Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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872 FXUS64 KBRO 231144 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 644 AM CDT Mon Sep 23 2024 ...New AVIATION... .SHORT TERM... (Today through Tuesday) Issued at 347 AM CDT Mon Sep 23 2024 The first full day of Autumn 2024 might still be called "Hotumn"...as temperatures will be more like late August day and night and combined with continued tropical humidity it will feel like 100 to 108. Similar temperatures will be had Tuesday...all courtesy of a continued flat subtropical 500 mb ridge that remains across northern Mexico through the Valley and into the western Gulf. Fortunately, the strength of the ridge is not like we saw in August and with lowering sun angle and lengthening nights conditions are not as sweltering...but that doesn`t mean it feels anything close to relief across the southern tip of Texas. As for sensible weather...Sunday was largely dry, as the sea breeze had little deep moisture to work with. Today shows a hint of slightly higher deep layer moisture easing in from the east...but only in the 800-600 mb layer and the increase is subtle. With no pronounced forcing, the best we`ll do is isolated (10-20 percent) rain chances, jumping inland along the sea breeze but likely petering out before reaching along/west of Brooks/Hidalgo. Skies clear out again tonight with near calm winds, but similar temperatures a few degrees above seasonal norms by early Tuesday. A possible slug of deeper moisture may reach the Lower Texas coast courtesy of an embedded weak short wave that attempts to slide west. However, that wave/shear axis may hang up offshore, and models hint at deeper moisture doing similar. By late Tuesday, we turn our attention to a deepening 500 mb trough diving southward through the eastern Plains, which should enhance rain chances beyond this period. Until then, sensible weather may feature better coverage along the coast to begin Tuesday before it, too, jumps inland along the sea breeze beginning in early afternoon. Thereafter, the usual diurnal rules apply...and locations generally along/east of IH-69E/US 77 should see an end to any convection by mid afternoon. Have modified the blended forecast to account...and be similar to this afternoon. That said, the additional moisture should favor slightly higher coverage of afternoon rain...though still below what the model blends are advertising which seems overcooked given deterministic solutions as well as 36-48 hour precipitation depictions from the convective-allowing models (CAMs) which are more "typical" isolated to scattered conditions. Finally...we`ll be watching tide conditions especially at South Padre Island today through Tuesday. The first of the season`s "King" tides have arrived and peak near 0.7 feet above normally high ground through Tuesday. Water levels are already running about 0.65 feet above predicted values. Expected values today and tomorrow are in the 1.2 to 1.4 feet above normally high ground and this may push water levels up on the beach, reducing available beach to use. That said, with wave/swell energy very limited, sea water should not reach the dunes...but we may need to consider a Coastal Flood Statement as early as this morning if visual conditions warrant one. && .LONG TERM... (Tuesday night through Sunday) Issued at 347 AM CDT Mon Sep 23 2024 We look to begin the long term period with an upper level trough situated across the Central US. As the trough pushes further east, the southern portion looks to break off and develop a closed low over the ArkLaTex region Thursday. Both the GFS ans ECMWF have this closed low interacting with a possible tropical system late in the week, pushing the closed low southwest deeper into Texas. At the surface, PWAT values between 1.6 and 1.9 inches and CAPE values around 1000 J/kg could support showers and thunderstorms Developing Wednesday and Thursday. A stationary front across Central Texas and and the daily sea breeze could provide forcing to support isolated to scattered showers and thunderstorms Wednesday. Recent runs of the GFS and ECMWF have the frontal boundary pushing south early Thursday, with isolated to scattered showers and thunderstorms possible along the front. Dry air behind the front looks to limit additional rain chances through the remainder of the period. High temperatures look to be in the low to mid 90s Wednesday then falling to the upper 80s to low 90s with the frontal passage Thursday. High temperatures look to return to the low to mid 90s Friday, and remain there through the remainder of the period. Likewise, low temperatures look to range from the low to mid 70s Tuesday and Wednesday nights, before dropping into the 60s Thursday night. Low temperatures look to return to the low to mid 70s over the weekend. The combination of Frontal passage and the arrival of long period swell on Thursday will likely produce hazardous beach conditions Thursday and Friday. There will likely be a high risk of Rip and Longshore currents, and some minor coastal flooding cant be ruled out. && .AVIATION... (12Z TAFS) Issued at 639 AM CDT Mon Sep 23 2024 Little change the the forecast except to extend it out to 12Z (7 AM) Tuesday and add a VCTS for McAllen/Miller based on updated guidance including Convective Allowing Models (CAMs) that hint at such coverage, enough to warrant a mention. Otherwise...arriving sounding here in Brownsville is still plenty dry above the low level condensation level, which strongly suggests only isolated precipitation at best this afternoon. Based on this, elected to hold onto VCSH/VCTS for the early to mid afternoon (Harlingen) and mid to late afternoon (McAllen). Otherwise...global models continue to hint at a slug of deeper moisture moving toward the coast or just inland by daybreak or soon after. Not sold on anything more than another round of scattered low MVFR skies prior to 7 AM so that was added to Brownsville, with winds near calm. && .MARINE... Issued at 347 AM CDT Mon Sep 23 2024 Today through Tuesday...Winds (easterly) and seas will be light and slight, respectively, with surface high pressure locked into the northern half of the Gulf. However, boating may become a bit more difficult especially Tuesday as shower coverage increases to scattered to numerous with isolated thunderstorms. Lightning and briefly torrential rains along with some gusty winds and choppy waters will be the primary concerns...favoring the waters beyond 10- 20 nm out. Tuesday night through Sunday...Generally favorable marine conditions look likely through Wednesday night as light to moderate winds and slight seas continue along the Lower Texas Coast. Conditions look to deteriorate Thursday, with the passage of a cold front and the arrival of swell from a possible tropical system in the Eastern Gulf. This combination will likely result in confused seas and as northerly winds and waves combine with easterly swell. Small Craft Should Exercise Caution headlines and Small Craft Advisories will likely be needed for the Gulf waters Thursday and Friday. Additionally, winds could approach criteria for Small Craft Should Exercise Caution headlines on the Laguna Madre with the frontal passage on Thursday. Favorable marine conditions look to return Saturday as light to moderate winds and slight seas persist through the remainder of the period. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 93 78 93 76 / 20 10 30 30 HARLINGEN 94 74 94 73 / 20 10 30 10 MCALLEN 97 78 97 77 / 10 0 30 20 RIO GRANDE CITY 95 75 95 75 / 10 10 20 20 SOUTH PADRE ISLAND 88 81 88 80 / 20 20 40 30 BAYVIEW/PORT ISABEL 90 76 90 76 / 20 10 40 20 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ AVIATION...52-Goldsmith