Area Forecast Discussion
Issued by NWS Houston/Galveston, TX
Issued by NWS Houston/Galveston, TX
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058 FXUS64 KHGX 302112 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 412 PM CDT Thu May 30 2024 ...New SHORT TERM, LONG TERM, MARINE... .SHORT TERM... (This evening through Friday Night) Issued at 332 PM CDT Thu May 30 2024 Our primary concern as of writing this AFD (3PM) is the building convection over portions of N Texas this afternoon. The overall synoptic pattern continues to features a train of shortwaves embedded in the WNW to NW flow aloft. One such shortwave in conjuction with bountiful LL instability and moisture is enhancing the aforementioned convection which has recently evolved into a more organized line of thunderstorms. Some cold pooling is evident as per the surface obs in the MCS`s wake. The convection as been somewhat pulsy, with outflow boundaries outrunning the convection along the line`s western flank. CAMs guidance is all over the place regarding the line of storms and its potential time of arrival in our CWA. But structurally speaking, the guidance that has best initialized the line features a more progressive forward motion, bringing storms into our northern counties by this evening. Therefore, we are starting to lean more towards a scenario similar to the ARW which has the line reaching our northern most counties (Piney Woods area) by 5-7PM and potentially the Brazos Valley by 6-8 PM if the western flank doesn`t fall apart. If the line continues to hold together, then these storms could reach the I-10 corridor by 10PM-12AM and the coast by 1-2AM. The primary concern will be damaging wind gusts and hail along with localized flooding. The LL shear profile is not a quintessential tornado environment but we still cannot rule out an isolated thunderstorm capable of a tornado. If the line does not hold together enough to push through our region, then instability would be saved for another possible MCS that approaches from the northwest later tonight thanks to another shortwave. So in other words, if these evening storms behave more like the ARW, then there may not be enough instability left for the next round of thunderstorms. There would be no (or maybe just weaker) late night / early morning storms. But if the ARW scenario does not pan out, then that would open the door for a round of thunderstorms (possibly severe w/ hail and damaging winds) later tonight into the early morning hours on Friday. So what should you do with such an uncertain forecast? Remaining weather aware is a good start. Have multiple ways of receiving warnings. Generally speaking, stay in tune with the weather this evening and tonight. This is one of those forecasts that can easily change due to the complexity of the situation. We will obviously be keeping a very close eye on the radar this evening and tonight. Frequent updates to the forecast may be warranted. Friday`s forecast will depend on how tonight unfolds. An early morning MCS featuring a period of low clouds and showers in its wake could keep temperatures cooler than currently predicted (85-90F in the current forecast) and possibly limit the intensity of afternoon/evening convection. However, if Friday starts out with less rain/thunderstorm activity, then the environment may become hotter and more unstable. With the continuance of the mid/upper level shortave train, Friday will be another day to watch for strong to severe thunderstorms, with damaging winds being more of a concern than hail. Self && .LONG TERM... (Saturday through next Wednesday) Issued at 332 PM CDT Thu May 30 2024 A shortwave trough will pass over the Red River Valley Saturday morning, bringing another round of showers and thunderstorms through the afternoon. While these storms should be fairly progressive, PWs in excess of 1.8" will be sufficient to produce locally heavy rainfall within some of these storms. Therefore, WPC has most of SE Texas under a Marginal (level 1/4) risk of excessive rainfall on Saturday. Forcing from this shortwave, combined with sufficient wind shear and instability could produce strong to severe storms during this period as well. Therefore, SPC has areas along and north of the I-10 corridor under a Marginal (level 1/5) risk of severe weather for Saturday. If severe storms do develop, damaging winds and hail will likely be the main threat. Another, slightly stronger, midlevel shortwave will pass overhead Sunday morning, bringing yet another round of showers/storms. The parameter space for Sunday is still very similar to that of Saturday, so stronger storms with locally heavy rainfall will still be possible during that day as well. Ridging begins to build over Mexico early next week. Impulses riding the peripheral of this ridge (with this moisture-rich environment) could bring some isolated showers/storms through mid-week, mainly in areas north of I-10 closer to the Brazos Valley/Piney Woods area. NAEFS and GEFS 850mb temperatures surpass the 90th climatological percentile by Tuesday, with ridging expected amplify across the Plains on Wednesday as a Rex-block-like pattern develops over the Western CONUS. The latest suite of global models indicate 850mb temperatures reaching the 21-26C range by mid-week with robust WSW/SW flow in the lower levels. This all looks to bring hotter conditions, with highs reaching the upper 80s to mid 90s on Tuesday/Wednesday. Persistent onshore winds are also progged to keep dewpoints in the mid/lower 70s during this period, even when factoring in the effects of afternoon mixing. Heat Indices are estimated to reach 100-108 degrees by Wednesday, signifying an increasing heat risk for next week. Models suggest that a frontal boundary could trek southward through the Plains later in the week, bringing some mild relief from the heat. However, frontal systems have a tendency to stall out before reaching SE Texas during this time of the year, so relief may be much further away. In fact, if this boundary stalls out close to our area, pooling moisture and compressional heating could further exasperate the heat risk. Regardless, we`re entering the climatological summer for SE Texas/the Houston, so practicing heat safety will become especially important in the coming weeks/months. Remember to drink plenty of fluids, wear lightweight clothing and be sure to take breaks out of the sun. Heat is the #1 weather-related killer in the U.S. each year, so be sure to not underestimate the danger it poses. 03 && .AVIATION... (18Z TAF Issuance) Issued at 1236 PM CDT Thu May 30 2024 The forecast through tomorrow is extremely complex and unfortunately features high uncertainty. Isolated to widely scattered shra/tsra activity is possible this afternoon. However, the primary concern is this evening through tomorrow morning when a line of thunderstorms could move through our regions. The timing of tsra is the most uncertain aspect of the forecast. Our current TAFs have trended earlier than the previous update. The uncertainty is why we have not opted for TEMPO / PROB30 groups because confidence remains too low to pin point exact timing. This is the type of forecast that can easily change, likely warranting amendments. The primary concern with these storms will gusty winds and hail. There may be a period of low clouds and shra in the wake of the line. && .MARINE... Issued at 332 PM CDT Thu May 30 2024 Light to moderate onshore flow and seas of 3 to 6 feet are expected through mid next week, warranting caution flags at times, especially during the overnight hours. Rounds of showers and storms will be possible into the weekend, with rain chances tapering off next week. Some of these storms could become strong to severe, producing damaging wind gusts and locally elevated seas. Persistent onshore flow will bring a high risk of rip currents into the upcoming work week. 03 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 71 86 73 88 / 50 60 30 50 Houston (IAH) 75 88 75 88 / 40 50 30 60 Galveston (GLS) 79 87 78 86 / 30 40 30 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Severe Thunderstorm Watch until 9 PM CDT this evening for TXC041-051-225-313-455 GM...Small Craft Should Exercise Caution from 7 PM CDT this evening through Friday morning for GMZ330-335-350-355-370-375. && $$ SHORT TERM...Self LONG TERM....03 AVIATION...Self MARINE...03