textproduct: Houston/Galveston

SHORT TERM

(Today through Friday Night) Issued at 415 AM CST Thu Dec 26 2024

In advance of a mid-upper trough, a surface low pressure area will develop in northwest Texas and track ene toward the ArkLaTex today. A strengthening 35-50kt low level jet will transport deeper Gulf moisture into the region with PW's climbing to 1.4-1.6" (abnormally high for this time of year). Expect scattered showers early this morning to transition into thunderstorms and increase in areal coverage late this morning and afternoon with daytime heating, the approach of the LFQ of an upper jet on the backside of the mid-upper trough, and a surface trof/front moving toward the area from the west.

There is a threat of severe weather across all of southeast Texas today. That being said, latest guidance seems to point toward areas along and east of a line from roughly Madisonville-Freeport possibly having the overall most favorable set-up.

Not everyone will see severe storms, but those that do...some significant impacts are not out of the question. All severe wx modes are in play:

- Tornadoes: environment will become favorable for discrete rotating storms especially late morning to late afternoon. - Hail: cooling mid levels of the atmosphere will enhance updraft strength and hail growth zone. Hail larger than quarter size will be likely in the stronger cells. - Wind damage: strong winds aloft will be prone to mix to the surface in/near storm downdrafts. - Heavy rain/flash flooding/rivers: deep moisture is forecast to be in place as will a somewhat favorable set-up for some storm training. Several inches of rain could fall in a short time period leading to some localized issues. Most of the area saw 1-4" of rainfall yesterday which should limit how much the ground can absorb. Should any storms train over locations that saw the most significant rains, runoff is more prone to lead to some street flooding. Though widespread river problems are not anticipated, we'll need to keep an eye on rises on some watersheds. - Hazardous marine conditions: similar to the above...hail, wind gusts >34kt, and waterspouts will be a possibility. Risk probably higher east of Sargent.

Prevalent discrete storms prior to around 5pm should transition to a more linear mode as the surface front makes its way toward the US59- I69 corridor late in the day. A thin band of storms will probably continue southeastward and off the coast sometime around 9pm.

Things should quiet down overnight as the storms pass to the east and southeast and a drier airmass filters in. Coastal locations could see some isolated rain chances return late Friday night as onshore winds gradually bring some moisture back inland. 47

LONG TERM

(Saturday through Wednesday) Issued at 415 AM CST Thu Dec 26 2024

There's a bit of uncertainty on Saturday in terms of if the lingering frontal boundary from Thursday's FROPA is still sitting nearby in a quasi-stationary state, but either way we are expecting to be in onshore flow in the warm sector of a developing surface low near the TX/OK border. This is being pushed by yet another midlevel shortwave trough that swings through the Southern Plains, but this one is not expected to be as potent as the one from Christmas Eve and Thursday. PW values surge to near or above the 90th percentile (~1.37") ahead of an approaching frontal boundary. While we will have an axis of instability in place and modest bulk layer shear, the environment for strong to severe storms looks to be more favorable to our north and east. That's not to say that we can't see a strong storm or two, but the environment for stronger storms gets more favorable the further north and east you go. A broken line of showers/storms is expected to accompany the cold front as it pushes through Southeast TX, especially as it nears the coast due to greater moisture availability.

Cooler and drier air filters in behind the front as we trade out our high temperatures in the mid to upper 70s on Saturday to the upper 60s/low 70s on Sunday. Low temperatures will be in the 40s/50s over the weekend. Surface high pressure kicks out to the east by late Sunday allowing for onshore flow to return. We'll be in more of a southwesterly flow at the surface and 850mb on Monday along with drier air in place. 850mb temperatures will reach near the 99th percentile, so we'll see some fairly warm temperatures on Monday with highs in the upper 70s and I wouldn't be surprised to see some low 80s as well.

Another midlevel shortwave sweeping through the Central Plains will generate surface low pressure with a subsequent cold front pushing into Southeast TX Monday night/Tuesday morning. There won't be enough moisture in place for rain chances to return with this FROPA, but there will be plenty of even cooler and drier air in its wake. The details are a bit murky, but there looks to be a reinforcing front some time on New Year's Day (Wednesday) as well. So, we'll be entering 2025 in style with high temperatures generally in the low 60s (some upper 50s mixed in up north) and low temperatures in the 30s/40s. This is good news for those wanting an early look into the New Year's Eve (Tuesday) forecast to plan for outdoor activities as you likely will not need a rain jacket. I say likely because the GFS is currently the only deterministic model that's showing some rain chances...but both the NBM and LREF ensembles show a less than 5% probability of measurable rainfall around midnight on January 1st. A jacket is recommended though especially if you'll be outside for an extended period of time as we'll have widespread temperatures in the 40s Tuesday night into Wednesday.

Batiste

AVIATION

(12Z TAF Issuance) Issued at 415 AM CST Thu Dec 26 2024

IFR and LIFR conditions, patchy fog and scattered showers will be the problem into mid morning. Heading into the late morning and afternoon, ceilings will lift into a mix of MVFR/VFR territory, but thunderstorms will develop and increase in coverage...some probably severe (see above). Overall conditions will improve later this evening as storms push out of the area. Will however need to keep an eye on some patchy fog development later tonight with wet ground in place and lowering wind speeds. 47

MARINE

Issued at 415 AM CST Thu Dec 26 2024

Light southerly to southeasterly winds this morning will gradually increase throughout the day as the next storm system approaches. These elevated winds warrants at least caution flags into late tonight. A cold front will accompany this storm system, and there will be showers and thunderstorms both ahead of and along the frontal boundary. Some of these storms may become strong to severe and be capable of producing strong winds, hail, and frequent lightning. Tornadoes and/or waterspouts cannot be ruled out. The cold front will push towards the coast by this evening, but is expected to linger near the coast into Friday. Onshore flow returns by Friday as the lingering boundary retreats northward. As a result, rain chances remain in forecast till another cold front pushes through on Saturday leading to a period of northerly flow before onshore flow returns again late in the weekend.

Until Saturday's cold front pushes past the coast, there will be potential for sea fog during the overnight to early morning hours as dew points remain in the low to mid 60s paired with water temperatures in the low 60s.

Batiste

PRELIMINARY POINT TEMPS/POPS

College Station (CLL) 72 50 70 53 / 80 10 0 10 Houston (IAH) 74 57 72 60 / 90 60 10 20 Galveston (GLS) 70 62 69 63 / 60 60 10 40

HGX WATCHES/WARNINGS/ADVISORIES

TX...None. GM...Small Craft Should Exercise Caution from noon CST today through this evening for GMZ330-335.

Small Craft Should Exercise Caution through this evening for GMZ350-355-370-375.