Area Forecast Discussion
Issued by NWS Brownsville, TX
Issued by NWS Brownsville, TX
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213 FXUS64 KBRO 170429 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1129 PM CDT Sun Jun 16 2024 ...New AVIATION... .SHORT TERM... (Tonight through Monday night) Issued at 243 PM CDT Sun Jun 16 2024 Key Messages: * The National Hurricane Center (NHC) has upgraded the potential for tropical cyclone development over the Bay of Campeche to a 30% chance over the next couple of days and a HIGH (70%) chance over the next 7 days. * Showers and thunderstorms are expected to develop over at least parts of Deep South Texas as early as Monday * Hazardous Marine conditions are expected to develop as early as Monday Night The short term forecast period will feature the onset of what is expected to be a potentially high impact weather event this week over Deep South Texas and the Rio Grande Valley. All eyes are focused on the southwestern Gulf of Mexico and the potential for tropical cyclone development in the days ahead. Latest satellite and radar observations show a large disorganized area of showers and thunderstorms over Central America, the Yucatan Peninsula, and adjacent waters of the northwestern Caribbean. The latest Tropical Weather Outlook from the National Hurricane Center (NHC) has upgraded the potential for tropical cyclone development over the Bay of Campeche to a 30% chance over the next couple of days and a HIGH (70%) chance over the next 7 days. With the local forecast area situated in an area of weakness between two anomalously strong ridge complexes, one being a strengthening or emerging 594-600 dam sub-tropical heat dome over the eastern U.S. and another heat ridge to our west over central/western Mexico and parts of the Desert Southwest, deep tropical moisture that resulted in a deluge over parts of Florida last week will shift westward this week. Through Monday night or the short term period, deep tropical moisture will be pulled into the region from this developing tropical system. Between this evening and Monday evening, dewpoint (Td) temperatures, integrated water vapor transport (IVT), and precipitable water (PWAT) values are expected to increase. In fact, PWATs are expected to increase from ~1.5 inches this afternoon/evening to 2 inches or so by Monday night. That said, shower and thunderstorm chances will begin to expand and increase in coverage and probability from east to west beginning on Monday. Through tonight, not much is expected. Latest MSAS surface analysis, radar, and satellite observations show rain with some embedded thunder well offshore. This activity through tonight is expected to largely remain offshore. There could be a shower or perhaps a thunderstorm reach the coastal areas, particularly from I-69E and points east tonight. Have low grade (20-30%) PoPs through tonight to reflect this potential/risk. Otherwise, expect for another warm and muggy night with overnight lows in the mid 70s to near 80F. During the day on Monday, the combination of peak sfc based differential heating and the continued influx of tropical moisture amid onshore winds, will result in the potential for some diurnal showers and thunderstorms. Coverage looks to be isolated to scattered at best. Have 20-40% chance PoPs across much of the CWFA with categorical PoPs from the coastal areas into the Gulf Waters. The latest convective outlook from the Storm Prediction Center (SPC) has much of the area, basically outside of Zapata County, under a general outlook/risk for thunderstorms on Monday. Otherwise, expect for another very warm to hot and humid day across the area with daytime highs ranging from the mid 90s east to lower 100s west. Increased cloud coverage on Monday is the main reason for the slightly cooler temperatures compared to today. Nonetheless, with the increase in dewpoint (Td) temperatures, another Special Weather Statement (SPS) may be necessary for Monday with forecast heat indices ranging between 105-11F degrees. Monday night will be another warm and muggy one with overnight lows in the mid 70s to near 80F. && .LONG TERM... (Tuesday through next Sunday) Issued at 243 PM CDT Sun Jun 16 2024 Key Messages: * Tropical Cyclone Development in SW Gulf now at 70 percent * Increasing Rain Chances with Periods of Heavy Rainfall Mid to Late Week * Substantial Beneficial Rainfall Likely with Areas of Flooding Possible The most imminent element and highest confidence of the long term forecast is the substantial increase of atmosphere moisture and the chance of rain with a good likelihood of heavy rainfall and potential flooding concerns. The other concern of course is the potential Tropical Cyclone development in the Gulf of Mexico. NHC continues to gradually bump up probabilities (30% in 2 days, 70% 7 days) for an area of disturbed over Central America and Southern Mexico which is expected to drift into the Bay of Campeche Monday or Tuesday. Current, projections is for this potential tropical entity to move into Central Mexico Gulf coast sometime Wednesday. Another spin up low pressure area is shown by the deterministic models to form over the southcentral Gulf next Friday or Saturday and drift northwest next Weekend. There is a lot uncertainty with this second entity. As has been mentioned several times, despite any tropical cyclone develop the moisture content of the overall atmosphere across the Western Gulf of Mexico and South Texas is very likely to increase substantially as spokes of energy rotates around the Central American Gyre (CAG) sending deep tropical moisture north and west between ridges along the both the Pacific and Atlantic coast. Although details on where the heaviest rain may fall and how much may accumulate over the next 3-7 days is highly uncertain, there is increasing confidence in the model consistency of an extended period of widespread rainfall some of which will be heavy and producing potential flooding. Showers and thunderstorms will be efficient rainmakers as GFS/ECMWF as well as ensemble models indicating specific humidity and pwats at 3-4 standard deviations from normal. Wednesday and Thursday continue to be the days with most extensive rainfall but any band or cluster of showers/thunderstorm Tuesday through next Saturday can easily produce 2-4 inch/hr rainfall rates. Conservatively, general rainfall amounts over the next 7 days may range 3 to 7 inches (WPC QPF) with locally higher amounts. No flood Watches are imminent with antecedent soils very dry and can receive a good amount of water. However, if these wet conditions do materialize and the potential for excessive rainfall may lead to areas of flooding. WPC Excessive Rainfall Outlook (ERO) has a marginal to slight risk for rainfall exceeding Flash Flood Guidance Tuesday-Thursday for all or portions of Deep South Texas. Coastal and local beaches will be highly likely to see a long period of hazardous conditons as the pressure gradient strengthens over the Gulf and the entrainment of showers and thunderstorms. High rip current risk, coastal flooding, high surf and gale force gusts are all possible with periodic advisories or warnings through next weekend. Temperature forecast will be a "Nothing Burger" for once with the increased cloud cover and rainfall allowing temperatures to stay near or drop below normal. && .AVIATION... (06Z TAFS) Issued at 1126 PM CDT Sun Jun 16 2024 A TEMPO has been added to the TAFs for BRO and HRL for the Monday morning potential for convection. Otherwise, VFR will prevail at all of the aerodromes through the next 24 hours, with light winds at night becoming breezy during the daytime. Partly to mostly cloudy skies will also occur. && .MARINE... Issued at 243 PM CDT Sun Jun 16 2024 Tuesday through Sunday...Marine conditions will be deteriorating through the week and likely remaining adverse to hazardous next weekend as winds, seas as well as showers and thunderstorms increase. One and possibly a second tropical low pressure area could form and pass over the southwestern and central Gulf of Mexico respectively. NHC is monitoring possible tropical cyclone development over the Bay of Campeche Tue/Wed and another potential tropical low next Fri/Sat in the South Central Gulf. The first potential cyclone low has a 30% of development in next 2 days and 70% in the next 7 days. A tightening pressure gradient between the overall lower pressure over the Southern Gulf and Southern Mexico to combine with high pressure extending into the northern Gulf to produce a fresh to strong easterly fetch of winds across much of the Gulf of Mexico. An Extended period of Small Craft Advisories is likely from Tuesday through at least Friday mainly due to elevated seas/swells with a medium probability (40-60%) of seas exceeding 10 feet. Strongest winds Wednesday, Wed night and Thursday may gust near gale force at times. Stay tuned to the latest marine forecast for any possible Tropical cyclone advisories, Watches or Warning through the next week. (Tonight through Monday Night): Marine conditions are expected to gradually deteriorate and become more and more adverse through Monday night. A potential developing tropical cyclone over the Southwestern Gulf will help to enhance the pressure gradient. This will result in light east-southeast winds becoming more moderate on Monday and Monday evening. Increased ocean swells from higher winds and seas over the middle parts of the Gulf of Mexico will result in higher seas Monday into Monday night. SCEC conditions are possible for the Gulf Waters as early as Monday and Small Craft Advisory (SCA) conditions are possible for the Gulf Waters as early as Monday night. Lastly, a MODERATE RISK of rip currents are expected at the local beaches on Monday. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 80 94 81 92 / 30 60 50 80 HARLINGEN 76 95 78 93 / 20 50 40 70 MCALLEN 80 98 80 96 / 10 30 20 60 RIO GRANDE CITY 79 99 78 95 / 0 10 10 40 SOUTH PADRE ISLAND 83 87 83 87 / 50 60 60 80 BAYVIEW/PORT ISABEL 80 91 80 90 / 40 60 50 80 && .BRO WATCHES/WARNINGS/ADVISORIES...None. && $$