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 100010 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 610 PM CST Tue Feb 9 2021 .AVIATION [00Z TAF Issuance]... A cold front progressed through the northern half of the area today bringing a northerly wind to CXO and terminals northward. This boundary will stall out between CXO and IAH, and then sorta wobble back and fourth slowly between the I-10 corridor and the coast through the day tomorrow. With this stationary boundary spread across the area, scattered showers and even isolated thunderstorms beginning tomorrow afternoon. Otherwise, expect LIFR to IFR conditions to develop tonight with CIGs of around 300 to 700ft that persist through tomorrow. Patchy fog will also develop tonight with the highest areal coverage being along the coast. HOU, SGR, LBX, and GLS could get visibilities dropping below a mile at times, but patchy fog will be possible across the entire area. Fowler && .PREV DISCUSSION /Issued 339 PM CST Tue Feb 9 2021/... .DISCUSSION... A cold front has sagged into Southeast Texas today, and will remain mostly stationary in the area through tomorrow, until it finally clears the area sometime on Thursday morning. This front will become a focus for showers and a few embedded thunderstorms, particularly Wednesday night and Thursday. Once that front finally clears, colder and drier air will surge into Southeast Texas, beginning a prolonged cold snap that will last well into next week. While we have high confidence in seeing a long stretch of below normal temperatures, there is still some uncertainty in precisely how severe this cold snap will be, and if we`ll see any wintry precipitation. Stay tuned for the latest forecast information - particularly if watches, warnings, or advisories are needed for significantly abnormal cold. .SHORT TERM [Through Wednesday Night]... Satellite imagery and surface observations show that a cold front has made its way to roughly US-59/I-69, leaving a stretch of the Gulf coast in the warm, humid, pre- frontal airmass. Behind that front, temperatures have remained cold underneath a relatively thick, low stratus cloud deck. Temperatures there have remained mired in the low to mid 50s, while dewpoints have fallen into the 40s. On the warm side of that front, highs in the 70s are being seen, with dewpoints in the low mid 60s! Clouds in this region are a bit more cumuliform...ish, while the humid air over the relatively cold Gulf waters has helped generate a significant area of sea fog. The sea fog has prompted marine dense fog advisories on the waters, and for more details on that, check the marine section further down. Overnight, as long as winds become relatively light as expected, land areas will also see overnight fog return. Unlike last night, which saw widespread dense fog across Southeast Texas, the most dense fog should be confined a little better to coastal areas. Still, at least some fog is likely to push its way inland, particularly if the stalled front retreats at all overnight. Beyond the fog, there will be some low potential for showers overnight, mainly right on the frontal surface where lifting of the deeper onshore flow will be most significant. The front has outrun its upper support considerably, so I`m not sure how effective we`ll be at squeezing out a lot of showers, but the isentropic upglide over that boundary may help us get a few showers here and there. Rain potential should be expected to gradually increase through the day Wednesday, and particularly Wednesday night as an upper trough finally comes to provide a little help to the surface feature. Guidance indicates a little bit of instability being generated as air cools aloft. It`s not going to be a lot of thunderstorm fuel, but it should be enough to get a few of the friskier embedded cells to generate some lightning strikes here and there. The best shot for this is likely to be in the afternoon Wednesday and/or Thursday, which means we have now arrived at the segue to the long term section. .LONG TERM [Thursday Through Tuesday]... Fairly high rain chances will be ongoing across SE TX on Thurs with the passage of the strong cold front. The bulk of the precipitation should be showers, but still cannot rule out isolated thunderstorms given the modest lapse rates/weak instability. All this activity is expected to move off the coast with the front by early Fri morning. Rainfall totals should average from 1/2 to 1 inch over the CWA with isolated higher amounts from 1 to 1.5 inches possible. Otherwise, the main forecast issue with this portion of the forecast looks to be the potential for some very cold/well below normal temp- eratures for an extended period (Thurs night through Mon night), and perhaps a slight chance of precipitation during the same time frame. Progs of a series of strong surface highs moving down from the High Plains (1041mb to 1047mb) into the Central Plains from Thurs on in- to the weekend will help maintain a strong/persistent CAA into the state. Will continue to lean on the side of the colder GFS/Canadian solutions for our temperatures. This pattern could produce extended periods of freezing/below freezing temperatures this weekend...with possibly a Freeze Warning for our coastal counties. Slightly better consensus/slowly increasing confidence with the likelihood of colder weather does make this a very good time to remind everyone to check their cold weather preparations (both inside and outside) for this potentially prolonged cold snap. As for the chances of precipitation...models are continuing to show a series of embedded shortwaves moving across the area through this weekend. As it usually is with the SW flow aloft, the timing of said shortwaves is expected to be an issue. Given the very cold air mass in place over SE TX...there could be some light mixed precipitation (rain-snow/sleet mix) over the CWA at times during this time frame. As all of this is still a ways away, confidence remains very low for this even verifying at this time. .MARINE... While webcams show that we`ve gotten a fair amount of improvement in visibility on both Galveston and Matagorda bays, we also see from webcams on the Gulf coast and from satellite that dense fog has not retreated much more than that. The dense sea fog advisory that`s been in place all day for the nearshore Gulf waters will continue through the night, and will likely have to be extended deeper into Wednesday. Meanwhile, while things have gotten nicer on and around the bays this afternoon, we should see visibility deteriorate again this evening as the sea fog returns and socks things in overnight. Winds are expected to veer a touch more southerly on Wednesday, which may help provide modest improvement tomorrow. But ultimately, the environment will remain conducive for sea fog until this cold front fully clears the waters on Thursday. Though dense fog should clear in its wake, the front will also usher in a prolonged stretch of cold, unsettled weather all the way to the Gulf coast that will persist deep into next week. On the waters, elevated northerly winds and seas should continue through this stretch. Be on the lookout for caution flags and/or small craft advisories as needed. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 44 51 44 51 37 / 30 60 70 80 40 Houston (IAH) 57 69 56 64 44 / 30 30 70 80 60 Galveston (GLS) 59 65 61 66 48 / 20 30 70 80 70 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Dense Fog Advisory until 6 AM CST Wednesday 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. Dense Fog Advisory until 6 AM CST Wednesday for the following zones: Galveston Bay...Matagorda Bay. && $$ DISCUSSION...Luchs SHORT TERM...Luchs LONG TERM...41 AVIATION...Fowler MARINE...Luchs
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