Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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159 FXUS64 KBRO 281739 AFDBRO Area Forecast Discussion National Weather Service Brownsville TX 1239 PM CDT Sun Apr 28 2024 ...New UPDATE, AVIATION... .UPDATE... Issued at 1233 PM CDT Sun Apr 28 2024 Lowered the Max T grids slightly for this afternoon due to the amount of cloud cover around and temperatures not warming as fast. Only minor adjustments made to the hourly temps and Max T grids to reflect current observations and forecast trends. See previous discussion below. && .SHORT TERM... (Today through Monday) Issued at 317 AM CDT Sun Apr 28 2024 The start of the short term forecast period will see the influences of an upper-level trough diminish over Deep South Texas and the Rio Grande Valley, which will see the southwesterly flow aloft become more zonal. SPC has Deep South Texas and the Rio Grande Valley in a General Thunderstorm Outlook for today and Monday. However, part of Northern Zapata is in a Marginal Risk (level 1 of 5) for severe weather on Monday. For the showers and thunderstorms on Sunday, a cold front and dry line upstream could merge north of the region. While previous runs of CAMs models showed that theses showers and thunderstorms could move into the Northern Ranchlands, the current run does not reflect this happening. NBM does try to produce isolated showers and thunderstorms for Northern Ranchlands still. Looking into forecast soundings, shows that the environment stays pretty capped leading an unfavorable environment for showers and thunderstorms. Thus keeping rain chances at 20 percent for today. For tomorrow, the situation is a bit different with an mid-level shortwave potentially aiding in the development of showers and thunderstorms. The atmosphere becomes marginally unstable with MUCAPE around 2000 J/kg with model soundings indicating a weakening of the cap later Monday, which would open a brief opportunity for showers and thunderstorms to develop. However, a weak mid-level ridge to the south of the area maintains mid-level dry air which could hinder the development of the mentioned showers and thunderstorms. Model and WPC QPF is also pretty limited, thus making the development of showers and thunderstorms questionable at best for Monday. As for temperatures, with the southerly to southeasterly flow at the surface bringing in more humid, warm air, temperatures are expected to stay pretty warm for the short term forecast period. High temperatures for today and Monday are expected to be in the 90s for most of the area, except along the coast and on the island. As for the low temperatures for tonight, all of Deep South Texas and the Rio Grande Valley is expected to be in the 70s. Lastly, for anyone planning on going to the beach, High Risk of Rip Currents has been extended through Monday on all the beaches as the wave heights around 6 and swell period remain high around 8 seconds. && .LONG TERM... (Monday night through Saturday) Issued at 317 AM CDT Sun Apr 28 2024 For the long term there will be a quasi-zonal midlevel flow covering much of the CONUS with a few shortwaves riding over the top of the subtropical ridge centered over Central Mexico. Farther north low pressure troughs will be traversing the Rockies and North and Central Plains with the strongest trough possibly pushing a surface cold front into Central Texas next Friday and Saturday. Southerly flow persist through the week with a moderate pressure gradient maintaining a steady flow of low level moisture (modest dew points in the U60s/M70s) and warm temperatures. Rain chances continue to look limited with best chances Tuesday and Wednesday and again Friday and Saturday. There remains uncertainty on the timing of the shortwaves and areal coverage among latest model projections with best overall coverage favoring Tuesday with 20-30% for most of the region with northern and Western areas of Deep South Texas seeing best chances, albeit low Wednesday, Friday- Saturday. It is May (in a few days) and the atmosphere is likely to be in a conditional instability state. Forcing from the above mention shortwaves or outflow from storms further north may be sufficient to produce a few strong thunderstorms any of the days mentioned. Some of the storms may be accompanied by gusty winds, moderate to heavy rainfall and some hail. Seasonal warm to hot temperatures with the region under the influence of the northern edge of the subtropical ridge. Maximum Temperature anomalies range from 2-5 degrees above early May averages, while Minimums look to be a bit warmer 4-7 degrees above mainly due to higher dew points as Gulf water temperatures are already in the mid to upper 70s. Heat indices also, will show an increase through mid week with maximums ranging 100-106 degrees. && .AVIATION... (18Z TAFS) Issued at 1233 PM CDT Sun Apr 28 2024 Through 18z Monday.... Key Messages: * VFR-MVFR ceilings expected to continue through today. * MVFR-IFR ceilings are expected to develop tonight. * Ceilings expected to improve to at least MVFR levels on Monday. * Southeast winds, gusty at times, are expected to weaken this afternoon into this evening. As of this update, VFR to MVFR conditions were taking place at the terminals under a SCT-OVC deck of strato-cumulus clouds as indicated on the latest GOES-16 Visible Channel with ceilings ranging between 2,500-4,000 feet AGL. Latest surface analysis reveals a weak low pressure area over the area this afternoon. However, the latest forecast model and satellite trends indicate some clearing off to the west thanks to the strong April sun angle and rather weak upper level divergence taking place. This should allow for some improving sky coverage into the middle parts of this afternoon. That said, flying conditions due to ceilings could waffle back and forth between VFR to MVFR today. As we shift towards tonight, forecast models are suggesting marine influences to increase with increasing low level clouds (low stratus) from the Gulf. With plenty of low level moisture in place, MVFR to IFR conditions are expected to develop and take over the TAF sites tonight. As we shift into Monday, any MVFR to IFR ceilings/clouds are expected to improve to at least MVFR conditions. Moderate to at times gusty winds out of the southeast 10-15 kts this afternoon are expected to weaken as the day progresses as the surface pressure gradient continues to weaken. Tonight into Monday, southeast winds are expected to be at around 10 kts. && .MARINE... Issued at 424 AM CDT Sun Apr 28 2024 Decided to extend the Small Craft Advisory for the Laguna Madre until 5 PM. Observation decks along the Laguna continue to hover at or just below 20 kts. Pressure gradient remains sufficiently strong as well as low level inflow is likely to be enhanced by ongoing convection over Central and North Texas allowing winds to reach and exceed 20 knots beyond 7 AM. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 77 91 77 90 / 0 20 10 20 HARLINGEN 74 92 74 91 / 0 20 10 20 MCALLEN 76 94 77 93 / 0 20 10 20 RIO GRANDE CITY 73 94 75 94 / 0 30 10 20 SOUTH PADRE ISLAND 76 81 76 81 / 0 10 20 20 BAYVIEW/PORT ISABEL 75 87 75 88 / 0 20 20 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Monday evening for TXZ451-454-455. GM...Small Craft Advisory until 5 PM CDT this afternoon for GMZ130- 132-135. Small Craft Advisory until 7 AM CDT Monday for GMZ150-155-170- 175. && $$ UPDATE...23-Evbuoma SHORT TERM...64-Katz LONG TERM....59-GB AVIATION...23-Evbuoma