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 132331 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 531 PM CST Wed Jan 13 2021 .AVIATION [00Z TAF Package]... VFR conditions will generally persist through the duration of the TAF package as clear skies continue through the evening. As we saw last night, saturation near the surface may once again prove favorable for the development of some patchy fog at LBX/CXO between around 10Z - 14Z, though ample dry air aloft and slightly stronger surface winds may inhibit this. For now, have taken both sites down in visibility slightly and will monitor for potential changes in the 06Z package. A surface cold front remains on track to push into SE TX tomorrow, though with limited moisture availability precipitation is not expected. A northwesterly wind shift will occur behind the front, around 19-20Z north of Houston, 21-22Z in the metro area, and closer to 00Z along the coast. Cady && .PREV DISCUSSION... /ISSUED 259 PM CST Wed Jan 13 2021/ SHORT TERM [Tonight through Thursday Night]... High pressure over the northern Gulf will bring clear skies and cool temperatures to the region tonight. As the high drifts east, light winds will become S-SW and low level moisture will begin to increase. Fcst soundings show favorable conditions for some radiation fog to develop is surface winds fully decouple. Despite the SREF not showing much fog potential, feel some mention of patchy fog will be needed in the weather grids for late tonight into early Thursday. The fog will be shallow and will burn off quickly tomorrow morning. The surface high will move toward the eastern Gulf as low pressure over North Texas moves NE and a cold front edges into SE TX by early afternoon. The cold front will cross the rest of SE TX by sunset. Frontogenesis does increase in the 850-700 mb layer on Thursday afternoon as the front crosses the region so despite limited moisture (PW values around 0.50 inches or less), there might be enough forcing to generate a few showers along the front. MaxT values on Thursday are a bit tricky and will be dependent on when the front moves through the area. 850 mb temps are very warm and MaxT values could be warmer than fcst if the front slows and cooler if the front is faster. Leaned toward the quicker NAM/CAM guidance which brings the front through between 18-21z. Skies will be clear in the wake of the front and cool temperatures will prevail through Friday morning. 43 LONG TERM [Friday through Tuesday Night]... Upper-level low system deepens across the Great Lakes, pushing its associated front into central Gulf of Mexico by early Friday morning. In the wake of this front, breezy to windy conditions are expected, mainly along the coast. Thermal profiles suggest winds generally above 30 knots at the top of the boundary layer. This could produce wind gusts around 30 to 40 mph or greater when mixing down to the surface. Winds will diminish late night as the pressure gradient relaxes. With mostly clear skies and northwest winds, another cold night is expected Friday night. Have leaned towards the bias-corrected CONSALL to produce low temperatures mainly from the low to mid 30s(inland) and from the mid 30s to low 40s (coastal). Surface ridging prevails Saturday through Sunday before a coastal low over far southeastern TX moves along the Upper TX coast by Sunday. Precipitation-wise, not much is anticipated with this low system. PWAT values remain less than 1.00" with better opportunities over the Gulf waters. The main active period arrives Tuesday and Wednesday with potential for widespread rainfall. A strong closed upper-low will develop and deepen over the Desert Southwest early next week, bringing back onshore flow over the region. Persistent south to southeast flow at the surface will result in stronger moisture advection with PWAT values increasing greater than 1.5 inches (per ECMWF/CMS) and even over 2.0 inches per GFS. As this happens, an inverted surface low (or coastal low) will move through supporting a northward lifting axis of showers and storms on Tuesday. The better convergence zone develops late Tuesday night into Wednesday as the associated surface front moves through; therefore, have raised PoPs during this time-frame. 05 MARINE... Southwest flow regime prevails tonight through Thursday afternoon as surface high pressure moves eastward into central/eastern Gulf. A cold front will cross the region on Thursday, approaching the coastal waters by Thursday night. Strong north to northwest winds are expected behind the FROPA with gusts around 35 knots or greater at times. Elevated seas from 5 to 8 ft are also anticipated offshore. Winds and seas will gradually diminish by early Saturday. SCA headlines will be likely through this period. As the front progresses eastward into central Gulf; low tide and/or water levels conditions are expected; mainly at Galveston Bay. Surface high pressure builds in over south-central TX, leading to benign weather conditions for our waters.Onshore flow returns by early next week ahead of the next system moving through the coastal waters Tuesday and Wednesday. This scenario will once again bring SCA conditions with strong winds and elevated seas along with showers and storms through late Wed. Another marine concern will be the potential for sea fog prior to front Monday night into Tuesday, though confidence is low at this time. 05 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 58 39 64 36 56 / 0 0 0 0 0 Houston (IAH) 60 40 68 41 58 / 0 0 0 0 0 Galveston (GLS) 57 48 66 45 59 / 0 0 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$
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