709 FXUS64 KHGX 210405 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1105 PM CDT Fri Aug 20 2021 .AVIATION [06Z TAF Issuance]... A brief window of MVFR to IFR ceilings is expected over the Brazos Valley, near the KCLL site by early Saturday morning. Otherwise, VFR conditions are expected through the TAF period. Ridge aloft will dominate the region, bringing drier conditions through the period. South to southeast winds will prevail, strengthening to 10 knots by late Saturday morning. 05 && .PREV DISCUSSION /Issued 617 PM CDT Fri Aug 20 2021/... .SHORT TERM [Today Through Saturday Night]... Our radar has been quiet this morning and afternoon as high pressure and drier air begins to settle in across SE TX. Satellite derived PWs reflect this with the driest air located along the coast at 1.6" and moist air located north and east of our CWA at approximately 2.0". Also visible on satellite are fair weather cumulus clouds due to a stubborn 850mb cap and subsidence preventing deep convection today. This stubborn capping inversion has also prevented gusty winds from mixing down to the surface, so light to moderate onshore flow has also been the story for today as well. That being said, rain chances are minimal today at 15% PoPs and will drop into the single digits overnight. Although temperatures are expected to peak in the mid 90s this afternoon, relatively drier air infiltrating from the high pressure will keep heat index values around 105 to 107 degrees, just shy of heat advisory levels. If anything, overnight lows tonight will be warm and hover in the mid to upper 70s inland and in the lower 80s along the coast. Tomorrow's weather will be very similar as high pressure and upper level ridging strengthens overhead. PoPs will peak in the afternoon, but will still be less than 20% and mainly for areas south of I-10. Daytime temperatures will climb even further and reach the upper 90s, but drier air will keep dewpoints lower so heat index values are expected to peak around 105 to 107 again. If headed outdoors this weekend, make sure to practice proper heat safety such as drinking plenty of fluids, wearing loose fitting clothing, finding shade, etc. Overnight lows tomorrow night will still be warm and in the mid to upper 70s. Long story short: It's late August in Southeast TX. It's hot. KBL .LONG TERM [Sunday Through Friday]... The temperatures Sunday through Tuesday will have you "feelin' hot hot hot!". Let's be real...that song will likely apply for the rest of August. It won't just feel hot...it will BE hot! Afternoon temperatures Sunday through Tuesday will be among the hottest of the year so far with some locations reaching the triple digits. Currently thinking that the best shot of triple digits will be on Monday with slightly warmer 850mb temperatures. These hot temperatures are the result of an upper-level ridge shifting in from the east and drying out the atmospheric profile over Southeast Texas. Plentiful dry air in the mid-levels will mix down to the surface, so while the air temperatures will reach the upper 90s/low 100s, we're anticipating heat index values to remain just below the threshold for a Heat Advisory (it'll be really close though). The dry air will also keep PoPs slim to none through Tuesday, so not looking at any real chance of any cooling showers/storms. With this in mind, if you have any outdoor plans over the weekend/early next week, please practice heat safety. Even if a Heat Advisory is not issued, temperatures will still be incredibly hot and the impacts will be the same. Drink plenty of water, take breaks from being in direct sunlight, wear light- colored/loose- fit clothing, look before you lock, and read up on the warning signs of heat exhaustion/heat stroke. Going into late Tuesday/Wednesday, the upper-level ridge extends northward and subsequently slightly weaken (594 dam to 591 dam). This will allow low-level moisture to return back into Southeast Texas with PW values increasing to 1.8"-2.0". Additionally, a couple of shortwaves could sneak around the backside of the ridge. Higher amounts of moisture will be relegated to the southern half of the CWA, so this is where PoPs will be the highest. With convective temperatures in the upper 80s/low 90s, it won't take much heating to get showers/thunderstorms to pop. This will be a return to our typical summertime pattern of showers in the morning along the coast and the seabreeze pushing inland that leads to enhanced moisture convergence along the boundary which results in scattered thunderstorms. Although the ridge is slightly weakened, we will still have hot temperatures in place (highs in mid/upper 90s). With increased moisture and relatively light winds due to a weak pressure gradient, trends are pointing towards elevated heat index values for Tuesday/Wednesday so wouldn't be surprised if we end up crossing the Heat Advisory threshold. Drier air pushes back in from the east in the latter half of the work week with PW values decreasing to 1.6"- 1.9", so PoPs and heat index values will be slightly lower. Batiste .MARINE... Light to occasionally moderate onshore flow will continue to persist over the weekend and into next week. The marine impacts from Grace are already evident with increasing swells and wave heights. Offshore seas are expected to reach 7 to 8 feet by tonight with nearshore seas rising to around 4 to 5 feet. Elevated seas will linger through Saturday before beginning to recede going into Saturday night. Additionally, strong rip currents along with elevated water levels during high tide will be a concern through at least Saturday evening. Batiste && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 76 97 75 98 75 / 0 10 0 0 0 Houston (IAH) 78 97 77 98 76 / 0 20 0 10 0 Galveston (GLS) 84 92 83 91 82 / 10 20 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...SMALL CRAFT SHOULD EXERCISE CAUTION through Saturday evening for the following zones: Coastal waters from Freeport to Matagorda Ship Channel TX out 20 NM...Coastal waters from High Island to Freeport TX out 20 NM. Small Craft Advisory until 7 PM CDT Saturday for the following zones: Waters from Freeport to Matagorda Ship Channel TX from 20 to 60 NM...Waters from High Island to Freeport TX from 20 to 60 NM. && $$