FXUS64 KHGX 241834 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 134 PM CDT Fri Oct 24 2025 ...New MARINE, HYDROLOGY... .KEY MESSAGES... - A robust storm system will bring periods of moderate to heavy rainfall and strong to severe thunderstorms Friday night through Sunday morning: - A Flood Watch in effect from midnight tonight until 4AM Sunday morning. Please read the hydrology discussion for more details. - Two rounds of rain and thunderstorms are expected, the first late tonight into Saturday morning and the second late Saturday afternoon through early Sunday morning. - Damaging wind gusts over 60 MPH are the primary concern. However, large hail and a few tornadoes cannot be ruled out. - Moderate to strong onshore flow will lead to hazardous marine condition today through the weekend. In addition to gusty winds and elevated seas, there will also be a high risk of rip currents along area beaches and elevated tides. - Much cooler weather expected by the second half of the week. && .DISCUSSION... Issued at 1151 AM CDT Fri Oct 24 2025 As of noon, a well-defined mid/upper low is centered near the Colorado - New Mexico border. The low is part of a larger mid/upper trough with an associated strengthening mid/upper jet over northern Mexico and far west Texas. Ahead of the low exists strong mid/upper diffulence and robust positive vorticity advection enhancing large scale lift over the Lone Star State. This lift will become stronger as the low drifts east to southeast today into tonight. LL pressure falls will be induced as the system's vorticity is vertically stretched on the leeward side of New Mexico's mountainous terrain, eventually fomenting the development of a deepening and eastward progressing sfc low over N Texas later today. The steepening gradient will be felt in the form of increasing southeasterly winds, particularly at the coast and over the Gulf / bay waters where Small Craft Advisories are in effect tonight into tomorrow. This gradient will also push a surge of deep, LL tropical moisture into southeast TX. The introduction of cooler temperatures aloft will increasingly enhance ML instability while the moist, tropical flow down below boosts instability in the low-levels. In addition, both bulk and LL shear will be on the rise as the mid/upper system and LL system work in tandem to create an increasingly veered and sheared vertical wind profile. All these factors favor a dynamic set up tonight and tomorrow, bringing a very good chance of rain and thunderstorms. Southeast Texas could certainly use the rain. Unfortunately, the set up also favors the development of strong to severe thunderstorms along with the potential for localized flash flooding. Please see the hydrology discussion below for details on the flood threat. Now let's dive into the details. The aforementioned set up is expected to bring two rounds of rain and thunderstorms to the region. These rounds do not include possible isolated to widely scattered activity this afternoon. Round 1 has already developed over portions of west Texas. Glancing at the radar, one might assume that these storms would remain west and north of the CWA given the current northeastward movement. But the storms are expected to congeal into a linear mode that begin to take a more eastward, and even southeastward, track as mesoscale processes start to play a larger role in storm motion. Overnight ML lapse rates steepen to 6.0 - 7.5 C/km as temperatures aloft cool, favoring sustained deep convection. The increasingly sheared and veering wind profile may allow for a few discrete cells to develop ahead of the line this evening / tonight. Generally speaking, the primary severe weather concern will be strong, damaging wind gusts over 60 MPH. But large hail and a few tornadoes are on the table as well. The obvious convective candidate for tornado genesis will be the discrete cells. But bows / notches along the line will need to be monitored for possible rotation as well. Regarding timing, the line of storms could reach the Brazos Valley as early as 11PM-1AM, the Houston Metro 3AM-5AM, and the coast by 4AM-6AM. But there are substantial differences in the CAMs regarding timing due to discrepancies in the rate of evolving cold pool and other mesoscale processes. For example, the RRFS suggests the line may not reach the Brazos Valley until ~6AM and the Houston metro ~8AM. HOWEVER, these timings pertain to the line and do NOT pertain to the potential discrete activity ahead of it. So keep in mind that thunderstorms could fire up a few hours ahead of the line. Southeast Texans will likely find ourselves under a much more stable atmosphere in the immediate wake of the morning storms on Saturday. Therefore, we may squeak in some nice weather late morning through the early/mid afternoon. Afternoon highs are expected to range from the upper 70s in our northern counties to low 80s in our southern counties. Given the situation, we cannot rule out the atmosphere becoming sufficiently starved of instability, limiting the potential of a second round of storms. But the guidance is very insistent that instability and moisture will surge just in time for the next round of showers and storms that could impact our northern counties by mid/late afternoon, the Houston metro by the evening hours, and the coast during the evening and overnight hours. Once again, there is a chance of severe thunderstorms and localized flash flooding (see hydro discussion). But we may need to see how the atmosphere is impacted by tonight's storms before we can assume high confidence in the severity of round 2. Believe it or not, there is good news in this AFD despite the gloomy tone thus far. A cold front is still forecast to push through the region on Tuesday, bringing a chance of isolated to scattered showers/storms. In its wake, it appears SE Texas may have our first "real" fall-like air mass. I'm talking upper 60s to low 70s for highs and 40s/50s for low by Wednesday and Thursday. If the 12Z ECMWF has anything to say about it, then temps could be even cooler! Self && .AVIATION... (12Z TAF Issuance) Issued at 539 AM CDT Fri Oct 24 2025 MVFR CIGS & isolated patchy fog this morning should be short lived as daytime heating ramps up. Winds remain predominantly ESE/SE today. Scattered to isolated showers are anticipated to move inland from the Gulf during the day, especially over areas SW/W of the city of Houston. Cannot rule out a thunderstorm or two, though again coverage will be sparse at this point in the forecast. Showers taper off early this evening, with a line of stronger thunderstorms expected to push through overnight into Saturday morning. Gusty winds, CIGs, and low visibility will likely accompany this line of storms. Some of these storms could become strong to severe producing heavy rainfall and damaging winds along with other severe hazards. Lingering showers trail behind the main line of storms, with a lull in rainfall likely Saturday afternoon. 03 && .MARINE... Issued at 131 PM CDT Fri Oct 24 2025 Southeasterly winds around 15-20 kt will prevail through the late afternoon hours. Caution flags remain in effect for both bays and the Gulf waters through 7pm. Winds will strengthen further going into tonight and reach the 20-25 kt range with gusts up to 30 kt through Saturday afternoon. This is also when we'll see seas increasing into the 5-8 ft range with occasionally higher seas. Mariners can expect Small Craft Advisories to go into effect for all of the waters beginning at 7pm tonight and extending into Saturday evening. These elevated winds are occuring in advance of and in association with an approaching storm system that will bring multiple rounds of widespread showers and storms. Some of these storms will be capable of producing heavy rainfall and strong wind gusts. The main windows for these stronger storms are late Friday night into Saturday morning and Saturday evening into early Sunday morning. Locally higher winds and seas are likely near any stronger storms. We cannot rule out gusts over 50 knots in the strongest storms. There are a few impacts to keep an eye on going into the weekend as a result of the elevated onshore flow. The first one being elevated water levels during times of high tide. Water levels during this afternoon's high tide will be around 3.5-3.9 ft above MLLW, which could lead to localized instances of minor coastal flooding. Saturday's high tide cycle looks to be in a similar range as well. In addition to this, the risk of rip currents is an upward trend today and through the weekend. As a result, decided to go forward with a Beach Hazards Statement through Saturday evening to cover both the localized minor coastal flooding potential and the high risk of rip currents. Batiste && .HYDROLOGY... Issued at 131 PM CDT Fri Oct 24 2025 A FLOOD WATCH WILL BE IN EFFECT FOR MOST OF SOUTHEAST TEXAS FROM EARLY SATURDAY MORNING TO EARLY SUNDAY MORNING. Ahead of the upcoming heavy rainfall event, grounds/soils are on the dry side. Majority of Southeast Texas is abnormally dry (D0) or in moderate drought (D1). There are a few portions of the area in severe drought (D2) including areas west of the Brazos River and parts of Madison/Walker Counties. So, in most areas the grounds will be able to take the rain and soak up quite a bit before it runs off. In the areas where the drought is a bit more severe, we'll see that rainfall become runoff much sooner. Our rivers/bayous are in good shape ahead of this event as well, so it would take quite a bit of rain to put those into flood. Even with ~4-6" of rain over a 24 hour period, we're only looking at scattered instances of action stage and a low end chance of isolated instances of reaching minor flood stage. The main concern would be if we get those higher-end 4-6" amounts in a short period time, which would be driven by high rainfall rates. In that scenario is when we could see issues with flashy rivers/bayous/streams and also street flooding especially in urban areas and areas with poor drainage. Flash flood guidance is generally in the 3-5" range for one hour and 4-6" range for three hours. It's within the realm of possibilities that we could see high rainfall rates (2-3+"/hr) that could cause instances of flash flooding. We will also need to monitor where the axis of heavy rain will fall during the main storm windows (tonight into Saturday morning and Saturday evening into early Sunday morning). If there are instances of prolonged heavy rainfall over the Houston metro area, then we'd need to watch the bayous a bit more closely to monitor for potential impacts. Thankfully, there is expected to be a lull between the rounds of heavy rain late Saturday morning into the afternoon to allow for drainage, but elevated water levels along the coast during high tide could briefly inhibit that drainage. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 67 79 64 80 / 90 90 70 10 Houston (IAH) 71 81 69 83 / 70 90 90 30 Galveston (GLS) 76 83 72 83 / 70 80 90 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Flood Watch from 1 AM CDT Saturday through late Saturday night for TXZ163-164-176>179-195>200-210>214-226-227-236>238-300- 313-336>338-436>439. Beach Hazards Statement through Saturday evening for TXZ436>439. GM...Small Craft Should Exercise Caution until 7 PM CDT this evening for GMZ330-335-350-355-370-375. Small Craft Advisory from 7 PM this evening to 7 PM CDT Saturday for GMZ330-335-350-355-370-375. && $$ DISCUSSION...Self AVIATION...03 MARINE...Batiste