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
286 FXUS64 KHGX 140023 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 723 PM CDT Tue Apr 13 2021 .SHORT TERM [Tonight Through Wednesday]... Quick update sent for current trends and the expectation that outflow from LA storms will push in and initially help to get showers going then as s/w arrives late evening scattered showers and thunderstorms should develop and persist through around 3 am gradually shifting west then back to the east. Warm temperatures again this evening...especially over the southern areas. Current looking for a tie on the record high minimum at Galveston at 74 (unless the outflow from the LA storms pushing west over the nearshore waters dips temps down to 72). Sea fog near shore and in the bays and may need a dense fog advisory for the coastal areas and will be monitoring webcams/obs and trend closely this evening. 45 && .AVIATION [00Z TAF Issuance]... Sea fog has moved ashore near GLS and expect fluctuations in VISBY from 1/4 to 2 miles this evening there. Cold front stalled near a DKR-CLL-66R line but should slowly sag south later this evening. Unstable airmass over the areas along and south of the front expect scattered showers and thunderstorms to develop. At this point expecting more or less 2 rounds of storms...the first this evening/early morning a lull then redevelopment late morning/afternoon. Will continue with the previous forecast trend of lowering VFR/MVFR CIGS overnight into IFR and possibly getting into LIFR. Very slow improvement 13-16z in CIGS then most sites should at least be MVFR if now VFR though with the continued threat of SHRA/TSRA. Widespread IFR/LIFR Wednesday evening. 45 && .MARINE... Expanded the marine dense fog advisory up into the eastern nearshore waters and Galveston Bay. 11 .PREV DISCUSSION /Issued 327 PM CDT Tue Apr 13 2021/... .LONG TERM [Thursday through Tuesday]... On Thursday, Southeast Texas will be in predominantly zonal flow aloft as it is sandwiched between two upper-level lows, with one UL low located over The Great Lakes and the other located near Utah. A weak frontal boundary will be positioned just offshore of our coast as well. Small and embedded shortwaves will push through this zonal flow which will be just enough upper-level support to invigorate showers and isolated thunderstorms on Thursday around the frontal boundary. Forecast soundings show significant dry air aloft during this time frame, so convection should be relatively shallow. By Friday, the upper-level trough over Utah will begin to push southeast. Leeside cyclogenesis will help strengthen a surface low and its associated cold front as this front approaches SE Texas. Moistening mid-levels from WAA and Gulf moisture will help saturate forecast soundings and increase PWATs to around 1.9" across our region. This combined with some instability and a frontal lifting mechanism will increase our chances for showers and thunderstorms on Friday. This front is expected to stall near the coast again with the GFS showing it stalling offshore and the ECMWF showing it stalling in our southern CWA. Therefore, rain chances Friday and onwards depends on where this front stalls. However, in the wake of Friday`s front, NE flow resumes along with CAA and slightly cooler and drier conditions. This intruding dry air will help limit the coverage of these showers as well. From Friday night onwards, surface winds will remain N-NE and skies will be partly cloudy. Daytime highs will struggle to reach the 70s this weekend. Partly cloudy skies will slightly enhance radiational cooling, so overnight lows this weekend will struggle to reach 50 north of I-10 whereas areas south will hover in the low 50s. As a high pressure builds in further south on Monday and washes out most rain chances, winds become light and variable, slowing down that CAA and allowing temps to climb back up to the mid-70s on Tuesday. KBL .MARINE... A couple of issues will affect mariners tonight. The first, is dense sea fog affecting the southern Gulf waters adjacent to Matagorda Bay. Visibility at platforms over the Gulf have wavered between 1/4 and 1/2 NM. Will extend the Marine Dense Fog Advisory for the 0-20 NM waters from Freeport to Port O Conner through 06z. It may need to be extended and expanded to include the bay. Over the eastern Gulf waters, the pressure gradient is expected to tighten significantly this evening as the gradient tightens in response to a developing coastal trough and as the inflow into a developing convective complex over NE TX increases. A SCEC has been issued for the eastern waters for tonight. Winds will become east on Wednesday as low pressure develops over South Texas. The low will meander over South Texas and surface winds will be SE ahead of the next cold front that will move into the coastal waters on Friday night. A strong N-NE flow will develop Saturday and Sunday and a SCA will likely be required over parts of the coastal waters. 43 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 67 77 58 71 59 / 60 50 50 30 40 Houston (IAH) 71 82 62 74 62 / 60 70 60 30 30 Galveston (GLS) 74 80 67 75 68 / 40 40 60 30 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Dense Fog Advisory until 5 AM CDT 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...Galveston Bay. SMALL CRAFT SHOULD EXERCISE CAUTION until 5 AM CDT Wednesday for the following zones: Coastal waters from High Island to Freeport TX out 20 NM...Waters from High Island to Freeport TX from 20 to 60 NM. && $$ SHORT TERM...45 MARINE...11
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