


Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
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569 FXUS64 KHGX 181803 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1203 PM CST Tue Feb 18 2025 ...New AVIATION... .SYNOPSIS... Issued at 357 AM CST Tue Feb 18 2025 It has been a very swingy winter this year, where we have routinely found ourselves very much above normal...until we are very much not. An advancing cold front will give us a shot at showers and thunderstorms today, followed by a shot of air behind the front that will remind us that it is indeed still winter. Though wintry precip does not appear in the cards at this time, we`ve got a cold stretch ahead of us. Here are the highlights: - Showers and storms ahead of and along the front will generally be manageable, but there will be some potential for 1-2 inch per hour storms around and east of the Houston metro. There is a marginal risk (threat level 1 of 4) for excessive rain due to this potential. - On the waters, strong winds behind the front tonight and Wednesday are prompting a gale warning on all coastal waters and a wind advisory on coastal peninsulas and islands. Folks right on the Gulf will want to get those loose items secured today before the front rolls through. - Cold air surges in behind the front on gusty north winds; look for wind chills below 20 degrees north and west of the Houston metro. These areas have a cold weather advisory in place. - Tomorrow night, even colder air has prompted an extreme cold watch as the coldest wind chills look to drop to the high single digits. In portions of the Houston metro, potential wind chills range from 25 degrees down to around 15 degrees. A hard freeze is most likely north of the Houston metro, though it could extend into the northern suburbs and into rural areas well west of the metro. && .SHORT TERM... (Today through Wednesday Night) Issued at 357 AM CST Tue Feb 18 2025 This winter has seemed like it`s either been full out spring, or it has been winter. A cold front currently up around the Red River is on its way southward today is going to put us right back in a reminder that February is still a winter month. Until then, however, we`ll have a roughly seasonable day - perhaps a bit colder thanks to cloud cover - along with increasing potential for showers and an isolated thunderstorm. Expect chances for a smattering of showers to gradually grow later this morning, with rain showers becoming likely late this afternoon into this evening, before the frontal passage puts an end to any rain potential late tonight. One thing we will want to watch out for is locally heavy rain. Forecast soundings are...not impressive at all, and I`d expect rain rates to be pretty manageable. That said, mean LREF precipitable water values are around/above the 90th percentile across Southeast Texas, and around the 97th percentile coastward of I-10, so we do have ample moisture available. CAM guidance does show some convective pattern to the rainfall late this afternoon into the evening, in spite of the generally lousy soundings. So, if we can manage one or two decently strong storms, those particular cells could produce 1-2 inch per hour rain rates. HREF guidance suggests a 40 percent chance of 1 inch per hour rain around the Houston metro, and a 60-80 percent chance of 1 inch per hour rates east of the metro, along with a 10ish percent chance of 2 inch per hour rain rates. While not all that scary, it does show that there is some signal that the strongest storms will be capable of tapping into the unseasonable amounts of moisture available to today`s rains. It seems to match up well with WPC`s marginal risk for excessive rain (threat level 1 of 4) today/tonight. Deeper into the night tonight, and even more so tomorrow night, focus turns towards incoming cold air. On the plus side, rain doesn`t look to linger too long after the frontal passage, and the arrival of the wintry air does look to lag a little bit behind the front, which should keep any concerns for anything frozen falling out of the sky at bay. Temperatures, on the other hand, are showing a stronger potential of reminding us that yes, it is still winter in Southeast Texas. Expect temperatures to fall into the low 40s and 30s across the area late tonight into the first hours of Wednesday morning. Freezing temps should be fairly limited in area, held behind a line arcing from roughly Columbus to Navasota to Huntsville to Crockett. Paired with the expected strong north winds though, and we`re still looking at some cold wind chills late tonight. Expect those to bottom out in the teens and 20s for all but right on the immediate Gulf coast, and low enough to require a cold weather advisory along the western edge (where winds are strongest) and northern edge (where temperatures are lowest) of our forecast area. This is where we can expect wind chill to be driven below 20 degrees, and into the 10-15 degree range at their lowest up around Caldwell. Don`t look for things to get much better tomorrow, as continued cold air and lingering cloud cover to hold daytime highs down well below average. Even our warmest spots right on the Gulf will struggle to reach 50 degrees, while folks up in that Caldwell-B/CS-Madisonville-Crockett stretch may not even do better than the upper 30s! This, of course, sets us up for an even colder night tomorrow night. Cloud cover will be diminished, allowing for more efficient cooling. And while winds shouldn`t get too calm, that will be a double-edged sword. Sure, it may mitigate just how cold the temperatures fall, but it will also drive wind chills down even lower. For now, I`ve got an extreme cold watch issued for points at and northwestward of Palacios to Houston to Livingston for the potential to see wind chills below 15 degrees. Ultimately, I expect the potential to meet the extreme cold threshold (10 degrees north, 15 degrees south) will be more limited to the north and west, with some only reaching the threshold for wind chills justifying a cold weather advisory (20 north/25 south) elsewhere. But here at the watch phase, I don`t have the confidence to place precisely where that line is going to be. For now, I will roll with placing a watch roughly in line with the 50 percent probability contour for reaching the warning threshold. && .LONG TERM... (Thursday through Monday) Issued at 357 AM CST Tue Feb 18 2025 1045mb surface high centered over the Central Plains starts to slowly tack east on Thursday. While CAA slowly weakens, this cold- dry airmass is progged to remain in place just a tad bit longer. Lofted moisture with building cloud cover should limit overnight cooling, keeping lows for Friday morning in the 20s to 30s. These overcast conditions will also limit heating on Friday, keeping highs a tad cooler that afternoon compared to Thursday, but still generally in the upper 30s/upper 40s. Our next bout of active weather comes from a mid/upper level trough, which will be passing through the Four Corners on Friday. As it draws closers to SE Texas, a coastal trough/Gulf low will set up over the Western Gulf coast. The influx of moisture from this feature with forcing aloft from the trough should bring increasing rain chances, resulting in cold and dreary conditions on Saturday. PWs remain tame, generally around 1.0-1.3" and with a shallower warm cloud layer and lacking instability, the threat of heavy rainfall with this system remains low for the time being. The upper trough and associated surface features should push off to the east overnight, with rain chances tapering down Sunday Morning. Thinning sky cover should bring a brief warm-up on Sunday, even moreso on Monday as surface high pressure is pushed into north/northeast Gulf, thus establishing onshore flow an WAA. Uncertainty grows high by this point in the forecast, though signs point towards more active weather in store for later next week. && .AVIATION... (18Z TAF Issuance) Issued at 1158 AM CST Tue Feb 18 2025 A mix of MVFR to high-end IFR ceilings can be expected this afternoon, along with periods of light showers. A cold front is expected to move through Southeast TX late this afternoon/early evening. At the moment, the time of arrival of the front is around 00Z Wed near CLL, between 02-03Z Wed near IAH/HOU and after 05Z at GLS. Showers with isolated thunderstorms are expected ahead of the boundary, with showers tapering off from west to east late this evening. Behind the front, gusty northwest to north winds are expected. Gusts in excess of 30 knots are possible at times. Ceilings should gradually improve to MVFR and VFR by Wednesday morning. JM && .MARINE... Issued at 357 AM CST Tue Feb 18 2025 Onshore flow strengthens today ahead of an approaching strong cold front, warranting the need for caution flags at times while showers and thunderstorms develop across the region. Patchy sea fog could form ahead of this cold front as winds ease up, especially over the southwestern waters near Matagorda bay. The cold front will push off the coast late Tuesday night, bringing strong offshore winds, frequent gusts to Gale force and seas of 6 to 9 feet in it`s wake. Lower water levels could develop in the bays, especially at low tide. Gale warnings will be in effect from midnight through Wednesday afternoon for these rough conditions. Small Craft Advisories will likely be needed across the Gulf waters and bays afterwards into the weekend, especially on Friday and Saturday as a coastal trough forms offshore. This feature should bring another round of showers and thunderstorms across the waters. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 62 29 40 22 / 70 60 0 0 Houston (IAH) 63 38 46 28 / 60 80 0 0 Galveston (GLS) 65 43 50 33 / 70 80 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Cold Weather Advisory from 3 AM to 10 AM CST Wednesday for TXZ163-164-176-177-195>198-210-211-226-235. Extreme Cold Watch from late Wednesday night through Thursday morning for TXZ163-164-176>179-195>199-210>213-226-227-235- 236-335. Wind Advisory from midnight tonight to 3 PM CST Wednesday for TXZ436>439. GM...Gale Warning from midnight tonight to 3 PM CST Wednesday for GMZ330-335-350-355-370-375. Small Craft Advisory until 9 PM CST this evening for GMZ335-355- 375. && $$ SHORT TERM...Luchs LONG TERM....03 AVIATION...JM MARINE...03