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 242321 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 621 PM CDT Mon May 24 2021 .AVIATION... Still a few lingering shra/tsra over the area but these will wane by 02z with a mix of VFR and MVFR ceilings developing between 05-08z. Another short wave will move across the southern plains on Tuesday and as the trough axis crosses SE TX coupled with PW values of around 1.90 inches, it seems reasonable to expect another band of showers and thunderstorms to develop across area TAF sites. Will carry a VCSH for the AM with a VCTS for the afternoon. 43 && .PREV DISCUSSION... /ISSUED 345 PM CDT Mon May 24 2021/ DISCUSSION... Today`s heaviest rain bands set up further up the coast, necessitating the shift of the flood watch up from Matagorda Bay closer to the west side of Galveston Bay, including the Houston metro. As rains started to pile up, flood advisories came out, followed by a flash flood warning that focused on northeast Harris County, where 5 to 7 inches, and localized totals up to 13 inches have been seen today. Estimated return intervals for the rainfall seen in the flash flood warning area range from 5 to 10 years. Though today`s rains are expected to wind down this evening as we lose solar heating, the broader environment will remain supportive of continued rain tomorrow, and perhaps again on Wednesday before we transition to a weather pattern that has a greater influence from high pressure. Keep an eye on the weekend, however. If ridging holds strong, it should be nigh summer-like. But there are indications that a weak front will try to slide down. If it makes it far enough, we could start to see some chances of rain slide on down from the north with it. SHORT TERM [Through Tuesday]... Flash flood watch in effect until 9 pm for a portion of the area. This should be allowed to expire...but will probably need another one for Tuesday before the drying trend really kicks in. Rainfall today was generous to say the least...2 to 4 inch amounts were very common in the corridor from Freeport to Houston to eastern Montgomery county. A few larger areas in there got 4-7 inches of rain. Areas around Mount Houston in NE Harris got hit the hardest today and this is on top rains from last week. Storms should be dissipating early this evening and the remainder of the night should be quiet. Tuesday morning speed convergence should lead to spotty showers near the coast and up into the southwestern areas... that with heating become scattered across the region transitioning to showers and thunderstorms mainly over the western areas but small features could alter that plan...think this morning. PW remains high and s/w moving in from the SJT area will be yet another arrow in the quiver for storms. A flash flood watch will likely be needed again Tuesday for a portion of the area. LONG TERM [Tuesday Night Through Monday]... The mid-week becomes the waiting game. For some time we`ve anticipated a shift to a more ridge-dominated pattern, and for various reasons, that shift keeps staying off in the long term. But, eventually, that is precisely what`s going to happen. Guidance suggests a shortwave for Tuesday night and Wednesday that would be capable of enhancing afternoon convection on and around a seabreeze. So, while Wednesday looks like yet another day with showers and thunderstorms popping up, I`m expecting it to feel more like an amped-up "regular" day, rather than the firehouse of tropical moisture we`ve seen of late. I`m also quite aware I`ve said something like this on at least one occasion already this string of shifts, so I`ve got this Wednesday written down in metaphorical pencil. Deeper into the week, there is greater confidence in high pressure taking hold of the situation. Increased subsidence should finally overwhelm the persistent onshore flow, and give us at least a couple nice, dry days with a warming trend from highs around 80 to highs in the mid to upper 80s. There`s a decent chance that the weekend is a little more of the same, but the Euro has introduced a fairly unpleasant idea that is showing up in some more of the guidance. It droops a weak front down into Southeast Texas, and with it, some increased rain chances. Now, taking a broader look at the entire envelope, and rain is still more of an outside possibility. There`s rainfall in the median NBM solution only as far south as Crockett on Saturday. Buuuut...the 90th percentile NBM values have at least light rain all the way to the coast, and widespread half an inch to one inch rainfall from I-10 northward. So...while another solid round of rain is probably still an outlier at this point, we`ll have to watch how this potential scenario evolves before we can say with much confidence how (not) pleasant the coming weekend will be. MARINE... Moderate southeast winds and elevated seas will continue into the mid-week, which will continue to keep tides noticeably above astronomical tidal values. Of late, the winds have brought tides near, but not quite to advisory levels, and this is expected to carry on. Additionally, the persistent onshore winds are expected to keep rip currents as a dangerous threat to those choosing to take a swim in the Gulf. Periods of showers and thunderstorms are expected to persist tomorrow, and potentially even Wednesday before high pressure brings in some drier days. A drier weather pattern with weakening winds and gradually subsiding seas will settle into the area for late in the week and stretch into the weekend. A weak front may try to approach Southeast Texas on Saturday, but is unlikely to reach the waters. The main impact, if any, would be a slight backing of winds to have a little more of an easterly component. HYDROLOGY... Numerous flood warnings continue again today. But, despite the heavy rain in Harris County today, rivers and bayous have been able to come down enough to generally withstand the rain. That said, even on rivers that are not over or expected to reach flood stage, river levels are likely to be elevated and running quickly. Continued rainfall will - at best - slow improvement, and at worst exacerbate conditions. We can look for more sustained improvement in weather conditions once this rainy pattern comes to an end and drier conditions begin to prevail. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 70 83 71 86 71 / 50 70 20 30 0 Houston (IAH) 71 83 72 85 72 / 30 60 10 40 0 Galveston (GLS) 75 81 76 82 76 / 30 40 10 10 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk through Tuesday evening for the following zones: Bolivar Peninsula...Brazoria Islands...Galveston Island...Matagorda Islands. Flash Flood Watch until 9 PM CDT this evening for the following zones: Austin...Coastal Brazoria...Colorado...Fort Bend... Grimes...Inland Brazoria...Inland Harris...Montgomery... Waller...Washington. GM...NONE. && $$
