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 282341 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 541 PM CST Sun Feb 28 2021 .AVIATION... Like the past several evenings, aviation conditions are starting out from IFR at the coast to VFR well inland. Look for cigs to fall fairly quickly in the 2-6z timeframe areawide and most locations should be IFR by the end of that period. A cold front will be moving into the CLL area around 3z and continue to sag slowly southward overnight and Monday. Anticipate the boundary to be positioned along the US59-I69 corridor by sunrise and eventually southeastward and off the Galveston coastline by 20z. Look for areas of rain along and north of the front thru the period...and perhaps some shra/tstms mixed in at times. Terminals north of the metro area could see some tonight, with the more "favorable" environment for the metro terminals occurring during the day Monday. Not anticipating much improvement in overall cigs which should remain in the 500-122ft range for the majority of the day. 47 && .PREV DISCUSSION... /ISSUED 328 PM CST Sun Feb 28 2021/ SHORT TERM [Tonight Through Tuesday Night]... Warm and humid across the region with southeast and southwest winds. Temperatures soared up into the lower 80s inland with the southwesterly flow. Tonight expect skies to become cloudy as WAA pattern is firmly entrenched ahead of the approaching cold front. The front should move through the inland areas between around 9 pm and 9 am slowing as it gets deeper into SETX. As the upper low over 4-Corners slips eastward the the cold front slows down Monday then starts to pick up speed and moves east allowing a strong Pacific ridge to settle into the area Monday night/Tuesday. In the meantime though will have some instability to work with mainly beneath the cap (700mb temperatures at 18z over IAH were still 10C per AMDAR) but with the arrival of some cooler air aloft the showers this evening should become mixed with thunderstorms and still have a threat of a few strong thunderstorms across the north the main focus will more likely become heavy rainfall. Rainfall rates of 1-2"/hour will be possible and well within the realm of the possible to see accumulations of 2-3" across the areas from College Station to Groveton northward. Isolated heavier amounts certainly possible. As the front nears the coast Monday morning loss of the deeper instability takes place though still with an axis of lift centered over the northern counties. CAMs have split into two camps with some stronger storms focused near the front and out over the Gulf while the other focus on a band from Matagorda Bay to Lake Livingston northward through Monday evening. For now will maintain the heavy rain mentioned through noon Monday and primarily over the northern 2/3 of the area. Sea fog lurking just offshore should spread back into the coastal areas tonight and will preemptively issue a Dense Fog Advisory for the barrier island that will probably need expanding later tonight. The warm nights come to an end as cooler air arrives highs Monday will probably remain in the 50s to mid 60s across the region falling into the 40s inland and near 50 coast by early Tuesday morning. 45 && LONG TERM [Tuesday through Sunday]... Upper-level trough finally ejects into the Middle MS Valley on Tuesday. Some lingering showers will still be possible early in the morning before upper-level subsidence leads to drier conditions by late morning. Decent CAA will take place with northwest winds and surface dewpoints dropping into the 40s. Highs will range from the mid 50s to low 60s. With skies clearing and colder air moving in, a cold night is expected with overnight lows from the upper 30s (far inland) to near 50 (coastal zones). Surface high pressure will remain in control across the region Wednesday and Thursday with mostly clear skies and light winds. Wedenesday`s high will be warmer but still near to slightly below normal for this time of year. Highs will generally be in the 60s. Surface high pressure will scoot eastward Wed night into Thursday, bringing a return of south winds. This will result in temperatures back to near seasonal normal for Thursday. The next chance of precipitation will be possible towards the end of the week as an upper-level trough and surface front move through. Deterministic and ensemble means have trended further north/northwest with the upper-level trough; therefore, its impacts across southeast TX could be minimal. The ECMWF and Canadian suggest increasing PWAT values and bring a frontal boundary all the way to the coast by late Friday night. The GFS, on the other hand, struggles and keep the surface low somewhat weak/disorganized over central TX. Given that, have lowered PoPs and kept low-end chances Friday into late Friday night. Ridge aloft builds in over the weekend, leaving us with pleasant weather conditions. Daytime highs will be in the 60s to low 70s. Overnight lows will be in the 40s and 50s. 05 && .MARINE... The primary weather hazard in the near-term continues to be sea fog. While visibility has improved at the bays, areas of dense fog persist over the nearshore waters. The environment looks favorable for dense fog to re-develop and/or expand tonight given persistent onshore flow and surface temperatures/dewpoints. With that said, have issued a Marine Dense Fog Advisory for the 0-20 nm waters through noon CST Monday. Will continue to monitor for further updates this evening, as fog may also redevelop over the bays. A cold front will move over the coastal waters Monday afternoon, bringing scattered showers and thunderstorms through late night. Behind the front, dry northwest winds will filter in, diminishing the fog threat. The fog threat decreases, but north-northwest gusty winds and elevated seas will be possible Monday night into late Tuesday. A SCA will be possible during this time-frame. Surface high pressure develops over east/central TX Wednesday, shifting eastward by Thursday. This will result in east to southeast winds into the end of the week. An area of low pressure system develops over north/west TX Thursday into the weekend, keeping moderate northeast flow over the Gulf waters. 05 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 52 54 43 58 37 / 70 90 80 20 0 Houston (IAH) 63 64 48 59 41 / 70 80 70 20 0 Galveston (GLS) 63 67 52 59 47 / 10 60 70 30 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Dense Fog Advisory until 7 AM CST Monday for the following zones: Brazoria Islands...Galveston Island and Bolivar Peninsula...Matagorda Islands. GM...Dense Fog Advisory until noon CST Monday 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. && $$
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