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
000 FXUS64 KHGX 102359 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 659 PM CDT Mon May 10 2021 .AVIATION [00Z TAF ISSUANCE]... Line of strong SHRA/TSRA will continue across Walker, Trinity, San Jacinto and Polk counties through early tonight and are expected to gradually dissipate with the loss of heating. Models still show some isolated activity overnight but so far most of them have been too aggressive for what we have actually been getting. Thus, have not included any wx for tonight on this TAF set and will likely handle any popup wx with TEMPOs. MVFR to IFR cigs will be the main concern during the overnight hours. There is also a potential for patchy fog given the small dew point spreads and light VRB winds. Tuesday, have dialed back on mentioning wx for the morning hours, though still a possibility. SHRA/TSRA activity is more certain to occur during the afternoon hours, as daytime heating ramps up and peaks. S winds at around 10 KTS expected Tuesday...VRB at times across CLL/UTS/CXO. 24 && .PREV DISCUSSION... /ISSUED 327 PM CDT Mon May 10 2021/ SHORT TERM [Remainder of the Afternoon through Tuesday Afternoon]... Temperatures have soared this afternoon with Huntsville hitting 93 and heat indices this afternoon of 103 (at Huntsville) with widespread 91-96. All this heat and humidity is priming the atmosphere and closely watching the area between Huntsville and Cleveland and Conroe area for rapid development of the thunderstorms. Isolated severe possible with a hail threat 4-7 pm along with with an inch or so of rain. This evening storms should wane quickly and then skies should cloud up before midnight with warm southerly flow except for the stationary frontal area near College Station-Groveton area. Spotty showers overnight are possible then skies should scatter out with heating 8-10 am Tuesday. This will again be priming the pump as PW increases back up to 1.8-1.9"/CIN decreases Tuesday and s/w of note arrives from the west in the afternoon/evening. This should lead to more widespread development of showers and thunderstorms with a threat for heavy rainfall mainly in the afternoon headed into the evening. 45 LONG TERM [Tuesday Night Through Monday]... The slow-moving cold front will be a key part of the forecast for Tuesday night through Wednesday morning as the bulk of the showers and thunderstorms will develop along the frontal boundary. Interestingly enough, there is pretty good consensus with hi-res and global models which indicate that the cold front will be halfway through the CWA at 00Z Wednesday and along or just off of the coast by 12z Wednesday, so Wednesday morning appears to be the cutoff for the heavier rain. Tuesday night through Wednesday morning, widespread showers and thunderstorms are likely especially along and south of I-10, and with PW values near 2", locally heavy rainfall is possible especially along the coast. WPC has most of the CWA in a marginal risk in their Excessive Rainfall Outlook for Wednesday. Latest QPF run shows 1-2" of rain across the area through early Thursday, but higher isolated amounts are possible. Due to the post- frontal CAA, rainfall, and persistent cloud cover, leaned towards the cooler side of guidance with Wednesday high temperatures ranging from the upper 60s up north to the mid-to-upper 70s further south. PVA from a shortwave trough comes to an end early Thursday as the pattern transitions to mid/upper-level ridging, so PoPs have been tapered off after Thursday morning from the north to the south. Thanks to CAA prevailing through Friday morning, we will have a couple of days of below normal temperatures. Lows on Wednesday night and Thursday night will drop down into the upper 50s/low 60s. Surface high pressure slides off to the east on Friday and gradually reintroduce WAA to the region through southeasterly flow. Resultingly, high temperatures for Friday will reach the low 80s with mid 80s expected over the weekend and into early next week. In the latter half of the weekend, PoPs return as a shortwave trough approaches the region. Positioning and strength of any PVA is still a bit uncertain along with the availability of moisture. ECMWF is more progressive and aggressive (intentional rhyme) with moisture return with PW values exceeding 1.5" by Saturday night. Meanwhile, GFS and Canadian still indicate PW values around 1" at the same time. For now, the highest PoPs are on Monday but this will likely flip-flop throughout the week depending on where models place the shortwave trough. Looking a bit ahead, the upward temperature trend continues into next week so the rain would come as a temporary relief for those that receive it. Batiste MARINE... Light southeasterly flow continues to prevail ahead of a stationary front that is sitting inland over the northern portion of the CWA. This front will slowly move to the south and eventually move off of the coast on Wednesday morning. Showers and thunderstorms can be expected ahead of and along the frontal boundary with the highest PoPs late Tuesday through Wednesday morning. Moderate northeasterly flow will prevail in the wake of the front through early Friday with wind speeds at least above the caution threshold and bordering on the advisory threshold. Onshore flow returns by Friday afternoon as high pressure moves off to the east. Seas will gradually elevate over the weekend and into early next week with offshore wave heights reaching 6-7 feet by Sunday night. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 66 79 63 71 60 / 40 80 80 60 20 Houston (IAH) 76 88 67 75 62 / 20 30 70 70 20 Galveston (GLS) 76 84 72 78 67 / 10 10 60 70 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk until 7 PM CDT this evening for the following zones: Bolivar Peninsula...Brazoria Islands... Galveston Island...Matagorda Islands. GM...NONE. && $$ Aviation...24
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