Area Forecast Discussion
Issued by NWS Houston/Galveston, TXVersions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000 FXUS64 KHGX 312318 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 618 PM CDT Wed Mar 31 2021 .AVIATION [00Z TAF Issuance]... A gradual clearing is underway with this afternoon`s cold front having cleared the coast. A few showers continue to linger around the barrier islands, though activity is expected to diminish within the next couple of hours. All sites aside from LBX now report VFR cigs, which should continue to lift and eventually give way to clear skies as a drier airmass continues to move into the area. Winds will remain elevated overnight, with gusts reaching near 30 knots near the coast and around 20 knots inland. Tomorrow, expect clear conditions with northerly winds of around 10 to 15 knots. Cady && .PREV DISCUSSION... /ISSUED 334 PM CDT Wed Mar 31 2021/ SHORT TERM [Tonight through Thursday Night]... A cold front located along the coastal counties as of around 3 PM CDT will continue southward into the coastal waters late this afternoon and evening, resulting in scattered showers and isolated thunderstorms mainly along the frontal boundary. Rain chances inland will cease this evening/early tonight as the front moves further into the Gulf waters. Behind the front, surface temperatures have only dropped about 5 to 10 degrees. However, as colder and drier air comes through and skies slowly scatter out tonight, temperatures will have a more pronounced dip, with lows decreasing into the upper 30s to lower 40s along areas north of I-10, the mid to upper 40s along areas south of I-10, and the low 50s along the coastal areas. Post-frontal northerly winds will continue to be a concern, with moderate to strong gusty winds affecting most of the CWA through late tonight, except the coastal areas where hazardous wind conditions are expected along the Barrier Islands and surrounding waters due to winds of 20 to 30 MPH with gusts of up to 40 MPH through Thursday morning. For the rest of the day Thursday, breezy conditions will prevail for most of the morning. Mostly sunny skies along with high temperatures in the mid 60s areawide will result in a pleasant and soon to be rare SE TX day. Winds will relax late afternoon into Thursday night, becoming calm to light, and shifting more easterly as high pressure moves across TX. 24 LONG TERM [Friday Through Wednesday]... There is...not much to speak of in the long term. By Friday morning, the deep upper trough will have made its way to the Eastern Seaboard, and a ridge will be building over Texas. Down at the surface, high pressure will be making its way from the Ohio Valley into the Mid-South. And beyond that...it`ll just be tracking these high pressure features as they drift around and generally dominate our weather through the first half of next week. The only really notable deviation from this will be Sunday into Monday, as a weak shortwave trough rounds the building ridge and drives over the area. As it passes overhead, I certainly can`t tell your the rain chances will be nil, but when I say this is where the highest PoPs of the long term are, this is very much in the relative sense. There was not a very coherent signal for rain, increasing temps just above the deck will increase capping, and precipitable water values are only progged to be just high of one inch, so I capped PoPs just under the "slight chance" wording for now. If there becomes a broader consensus for some weak showers, we can always nudge those PoPs up a bit. Really, the main story for the long term will boil down to the warming trend expected as we get deeper into next week. With ridging aloft and a surface high to the east feeding us low level flow from the Gulf, an increase in temperatures is virtually certain - the question becomes how hot will we get? The statistically post-processed deterministic NBM temps have been on the cool side, though it did trend up today. Looking at the distribution of this consensus, however, we may want to be on the lookout for temps drifting even higher. For example, on Wednesday, the deterministic high at KIAH is 85 degrees, while the median of the NBM distribution is 89. The 75th percentile is 92 degrees, so there`s even an outside shot we could see our first 90s of the year next week. I did not really look to overshoot the post-processed guidance just yet - while the pattern is very high confidence for a warmup, it`s also not a terribly beefy ridge we`re looking at, either. I don`t know that I want to get real carried away with trying to deviate from a fairly reliable model consensus just yet. But...it`s something to be on the lookout for, and if confidence increases in abnormally warm temps, we may start to cheat those forecast values upwards in the coming days. Luchs MARINE... A cold front is nearly to the coast, and as it finally pushes out over the waters, it will turn winds to northwesterly and drier air will put an end to the sea fog threat. However, webcams on the coast are showing that visibility is starting to degrade again, and sea fog will be trying to make its way back towards shore in its short remaining time. Think the front will move quickly enough to keep it from being a big deal, but we may see a very brief window of some more dense fog late this afternoon/early evening before it gets scoured out for good. Once the front is through, of course, look for strong northerly winds to build, continuing into tomorrow morning. Have stayed with the gale warning in place, as winds - particularly beyond 20 nm out should be good sustained gale, along with frequent gale-level gusts across the waters. Beyond that, high pressure behind the front will settle down from the Mid-South to over the Gulf of Mexico over the next several days, which will turn northerlies to more northeasterly, and return to onshore flow by early next week. Luchs FIRE WEATHER... With drier air surging in behind today`s cold front, we can look for very dry conditions tomorrow and Friday, with relative humidity bottoming out around or below 25 percent each day. Winds by tomorrow afternoon will be diminishing, but we could still see some sustained winds to up around 15 mph at the coast, and gusts to that level further inland. This overlap shouldn`t be for a significant period of time and mitigate the threat of severe fire weather conditions, but things will definitely be more conducive for fire spread than a `typical` spring day. While RH will be similarly low on Friday, winds will be lighter and beginning to turn increasingly onshore. With onshore flow firmly established by Saturday, expect RH to be higher for the weekend and beyond. Luchs && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 40 65 39 69 45 / 0 0 0 0 0 Houston (IAH) 46 68 43 67 47 / 10 0 0 0 0 Galveston (GLS) 52 66 53 63 56 / 20 0 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Wind Advisory until 9 AM CDT Thursday for the following zones: Bolivar Peninsula...Brazoria Islands...Galveston Island... Matagorda Islands. GM...Gale Warning until 10 AM CDT Thursday for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM...Galveston Bay...Matagorda Bay...Waters from Freeport to Matagorda Ship Channel TX from 20 to 60 NM... Waters from High Island to Freeport TX from 20 to 60 NM. && $$
