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 072349 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 549 PM CST Thu Jan 7 2021 .AVIATION... Clouds continue to impinge on the Houston terminals and models not handling the cloud shield all that well. Fcst soundings suggest that clouds will be in and out for much of the night with a mix of MVFR/VFR ceilings. There could be a brief break in the cloud cover toward morning with additional clouds building back into the area early tomorrow afternoon before skies clear completely late in the day. 43 && .PREV DISCUSSION... /ISSUED 359 PM CST Thu Jan 7 2021/ SHORT TERM [Tonight Through Friday Night]... Wrap around clouds continue over the northeastern 1/2 of the region and will probably sag slightly further south into the early evening then dissipate from south to north before midnight. Cool temperature overnight with northerly winds. Skies remain mostly clear to clear Friday so anticipate another dry day warming up a few more degrees in the afternoon. High pressure over N TX slides east and weakens as the next big weather making upper trough drops into Utah turning winds northeast Friday night. Temperatures will likely dip to near freezing over the north beneath the mostly clear skies. On a different note...NWS storm survey results in Texas City indicated an EF-1 tornado on the ground for around 0.7 of a mile with winds approaching 110 miles per hour last night around 613 PM. For more detail see the PNSHGX issued earlier. 45 LONG TERM [Saturday Through Thursday]... The main focus of the long term period continues to be the potential for snow and rain/snow mix across the northern half of the area this weekend. While it remains quite a complex and messy forecast, there`s increasing confidence that portions of SE Texas will receive their first measurable snowfall in over two years late on Sunday into early Monday. The deterministic EC/GFS solutions have come into a bit better agreement regarding the synoptic pattern leading up to the event during the earlier part of the weekend. As a 300mb longwave trough/upper low approaches the Four Corners region overnight on Saturday/early on Sunday, a surface cold front will advance towards the northern counties. Meanwhile, a developing coastal trough/surface low in the southwestern Gulf will push towards the offshore waters, with associated moisture advection pushing total PWs to around 1.0 in by Sunday afternoon. Furthermore, the region will lie within the favorable left front quadrant of an upper jet streak associated with the aforementioned upper low, providing ample upper-level divergence for efficient/widespread precipitation. Precipitation on Sunday will initiate as rain across the entirety of the area. However, model soundings and 850mb temperatures to the north of the Columbus-Conroe-Livingston line continue to show favorable profiles for mixed phase precipitation to snow as temperatures drop during the evening and overnight hours. NAM continues to be fairly aggressive in depicting frontogenetically enhanced snowfall across the northern third of the area during this time frame, but given warmer temps with limited winter precip in GFS solution and less aggressive EC solution, have opted to forecast a "middle ground" for the time being. In general, snowfall amounts (if accumulation does take place) will be largely driven by mesoscale forcing and thus are not focusing on specific totals for now. However, confidence is building that we`ll see some form of measurable snow during this event as model solutions continue to converge. The rainfall threat from this event across the Houston metro and areas south must also not be disregarded. The aforementioned synoptic pattern will also prove favorable for the development of locally heavy rainfall as the surface front/coastal low traverse the area on Sunday and Monday. A colder and quieter period is expected in the wake of the frontal passage on Monday as the coastal low advances into the central Gulf. Daytime highs in the upper 50s/lower 60s and overnight lows generally in the 30s expected through mid-week as surface high pressure develops over the area. A warming trend is expected by mid- week as a more southwesterly flow pattern develops. No precipitation is anticipated between Tuesday and Thursday at this time. Cady MARINE... SCEC flags hoisted for the 20-60nm waters tonight through midnight as winds of 15 to 20 knots gradually diminish after midnight. Offshore flow will continue through Saturday morning then become more easterly Saturday night strengthening and will looking for SCA conditions with winds of 20-30 knots and seas building to 5-8 feet nearshore and 7-10 feet Sunday and Sunday night as the coastal low tracks up the coast. Still some question as to the exact track so this forecast is more in the middle of the pack for the winds...if the system tracks more offshore then winds will likely be stronger and weaker if it tracks as far north as Galveston. Stay tuned. The impacts from this will be beach and low lying coastal flooding, strong rip currents and may warrant a coastal flood warning for more significant impacts with the persistence of these stronger winds. The cold front should shove off the coast early Monday and the strong winds should start tapering off Monday afternoon. 45 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 34 53 31 52 39 / 0 0 0 0 10 Houston (IAH) 38 56 35 54 41 / 0 0 0 0 10 Galveston (GLS) 47 54 44 52 49 / 0 0 0 0 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ Discussion...99 Aviation/Marine...99
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