150
FXUS64 KBRO 211835
AFDBRO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
135 PM CDT THU MAY 21 2026
..NEW DISCUSSION, AVIATION, MARINE
KEY MESSAGES
UPDATED AT 118 PM CDT THU MAY 21 2026
KEY MESSAGES:
- HEAVY RAINFALL WITH THE POTENTIAL FOR FLASH FLOODING WILL BE A
CONCERN THROUGH THE WEEKEND. A FLOOD WATCH IS IN EFFECT THROUGH
MONDAY MORNING.
- ANOTHER ROUND OF SEVERE WEATHER IS POSSIBLE THIS EVENING AND
OVERNIGHT. THE STORM PREDICTION CENTER HAS ZAPATA AND WESTERN
PORTIONS OF JIM HOGG COUNTIES UNDER A MARGINAL RISK (LEVEL 1 OF
5) FOR SEVERE WEATHER. THE PRIMARY HAZARDS ARE DAMAGING WIND
AND LARGE HAIL.
- DAILY RAIN CHANCES ARE FORECAST TO CONTINUE INTO NEXT WEEK,
WITH THE HIGHEST PROBABILITIES FOR RAIN FORECAST TO OCCUR
SATURDAY AND SUNDAY.
DISCUSSION
ISSUED AT 118 PM CDT THU MAY 21 2026
AN UPPER LEVEL TROUGH LOOKS TO REMAIN SITUATED ACROSS THE WESTERN
US, RUNNING ALONG THE ROCKIES INTO NORTHERN MEXICO. A SERIES OF
EMBEDDED SHORTWAVES WILL ROTATE THROUGH THE SOUTHERN PERIPHERY OF
THE TROUGH, AMPLIFYING FORCING ACROSS DEEP SOUTH TEXAS THROUGH THE
WEEKEND. THE STRONGEST OF THESE SHORTWAVES, PAIRED WITH A 250 MB
JET STREAK WILL LIKELY LEAD TO STRONG UPPER LEVEL DIVERGENCE AND
INCREASED SYNOPTIC FORCING OVER DEEP SOUTH TEXAS SATURDAY.
AT THE SURFACE, A STALLED FRONTAL BOUNDARY ACROSS CENTRAL TEXAS
WILL LIKELY REMAIN STATIONARY THROUGH FRIDAY BEFORE RETREATING TO
THE NORTH GOING INTO THE WEEKEND. EASTERLY TO SOUTHEASTERLY
SURFACE FLOW ACROSS DEEP SOUTH TEXAS WILL CONTINUE TO ADVECT
ADDITIONAL MOISTURE INTO THE REGION. PWAT VALUES ARE FORECAST TO
PEAK ON SATURDAY, GENERALLY RANGING FORM 2 - 2.3 INCHES SATURDAY
AFTERNOON AND LIKELY EXCEEDING THE 90TH PERCENTILE.
THESE FACTORS WILL LIKELY SUPPORT MULTIPLE ROUNDS OF SHOWERS AND
THUNDERSTORMS THROUGH EARLY NEXT WEEK. A FLOOD WATCH IS IN EFFECT
FOR ALL OF DEEP SOUTH TEXAS THROUGH MONDAY MORNING. ANOTHER ROUND
OF CONVECTION IS POSSIBLE THIS EVENING AND OVERNIGHT, HOWEVER THE
LATEST CAMS SUGGEST THE CONVECTION MAY DISSIPATE AS IT MOVES
THROUGH THE WESTERN TO CENTRAL PORTIONS OF THE CWA. FLOODING WILL
LIKELY BE A CONCERN THIS EVENING FOR PORTIONS OF ZAPATA, STARR,
AND JIM HOGG COUNTIES THAT RECEIVED 3-4 INCHES OF RAIN WITH THE
STORMS THIS MORNING. ADDITIONALLY, SOME OF THESE THUNDERSTORMS
COULD BECOME STRONG TO SEVERE, WITH DAMAGING WIND OR LARGE HAIL
POSSIBLE. THE STORM PREDICTION CENTER HAS ZAPATA AND WESTERN
PORTIONS OF JIM HOGG COUNTIES UNDER A MARGINAL RISK FOR SEVER
WEATHER THIS EVENING. RAIN CHANCES FRIDAY AFTERNOON WILL LIKELY
BE LIMITED TO THE EASTERN HALF OF THE CWA, AND LIMITED TO AROUND
20-30%.
THE COMBINATION OF SYNOPTIC FORCING AND ELEVATED MOISTURE VALUES
WILL LIKELY SUPPORT WIDESPREAD SHOWERS AND THUNDERSTORMS SATURDAY.
NEARLY ALL OF DEEP SOUTH TEXAS IS UNDER A SLIGHT RISK FOR
EXCESSIVE RAINFALL (LEVEL 2 OF 4), EXCEPT FOR WESTERN PORTIONS OF
STARR AND ZAPATA COUNTIES WHICH REMAIN UNDER A MARGINAL RISK
(LEVEL 1 OF 4).
RAIN CHANCES WILL CONTINUE SUNDAY AND MONDAY AS THE SOUTHERN
PORTION OF THE TROUGH SLOWLY MOVES ACROSS THE STATE OF TEXAS. RAIN
CHANCES MAY BRIEFLY DECREASE MONDAY NIGHT INTO TUESDAY, BEFORE THE
NEXT TROUGH MOVES INTO THE THE SOUTHWEST MID WEEK BRINGING
ADDITIONAL RAIN CHANCES TO THE AREA.
AVIATION
(18Z TAFS)
ISSUED AT 118 PM CDT THU MAY 21 2026
VFR CONDITIONS ARE FORECAST TO CONTINUE THROUGH THE AFTERNOON,
WITH MVFR CONDITIONS LIKELY RETURNING THIS EVENING. THERE IS A LOW
PROBABILITY FOR SHOWERS AND THUNDERSTORMS TO DEVELOP OVERNIGHT,
HOWEVER THE LATEST HIRES GUIDANCE HAS THESE STORMS DISSIPATING
BEFORE MAKING IT TO ANY OF THE TAF SITES. AS SUCH, THE PROBABILITY
FOR ANY THUNDERSTORMS ARE TOO LOW TO INCLUDE IN THE TAFS.
MARINE
ISSUED AT 118 PM CDT THU MAY 21 2026
GENERALLY FAVORABLE WINDS AND SEAS ARE FORECAST TO CONTINUE
THROUGH THE PERIOD, HOWEVER SHOWERS AND THUNDERSTORMS WILL BE
POSSIBLE DAILY, WITH THE HIGHEST PROBABILITIES FOR STORMS AROUND
60-70% OVER THE WEEKEND. HEAVY RAINFALL, FREQUENT LIGHTNING, AND
STRONG WINDS WILL BE POSSIBLE WITH ANY THUNDERSTORMS THAT DEVELOP
OR MOVE OVER THE WATER.
PRELIMINARY POINT TEMPS/POPS
BROWNSVILLE 77 91 78 91 / 20 20 20 50
HARLINGEN 73 91 75 92 / 30 20 30 60
MCALLEN 75 93 77 92 / 30 10 30 60
RIO GRANDE CITY 72 93 75 92 / 40 10 40 60
SOUTH PADRE ISLAND 79 85 80 85 / 20 10 20 40
BAYVIEW/PORT ISABEL 76 90 78 90 / 20 20 20 50
BRO WATCHES/WARNINGS/ADVISORIES
TX...FLOOD WATCH THROUGH MONDAY MORNING FOR TXZ248>255-351-353>355-
451-454-455.
GM...NONE.
SHORT TERM...60-BE
LONG TERM....60-BE
AVIATION...60-BE
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