Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000 FXUS64 KHGX 230440 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1140 PM CDT Sat Jul 22 2017 .AVIATION... An upper low over the western Gulf will meander near the coast into Sunday and some showers will be possible along the immediate coast toward sunrise Sunday morning. Daytime heating will trigger another round of afternoon storms...impacting mainly the Houston terminals and KCXO and KSGR. Convective temps on Sunday are around 89 degrees and PW values will reach 2.15 inches by 21z with soundings showing a weak capping inversion developing near 850 mb but this looks breakable during peak heating. Shra/Tsra will dissipate quickly Sunday evening with the loss of heating. A fairly thick mid/upper cloud deck will linger over the area Sunday night. 43 && .PREV DISCUSSION... /ISSUED 919 PM CDT Sat Jul 22 2017/ UPDATE... Earlier evening convection has dissipated, with northern portions of Harris County receiving anywhere from 1 to up to 3 inches. Cannot rule out a few more isolated showers and maybe a thunderstorm or two along the coastal counties and across the coastal waters tonight as a mid to upper level weakness evident on evening RAOBs meanders across the area, but have low confidence on how far inland this activity will actually push given increasingly southwest low level flow in response to surface ridging over the northern Gulf. As a result, have lowered rain chances inland for night while maintaining 20 PoPs along the coast and for the waters. Otherwise, made minor updates for hourly trends with overnight lows in the mid 70s to low 80s. Huffman PREV DISCUSSION... /ISSUED 351 PM CDT Sat Jul 22 2017/ DISCUSSION... Precipitation not quite as widespread across SE TX this afternoon likely owing to the extensive clouds and persistent storms offshore (limiting stability and preventing decent inflow respectively). While temperatures have been a touch lower than yesterday, the higher dewpoints are keeping heat index values elevated (100-106F) so far today. With the upper low lingering around the coast between GLS and LCH through tomorrow am a bit hesitant to lower POPS too much...especially for our eastern and coastal counties. Progged PWs from 2.0 to 2.2 inches do appear supportive of some decent rains tomorrow. However...do agree that the main issue with the upcoming forecast could be the rising heat/heat indicies for next week. As this low washes out, we should see the upper ridge out west begin building east into the Central/Southern Plains. Rain chances will decrease starting Monday save for some isolated development at or along the seabreeze. Daytime highs are progged to be in the upper 90s to around 100 for central/northern parts of our CWA, and with dewpoints remaining in the 70s, this could translate to heat index values at or near our heat advisory criteria of 108 degrees. 41 MARINE... The upper level low pressure system is continuing to fill into the region and aid in the development of showers and thunderstorms this afternoon. Although coverage this afternoon has diminished in comparison to this mornings convection, lingering showers and an isolated thunderstorm or two can be expected over the waters through the remainder of this evening. Gusty winds can also be anticipated with these stronger storms. Onshore flow overnight will begin to increase in wind speed as the pressure gradient tightens over SE TX Sunday into Monday. Winds should increase to between 10-15 knots tonight and hold through Sunday. Sunday night into Monday winds again will pick up in speed and stay closer to 15 knots before diminishing late morning on Monday. Therefore, we will be flirting with SCEC criteria while this tighter pressure gradient holds place. Seas will also pick up during this time from 2 feet to 2-4 feet. By Tuesday an area of high pressure begins to build in resulting in a lowering in wave height and weaker onshore flow. Conditions will also be drier through next Friday. Hathaway && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 77 95 77 98 76 / 10 30 20 10 10 Houston (IAH) 79 91 80 96 78 / 10 50 30 20 10 Galveston (GLS) 82 88 84 91 82 / 20 50 20 20 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ Discussion...14 Aviation/Marine...43

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