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
881 FXUS64 KHGX 142334 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 634 PM CDT Wed Apr 14 2021 .AVIATION [00z TAF Issuance]... Activity long the weak frontal boundary should be waning with the loss of daytime heating these next couple of hours. At this time, not terribly confident that this line will move very far offshore overnight given the lack of low-level push...probably stalling at the coastline well after midnight. CIGS should fall again tonight to mostly IFR with patchy areas of -DZ/-RA. Sea fog will remain a factor along the coast (mainly GLS). Modest improvements expected by late tomorrow morning, but progs of another east moving short- wave along with daytime heating/proximity of the frontal boundary should produce widespread VCSH (and possibly VCTS) chances by the afternoon tomorrow. 41 && .PREV DISCUSSION... /ISSUED 336 PM CDT Wed Apr 14 2021/ SHORT TERM [Today Through Thursday]... Weak frontal boundary/wind shift has pushed to to around the I-10 corridor. Seabreeze to the south has moved a few miles inland. Resulting llvl convergent zone situated in between both. Further aloft a weak shortwave was noted on w/v imagery across south Tx. Shra and a few tstms have initiated across southern parts of the area. Assuming cloudiness remains about the same, or thins, we`ll have a few hours of daytime heating left. This and some enhanced lift from the shortwave may allow a couple strong to severe cells to develop between now and sunset. Forcing isn`t overly impressive, but with somewhat steep lapse rates aloft there could be a hail threat and strong winds in cells where stronger updrafts become established. Localized heavy downpours can never be ruled out with 2" PW`s in place and a slow moving boundary/focusing mechanism. Precip will weaken and coverage begin diminishing with the loss of heating. The boundary should push toward the coast, perhaps 10-30 miles offshore later tonight. Llvls of the atmos saturate however, so chances of -ra and/or drizzle will remain in the fcst overnight. Sea fog closer to the coast and offshore will be an issue until ne winds increase late tonight. Cloudiness will remain in place Thurs. Combination of that and cooler temps should minimize overall instability for most of the day. That said, guidance pointing toward another shortwave embedded in the zonal flow heading toward the region during the late afternoon hours and generating some precip. Better chances/coverage should be situated across the nw/n parts of the area...and some of the 12Z hires guidance pointing toward the possibility of some elevated stronger cells near the Brazos Valley late in the afternoon and evening. So, future shifts will need to keep an eye on hail threats up that way. 47 LONG TERM [Thursday Night Through Wednesday]... Going into Thursday night with lingering cloud cover, overnight low temperatures will be rather mild in the low-to-mid 60s. As the previous cold front becomes washed out off the coast, winds will start out as easterly on Thursday night/Friday morning then transition to a southeasterly wind. Resultingly, there will not be a decrease in the moisture in the area as PW values hold steady around 1.5"-1.8" through Friday afternoon. Another stronger cold front will approach the region going into Friday night. Instability in the area will range from 1000-1500 J/kg. This should be enough to develop scattered thunderstorms along the frontal boundary, especially in the southern half of the CWA. Jet dynamics aren`t exactly favorable for upper-level support, so the showers and thunderstorms that do develop will be the result of low-level convergence along the front. Favorable jet dynamics do come into the equation on Saturday as a departing jet streak places the region in the right entrance region, so PoPs linger throughout the day. With instability quickly dropping post-FROPA, expecting only scattered coverage of rain showers on Saturday. How about those post-FROPA temperatures? Well if you missed below normal temperatures, then you`re in luck! Overnight lows on Friday will feature low-to-mid 50s with lows in the 40s expected for both Saturday and Sunday. In the daytime over the weekend, afternoon high temperatures will struggle to reach the 70s thanks to CAA prevailing through Monday morning. Surface high pressure moves overhead on Monday and then slides off to the east by Tuesday, so temperatures will be on an upward swing going into early next week. Fortunately, only looking at highs in the mid-to-upper 70s for Tuesday and Wednesday. Backtracking a little bit to Tuesday...GFS and ECMWF are in agreement on a weak coastal low developing in the western GoM , but there is disagreement on how far north this low moves and also how much moisture is associated with it. Leaned more towards the ECMWF which keeps the low further south and our area dry, so PoPs are minimal throughout the first half of next week. It is worth noting that although the ECMWF indicates some spotty rain showers in the afternoon/evening hours next week, forecast soundings indicate that there will be too much dry air both aloft and near-surface to get any significant precipitation to reach the ground. Batiste MARINE... Isolated strong to severe thunderstorms are possible through the evening hours today in the Bays and nearshore Gulf waters as a weak cold front sits just north of the coast. Lingering coastal flooding around Galveston Bay will continue to gradually decrease throughout the day. The front will slowly move off the coast on Thursday with winds becoming briefly northeasterly followed by a quick shift to easterly by Friday morning. Onshore flow returns by Friday night ahead of another stronger cold front that will push through the coastal waters on early Saturday morning. Moderate to strong northeasterly winds will develop in the wake of this front throughout the weekend with caution to advisory level winds anticipated. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 59 70 61 75 52 / 30 50 60 70 40 Houston (IAH) 63 72 64 75 58 / 50 30 40 70 50 Galveston (GLS) 67 74 69 76 64 / 70 30 20 50 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk until 8 PM CDT this evening for the following zones: Bolivar Peninsula...Brazoria Islands... Galveston Island...Matagorda Islands. Coastal Flood Advisory until 7 PM CDT this evening for the following zones: Bolivar Peninsula...Chambers...Coastal Galveston...Coastal Harris...Galveston Island. GM...NONE. && $$
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