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
458 FXUS64 KHGX 230440 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1140 PM CDT Thu Apr 22 2021 .AVIATION [06Z TAF Issuance]... Scattered to widespread light rain has began to move across the region late this evening, bringing MVFR to high-end IFR ceilings. Conditions will continue to deteriorate tonight into Friday night as a warm front lifts north into the region and a cold front moves through late Friday night into Saturday. Expect widespread MVFR to IFR cigs through most of the TAF period. Scattered showers and thunderstorms will be on the increase by mid-morning, with better chances in the afternoon and evening. Gusty southeast to south winds are expected Friday afternoon and evening with gusts as high as 25-27 knots at times. 05 && .PREV DISCUSSION /Issued 648 PM CDT Thu Apr 22 2021/... .SHORT TERM [Today Through Friday Night]... High pressure over LA and falling pressures near El Paso and surface cyclogenesis in SE CO will maintain the light to moderate easterly flow and should strengthen WAA pattern into tonight/Friday. A very strong cap will start off the overnight hours and as the low levels get more moist will have both and increase in the thickness of clouds this evening but also an increase after 7-9 pm of rain chances. Light sprinkles/-SHRA late tonight should continue throughout the night as the upper trough moves into AZ and overhead the first of the subtropical jet influences come to bear. LLJ cranks up from S TX up into Wrn Hill County and then up into western OK which will also make for a warm night across SETX. Lows only dipping into the lower to mid 60s north and may even be rising toward morning there. Friday around sunrise expect coverage of showers to increase to the west and northwest and have the potential for some isolated discreet storms to get going along and south of the warm front lifting up through the east/northeastern counties. This would most likely be in the 1 pm to 5 pm Huntsville to Liberty northeast in a very high shear - low CAPE environment, 0-1km SRH >200 and CAPE 600-1800. Brief tornadoes or possibly strong gusty winds the issue but again these chances look slim. With the approach of the upper trough expect steepening upper level lapse rates more time to destabilize the lower levels and erode the cap across the northwest and northern areas late afternoon into the evening. The shear/temp profiles morph quickly toward a wind and hail threat and HREF keeps most of the threat just north of the area but does have a few outliers impacting the northern areas. SPC does have SETX in a slight risk though with the coming runs some of this may get shaved off closer to the coast where the cap may be too strong. The late afternoon threat up north swings through during the evening again mainly focused over the areas from Brenham to Huntsville to Livingston with threat for moderate to strong thunderstorms a little further south into the Houston area. The drier air arrives in the late evening and rain chances start dropping and shifting away to the northeast and east. May get a flare up of storms along the 925-850mb front in the southern portions of the area that initiate with the upper trough passage and these could have some gusty winds that move into the coastal areas and waters along or ahead of the mild Pacific cold front. Much need rainfall of 0.25 to 2" should be common across the region and some isolated swaths of near 3" possible. May be enough for some spotty flooded streets but the threat looks low for that. 45 .LONG TERM [Saturday Through Thursday]... By Saturday morning, some lingering showers are possible along the coast as the cold front continues to push offshore. Soon after by Saturday afternoon, a surface high pressure and upper-level ridge will build in across TX. Therefore, skies will clear and not much of a cool down is expected with daytime highs reaching the 80s again across our CWA. However, clear skies overnight will enhance radiational cooling along with NE winds which will bring in cooler and drier air and drive overnight lows into the low-to-mid 50s north of Houston and near 60 everywhere else (approximately 10 degrees cooler than the night before). By Sunday, E-SE flow will resume and help to increase cloud cover and moisture across SE Texas. Daytime highs will still be in the mid-80s on Sunday and Monday and overnight lows will be in the 60s. Rain chances return mid-week next week as a leeside low and a surface front develops across The Central Plains late Tuesday. Strong WAA and a low-level jet will drive up moisture and temps as overnight lows are expected to reach the very muggy 70s. Showers and isolated storms are possible ahead of the frontal passage. By Wednesday, the surface front is expected to push across our area. However, global models are in a disagreement regarding the timing, intensity, and duration of this cold front. KBL .MARINE... Currently, easterly winds around 20 knots will persist this afternoon and evening and slowly become southeasterly overnight. Winds might subside slightly back into SCEC criteria tomorrow, but will pick back up to SCA criteria by Friday evening and ahead of the next cold front. Some showers and thunderstorms are possible Friday night and into Saturday morning as the cold front pushes off the coast. Due to persistent moderate to strong winds, rip currents will be a risk through this weekend as well. Behind the frontal passage, offshore flow will be brief on Saturday and onshore winds will return by Sunday as a high pressure builds in. KBL && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 62 77 64 82 54 / 30 80 50 0 0 Houston (IAH) 64 77 68 86 58 / 40 80 60 10 0 Galveston (GLS) 69 76 71 82 66 / 30 60 40 10 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Friday afternoon for the following zones: Bolivar Peninsula...Brazoria Islands...Galveston Island...Matagorda Islands. GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Friday afternoon for the following zones: Galveston Bay...Matagorda Bay. Small Craft Advisory until 4 PM CDT Friday 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...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. && $$
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