A BIT BY CLOUD COVER AND
ONSHORE EASTERLY WINDS.

AMPLIFIED UPPER PATTERN EXHIBITS A VERY SHORT WAVELENGTH OF THE
PASSING TROUGH TO ANOTHER ONE APPROACHING FOR FRIDAY AND INCREASING
DIVERGENCE OVERNIGHT COUPLED WITH THE ATTENDANT INCREASE IN
SOUTHEASTERLY WINDS/WARM ADVECTION KEEPS A SLIGHT CHANCE OF SHOWERS
IN THE FORECAST THURSDAY NIGHT INTO FRIDAY MORNING. DEWPOINTS WILL
BE ON THE RISE AND HELP KEEP LOWS IN THE LOW TO MID 60S.

ON FRIDAY A TROUGH DEEPENS/AMPLIFIES OVER THE SOUTHWESTERN US WHILE
RIDGING INTENSIFIES OVER THE WESTERN GULF OF MEXICO. THIS PUTS US IN
A BROADLY DIVERGENT FLOW...WITH THE GFS SHOWING A WEAK 250/500MB
PERTURBATION RIDING ALONG THE SOUTHWESTERLY UPPER FLOW. IMPORTANTLY
THOUGH THE 700MB WINDS WEAKEN IN THE APEX OF THE UPPER RIDGE AND
WINDS FROM 850MB TO THE SURFACE BECOME MORE EASTERLY THAN SOUTHERLY.
THE WEAK UPPER ASCENT LIFTS RESIDUAL CAPPING AND WE GET A FAIRLY
FAVORABLE ENVIRONMENT FOR ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS. ORGANIZED LOW LEVEL CONVERGENCE IS LACKING BUT
MESOSCALE BOUNDARIES AND DAYTIME HEATING WOULD LIKELY BE ENOUGH TO
PRODUCE CONVECTION IF TEMPERATURES ARE NOT TOO LIMITED BY LOW CLOUD
COVER. CONTINUED 20-30 PCT POPS IN THE WESTERN HALF OF THE CWA INTO
THE EVENING WITH BOTH GFS/ECMWF GENERATING CONVECTION ON THE SIERRA
MADRE MOUNTAINS FRIDAY AFTERNOON WITH STEERING FLOW POINTED TOWARDS
OUR WESTERN ZONES.

AS THE SOUTHWESTERN US UPPER LOW APPROACHES OUR PRESSURE GRADIENT AT
850/700MB TIGHTENS AND TERRAIN INDUCED CAPPING INCREASES BY SATURDAY
MORNING. MORNING SHOWERS UNDER THE DEVELOPING INVERSION APPEAR
POSSIBLE AMID RICH MOISTURE TRANSPORT ON SOUTHEASTERLY WINDS BUT
WITH THE BEST UPPER LEVEL ASCENT REMAINING TO THE NORTH KEPT THE
FORECAST ON THE DRY SIDE...ONLY USING THUNDERSTORM WORDING IN THE
LATE AFTERNOON/EVENING IN ZAPATA/STARR COUNTY AND VICINITY WHERE
SIERRA MADRE INITIATED CONVECTION MAY TRACK BEFORE DISSIPATING. HIGH
TEMPERATURES LOOK TO WARM ABOUT 2 TO 4 DEGREES FROM FRIDAY TO
SATURDAY WITH LOWS PICKING UP IN TANDEM AMID INCREASING
DEWPOINTS/LOW MOISTURE.

SUNDAY WE HOLD ONTO THE FAIRLY RAPID WEST SOUTHWESTERLY 700MB FLOW
AND HOLD MID LEVEL CAPPING IN PLACE. GFS/ECMWF ALSO DEPICT DRIER AIR
MOVING INTO THE 850MB VICINITY FROM UNDER THE MID GULF RIDGE.
CONTINUED A GENERALLY WARM AND DRY FORECAST FOR THE AREA SAVE A
SLIGHT CHANCE OF THUNDER IN THE WESTERN ZONES ONCE AGAIN FOR SIERRA
MADRE INITIATED THUNDER.

PRETTY CONSIDERABLE DISAGREEMENT BETWEEN THE ECMWF AND GFS
DETERMINISTIC GUIDANCE REGARDING THE STRENGTH/POSITION AND
DISPOSITION OF A WESTERN US LOW ON MONDAY THE EVOLUTION OF WHICH
WOULD PLAY A ROLE IN OUR MONDAY/TUESDAY WEATHER BUT THERE IS PRETTY
GOOD AGREEMENT THAT AN UPPER TROUGH WILL BE CLEARING THE AREA WITH
OUR MID LEVEL WINDS BECOMING LIGHTER AND MORE ZONAL. EAST
SOUTHEASTERLY LOW AND MID LEVEL FLOW CONTINUES AND REINTRODUCED
MORNING SHOWER AND AFTERNOON THUNDERSTORM SLIGHT CHANCES ACROSS A
FAIR CHUNK OF THE CWA IN THIS REGIME. AGAIN LOW CONVERGENCE WILL BE
LACKING BUT WITH RICH BOUNDARY LAYER MOISTURE AND A GENERAL LACK OF
MID LEVEL CAPPING A FEW CELLS COULD POP. HELD ON TO A DRY FORECAST
ON TUESDAY WITH BOTH GFS/ECMWF DEPICTING ANOTHER PUNCH OF 850MB DRY
AIR BUT WITH DIFFERENCES IN THE UPPER AIR PATTERN GROWING LARGE THAT
SOLUTION IS LOW CONFIDENCE. /68-JGG/

MARINE...
NOW THROUGH WEDNESDAY NIGHT...MARINE CONDITIONS ARE IMPROVING AS
HIGH PRESSURE SPREADS OVER THE AREA. WINDS WILL VEER TO EAST TONIGHT
AND BECOME MODERATE SOUTHEAST ON WEDNESDAY AS ELEVATED WAVE HEIGHTS
DECREASE TO MODERATE. CONTINUED ADVISORY FLAGS NEAR SHORE UNTIL 00Z
AND OFFSHORE UNTIL 05Z WHILE WAVE HEIGHTS CONTINUE TO SETTLE DOWN.

THURSDAY THROUGH THROUGH SATURDAY...
RELATIVELY FAVORABLE MARINE CONDITIONS ARE FORECAST THURSDAY THROUGH
SATURDAY. MODERATE EAST WINDS MAY INCREASE TO NEAR EXERCISE CAUTION
LEVELS AS THEY SHIFT NORTHEAST ON FRIDAY BEFORE SHIFTING BACK TO THE
SOUTHEAST ON SATURDAY AND BECOMING MORE MODERATE. SEAS SHOULD REMAIN
GENERALLY MODERATE THROUGH THE WEEKEND.
&&

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

$$

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