Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
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902 FXUS64 KHGX 010510 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1210 AM CDT Wed May 1 2024 ...New AVIATION... .SHORT TERM... (This evening through Wednesday Night) Issued at 230 PM CDT Tue Apr 30 2024 Isolated storms have developed near the coast/over the Gulf of Mexico this afternoon. Otherwise the rest of SE Texas remains dry with benign conditions expected through the end of the day. Patchy fog will be possible overnight, potentially becoming dense at times during the early morning hours of Wednesday, with fog chances greatest in areas east of I-45. Fog development will vary greatly depending how the lower stratus deck behaves during this overnight period. Ample moisture and cloudy skies should bring lows for Wednesday morning in the mid 60s to lower 70s. On Wednesday, an upper level trough will dig into the Northern Great Basin, spinning up another surface low over the Rockies. This will tighten the pressure gradient, strengthening onshore flow and increasing moisture advection. A plume of 1.75-2.00"+ PWs fills in from southwest to northeast during the afternoon hours. Weak impulses aloft coinciding with this moisture influx may bring isolated to scattered storms across the area during the daytime hours. Shower/storm activity briefly diminishes late in the afternoon/early evening as diurnal heating and instability decreases. A shortwave trough is expected to sweep across Central Texas Wednesday night, bringing numerous showers and thunderstorms overnight into Thursday morning. With support from the shortwave, plentiful moisture, modest instability and support from a 30-35 knot LLJ, some of these storms will capable of producing locally heavy rainfall. WPC has portions of the Brazos Valley/Piney Woods area under a Slight (Level 2/4) Risk of excessive rainfall for Wednesday night/early Thursday, with a marginal (level 1/4) risk extending further south to around the I-10 corridor. These areas have experienced recent heavy rainfall & flooding, with CREST showing swaths of 40-68% soil moisture north of Conroe. 1Hr FFG for these locations range from 2-3", so Flash Flooding may develop rather quickly if any stronger storms were to move over these areas, especially over Trinity & Walker counties. The threat of flooding continues into the long term with the arrival && .LONG TERM... (Thursday through next Monday) Issued at 230 PM CDT Tue Apr 30 2024 Continued thunderstorm activity will press on into the early part of Thursday, thanks to robust moisture availability and the passage of a midlevel shortwave trough. While recent global model runs continue to show the QPF max just to the northeast of the area, this could nonetheless result in an additional 2-3 inches of rainfall across portions of Brazos, Madison, Houston, and Trinity Counties through late Thursday. Rainfall totals across the Northern Houston Metro area during this time could reach as high as 1-1.5 in, while areas along and south of the I-10 corridor should generally remain at 0.25 in or below. Some locally higher totals are possible, though greater clarity regarding the extent and timing of this potential is expected tomorrow as this period enters the time range of high resolution forecast models. Additionally, rainfall both over the area and upstream may further exacerbate ongoing flooding along area rivers and creeks, particularly across the San Jacinto and Trinity river basins (see Hydrology section below). Some additional weak shortwave activity embedded within an otherwise mostly zonal midlevel flow will continue to result in rainfall chances through the end of the week, although the potential for heavier rainfall as we expect late Wednesday into Thursday will be lower. Despite this, a persistent onshore flow regime will continue to contribute to elevated moisture levels which will continue to support the development of scattered thunderstorms. Some additional lighter rain totals of up to an inch are possible through Saturday, with the greatest rainfall chances remaining north of the I-10 corridor. Drier conditions look to return heading into the weekend as a midlevel ridge builds over the area while a surface frontal boundary stalls to our north. This will be accompanied by a warming trend, with temperatures rising gradually into the mid to upper 80s by the end of the week. By Monday, most locations will border on the 90 mark with even higher temperatures possible on Tuesday. With this being an early season heat event and high moisture levels still in place, heat safety precautions may need to be taken. Early indications show max WBGT values of 81-83 on Monday and 82-85 on Tuesday. Cady && .AVIATION... (06Z TAF Issuance) Issued at 1153 PM CDT Tue Apr 30 2024 No major changes from the previous TAF package. Still expecting CIGs to fall as we approach sunrise...with mostly MVFR conditions (with a few spots of IFR). Onshore winds will be increasing through the day, on into Weds evening (with gusts up to 20-24kts possible). We should get some spotty activity by the afternoon...but the bulk of the more organized storms/rain should be during the latter part of this pack- age. The best chances for the storms will be generally across north- ern third/half of the CWA. 41 && .MARINE... Issued at 301 AM CDT Tue Apr 30 2024 Persistent moderate onshore winds are expected through the remainder of the week and into the weekend, with wind speeds at times occasionally bordering on Advisory thresholds. Periods of showers and storms are possible during the course of the rest of the week, particularly on Thursday. However, the bulk of the rain should remain inland. Rain chances diminish heading into the weekend, with onshore flow remaining in place. Cady && .HYDROLOGY... Ongoing flooding along area rivers, particularly the Trinity and San Jacinto, continues to persist. The following river points continue to remain at or above flood stage as of this afternoon: - Trinity River (Goodrich): Major Flood Stage - Trinity River (Liberty): Moderate Flood Stage, rising to Major Flood Stage - Trinity River (Riverside): Moderate Flood Stage - Trinity River (Romayor): Action Stage, rising to Moderate Flood Stage - Trinity River (Moss Bluff): Minor Flood Stage - Menard Creek (Rye): Major Flood Stage - San Jacinto (New Caney): Action Stage, rising to Major Flood Stage - San Jacinto (Cleveland): Moderate Flood Stage Additional rainfall over the next few days, both over the area and upstream, may result in prolonged and potentially further exacerbated river flooding. Remember to heed any instructions from your local officials and to never travel through flooded 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. Cady && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 68 85 71 84 / 0 30 50 60 Houston (IAH) 70 84 74 85 / 10 30 30 40 Galveston (GLS) 73 79 73 81 / 10 20 20 20 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...03 LONG TERM....Cady AVIATION...41 MARINE...Cady