Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 271743
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1243 PM CDT FRI MAR 27 2015

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

&&

.AVIATION...DRY AIR IN THE AREA WITH SURFACE RIDGE BUILDING
OVER DEEP SOUTH TEXAS WILL MAINTAIN LIGHT A NORTH WIND TODAY.
SURFACE HIGH WILL SHIFT TOWARDS THE EAST VEERING WINDS TO
THE SOUTHEAST INTO TOMORROW. THE GRADIENT WILL STRENGTHEN
INCREASING WINDS WITH DAYTIME HEATING. SOME GUSTS COULD BE
BETWEEN 20 TO 25 KNOTS WITH VFR CONDITIONS THROUGH THE NEXT
24 HOURS.

&&

.PREV DISCUSSION... /ISSUED 631 AM CDT FRI MAR 27 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...DRY SURFACE RIDGING BUILDING OVER DEEP SOUTH TX IN
THE WAKE OF THE FROPA YESTERDAY WILL MAINTAIN VFR CONDITIONS
THROUGHOUT THE NEXT 24 HOURS FOR ALL OF THE RGV AIRPORTS. IR SATL
SHOWS SOME PATCHY CIRRUS MOVING OVER THE AREA FROM THE WEST AND
SOUTH. THE SURFACE FLOW WILL START TO SHIFT AROUND FROM THE EAST
TO SOUTHEAST LATER THIS AFTERNOON.

PREV DISCUSSION... /ISSUED 347 AM CDT FRI MAR 27 2015/

SHORT TERM /NOW THROUGH SATURDAY/...500 MB AND SURFACE RIDGING WILL
BE BUILDING BACK IN OVER DEEP SOUTH TX IN THE WAKE OF THE FROPA
YESTERDAY. A FAIRLY DRY REGIME WILL REMAIN IN PLACE OVER THE RGV
THROUGH SAT WHICH WILL MAINTAIN ZERO POPS AND LIMITED CLD COVERAGE.
A FAIRLY LIGHT NORTHERLY SURFACE FLOW WILL PERSIST TODAY BUT THIS
FLOW WILL SHIFT AROUND FROM THE S-SE TONIGHT INTO SAT WHICH WILL
ALLOW THE WAA AND LOW LEVEL MOISTURE ADVECTION TO RETURN TOMORROW.
THIS WILL ALLOW THE TEMPS TO WARM UP PRETTY QUICKLY THROUGHOUT THE
SHORT TERM PERIOD. THE SHORT TERM TEMP GUIDANCE IS IN PRETTY GOOD
AGREEMENT THROUGH SAT. WILL GO WITH A GENERAL BLEND OF THE SHORT
TERM TEMP GUIDANCE LEANING TO THE WARMER SIDE OF GUIDANCE FOR
HIGHS.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... MID LEVEL RIDGING WILL
BE CLEARING THE AREA SATURDAY NIGHT INTO SUNDAY INCREASING CENTRAL
GULF OF MEXICO RIDGING IN THE LOWER LEVELS. THIS WILL SET THE STAGE
FOR WARM AND PLEASANT/DRY WEATHER SUNDAY AND MONDAY OF THIS WEEK
WITH HIGHS IN THE LOW TO MID 80S AND LOWS IN THE MIDDLE 60S.

TUESDAY A RIPPLE IN LARGELY ZONAL EAST TO WEST FLOW SLIDES ACROSS
SOUTH TEXAS. THE TROUGH GIVES US GOOD LARGE SCALE ASCENT AND I
SUSPECT 500MB TEMPERATURES MAY BE A LITTLE TOO WARM IN GFS/ECMWF
GUIDANCE. SURFACE MOISTURE IS A BIT LACKING WHEN THE SYSTEM ARRIVES
WITH SOME RESIDUAL TERRAIN INDUCED DRY/WARM AIR IN THE 700MB LAYER
BUT THERE SHOULD BE ENOUGH LOW LEVEL CONVERGENCE FOR AT LEAST A
CHANCE OF SHOWERS AND THUNDERSTORMS...WITH THE BEST CHANCES NORTH OF
THE VALLEY. FOR NOW CONTINUED WITH ROUGHLY 40 PCT POPS IN THE RGV
METRO AND ALONG THE RIVER AND 50S IN THE HBV/BKS AREA. 00Z GFS
APPEARS TO SUFFER FROM GRID SCALE FEEDBACK WITH VORT BOMBS
GENERATING SPURIOUS UPPER AIR ACTIVITY SO QPF WAS LARGELY
DISCOUNTED. ECMWF QPF SEEMS REASONABLE ENOUGH WITH SCATTERED TO
PERHAPS LOCALLY NUMEROUS SHOWERS AND STORMS BUT PRECIP OVERALL IS
DEFINITELY NOT A LOCK. WILL BE WORTH CONTINUING TO MONITOR AS THIS
ZONAL SHORT WAVELENGTH/PROGRESSIVE TROUGH IS A KNOWN SEVERE WEATHER
ANALOG FOR THE AREA ALTHOUGH THE CURRENT GLOBAL MODEL GUIDANCE IS
NOT ESPECIALLY IMPRESSIVE IN TERMS OF BOUNDARY LAYER INSTABILITY DUE
TO A LACK OF NEAR SURFACE MOISTURE WITH DEWPOINTS IN THE MID 60S.

ZONAL FLOW PERSISTS ALOFT BEHIND THE TROUGH WITH GENERAL RIDGINESS
OVER FLORIDA AND WEAK LEE TROUGHING OVER THE PLAINS THAT KEEPS A
PERSISTENT SOUTHERLY BREEZE OVER THE AREA THROUGH THE REMAINDER OF
THE PERIOD. HIGH TEMPERATURES STEADILY WARM UP ESPECIALLY BY FRIDAY
WHEN LOW LEVEL MOISTURE REACHES A RELATIVE MINIMUM. BEYOND THE RANGE
OF THE CURRENT FORECAST AF FAIRLY ROBUST COLD FRONT IS INDICATED IN
GFS/ECMWF GUIDANCE...SO WILL BE WORTH WATCHING THAT GOING FORWARD.
/68-JGG/

MARINE...NOW THROUGH SATURDAY...CURRENTLY BUOY020 REPORTS A NORTH
WIND AT 23G27KT WITH SEAS AT 7 FEET. THE STRONG NORTHERLY POST
FRONTAL SURFACE FLOW WILL LINGER THROUGH THE EARLY MORNING HOURS AND
WILL ACCORDINGLY MAINTAIN THE SCA THROUGH 7 AM. THE PGF WILL WEAKEN
THROUGHOUT THE REST OF THE MORNING HOURS ALLOWING THE WINDS AND SEAS
TO FALL BELOW SCA LEVELS. AFTER THE ROUGHER GULF CONDITIONS WEAKEN
THIS MORNING A LIGHT AND VARIABLE WIND FLOW WILL PREVAIL THROUGH
TONIGHT WITH THE SOUTHERLY SURFACE FLOW STARTING TO INCREASE BY
SATURDAY AFTERNOON AS THE SURFACE RIDGING SHIFTS EAST.

SATURDAY NIGHT THROUGH WEDNESDAY... STEADY MODERATE SOUTH TO
SOUTHEASTERLY WINDS ARE FORECAST SATURDAY NIGHT THROUGH WEDNESDAY
WITH MODERATE SEAS. WIND SPEEDS MAY REACH EXERCISE CAUTION LEVELS IN
THE AFTERNOON ON THE LAGUNA MADRE EACH DAY.

&&

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

$$

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