Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
489 FXUS64 KHGX 201906 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 106 PM CST Thu Nov 20 2025 ...New DISCUSSION, MARINE... .KEY MESSAGES... - Near record warmth again today and potentially tomorrow for metro and coastal locations. - Some storms in/near the Brazos Valley and Piney Woods tonight. With showers and isolated storms possible farther south on Friday. - Another system is expected to enhance shower and thunderstorm activity Monday into Tuesday. && .DISCUSSION... Issued at 1150 AM CST Thu Nov 20 2025 As expected, the long talked about mid/upper system has transitioned into a negatively tilted trough, with an axis extending from Nevada to the Chihuahuan Desert in northern Mexico. Strong diffluence and robust mid/upper moisture transport from the tropical Pacific is exceptionally evident on water vapor imagery across portions of SW and south-central CONUS. The lower levels have become increasingly moisture rich, while lift and vorticity stretching are inducing low pressure over W Texas. This low will have an associated cold front that will push eastward over the next couple of days, while the parent mid/upper level system also pushes east. This initially sounds like a slam dunk for widespread showers and thunderstorms across SE Texas, especially when one looks at moisture and shear parameters. But the aforementioned, robust diffluence will concentrate the bulk of the synoptic lift to our west and north, focusing the best chance of heavy showers and thunderstorms over central and northern Texas. To those hoping for widespread drought busting rains, our profound apologies. But well above average PWATs coupled with the eventual approach of a weakening cold front and some enhanced mid/upper lift should allow for some shower and thunderstorm activity over the next few days. For today, expect another warm and humid afternoon. Temperatures are expected to be near records once again. Isolated to widely scattered showers and maybe an isolated thunderstorm are expected. Many of you will remain dry. Looking at visible satellite, there is a noticeable enhance stream of cumulus extending from the Gulf to Galveston Bay and up the Trinity River basin. I suspect that will be a favorable zone for widely scattered showers. The heaviest rain and storms this afternoon are currently well to our north and west as expected. But we cannot rule out some of that thunderstorm activity impacting our northernmost counties between the Brazos Valley and Piney Woods later this evening. By early Friday morning, the weakening frontal boundary reaches our northern counties. CAMs guidance is quite varied regarding how much convective activity will be associated with the boundary. This likely has to do with the mixed signals being analyzed by the guidance. On one hand, we will have frontal induced sfc convergence coupled with high PWATs and an enhanced LL/ML jet. On the other hand, larger synoptic scale forcing are lackluster. For now, we are calling for scattered activity, with the potential for locally heavier showers and thunderstorms. Some of your parched yards will be blessed with shower, maybe even a heavier thunderstorm. But others may end up remaining dry. Could not rule out an isolated stronger thunderstorm given the shear. The front stalled and becomes increasingly diffused. But it`s presence warrants PoPs lingering into Saturday thanks to potential enhanced sfc convergence. The next system approaches from SW CONUS by early next week. PoPs on Sunday are low. It`s not until Monday that we expect the system to bring the next round of showers and thunderstorms. Though Monday`s system looks similar to the current set up, there is model support for a stronger frontal boundary that pushes through, which has implications on lift. Therefore, maybe we can muster more rainfall and thunderstorm from Monday`s system. We shall see. The aforementioned stronger front is a sign of a potential pattern change as we approach the Thanksgiving Holiday. The current split flow pattern is expected to transition into a more polar jet dominate pattern next week. Guidance suggests that this could start as early as Monday`s storm system, which may end up linking up with the Polar Jet as it departs our region by Tuesday. The pattern looks to remain amplified. But the Polar Jet doing the amplification would send cold, winter-like air southward wherever a deep trough resides. Long range teleconnections guidance has managed to flip flop somewhat over the last day, with global ensembles trending more positive with the Arctic and North Atlantic Oscillations. Perhaps this explains long range guidance`s more progressive flow pattern as opposed to a blocking pattern. This entire paragraph is pretty much a long winded way to say that I think we will see stronger cold fronts next week, but I`m am 1) unsure of where exactly the core of the coldest air will go and 2) thinking we may end up experiencing a bit of a temperature roller coaster ride if indeed the pattern is progressive. Our current forecast shows temperatures falling to near normal Tuesday and Wednesday (highs in the 70s and lows in the 50s). The very early outlook for Thanksgiving indicates relatively cool conditions, with temperatures to skewing a tad below average. But this could change so stayed tuned! Self && .AVIATION... (12Z TAF Issuance) Issued at 548 AM CST Thu Nov 20 2025 Mix of LIFR to VFR conditions will continue early this morning. Areas of patchy to dense fog currently over areas south of I-10, but is expected to burn off by 14-15Z. The low cigs will gradually lift during the morning hours and may scatter out in the afternoon to early evening hours, but are expected to lower again during the night hours. The chance for showers and storms are expected to increase tonight and continue into Friday. Some storms could produce periods of heavy rain and gusty variable winds. Cotto && .MARINE... Issued at 1150 AM CST Thu Nov 20 2025 Light to moderate onshore flow, 2-4 foot seas, and isolated to widely scattered showers are expected through tomorrow. As a weakening front approaches on Saturday, winds may become lighter and somewhat variable while the risk of scattered showers and thunderstorms increases. Onshore flow increases on Sunday, perhaps reaching caution flag levels by Monday into early Tuesday as a frontal boundary approaches. The front may bring a another chance of showers and thunderstorms. A northeasterly flow regime sets up in the front`s wake. Reinforcing fronts may bring stronger winds and higher seas later next week. But confidence in the forecast that far out is low at this time. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 67 81 62 77 / 60 60 30 20 Houston (IAH) 70 85 67 83 / 20 50 40 30 Galveston (GLS) 71 79 70 79 / 10 30 30 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ DISCUSSION...Self AVIATION...Cotto MARINE...Self