Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
603 FXUS64 KHGX 181855 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1255 PM CST Tue Nov 18 2025 ...New DISCUSSION, MARINE... .KEY MESSAGES... - Near record warmth will continue areawide through at least Wednesday. Southern counties could be near records through Friday. - Periods of late night and early morning fog possible on a daily basis. - Rain chances increase Wednesday into Thursday ahead of an approaching disturbance. There is potential for heavier showers and thunderstorms late Thursday into Friday. && .DISCUSSION... Issued at 1121 AM CST Tue Nov 18 2025 Satellite imagery shows a well defined mid/upper low pressure system moving into southern California. An associated diffluent southwesterly jet is bringing lift and tropical Pacific moisture into SW CONUS. For SE Texas, this system is not effecting our atmosphere today, with mid/upper ridging remains dominant. Sfc high pressure over SE CONUS is keeping the low-levels on an onshore flow regime, pushing warm and humid Gulf air into our region. Temperatures are expected to be near record territory again today, with highs mostly in the mid/upper 80s. Many locations will struggle to dip below 70 tonight, with patchy fog possible once again. Now back to that mid/upper low over southern California. The low will crawl eastward across SW CONUS and northern Mexico on Wednesday. Despite being well west of our area, the system may introduce just enough lift over our warm and increasingly PWAT rich environment to spark off isolated to widely scattered showers Wednesday morning and afternoon. HRRR seems to think there could be an isolated rumble of thunder as well. Best chance of a shower appears to be west of I-45, where we have 20-30 PoPs. The PoPs are lower (but not zero) east of I-45. Temperature wise, expect another toasty day on Wednesday. The mid/upper low at first glance appears to have a relatively symmetrical vorticity field. But a deeper look shows that vorticity is strongest on the west and southwest side of the low. As the parent low`s angular momentum pushes the vorticity maxima southeastward into Mexico, the overall vorticity structure becomes increasingly elongated and trough-like. This is evident in the global models which transform the system from a closed mid/upper low to a negatively tilted trough axis extending from Nevada to the Chihuahuan Desert. By this point, the aforementioned diffluent mid/upper jet will push eastward over Texas, increasing lift and shear. Therefore, it should be no surprise that PoPs trend higher on Thursday, generally 40-50%. But the best chance of showers and thunderstorms appears to be Thursday night and Friday. The position of the trough will help to foment a surface low pressure system over NW Texas and Oklahoma Thursday afternoon. An associated frontal boundary will surge eastward as shear and synoptic ascent increase. By Thursday night, the jet overhead is expected to bring 40-50kt 0-6km bulk shear with LL shear (0-1km and 0-3km) in the 20-30kt range. CAPE will exist but does not appear too impressive, with LREF means below 1000 j/kg. But one should never underestimate a low CAPE / high shear environment`s potential to produce a few strong to severe thunderstorms. The primary concern would be locally damaging wind gusts and tornadoes. Given the well above average PWATs, we will also have to monitor the potential for localized flash flooding as well. However, when looking at the mid/upper pattern, the strongest diffluence is expected to be west and north of our region, meaning that the best chance of heavy thunderstorms will be over central and northern Texas. That being said, heavy north Texas rains can translate to downstream river flooding in our neck of the woods. So if the lack of diffluence in our region keeps rainfall totals lower than expected, just know that rainfall north of our area can still have an impact in SE Texas. The front is expected to decelerate over our region on Friday, becoming stalled and diffused by the weekend. Residual lift will keep PoPs in the forecasts through at least the weekend. Meanwhile, a system that`s currently south of Alaska is expected to dive southward into SW CONUS over the weekend, possibly bringing a better chance of showers and storms to our region by Monday. When will things get cooler? This is a question we are getting a lot these days. The approaching system is decoupled from the polar jet thanks to a split flow pattern. So don`t expect cold temperatures in the wake of the system. But I took a deep dive into the large scale teleconnections that can act as weather tea leaves for the long term. Recently, pretty much all of the teleconnections (NAO, AO, PNA, MJO, ENSO) have either favored a warm signal for our region or have exhibited a more neutral signal. But the teleconnections are trending towards more mixed signals as we head into next week and the Thanksgiving Holiday. For now, our forecast shows a slow cooling trend late this week into early next week. By Monday and Tuesday, most locations could be close to normal, with highs in the 70s and lows in the 50s to low 60s. We shall see if the increasingly negative NAO and AO allow for a southward plunge in the polar jet over North America. Time will tell.... Self && .AVIATION... (12Z TAF Issuance) Issued at 544 AM CST Tue Nov 18 2025 Mix of stratus and fog bringing IFR to low MVFR conditions from roughly northwest of LFK-CXO-VCT again early this morning, with clearer sky but still some patchy fog coastward. Toplines do best to line up with obs and recent satellite trends, most notably to be a little more optimistic at IAH. Prevailing is now VFR through the morning, but with stratus hanging out nearby on almost all sides, keep an MVFR TEMPO for brief CIGs. As with past days, VFR should emerge area-wide by late morning with S -> SE winds increasing to around 10 knots for the afternoon. Winds diminish after dark, with potential for degradation in flight conditions again overnight. With lighter winds, some guidance is getting quite aggressive with fog. For now, will align with more optimistic guidance and keep impacts more limited to higher MVFR, with only IFR TEMPOs at known problem sites CXO/SGR. This potential will need to be evaluated through the day. && .MARINE... Issued at 1121 AM CST Tue Nov 18 2025 Southeast flow averaging 10-15 knots and 2-4 foot seas are expected through Thursday. Isolated to widely scattered showers and storms are possible on both days. A more robust system may bring a better chance of showers and thunderstorms late Thursday into Friday. Though winds and seas should generally be benign, we cannot rule out locally higher winds and seas near thunderstorms. Winds may become directionally more variable on Friday and Saturday as a weak front approaches from the north. The front should keep a daily risk of showers and storms in the forecast through the weekend. Onshore flow and seas may increase by early next week as the next system approaches from the west. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 67 84 68 82 / 10 30 10 50 Houston (IAH) 69 84 68 83 / 0 10 0 30 Galveston (GLS) 72 79 71 78 / 0 20 10 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...03 AVIATION...Luchs MARINE...03