FXUS64 KBRO 190545 AAB AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1245 AM CDT Fri Apr 19 2024 ...New AVIATION... .SHORT TERM... (Tonight through Friday night) Issued at 237 PM CDT Thu Apr 18 2024 The short term period will feature mostly rain-free conditions and above normal temperatures. The exception will be tonight, where there will be a brief period for showers, and potentially isolated thunderstorms, across portions of Deep South Texas. The latest radar and satellite imagery depict rain-free conditions and a steady influx of clouds across Deep South Texas. Temperatures will continue to warm into the upper 80s and low 90s through the afternoon hours, with temperatures steadily falling into the 70s tonight. Persistent southerly to southeasterly flow in the lower levels of the atmosphere will aid in increasing low level moisture content from the Gulf of Mexico, while southwesterly flow aloft will aid in mid and high level moisture content from the Pacific Ocean. Model guidance indicates precipitable water values will steadily increase upwards of 1.5 inches, which is around the 75th to 90th percentile for this time of year. As moisture content, and cloud cover, increase overnight, a weak mid-level shortwave will approach the region and bring a low chance of isolated showers and thunderstorms across portions of the region tonight. Although most guidance keeps the best potential for strong thunderstorms well to our north, model soundings reveal mid-level lapse rates around 7.5-8 C/km, which could support an isolated thunderstorm or two. Any activity will likely dissipate before daybreak on Friday. In addition to the potential for low rain chances across portions of the region, the influx of low level moisture and low surface winds may yield patchy fog across portions of the Northern Ranchlands and the Gulf waters tonight. Friday will feature a gradual clearing of cloud cover through the mid to late morning hours, and another warm afternoon with high temperatures ranging from the upper 70s along the Lower Texas beaches to upper 90s across the Northern Ranchlands. Another round of patchy fog will be possible Friday night across portions of the region. Lows will once again fall into the 70s region wide. && .LONG TERM... (Saturday through next Thursday) Issued at 237 PM CDT Thu Apr 18 2024 Key Messages: * Showers and thunderstorms remain a possibility Saturday night through Sunday as a cold front sweeps over the area. * Big airmass change to the cooler and drier side in the wake of the cold front Sunday and Monday. * Temperatures and humidity levels attempt to rebound Tuesday through Thursday of next week. The main weather concern during the long-term forecast period continues to focus on the risk/potential for showers and thunderstorms Saturday night through Sunday. We start off the long-term period on Saturday where we'll see another very warm and humid day before the big weather change. On the western flank of a departing sfc high pressure system to our east, southeasterly winds will continue to advect moist and warm air in the region. This will allow for daytime high temperatures to rise into the upper 80s to lower 90s across much of Deep South Texas (cooler near/along the coast). Subsidence amid continued influences from the sfc high will allow for another dry and tranquil weather day on Saturday. Deterministic forecast models and ensembles continue to advertise the potential for showers and thunderstorms developing Saturday night through Sunday in response to a cold front that's progged to sweep across the region. Models remain rather dispersed as far as the areal/spatial and temporal extent of showers and storms Saturday night into Sunday. That said, have 20-50% chance Pops to reflect a low to medium confidence on the threat/risk of showers and storms at this time stamp. As we sort out the more salient details with future model iterations, will have a better handle regarding this threat. With surface-based CAPE (SBCAPE) via the latest 12z runs sampled in excess of 1,000 J/kg, 0-6 km bulk shear values sampled between 30-45 kts, showalter values between 0C to -4C denoting a moderately to very unstable/buoyant airmass in place, and mid-level lapse rates between 7-8 C/km, it's certainly plausible that some storms could become strong to severe Saturday night through Sunday. With a weak/unfavorable jet structure support, a lot will depend on the forward momentum/strength of the frontal boundary and to what extent any ongoing upstream convective activity to our north will be able to hold together as it shifts into our region as there will likely need to be some forcing mechanism to help offset a cap that will be in place in what will likely be a conditionally unstable environment during this timeframe. Currently, the Storm Prediction Center (SPC) in Norman, Oklahoma has our cwa designated under a general outlook for thunderstorms. Depending on where the front is positioned, there could be another round of showers and storms Sunday afternoon/evening and maybe again during the day on Monday. The front is expected to be far south enough to result in a notable airmass change to the cooler and drier side Sunday and Monday, however. Daytime highs are progged to be in the mid 70s to near 80F both days with dewpoint values in the 60s. Tuesday through Thursday, temperatures and humidity levels attempt to rebound once again as the aforementioned cold front lifts northward over the area as a warm front or quasi-stationary front. && .AVIATION... (06Z TAFS) Issued at 1225 AM CDT Fri Apr 19 2024 Low cloud decks and light to moderate southeast winds prevail across Deep South Texas early this morning. MVFR ceilings are expected to prevail through around mid-morning, a brief period of IFR ceilings/MVFR visibilities will be possible at BRO until just after sunrise. Otherwise, VFR conditions are expected late morning into the afternoon. Low cloud decks/MVFR ceilings are forecast to return later this evening. && .MARINE... Issued at 237 PM CDT Thu Apr 18 2024 Tonight through Friday night...Light to moderate southeast winds with wave heights around 3-5 feet will prevail through the forecast period. Small Craft Should Exercise Caution conditions cannot be ruled out due to occasional gusts. Saturday through Thursday Night....Light to moderate winds and seas are expected to persist through the long- term period. There is a chance for showers and thunderstorms Saturday night through Sunday and possibly again on Monday. && .PRELIMINARY POINT TEMPS/POPS... BROWNSVILLE 74 87 73 79 / 0 0 20 50 HARLINGEN 72 89 70 78 / 0 0 20 40 MCALLEN 75 92 72 78 / 0 10 30 50 RIO GRANDE CITY 73 93 68 77 / 0 10 40 50 SOUTH PADRE ISLAND 74 79 73 74 / 0 0 20 40 BAYVIEW/PORT ISABEL 73 85 71 77 / 0 0 20 40 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...22-Garcia LONG TERM....23-Evbuoma AVIATION...63-KC