Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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477 FXUS64 KBRO 171730 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1230 PM CDT Mon Jun 17 2024 ...New AVIATION... .SHORT TERM... (Today through Tuesday) Issued at 304 AM CDT Mon Jun 17 2024 This portion of the total forecast is expected to be the start of the much-discussed and much- anticipated significant precipitation event for Deep South Texas and the Rio Grande Valley. The latest Tropical Weather Outlook from the National Hurricane Center lists a 60% chance of tropical formation over the southwestern Gulf of Mexico through the next 48 hours, and a 70% chance of tropical formation over the southwestern Gulf of Mexico through the next seven days. As this potential tropical system, combined with steadily-deepening tropical moisture (with precipitable water values ranging between 2 and 2.5 inches), moves towards the western coast of the Gulf of Mexico, isolated/scattered showers and thunderstorms today and tonight will become scattered to numerous on Tuesday across the BRO CWFA. Temperature-wise, above normal values are forecast for today and tonight, with daytime highs on Tuesday cooled to more near normal levels due to increased cloudiness and rain chances. Heat indices do not suggest a HEAT ADVISORY during the short term forecast period, so will cover the indices with a SPECIAL WEATHER STATEMENT today and tomorrow. Finally, slightly more adverse marine conditions, courtesy of an increase in winds and building of seas, will lead to an elevated risk of rip currents at the local beaches today through Tuesday. && .LONG TERM... (Tuesday night through Sunday) Issued at 304 AM CDT Mon Jun 17 2024 Key Messages: * Tropical Cyclone Development in the SW Gulf remains at 70 percent * Increasing Rain Chances with Periods of Heavy Rainfall around Mid through Late Week. * Substantial Beneficial Rainfall Likely with Areas of Flooding Possible Confidence remains high with increasing atmospheric moisture and the chances of rain increasing leading to periods of heavy rainfall and potential flooding concerns in the long term forecast period. The potential development of a tropical cyclone in the SW Gulf of Mexico has increased to 60 percent within the next 48 hours and 70 percent within the next 7 days, though the system will not be around that long. Currently the system is located over the Central America and Southern Mexico, but is expected to move into the Bay of Campeche either today or tomorrow. Current model guidance still shows the center of this system moving into Central Mexico late Wednesday into Thursday. The model guidance does still show that there is another spin up that forms towards the end of the long term forecast period as well, however confidence is not high on the second system at this point. Moving into the main event of the long term forecast period, the long awaited rainfall that is highly anticpated for Deep South Texas and the Rio Grande Valley. The moisture content of the atmosphere over the Western Gulf of Mexico and Deep South Texas is very likely to increase drastically as deep tropical moisture is transported north and west between the ridges along the Pacific and Atlantic coast. By the start of the long term forecast period the PWATS over the region are around 1.9 inches based on the GFS and the NAM, however the ECMWF has PWATS at 2.1 inches. PWATS continue to rise through the day on Wednesday eventually reaching its peak on Wednesday night at a value of 2.9 inches. The current total QPF is in the range of about 4 to 7 inches. While the soils are very dry and could take up quite a lot of rainfall, there is still the concern that some flooding could take place if heavy rain fall is persistent enough. WPC currently has a marginal to slight risk for Excessive Rainfall Tuesday through Thursday for parts or all of Deep South Texas and the Rio Grande Valley. Expect many hazards to be in effect for the beaches during the long term forecast period as well. An enhanced pressure gradient is going to strengthen the southeasterly flow that will in turn build even greater swell. The result of this will be an increase in Rip Current risk, coastal flooding, high surf, and possible gale force gusts. Lastly, the temperatures for the long term forecast period. With the expected cloud coverage from the rain, high temperatures are not expected to be too hot and actually close to normal. As such the high temperatures are expected to be in the range of upper 80s to low 90s. While the low temperatures are expected to be mostly in the 70s, with a few places getting into the 80s. && .AVIATION... (18Z TAFS) Issued at 1227 PM CDT Mon Jun 17 2024 Through 18z Tuesday....VFR conditions are taking place at all of the terminals under a FEW-SCT deck of cumulus to stratocumulus clouds with bases between 3,000-6,000 feet AGL and unrestricted visibilities. VFR conditions, by and large, are expected to prevail through the 18z TAF cycle. The main concern during the 18z period will be the risk for showers and thunderstorms developing (mainly during the afternoon and overnight hours). Forecast models continue to suggest the potential for showers and thunderstorms developing later this evening/tonight and then again during the day on Tuesday. These showers and thunderstorms are associated with a plume of deep tropical moisture advecting from a developing tropical cyclone over the Southwestern Gulf of Mexico. Any storms that do move over a TAF site will have the capabilities of briefly reducing cigs and/or visibilities down to IFR levels. Showers and storms will be isolated through tonight becoming more isolated to scattered during the day on Tuesday. Have Prob30 groups in the TAFs to reflect this potential. Otherwise, expect for VFR conditions to prevail. Winds will be out of the east 7-15 kts through this afternoon into this evening with occasional gusts between 20-25 kts. Winds will subside tonight out of the east at 5-10 kts. During the day on Tuesday, winds are expected to shift out of the northeast at 5-10 kts. && .MARINE... Issued at 304 AM CDT Mon Jun 17 2024 Today through Tuesday...This portion of the total marine forecast is highly dependent on the area of disturbed weather over Central America, the Yucatan Peninsula, the waters of the northwest Caribbean Sea and southern Gulf of Mexico, and the possible future development and movement of a tropical system within it. Overall, Small Craft Should Exercise Caution (SCEC) and Small Craft Advisory conditions (SCA) are anticipated along the Lower Texas Coast through the period, with SCEC likely needed today, and SCA needed tonight through Tuesday. Tuesday night through Sunday...Marine conditions are expected to be Hazardous Tuesday night and remain that way through the work week, with Saturday starting to see some improving conditions. An enhanced pressure gradient will generate moderate southeast winds and seas. Small Craft Advisory conditions are expected to be present Tuesday night through early Saturday for the Gulf waters. While hazardous conditions are expected to come to an end a little sooner for the Laguna Madre. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 80 92 78 89 / 50 80 80 90 HARLINGEN 76 93 75 88 / 30 80 80 90 MCALLEN 79 95 78 87 / 20 70 60 90 RIO GRANDE CITY 78 96 77 84 / 10 50 50 80 SOUTH PADRE ISLAND 83 87 80 86 / 60 80 90 90 BAYVIEW/PORT ISABEL 79 90 77 87 / 50 80 80 90 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk from 7 PM CDT this evening through Tuesday evening for TXZ451-454-455. GM...None. && $$ SHORT TERM...66-Tomaselli LONG TERM....64-Katz AVIATION...23-Evbuoma