Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
252 FXUS64 KHGX 201120 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 620 AM CDT Sun Jul 20 2025 ...New AVIATION... .KEY MESSAGES... Issued at 1239 AM CDT Sun Jul 20 2025 - Fair weather and hotter conditions are on tap for at least the first half of the week, with expected high temperatures drifting higher up into the 90s. - With heat index values to around 106, and generally plenty of sun, we`ll see wet bulb globe temperatures rise into the high risk range, and we`ll be near the threshold for a heat advisory through the week. - Whether or not an advisory is issued, those individuals who are vulnerable to heat, or will need to exert themselves strenuously outdoors should have a plan to stay ahead of heat illness this week. && .DISCUSSION... Issued at 1239 AM CDT Sun Jul 20 2025 From a purely meteorological standpoint, this forecast is well...really, really boring until the very end of the forecast period. And, we`ll get there, but even if the forecast itself is not super exciting, there are still some important things we need to talk about for the early part of the week from an impact standpoint for all these...normal...people all over Southeast Texas. And yes, if you are thinking ahead of my writing and going "hmm, late July, boring forecast, but impacts for people, sounds like heat" you would be absolutely correct. As ridging takes hold over the southern tier for the first half of this new week, we`ll watch temperatures drift their way up higher into the 90s for daily highs, especially well inland. But with light onshore flow continuing, we`ll still keep dewpoints up pretty high as well, which means heat index values are drifting upwards too. We should manage pretty decent daytime mixing, which should keep the humidity from getting too out of hand in the afternoon, but triple digit heat index values are a slam dunk, and while the most likely outcome is for peak heat index values in the 103-107 range, that`s still awfully close to our typical threshold of 108 for a heat advisory. Granted, because heat is such a tricky, nuanced thing, 108 is also not a hard threshold, either. So it will likely come down to a daily reanalysis of the situation to determine what the best decision on that front is. One aggravating factor will be the ample sunshine and fairly light winds. Both of those will increase the threat for heat stress, and this is seen in the rather widespread occurrence of the wet bulb globe temperature values in the high risk range. Because of this - regardless of whether or not there is an advisory - folks who will be working, exercising, playing, or somehow have to exert themselves in exposure of the worst conditions of the day should plan to take frequent breaks, hydrate, and all-around stay ahead of the threat of heat illness. One mitigating factor, though, is the historical context of the heat situation. HeatRisk shows us that temperatures will be on the hotter side, but not unusually outside the typical peak summer range. We get pretty widespread values of moderate impact most days, but that`s about it; maybe some speckles of high. This stinks in two ways - one, this can still be a threat to folks vulnerable to heat and two, when paired with the WBGT numbers it highlights how even just above average conditions in this area can quickly become dangerous. But...given that we`ve had some time to acclimate to our summer here in the usual peak heat time and we`re not that far from the climatological norm of "stupid hot", I`m actually not currently inclined to push hard for a heat advisory. That said, it`s close enough that even a small change upwards would require me to rethink that pretty seriously. Which, again, is why the need for any sort of heat headline will become a daily analysis. Okay, beyond the heat, let`s talk about more interesting things. As we get into the back half of the week, the ridging should weaken modestly. That weakening is pretty high confidence, though the precise amount is a bit less so. However, even the models most aggressively breaking down the ridge aren`t that much different from a multi-ensemble mean (per LREF clustering data). And even the ones least aggressive do so enough to allow another inverted trough to make its way westward across the Gulf in our direction for the end of the week. At the very least, this is going to bring the potential for showers and storms back to the area later in the week, perhaps from Thursday or so onward. At worst, well...let`s not talk about that yet. I`d rather not jinx things, especially since there does seem to be some pretty decent agreement amongst the guidance that this comes to us as just a slug of tropical moisture to boost our typical diurnal convective pattern. Nothing worse than a repeat of our recent 93L experience, and probably not even rising to that fairly meager level. One look at the NHC site will reveal no blobs of any color in the Gulf for the next seven days. And really, that`s exactly what a clear-eyed analysis of the situation will tell you. I just also prefer not to trust a trough over the Gulf in late July. And that brings us to what is, I think, a pretty responsible way to approach the forecast for late this week. Expect potential for afternoon storms to increase Thursday onward, and that`s about it. But also, make sure to check back through the week to ensure that nothing unexpected has happened. Believe me, if anything on this changes or even hints at changing, we`ll let you know. Also, if nothing changes, we`ll still let you know. Letting you know what we know (and when needed, what we don`t know) is kinda the whole reason why we`re here. && .AVIATION... (12Z TAF Issuance) Issued at 620 AM CDT Sun Jul 20 2025 A few isolated showers around GLS and lingering patchy fog at CXO this morning, but otherwise dry and VFR conditions will prevail throughout the day across the region. Southerly to southeasterly winds will be a bit gusty at times during the afternoon hours. Expect sustained winds around 10-15 kt with occasional gusts in the 15-20 kt range through sunset. Could see a repeat of patchy fog and/or MVFR ceilings developing at the northern terminals on early Monday morning. Batiste && .MARINE... Issued at 1239 AM CDT Sun Jul 20 2025 Fair and hot conditions are expected to prevail through the weekend, and only increase to isolated shower and storm activity at most until late next week thanks to high pressure building across the region. Expect low seas and light to occasionally moderate onshore winds to prevail. Our next chance for more organized rainfall should arrive towards the end of next week, but only the broad strokes can be drawn out with much certainty at this time. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 95 75 95 74 / 0 0 0 0 Houston (IAH) 95 77 95 77 / 10 0 10 0 Galveston (GLS) 89 83 90 83 / 20 0 10 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Luchs AVIATION...Batiste MARINE...Luchs