Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
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818 FXUS64 KHGX 040502 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1202 AM CDT Sat May 4 2024 ...New AVIATION... .SHORT TERM... (This evening through Saturday Night) Issued at 407 PM CDT Fri May 3 2024 Showers and thunderstorms are continuing to work their way through the northern half of SE Texas this afternoon. Some of these have produced heavier downpours as they have trained across already saturated areas, which of course exacerbates the ongoing flooding in locations that have previously received excessive rainfall. Current SPC mesoanalysis shows an area of deep moisture convergence north of I-10 along with a pocket of 1000-2000 J/kg elevated CAPE. Both deep moisture convergence and CAPE appear to trend downward over the next few hours, which should consequently lead to a downward trend in showers and thunderstorms. A lull in activity is expected overnight into Saturday with isolated showers/storms possible. At this point, any additional rainfall will only delay improvement in the current conditions. That being said, the decision has been made to maintain the current Flood Watch through Sunday. Going a little deeper into the overnight hours through Saturday morning...Hi-res guidance has been pretty spread out run-to-run as far as what development occurs during the overnight hours. Current thoughts are that PWAT values remain in the 1.5-1.7" range south of I-10 and 1.3-1.5" north of I-10. 500mb analysis shows another potential shortwave moving across SE Texas during the overnight hours with pockets of PVA. I don`t want to lean into the 18Z HRRR suggesting that the area will remain rain-free overnight while the 12Z HRRR brings a few showers/storms through the area...so have compromised by keeping PoPs on the lower end, and bearing in mind the current setup with deep moisture and repeated shortwaves. Saturday during the day appears to be fairly inactive as most of the activity will fire off well west of our CWA. Saturday night into Sunday will be the primary concern for the short- term (beginning of long-term). Another shortwave and pockets of PVA will track east across the area late Saturday night triggering an MCS structure. The MCS is projected to arrive along the western/northwestern CWA as early as Sunday morning (exact timing of arrival is more uncertain at the moment) and will move across SE Texas during the day Sunday. At the current moment the Flood Watch goes through 1 PM Sunday; however, this may need to be reassessed as this next system evolves. At this time additional rainfall totals of 1 to 3 inches and isolated higher amounts will be possible late Saturday night into Sunday. WPC keeps much of the area (with the exception of the immediate coast) in a Marginal Risk for Excessive Rainfall Saturday. Portions of the Brazos Valley and Piney Woods will be in a Slight Risk for Excessive Rainfall. For Sunday, WPC places the majority of the area north of I-10 in a Slight Risk for Excessive Rainfall with the rest of the area in a Marginal Risk. Impacts from excessive rainfall over the last few days are ongoing and any additional rainfall will exacerbate these impacts. Please continue to monitor the forecasts, follow instructions from local officials, and have multiple ways to receive warnings. Adams && .LONG TERM... (Sunday through next Thursday) Issued at 407 PM CDT Fri May 3 2024 As mentioned in the short-term, the beginning of the long-term period will feature a strong shortwave with an MCS that will impact SE Texas during the day Sunday. At the surface, a weak warm front will lift northward into SE Texas which will reinforce the warm and moist environment. At this time, projected additional rainfall amounts are in the 1-3" range with isolated higher amounts possible. Once the MCS exits the region, relatively dry weather is expected through much of the week. The forecast hazards shift from flooding to heat. Ground moisture is expected to stick around for awhile, and with 850mb temperatures reaching the 99th percentile Wednesday/Thursday, the combination of heat and humidity will lead to heat index values approaching or even reaching into the triple digits by mid week. Daytime highs will be in the 90s with dewpoints well in the 70s, creating hot and muggy conditions. As mentioned in the previous forecast, these values are 5 to 10+ degrees above normal climatological values. With recovery efforts likely continuing into next week, please be mindful of the increasing temperatures and heat indices. Wear light- colored/light weight clothing, drink plenty of water, take frequent breaks, and remember to look before you lock! Adams && .AVIATION... (06Z TAF Issuance) Issued at 1153 PM CDT Fri May 3 2024 A much quieter night is on tap with coverage through Sat afternoon remaining spotty as well. Moderate onshore winds are going to con- tinue overnight and should help to keep ceilings somewhat elevated until closer to sunrise. Winds will be strengthening a bit more as the day progresses on Sat as CIGs mix out. S/SE winds should be in the 6-12kt range tonight...then 12-20kts/G20-25kts tomorrow after- noon (higher near the coast). Did add the mention of VCSH(for now) to IAH (and CLL) as the next storm system approaches from the west tomorrow night through Sun morning. 41 && .MARINE... Issued at 407 PM CDT Fri May 3 2024 Onshore winds have remained elevated this afternoon, remaining near 20 to 25 knots. With this expected to prevail for the next several hours, in addition to seas reaching as high as 7 feet onshore, a Small Craft Advisory remains in effect until late this evening. Winds will diminish somewhat heading into tomorrow, with moderate onshore winds expected to prevail into next week. Scattered showers and storms will be possible tomorrow, with a more widespread and well organized line of storms arriving later on Sunday. This line of storms could produce some strong wind gusts, as well as periods of heavy rain. Cady && .HYDROLOGY... Issued at 302 AM CDT Fri May 3 2024 There is ongoing river flooding over parts of Southeast Texas, particularly along portions of the Trinity and San Jacinto rivers. The following river points are at, or forecast to go to Major flood stage: - Trinity River (Madisonville): Major Flood Stage - Trinity River (Liberty): Major Flood Stage - Trinity River (Goodrich): Major Flood Stage - West Fork San Jacinto (Conroe): Major Flood Stage - West Fork San Jacinto (Humble): Major Flood Stage - East Fork San Jacinto (Cleveland): Major Flood Stage - Caney Creek (Splendora): Major Flood Stage - Trinity River (Romayor): Minor forecast to go to Major - Navasota River (Normangee): Minor forecast to go to Major - Menard Creek (Rye): Moderate forecast to Major - Trinity River (Moss Bluff): Moderate forecast to go to Major - East Fork San Jacinto (New Caney): Moderate forecast to go to Major - Peach Creek (Splendora): Moderate forecast to go to Major - San Jacinto (Sheldon): Moderate forecast to go to Major Remember to heed any instructions from your local officials and to never travel through flooded areas or roadways. Please monitor updated forecasts via the NWS AHPS website and/or the new NWS NWPS webpage (https://water.noaa.gov/) as the river flood threat continues. JM && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 70 84 70 82 / 10 20 60 60 Houston (IAH) 72 84 72 82 / 10 10 30 50 Galveston (GLS) 73 80 73 80 / 10 10 20 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Flood Watch through Sunday afternoon for TXZ163-164-176>179- 195>200-212>214-300-313. High Rip Current Risk through Saturday evening for TXZ436>439. GM...Small Craft Advisory until 1 AM CDT Saturday for GMZ330-335-350- 355-370-375. && $$ SHORT TERM...Adams LONG TERM....Adams AVIATION...41 MARINE...Cady