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
659 FXUS64 KHGX 232351 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 651 PM CDT Tue Mar 23 2021 .AVIATION [00Z TAF Issuance]... There is high confidence in poor flight conditions late tonight into early tomorrow morning as last night`s cold front returns as a warm front headed the other way. It will be challenging to forecast whether that degradation will be from low ceilings, low visibility, or some mix of both. Take a bit of a kitchen sink approach here - model soundings suggest low stratus, and generally let that take the lead in being the dominant flight category - as low as LIFR/VLIFR at worst. However, it is about as likely that fog develops with clear overnight sky and light winds, and may need to shift the focus more towards fog next cycle if that shows its hand before stratus crops up. Fog seems especially a concern for the coastal terminals, as the surge of low level moisture should shove dewpoints above the relatively cool Gulf and Bay waters. Eventually, should see improvement to MVFR/IFR towards mid-day, but improvement may be slow and uneven. && .PREV DISCUSSION /Issued 354 PM CDT Tue Mar 23 2021/... .SHORT TERM [Tonight Through Thursday]... The current period of active weather is expected to continue through mid-week, with the main area of concern still being the approach of another surface cold front which could allow for the development of some stronger storms early on Thursday. This morning`s cold front has pushed well offshore, giving way to light to moderate north/northwest winds and generally clear conditions today. This is expected to continue into the evening, during which the clearer skies and CAA behind the departing front will result in slightly lower minimum temperatures (50s to low 60s) across inland locations. However, the aforementioned frontal boundary remains expected to stall and push northward overnight and into tomorrow, bringing a return to southerly winds and enhancing onshore moisture transport. This will likely prove favorable for the development of sea fog by tomorrow morning with surface dewpoints expected to surge back into the mid to upper 60s by the morning. SREF probabilistic guidance continues to strongly favor fog development and inland advection, showing a 50-70% chance of visibility below 3sm along the coast and towards the Houston metro area tomorrow morning. Marine fog may persist through the day on Wednesday and into early Thursday prior to the approach of the next cold front. PWs will quickly be on the rise into Wednesday with the return of onshore winds and the approaching warm front, reaching around 1.25-1.5in by the afternoon. Some shower activity is anticipated as the warm front pushes inland, though high-resolution guidance continues to show fairly isolated coverage. Meanwhile, an amplified upper trough will dig into the Four Corners region by late Wednesday, with associated surface cyclogenesis allowing for the development of a closed low over NE TX by the early hours of Thursday. As this feature`s eastward progression drags a surface cold front through our area, scattered showers and storms will develop along and ahead of it. Forecast soundings continue to show fairly strong instability (~1500-2000 SBCAPE) and ample effective layer shear (50-60+ kt), though development may be inhibited by the presence of a fairly strong capping inversion (CINH of -100 to -200). Should capping erode, there`s a chance for some severe storms to accompany the frontal passage, with the best chance for this to happen occuring east of I-45. Both the fog threat and precipitation threat should come to an end by Thursday afternoon as the front departs, with drier and cooler air filtering into SE TX in its wake. Cady .LONG TERM [Thursday Night Through Tuesday]... Weak surface high pressure behind Thursday`s storm system will quickly move off to the east Thursday night and Friday, and this will allow for onshore winds to return to the area. The next best chances for rain come Saturday afternoon through Saturday evening when the next system and it`s cold front moves across our region. Dry weather will then be in the forecast for the second half of the weekend and on into the first half of next week as high pressure gradually works its way eastward from the central states off toward the east coast and limits the return flow off the Gulf. For temperatures, lows in the 40s/50s Friday morning will warm into the 70s/80s on Friday, and both lows and highs will show a gradual warming trend until the weekend`s cold front. After that front, not much of a cool down can be expected with lows mainly in the 50s/60s and highs in the 70s/80s. Enjoy these nice temperatures while you can because you know what will be coming soon! 42 .MARINE... Precipitation has cleared the coastal waters, with the boundary pushing well offshore and relatively light north to northwest winds developing upon its departure. This offshore pattern will erode quickly overnight as surface high pressure behind the departing front drifts to the east, leading to the development of southeast winds. In addition to transporting Gulf moisture towards the TX coast, this pattern will be favorable for the development of marine fog overnight and through Wednesday. Probabilistic guidance remains confident in the fog threat lasting into the early hours of Thursday morning, by which a strong cold front will approach the area. Showers and storms, with some storms potentially becoming strong to severe, will accompany the frontal passage, with the boundary clearing the waters by Thursday afternoon. A third front looks to approach the coastal waters on Sunday and bring another round of rainfall. Cady && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 52 81 58 72 50 / 0 30 60 50 0 Houston (IAH) 58 80 66 77 54 / 0 40 50 60 0 Galveston (GLS) 64 75 67 77 61 / 0 40 20 50 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...Cady LONG TERM...42 AVIATION...Luchs MARINE...Cady
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