Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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170 FXUS64 KBRO 152325 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 625 PM CDT Sun Sep 15 2024 ...New AVIATION... .SHORT TERM... (Tonight through Monday night) Issued at 242 PM CDT Sun Sep 15 2024 Latest model suite continue to indicate a robust unsettled weather patterning persisting Tonight through Monday. Deep layer moisture (SFC-300mb) and weak impulses emanating from the Pacific Ocean and Gulf of Mexico linger over the forecast region producing scattered to numerous showers and isolated thunderstorms. Last night and this morning Soundings indicated record values pwats (2.69, 2.42 inches respectively) which is pretty impressive for September. WPC has expanded the Day 1 Marginal Risk for Excessive rainfall Outlook to cover all of the CWA with exception of the NE portions of Kenedy county. The heaviest rain thus far today has occurred over the Northern and Western Ranchlands where 1-3 inches have fallen. Flash Flood Guidance started out rather high in these areas, thus no immediate concerns of flooding at this time. As for the rest of today and tonight, convergence zone setting up from Cameron to Brooks county with a broken band of heavier showers and isolated thunderstorms. CAM and even deterministic blends show a continuing high chance of rain through the evening and overnight hours. Probability of seeing 1/2-1 inch of rain over the next 6-12 hours is low to medium or 20-40% (10-20% or 2 inches) with the counties bordering the Rio Grande (Starr, Hidalgo, Cameron) having the best chances. Pockets of 2-4 inches is not out of the question through Monday with some nuisance flooding possible where heavy rain rates occur. Moisture remains deep and robust Monday before models show more influence from the mid level ridge building over Texas suppressing the moisture late in the day and tomorrow night. Rain chances remain robust Monday before tapering off after sunset. Additional rainfall amounts of 1/2-1+ inches is possible. At this time, WPC does not have the CWA under any Excessive Rainfall outlook but this may change depending on what occurs over the next 12 hours. The thick cloud cover and rainfall is doing a number on temperatures today and will likely impact highs tomorrow. I lowered NBM highs for Monday by a degree or two and this may not be enough looking at what has happened today. Forecast highs Monday currently are in the 86-89 degree range. Overnight are expected to remain elevated as dew points will be in the 75-81 degree range. Any "cooler" temperatures will likely be brief and occur where rain cooled conditions develop. These areas are likely to warm back up to match the dew points maintaining the oppressive humid conditions. && .LONG TERM... (Tuesday through next Sunday) Issued at 242 PM CDT Sun Sep 15 2024 Global deterministic forecast models and ensembles continue to depict a 591 dam heat dome/ridge building over northeastern Mexico into Deep South Texas through the extended. This will yield slightly warmer/hotter than normal temperatures during the long-term period with mainly dry/rain-free conditions in place. Over the past week, forecast models have trended and favored more ridging developing over the region. Atmospheric moisture content will be lower compared to previous days/weeks with precipitable water (PWAT) values between 1.5-2.0 inches. Despite the lower values, it should be adequate enough to support a rogue or isolated chance for a shower or thunderstorm nearly each day. Subsidence, however, with the aforementioned mid- level ridging in place, will help to keep things mostly suppressed during the period. That said, expect for mainly dry or rain-free conditions to prevail through the long-term period with an isolated chance for a shower or storm nearly each day. Temperature anomalies will run slightly warmer/hotter than mid-late September standards through the extended. High temperatures are expected to be in the mid to upper 90s for much of the region and for much of the period. Moderate HeatRisk can be expected for the most part through the extended. There could be areas of major HeatRisk developing, especially in the Wednesday-Friday timeframe. Heat indices are expected to range between 105-111F on Tuesday and again on Saturday (slightly lower values on Sunday). Heat indices are progged to range between 108-115F Wednesday through Friday. That said, Special Weather Statements (SPS) to Heat Advisories may be needed during the expected. && .AVIATION... (00Z TAFS) Issued at 622 PM CDT Sun Sep 15 2024 Unsettled flying conditions are expected at the aerodromes through the next 24 hours courtesy of the approach and passage of a disturbance in the middle layers of the atmosphere. Both prevailing and TEMPO have been included in the last issuance of TAFs for convection. Generally light winds with mostly cloudy to cloudy skies will also occur. && .MARINE... Issued at 242 PM CDT Sun Sep 15 2024 Tonight through Monday night...Pressure gradient remain weak over the Gulf of Mexico as surface high pressure remains centered over the western Gulf and a stationary front remains draped across the northeast Gulf of Mexico. Light Southeast wind and slight seas observed over the Lower Texas coastal waters are expected to persist through the period. Main impact on the coastal waters will be scattered to numerous showers and isolated thunderstorms. Heavy rainfall, poor visibility within the heavy rainfall and possible waterspouts as well as lightning is possible within the unsettled weather conditions. Tuesday through Sunday....Outside of any convection, favorable marine conditions (light to moderate winds and light seas) are expected to prevail Tuesday through next Sunday. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 77 87 77 92 / 70 70 10 40 HARLINGEN 75 89 74 93 / 50 70 0 40 MCALLEN 77 89 78 97 / 70 70 10 30 RIO GRANDE CITY 75 86 75 93 / 80 70 10 30 SOUTH PADRE ISLAND 80 86 81 88 / 70 60 20 30 BAYVIEW/PORT ISABEL 75 87 76 91 / 60 60 10 30 && .BRO WATCHES/WARNINGS/ADVISORIES...None. && $$