textproduct: Houston/Galveston

KEY MESSAGES

- TORNADO WATCH in effect through 7 PM Tonight. Discrete storms capable of all severe hazards, including heavy rainfall as well, will be possible ahead and along a cold front.

- Cold front should slow as it approaches the Houston Metro late tonight with the severe/hydro threat diminishing as it slowly pushes off the coast Tuesday morning.

- A stronger, reinforcing front pushes through Wednesday morning, bringing cooler and drier conditions just in time for Thanksgiving.

MESOSCALE UPDATE

Issued at 1158 AM CST Mon Nov 24 2025

TORNADO WATCH IN EFFECT UNTIL 7 PM TONIGHT

Already got a quick spinup on radar early this afternoon, so it appears that severe weather threat is already underway. Currently keeping a close eye on our west/northwestern counties where instability is rather robust. CAMs were pinging this location earlier in the 12z model run, though it's destabilized rather quickly. Mesoanalysis shows some 2000-2500 ML CAPE with LCL heights under 750m. Decent shear on the whole though it and helicity are strongest further to the northeast. May see a few more spinups in this area with the current set of storms, especially as they track northeasterly into better helicity and shear.

We'll probably lose some of this instability over the western CWA as it's worked over by the current storms... though there are some gaps in coverage. One of these "Gaps" forming is around the Brazos/Washington/Grimes area. Short-range model updates are suggesting higher instability in this general area due to a gap in storm coverage that already seems to be manifesting on radar... so we could still see some severe wx develop in this area. Otherwise, we'll see the area of severe weather broadly expand northeastward leading up the FROPA as instability builds into this area with better dynamics and shear.

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DISCUSSION

Issued at 1158 AM CST Mon Nov 24 2025

Things are already kicking into high gear hear with storms beginning to fire up ahead of the cold front. The current environment shows PWs of 1.4-1.8 inches with model guidance indicated the potential to pool up to 1.9-2.0 inches ahead of the line. 300mb analysis showed ample omega north of the area with the RAP/GFS/NAM all showing SE Texas getting clipped by some of the stronger omega values as it tracks eastward with the upper trough. LLJ around 25-30 knots peaking near 40 knots in CAM models. On the whole, dynamics appear modest over the northern half of our CWA, primarily over the Piney Woods area near areas like Crockett & Livingston. Thermodynamics is a more interesting story, which continue to trend upwards with RAP analysis already 1500 J/KG of ML CAPE. More concerning is a rather consistent signal in the CAMs pinging on a bullseye of elevated CAPE in our west/northwestern counties, over 2500 J/KG with respect to ML CAPE and nearing 3000 J/KG in for SFC/ML CAPE in some models. Seems to come as a result of the area being plunged deeper in the warm sector with moisture pooling in advance of the FROPA... And before I could finish writing this discussion we had out first TOR warning in place over this area... so my concerns about this area appear to have been justified, especially now as now SPC's mesoanalysis is showing this deeper instability. Shear is still as robust as it was several day prior with bulk shear of 30-50 knots. 100-200 m2/s2 1km SRH with 20-30 knots of 1km bulk shear. LCL heights are also generally forecasted under 1500m with a good swap of the area under 1000m throughout most of the afternoon.

Seeing better agreement with timing too among models (at least earlier in the forecast), showing the cold front enter the Brazos Valley late in the afternoon, reaching College Station around 3-6PM. CAMs become a bit more split later tonight as the front nears the Houston Metro. Broadly it seems like it should slow and lose some of it's gusto (waning instability and being further removed from stronger upper level dynamics), moving through the city around 9PM- 1AM... could be even later as hinted at by the FV3 and NAM. The front should move offshore around 1AM-5AM, though again the FV3 is dragging its feet, wanting to keep the front on dry land till daybreak. Still is a very feasible outcome (and thus leaned closer towards the FV3 with this forecast), but again in such a scenario the line itself will be far less potent by that point, so the severe/hydro concerns shouldn't be prolongued either.

Main takeaway is that we're expected strong to severe storms ahead of and along an approaching cold front today & tonight. SE Texas is under a Slight (2/5) to Marginal (1/5) Risk of Severe Weather and Excessive Rainfall for today. These storms will be capable of producing damaging winds, large hail, tornadoes and locally heavy rainfall. The northern half of our CWA will be most at risk of these severe storms. The threat of heavy rainfall is on the whole lower, with the greatest risk much more confined to our north/northeastern most counties, where locally higher rainfall totals up to around 4 inches could occur. Though, any training storms could still result in some minor street flooding, especially in Urban areas/areas of poor drainage (i.e. Houston Metro). With respect to timing, the severe/rainfall threat has already begun. Storms on the whole should become weaker late tonight with the severe/hydro threat ending early Tuesday.

Rest of the forecast remains the same. An upper level low moving through the Northern Plains should push a reinforcing cold front through the area Wednesday morning. This will usher in cooler and much more seasonable weather for Thanksgiving. Morning lows for the holiday are forecasted to be in the 30s/upper 40s inland and 50s near the coast. Daytime highs on Thanksgiving are anticipated to be in the 60s/lower 70s. Conditions will also be dry too with no rain expected. Heading into Friday, we'll see onshore flow return and temperatures/rain chances rise into the weekend. Hints of another cold front remain on the horizon for Sunday into some time next week.

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AVIATION

(18Z TAF Issuance) Issued at 1112 AM CST Mon Nov 24 2025

Scattered TSRA has already developed across the region, warranting at least VCTS starting now for the TAFs north of I-10. These storms are expected to mostly impact our northern TAFs (CLL, UTS, and CXO) where there are TSRA TEMPO groups for said storms early this afternoon. But we will need to keep an eye on IAH as well over the next few hours. In addition, non- thunderstorm winds will be gusty, at times over 25 knots. Locally stronger winds, along with the risk of hail, is expected near the stronger thunderstorms. This evening and tonight, a line of thunderstorms is expected to push through the region. The timing of the line is indicated in the TEMPO groups in the TAFs. Drier air tries to filter into the region behind the front. But it may not be enough to prevent lowered vis/cigs late tonight and tomorrow morning. Vis/cig forecast confidence generally lower than normal tonight.

MARINE

Issued at 1158 AM CST Mon Nov 24 2025

Caution flags may be needed at times today through Tuesday as winds strengthen with a moderate to high risk of rip currents along Gulf- facing beaches. Showers and storms are expected today leading up to a cold front, which should more off the coast by Tuesday morning. Moderate to strong northerly winds develop Wednesday morning as a reinforcing front moves through the area, likely necessitating Small Craft Advisories through Thursday morning. These stronger offshore winds may bring negative water levels at low tide in the upper portion of Galveston bay. Onshore flow returns by Friday, increasing into the weekend as the gradient tightens ahead of the next weather system.

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PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 56 76 50 63 / 80 0 0 0 Houston (IAH) 65 80 55 68 / 80 10 0 0 Galveston (GLS) 72 79 61 70 / 60 40 10 0

HGX WATCHES/WARNINGS/ADVISORIES

TX...None. GM...Small Craft Should Exercise Caution until 6 PM CST this evening for GMZ330-335-350-355-370-375.