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 090430 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1030 PM CST Mon Mar 8 2021 .SHORT TERM [Tonight Through Tuesday]... Moistening of the atmosphere continues with southeasterly flow firmly in place. Expect a warmer night across the region with lows in the 50s to around 60. Nudged up temperatures inland west a degree or two based on current trends and the 00z NAM/RUC. Winds although light continue throughout the night. Clouds a mix of 4000-6000 foot and cirrus overnight. Dewpoints well offshore already in the upper 50s to lower 60s and this along with the aforementioned NAM indicating a slight increase in the chances for sea fog Wednesday morning near Galveston Bay. SE winds offshore creeping up and seas have slowly built with longer periods as well. Fluctuating at 5-6 feet looks likely through the night and much of Tuesday so have hoisted a SCEC for the 20-60nm waters. 45 && .AVIATION [06Z TAF Issuance]... VFR most of the forecast. Some SCT/BKN ceilings on tap Tuesday night across the west/northwest. Will also be looking for the increased threat of fog near Galveston Tuesday night. 45 && .PREV DISCUSSION /Issued 550 PM CST Mon Mar 8 2021/... .LONG TERM (Wednesday through Monday)... An upper level ridge will be located over the western Gulf with a developing SW upper flow over East Texas. At the surface, high pressure will be over the eastern US with low pressure over the central plains. A moderate to strong onshore wind will continue to draw low level moisture into SE TX under a strong and persistent cap in the 850-700 mb layer. Pw values remain under an inch on Wednesday but forecast soundings show a semi-saturated profile from the sfc to 850 mb so it`s possible to generate some very light showers beneath the cap, however, most of the area will remain dry. 850 mb temps support MaxT values near 80 degrees but with the level of mixing from the winds and expected cloud cover, will trim a few degrees and keep MaxT values in the mid 70`s. Fcst soundings show a saturated profile beneath 850 mb on Wednesday night and PW values reach 1.20 inches so feel the potential for additional streamer showers will persist. Capping will remain very strong so only showers and expected. Cloud cover and winds will keep MinT values on the warm side, probably remaining in the middle 60`s. Thursday through Saturday look about the same as Wednesday, albeit a bit warmer. Fcst soundings show a semi-saturated profile below 850 mb with a significant dry layer between 850 and 500 mb with strong capping in the 850-700 mb layer. PW values remain between 1.00 and 1.20 inches so can`t rule out an isolated shower but most of the area will remain dry. Forecast soundings also show some potential for more afternoon sun so went a bit warmer with MaxT values warming into the lower 80`s. Overnight lows will remain very warm with MinT values in the mid/upper 60`s. Have added patchy fog near Galveston Bay/nearshore waters and the adjacent coastal areas. Surface dew points are progged to increase into the middle 60`s. The water temperature is currently 60 degrees so there is some potential for sea fog. However the long and persistent S-SE fetch will bring warmer water toward the coast and this should help negate the sea fog potential. The real fun and games begin next weekend as a deep upper level low becomes cut off from the main flow over Southern CA Thursday night and the system slowly meanders across the southern Rockies through Sunday. The upper ridge over will remain stout so the upper level low is going to have go up and over the top of the Gulf ridge. The upper low will pivot into the central plains on Sunday and it will take on a negative tilt. There are still some significant timing differences between the faster GFS and the slower ECMWF, ICON and GEM solutions. Prefer the slower solutions as cut off systems with no real kicker to get it moving, tend to travel slower. At this time, feel the most active weather will occur late Sunday afternoon into Sunday night. Speaking of active, PW values reach 1.55 inches and coupled with some mid level instability and a very favorable jet structure (splitting jet and SE TX will lie in a 130 kt RRQ) should yield a good chance of thunderstorms on Sunday night. SPC has already placed a part of SE TX in an outlook area for Day 7. 43 .MARINE... High pressure over the eastern U.S. and low pressure in the lee of the Rockies will maintain a moderate to occasionally strong onshore flow this week. SCEC conditions will be possible over the offshore waters Tuesday night through Friday. The warmer/more moist air mass overriding the cooler shelf waters will create a favorable environment for sea fog mid week. The persistent onshore flow will also bring elevated seas to the coastal waters and more importantly, warmer water temperatures. The water temp/dew point spread will narrow and this will hinder fog development over the second half of the week. Have added patchy fog for the nearshore waters and Galveston Bay from late Tuesday night through Friday for the potential for sea fog but confidence on when, where and the duration of this sea fog event is low. 43 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 55 75 58 78 64 / 0 0 0 10 20 Houston (IAH) 56 75 60 78 65 / 0 0 0 10 10 Galveston (GLS) 61 70 61 71 64 / 0 0 0 10 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Tuesday afternoon 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. && $$ SHORT TERM...45
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