Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
564 FXUS64 KHGX 290508 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1208 AM CDT Sun Jun 29 2025 ...New DISCUSSION, MARINE... .KEY MESSAGES... Issued at 143 PM CDT Sat Jun 28 2025 - Shower/thunderstorm chances remain higher for Sunday than previous days, though confidence in the rainfall coverage is lower than normal. - Daily chance of showers/thunderstorms continue through the forecast period. - Temperatures expected to become hotter beyond Monday. && .DISCUSSION... Issued at 1200 AM CDT Sun Jun 29 2025 Usually I like to begin my discussion with the current state of the atmosphere. But today, I want to uncharacteristically start with the models. When glancing at all available short-term, hi-res, global, and ensemble data, one will notice quite the variance regarding the coverage of shower and thunderstorm activity for both today and tomorrow. Let`s start with today`s atmosphere. A plume of higher PWAT is approaching from the Gulf, thanks in part to Tropical Depression Two in the Bay of Campeche. This surge of tropical moisture is expected to bring widespread 2.0+ inch PWAT values to our region today, with these high values reaching our coastal counties during the early morning hours while areas farther inland reach these PWAT numbers by afternoon. Considering moisture levels will be higher today than previous days, we still think that general rainfall chances are higher than recent days. In addition, these high PWAT values may support locally heavy rainfall, especially in locations where deeper convection is favored. But there are factors that could limit today`s convection to a shallower and less widespread variety. For starters, there`s the much talked about plume of mid-level Saharan Dust. However, various satellite Saharan Air Layer analyses indicate that the dust levels aren`t as high as the often shared NASA Dust Extinction Aerosol Optical Thickness model suggests. In addition, the bulk of the dry mid-level air may not reach our area until Monday. So wouldn`t that suggest the high PWATs will win out? Well....there`s one other factor, vorticity. The National Hurricane Center`s forecast has Tropical Depression Two becoming a minimal Tropical Storm before moving ashore into Mexico this evening. As the system gets a little better organized, the overall vorticity field may contract somewhat. There`s a plethora of guidance suggesting a scenario like this, where a stream of enhanced vorticity becomes a potential focus for deeper convection offshore to our south. This scenario doesn`t completely rid our region of showers and storms. But the deeper convection to the south / offshore hogs some of the inflow and moisture, limiting the coverage and the depth of convection across our neck of the woods. Considering this forecast has managed to become more uncertain than I thought it was yesterday, I`ve decided to go along with the lower PoPs the NBM is selling. HOWEVER, PoPs across much of the region remain 50-70%, which is higher than recent days. The exception is across our Brazos Valley counties where PoPs are 20-40%. In the case of Monday, the battle will be between the LL tropical moisture and the increasing influence of the Saharan Air aloft. Monday`s PoPs range from 20-30% across our northern counties to 30-50% in our southern zones. For the remainder of the week, increased ridging and lingering mid- level dust results in a lower PoP regime with higher temperatures. Inland highs are expected to average in the mid 90s. But we are not expecting the atmosphere to be suppressive enough to eliminate the chance of diurnal showers/thunderstorms. Therefore, the daily risk of showers/storms remains in the forecast through the end of the week. Self && .AVIATION... (00Z TAF Issuance) Issued at 637 PM CDT Sat Jun 28 2025 VFR conditions ongoing, and expected to prevail through the period. SHRA/TS along the coast in the morning, spreading inland through the afternoon hours. Gusty winds will be possible in and around storms. Otherwise, winds generally out of the S/SE and light. Hazy conditions will be possible with incoming Saharan Dust; however, confidence is low on how concentrated the dust will be once it arrives, and how it will impact coverage of showers and storms during the day tomorrow. && .MARINE... Issued at 1200 AM CDT Sun Jun 29 2025 The National Hurricane Center is issuing advisories for Tropical Depression Two in the Bay of Campeche. The system is forecast to become a minimal tropical storm by the time it reaches the coast of Mexico near in the vicinity of Tampico. Despite this track well to the south of our region, moisture from the system is expected to bring scattered showers and thunderstorms to the area today. In addition, southeasterly swell is expected to increase somewhat later today, possibly reaching 5-6 feet in our marine zones farther offshore. For the rest of the week, we are expecting continued daily chances of isolated to scattered showers/thunderstorms, along with light to moderate onshore winds and 2-4 foot seas. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 92 75 93 74 / 30 0 20 10 Houston (IAH) 89 76 92 76 / 80 10 40 10 Galveston (GLS) 89 82 89 81 / 70 20 40 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Self AVIATION...Adams MARINE...Self