Area Forecast Discussion
Issued by NWS Brownsville, TX

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000
FXUS64 KBRO 210559
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1259 AM CDT THU MAY 21 2015

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

&&

.AVIATION...CIGS WILL BRIEFLY DROP TO AROUND 1500 OVERNIGHT...BUT
BREEZES WILL KEEP BREAKS IN THE LOWEST DECKS. DAYTIME CU FIELD
RETURNS EARLY TOMORROW AFTERNOON. WINDS WILL BE FROM THE SOUTHEAST
AROUND 10KTS OVERNIGHT...INCREASING TO AROUND 15 LATE TOMORROW
MORNING. SOME THUNDERSTORM ACTIVITY IS POSSIBLE LATE TOMORROW FOR
THE WESTERN VALLEY.

&&

.PREV DISCUSSION... /ISSUED 632 PM CDT WED MAY 20 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...DAYTIME CU FIELD BREAKING DOWN WITH LOSS OF PEAK
HEATING. BRIEF SCT THIS EVENING WILL RETURN TO BKN IN A COUPLE
HOURS. CIGS WILL BRIEFLY DROP TO AROUND 1500 OVERNIGHT...BUT
BREEZES WILL KEEP BREAKS IN THE LOWEST DECKS. DAYTIME CU FIELD
RETURNS EARLY TOMORROW AFTERNOON. WINDS WILL BE FROM THE
SOUTHEAST AROUND 10KTS OVERNIGHT...INCREASING TO AROUND 15 LATE
TOMORROW MORNING. SOME THUNDERSTORM ACTIVITY IS POSSIBLE LATE
TOMORROW FOR THE WESTERN VALLEY...BUT WILL NOT AFFECT KMFE IN THE
NEXT 24 HOURS.

PREV DISCUSSION... /ISSUED 338 PM CDT WED MAY 20 2015/

SHORT TERM /TONIGHT THROUGH THURS NIGHT/...WEAK 500 MB RIDGING
WILL PREVAIL OVER DEEP SOUTH TX THROUGHOUT MUCH OF THE SHORT TERM
PERIOD. HOWEVER A LITTLE FURTHER NORTH A SHORT WAVE WILL PUSH
THROUGH THE CENTRAL PORTION OF THE MIDWEST WHICH WILL PUSH A COLD
FRONT DOWN INTO CENTRAL TX LATER TONIGHT INTO THURS WHERE THE
FRONT WILL EVENTUALLY STALL TOMORROW AND TOMORROW NIGHT. IN
ADDITION TO THIS SURFACE FEATURE SOME SMALL POCKETS OF 500 MB PVA
WILL ADVECT OVER THE REGION WHICH WILL LIKELY ENHANCE UPPER LEVEL
DIVERGENCE FOR THURS AND THURS NIGHT. ALSO DAYTIME HEATING
TOMORROW WILL THEN HELP INCREASE THE SURFACE CONVERGENCE. THE
LATEST NAM FORECAST SOUNDINGS SHOW A PRETTY SIGNIFICANT INCREASE
OF PWATS AND CAPE VALUES ON THURS WHICH POINTS TOWARDS BETTER CONV
POTENTIAL.

THE NAM AND ECMWF MODELS ARE MORE BULLISH TOWARDS CONV TOMORROW
AND TOMORROW NIGHT WHILE THE GFS MAV NUMBERS COME IN MUCH DRIER
FOR DEEP SOUTH TX. SINCE THE MAV GUIDANCE IS THE OUTLIER WILL OPT
TO GO WITH A BLEND OF THE NAM AND ECMWF POPS WITH THE BEST
POTENTIAL LOCATED OVER THE NORTHERN AND WESTERN COUNTIES WHICH
WILL BE A LITTLE CLOSER TO THE FRONT.

SPC IS PLACING MUCH OF DEEP SOUTH TX IN THE MARGINAL SVR WX RISK
FOR THURS AFTERNOON AND EARLY EVENING. AT THIS TIME AM NOT
CONFIDENT ENOUGH TO INCLUDE A MENTION OF SVR CONV IN THE FORECAST.
WILL SEE HOW OVERALL CONDITIONS SET UP TOMORROW MORNING BEFORE
DECIDING WHETHER A MENTION OF SVR WX IS WARRANTED.

THE INCREASING CONV POTENTIAL MAY DECREASE THE AFTERNOON HIGH
TEMPS TOMORROW A BIT. WILL OPT FOR A GENERAL BLEND OF THE SHORT
TERM TEMP GUIDANCE FROM THE MAV/MET AND ECMWF FOR SHORT TERM TEMP
TRENDS.

LONG TERM /FRIDAY THROUGH TUESDAY/...H5 LOW WILL FROM SOUTHERN
CALIFORNIA FRIDAY NORTHEASTWARD AND BEGIN TO WEAKEN SATURDAY ACROSS
THE FOUR CORNERS SATURDAY THEN BECOME ABSORBED IN THE FLOW BY
MONDAY. ASSOCIATED TROUGH WILL MOVE ACROSS NORTHEASTERN MEXICO
SUNDAY THEN THROUGH OUR AREA MONDAY. H5 RIDGE AMPLIFIES ACROSS THE
SOUTHEASTERN CONUS EARLY NEXT WEEK WHILE WEAK TROUGHING DEVELOPS
ACROSS NORTHWESTERN MEXICO BY THE END OF THE PERIOD.

PREVIOUS SHIFT RAISED POPS THROUGH MUCH OF THE EXTENDED AND CONCUR.
THEREFORE...NO MAJOR CHANGES MADE TO THE LONG TERM. TIME HEIGHT AND
CROSS SECTIONS FOR THE LONG TERM SHOW A DEFINITE MOISTENING OF
THE LOW LEVELS AS COMPARED TO 24 HOURS AGO AND BELIEVE WE WILL
EXPERIENCE GOOD PRECIPITATION THROUGH TUESDAY. WPC 7 DAY QPF
AMOUNTS ARE INCREASING AND RIGHTFULLY SO WITH THE HIGHER AMOUNTS
IN THE RANCHLANDS. STRONG TSTORMS STILL POSSIBLE FRIDAY WITH
DECENT MID LEVEL SUPPORT AND A POSSIBLE MCS DEVELOPING THURSDAY
NIGHT TO OUR NORTHWEST AND MOVING INTO THE AREA FRIDAY. SPC
CONTINUES MARGINAL RISK FOR FRIDAY ACROSS MUCH OF THE AREA.

MARINE /TONIGHT THROUGH THURS NIGHT/...WILL ALLOW THE SCA FOR THE
LAGUNA MADRE TO EXPIRE AT 7 PM THIS EVENING AS THE PGF WILL START
WEAKENING AS SUNSET APPROACHES. AS THE FRONT PUSHES INTO CENTRAL
TX THROUGH TOMORROW EVENING EXPECT THE SURFACE GRADIENT TO WEAKEN
A BIT MORE WHICH WILL ALLOW FOR THE BAY WINDS AND SEAS TO SLACKEN
A BIT. SO DO NOT EXPECT SCA CONDITIONS FOR THE BAY AND GULF WATERS
THROUGH THURS NIGHT.

FRIDAY THROUGH SUNDAY...GENERALLY MODERATE SOUTHEAST WINDS
THROUGH FRIDAY NIGHT AND MODERATE SEAS. WINDS INCREASE SATURDAY AS
LOW PRESSURE STRENGTHENS ACROSS WEST TEXAS. SMALL CRAFT ADVISORIES
ARE POSSIBLE SATURDAY ACROSS THE LAGUNA MADRE AND SATURDAY NIGHT
ACROSS THE GULF WATERS. SUNDAY EXERCISE CAUTION CONDITIONS MAY EXIST
ON THE LAGUNA.

&&

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

$$

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