Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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032 FXUS64 KBRO 160443 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1143 PM CDT Sat Jun 15 2024 ...New AVIATION... .SHORT TERM... (Tonight through Sunday night) Issued at 157 PM CDT Sat Jun 15 2024 Quiescent weather conditions will be the theme through the short term forecast period as influences from a sfc high over the Gulf of Mexico remains intact. Additionally, the region will sit in between an emerging/strengthening 594-597 dam heat dome over the eastern U.S. and a Sonoran heat ridge over northern and western Mexico, and portions of the Desert Southwest. Warm and muggy nights, and very warm to hot and humid afternoons will persist. Overnight lows tonight and Sunday night are expected to hold in the mid 70s to near 80F degrees. Meanwhile, on Sunday, daytime highs are expected to climb into the upper 90s to lower 100s. With dewpoint (Td) temperatures in the upper 60s to mid 70s, heat indices on Sunday are expected to fall just below Heat Advisory and maybe even Special Weather Statement (SPS) criteria with values ranging between the 105-111F. Coinciding with max sfc based differential heating and associated with a plume of deep tropical moisture over the eastern Gulf, a few of the hi-res Convecting Allowing Models (CAMs) are hinting at the possibility of a few pop-up diurnal showers and thunderstorms on Sunday as winds continue out of the east-southeast. Most of the activity is expected to stay offshore. However, there is a low, yet, non-zero probability of a shower or storm reaching inland Sunday afternoon/evening. For now, have low grade 20% PoPs along and east of I-69E increasing to 40% over the barrier island including South Padre Island (SPI) and the near shore Gulf Waters, and 50-60% over the offshore Gulf Waters. Otherwise, expect for dry and tranquil weather conditions to prevail through Sunday night. && .LONG TERM... (Monday through next Saturday) Issued at 157 PM CDT Sat Jun 15 2024 The main concern in the long term forecast remains the high uncertainty of tropical development in the Bay of Campeche/SW Gulf of Mexico. The uncertainty resides first on the development of a broad low pressure area over the SW Gulf which current NHC Tropical Weather Outlook suggest not until early next week. Second uncertainty is if a tropical cyclone (TC) can form within the broad circulation and now this may not occur until the middle of next week according to the latest model analysis and NHC discussions. Environmental conditions from the Western Caribbean Sea east to the Bay of Campeche/SW Gulf are expected to become favorable for TC development (Doesn`t mean a TC is imminent) somewhere within the Central American Gyre thus NHC continues to message a 50 percent chance of TC development in the next 7 days. Synoptic pattern for the long term continues to show the Western Gulf of Mexico and the eastern two-thirds of Texas residing between the strong Bermuda Ridge extending eastward to the East U.S. coast and the Pacific Sub-tropical ridge noted over West- central Mexico. The low pressure weakness between the ridges will be an area for moisture transport northward leading to increasing rain chances despite any tropical development. Models continue to show a substantial surge of tropical moisture heading north spreading across the western Gulf and along the Lower Texas Monday night and over Deep South Texas Tuesday. The peak of the moisture surge at this time is likely Wednesday-Thursday and slowly tapering off (not ending) Friday and Saturday. Deterministic model PoP Guidance from NBM/ECMWF/Canadian as well as Ensemble models indicate anomalous precipitable water values around 3 standard deviations from normal or 2.25-2.8 inches. Weather Prediction Center (WPC) days 1-7 Total QPF values are now in the range of 2-5 inches with the higher amounts along and east of I-69C. The WPC Day-5 (12Z Wed-12Z Thu) Excessive Rainfall Forecast shows the entire Texas coast including all of Deep South Texas in a Slight Risk of exceeding Flash Flood guidance which remains rather high. Confidence is low on widespread flooding at this time, but with the amount of moisture content forecast any slow moving thunderstorm could dump 2-4 inches in short amount of time which will pose a threat of local ponding and flooding of streets and low-lying areas. To reiterate NBM and other deterministic models continue to show rainfall beginning as early as Monday night across the coastal regions spreading inland Tuesday. The bulk of the widespread substantial and beneficial rainfall is shown for Wednesday-Thursday with a continued good chance of scattered showers and thunderstorms Friday and Saturday. As for temperatures, highly variable due to the uncertainty of cloud cover and total areal coverage of rainfall any given day. Will trend potentially slightly lower than the NBM and may trend close to the GFS (Wed and Thu) where temperatures may finally lower to normal (low to upper 90s). Lows may struggle to lower outside of any rain cooled air so will maintain NBM trends of 75-80 degrees. Beach conditions to say the least but need to watch the most is the uncertainty. The increase of unsettled weather around mid to late in the week will increase the threat for increased rip current threat, high surf, coastal flooding and of course heavy rainfall along with some periods of gusty winds. && .AVIATION... (06Z TAFS) Issued at 1141 PM CDT Sat Jun 15 2024 VFR conditions are anticipated to prevail at the aerodromes through the next 24 hours. && .MARINE... Issued at 157 PM CDT Sat Jun 15 2024 Tonight through Sunday Night...Favorable marine conditions are expected to prevail through Sunday night, as a weak sfc pressure gradient remains in place over the Lower Texas Coast. Light to moderate winds and seas are expected along with an isolated to scattered threat for showers and thunderstorms. Monday through Saturday...Marine conditions in the long term with become increasingly unsettled as showers and thunderstorms increase in aerial coverage and the pressure gradient strengthens. What is uncertain is the potential for Tropical Cyclone (TC) in the Bay of Campeche or SW Gulf of Mexico. See the long term discussion for more details. Otherwise, a strengthening pressure gradient over the northern and western Gulf of Mexico is expected through midweek as strong high pressure along the eastern U.S. coast combines with developing broad low pressure over the Southern Gulf and over SE Mexico. Winds and seas may approach Small Craft Advisory conditions as early as Tuesday and continue through much of the week. Mariners are urged to monitor the latest coastal forecast and discussions due to the increase of thunderstorm chances all of next week at a minimum. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 80 95 79 96 / 0 20 30 50 HARLINGEN 76 97 76 97 / 0 10 20 40 MCALLEN 79 99 79 100 / 0 10 10 30 RIO GRANDE CITY 78 100 78 100 / 0 0 0 10 SOUTH PADRE ISLAND 83 88 82 88 / 10 20 40 60 BAYVIEW/PORT ISABEL 80 92 79 93 / 10 20 30 60 && .BRO WATCHES/WARNINGS/ADVISORIES...None. && $$