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
457 FXUS64 KHGX 042355 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 555 PM CST Thu Feb 4 2021 .AVIATION [00Z TAF Issuance]... Drier air and a cold frontal passage tonight will help lift and dissipate cloud ceilings back to VFR conditions. Winds will suddenly shift to the north with the frontal passage as well. Some isolated light showers are possible, but will be very brief should it pass over an airport. Therefore, didn`t include it in the TAF as a prevailing group. Tomorrow near 13-15Z, confidence increases for some scattered rain showers to develop, so included VCSH for a few hours and lowered the ceilings back to MVFR. && .PREV DISCUSSION /Issued 334 PM CST Thu Feb 4 2021/... .SHORT TERM [Today Through Friday Night]... It`s a hot one down here in southeast Texas and that`s due to a couple of reasons. An area of low pressure in the Central Plains has put us into a southwesterly flow. The warm temperatures down in south Texas are being advected into the area through warm air advection as we have winds perpendicular to isotherms (lines of constant temperature). The southwesterly winds are also eroding away the clouds over portions of the CWA which will allow for most of the shortwave radiation from the sun to make it to the surface. With 850 mb temperatures ranging from 16-18 degrees Celsius across the region, highs will be able to reach the low 80s out to the west and upper 70s elsewhere. This means we`ll have to keep an eye on record MaxT values today since those are also in the low 80s today for most locations. The area of low pressure is a key part of the forecast because as it traverses to the east, it will drag a cold front through the area in the late afternoon/evening hours today. Hi-res model guidance indicates that there will be a thin line of rain showers along the frontal boundary (mainly affecting areas east of I-45) as it passes through. Even though PWATs will be around 1.25", instability is lacking and there is an inversion around 850 mb so any rain that falls will trend towards being light and brief. This won`t be our only chance of rain before the weekend though. Before the cold front moves offshore, there is a window for patchy sea fog beginning this evening along the coast due to mild dew points in the low 60s and nearshore water temperatures in the upper 50s. The fog will move out of the area once the front pushes offshore by midnight. Temperatures tonight will range from the mid 40s up north to the mid 50s along the coast. A shortwave moving into the area on Friday morning in combination with upper-level divergence and leftover PWATs around 0.6" in the northern CWA and 1.2" along the coast will create enough lift to generate scattered elevated rain showers throughout the day. Resultingly, afternoon temperatures tomorrow will likely not make it above 60 degrees. High temperatures will be relegated to the mid-to- upper 50s. Friday night will be a cold one with lows in the upper 30s/low 40s. Batiste .LONG TERM [Saturday Through Thursday]... An upper level trough will be moving across North Texas into Arkansas during the day on Saturday. The associated cold front will pass through the region Saturday afternoon with it getting off the coast by sunset. Not much, if any, precipitation is expected with this FROPA with the best chance of showers being on the eastern portion of the area in the later part of the day. The main impact from this front will be the reinforcement of the cooler air over SE Texas, and kick out any lingering moisture that moved in over the area on Friday. High pressure slides in from the west on Sunday producing a fabulous day for SE Texas with mostly sunny skies, light winds, and high temperatures in the upper 60s. Though this high pressure does not stick around as it quickly exits to the east by Monday morning. This returns southeasterly flow into the region through midweek bringing low to mid 70 high temperatures back into the region by Tuesday. PWATs also creep up next week to 0.75 to 1 inch by late Monday as a weak shortwave trough crosses the area. This, combined with the surface moisture, will lead to the possibility of isolated showers, mainly near the coast, late Monday. A weak cold front will move through the area sometime Tuesday (timing right now is a bit uncertain), that may bring a brief northwesterly wind shift to the area. But, this front weakens/washes out as it heads into towards the coast and a general east to southeasterly flow returns by Wednesday. Wednesday through the end of the week is looking rather unsettled across the entire Gulf Coast as PWATs surge to 1.2 to 1.4 inches and a boundary slowly moves onshore. Scattered showers will be possible from essentially late Wednesday through the day on Thursday and into Friday. Low temperatures across the northern third of the area Tuesday night through Thursday night will be approaching freezing, so winter ain`t done with us quite yet. An upper level trough will be crossing the Four Corners region on Thursday which will be what eventually clears out the moisture beyond the end of the long term period. Fowler .MARINE... Can`t rule out a few hours of patchy sea fog ahead of an approaching frontal boundary that`ll be pushing off the coast around, or shortly before midnight. Will keep the existing SCA`s going for the offshore waters going through Fri afternoon and introduce some SCA`s for the bays and nearshore waters around 3am when northeast winds should approach the 20kt criteria. Winds should diminish and become more easterly Fri night as a weak coastal trof develops well offshore and moves off to the east Sat. A stronger front is forecast to move off the coast Sat evening and SCA`s may again be required as nrly winds increase. Onshore flow should resume late Sun as high pressure moves off to the east. Will be on the lookout for some sea fog Monday evening thru Tue evening as dewpoints climb into the lower 60s over the cooler shelf waters. A 3rd front, stronger than the previous two, is penciled in for Tue night. This should bring an end to any fog but will be accompanied by stronger NNE winds and building seas into midweek. 47 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 44 55 39 66 37 / 10 20 10 0 0 Houston (IAH) 48 56 43 65 42 / 20 30 20 0 0 Galveston (GLS) 52 57 50 63 49 / 20 20 20 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...Small Craft Advisory from 3 AM to 9 AM CST 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...Galveston Bay...Matagorda Bay. Small Craft Advisory until noon CST Friday for the following zones: 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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