textproduct: Brownsville/Rio Grande Valley

KEY MESSAGES

Updated at 203 PM CDT Fri Apr 24 2026

Key Messages:

- Very low (conditional) chance of severe weather with very large to giant hail tonight in Zapata and western Jim Hogg and Starr Counties.

- Elevated heat risk this weekend into next week, with apparent temperatures in the triple digits. A Major Risk (level 3 of 4) of heat related impacts is forecast Monday through Wednesday.

UPDATE

Issued at 203 PM CDT Fri Apr 24 2026

SPC has placed Zapata and western Jim Hogg and Starr Counties in a Marginal Risk (level 1 of 5) of severe weather tonight, with a hail intensity level 1, meaning hail of 2 inches or greater is possible. The risk is highly conditional, meaning the materialization of any storms is dependent on many factors. The environment is looking increasingly supportive for large (2"+, lime or greater size) hail, but confidence on initiation is low.

CRP 18Z sounding shows SBCAPE over 3000 J/kg, steep mid level lapse rates 8.8degC/km, and moister mid levels compared to BRO 12Z UA (50% RH). Expect a supercellular storm mode, if storms materialize. Confidence is lacking that upper-level moisture will be sufficient for giant hail, and initiation timed in place of most favorable conditions. CAMs have been hit or miss on whether supercells form over the Sierra Madre (and a further hurdle, making it to deep South TX). RRFS shows robust supercells across much of south TX, HRRR shows nothing, HRW-ARW shows activity remaining in Mexico, so confidence is low. Most likely timing is this evening/overnight, starting as early as 7 PM.

There is a high chance no storms form, or no storms make it across the Rio Grande into the BRO CWA. If storms do form this evening, highly localized very large to giant wind-driven hail is possible across the Rio Grande Plains and Upper RGV.

DISCUSSION

Issued at 133 PM CDT Fri Apr 24 2026

Increased cloud cover this morning has sorely limited surface heating; have bumped down high Ts today regionwide by a degree or two. (OUTDATED. SEE UPDATE) Today and tomorrow, SPC has placed western portions of the CWA in a general risk for thunderstorms (level 0 of 4). This morning's sounding shows steep 700-500 mb lapse rates and decent low level shear indicating a healthy environment for hail producing storms. CAPE is forecast to increase through the afternoon, but a very dry atmosphere above 850mb and limited forcing during max CAPE values decreases confidence. Thus, have kept PoPs for today and tomorrow low. If convection over the Sierra Madre is able to traverse into Deep South Texas this evening/tonight, thunderstorms with hail and strong winds are possible. Outside of this, ridging building over NW Mexico should suppress further rain chances for the remainder of the forecast.

This weekend through next week, the greatest impact will be heat, with triple digit heat indices across the region. High temperatures gradually climb through the weekend into the mid (east of 281) to upper 90s (80s along the immediate coast). "Feels like" temperatures climb to 111 Sunday and Monday in the upper Valley, the current hottest two days of the forecast. There is a Moderate to Major Risk of heat related impacts for much (all on Sunday) of the CWA through the forecast period. Southeasterly winds remain breezy each afternoon, strongest to the east of US 281.

AVIATION

(18Z TAFS) Issued at 1235 PM CDT Fri Apr 24 2026

Primarily MVFR with low cloud cigs for much of the 18Z cycle. Tried to be optimistic with clouds lifting this afternoon, but there is a chance MVFR will stick around at all sites, or at least bounce between VFR and MVFR into the evening. IFR conditions expected overnight between midnight and sunrise.

MARINE

Issued at 133 PM CDT Fri Apr 24 2026

Gentle to moderate southeasterly flow under a benign pattern will maintain 4-5 ft seas through the weekend into early next week. Primarily dry conditions are expected.

PRELIMINARY POINT TEMPS/POPS

BROWNSVILLE 75 90 75 91 / 0 0 0 0 HARLINGEN 72 92 72 94 / 0 0 0 0 MCALLEN 76 97 76 98 / 10 0 0 0 RIO GRANDE CITY 74 97 74 99 / 10 0 0 0 SOUTH PADRE ISLAND 75 82 75 83 / 0 0 0 0 BAYVIEW/PORT ISABEL 73 87 73 89 / 0 0 0 0

BRO WATCHES/WARNINGS/ADVISORIES

TX...None. GM...None.