305 FXUS64 KHGX 071724 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1224 PM CDT Wed Aug 7 2019 .AVIATION... Convective temperatures are between 90-92 degrees and these values have been met and scattered showers and isolated thunderstorms have begun to develop. Can't rule out a stray shower clipping one of the airports but probabilities look too low to mention in the TAFs so will leave out for now. Generally VFR conditions are expected for the next 24 hours except for KCLL where a brief window of MVFR/IFR ceilings will be possible towards sunrise Thursday. VFR conditions expected on Thursday. 43 && .PREV DISCUSSION... /ISSUED 949 AM CDT Wed Aug 7 2019/ DISCUSSION... High pressure aloft will expand over the southern plains today. 850 temps are between 19-21 C and this translates to surface temperatures in the middle and upper 90's. There should be quite a range in surface dew points today as areas along and east of I-69 will endure dew pts in the mid/upper 70's while some mixing of drier air aloft will bring dew points down into the upper 60's over the NW zones. Heat index values will range from 105-110 over the coastal/central zones and between 100-105 over the NW zones. This creates a bit of a dilemma on how to handle the Heat Advisory. Heat Advisory criteria should be met for areas along and east of I-69. Criteria probably won't be met over the north (108 et al...) but with neighboring offices using lower criteria and already issuing Heat Advisories, feel there isn't much of an option but to issue the Advisory for the entire CWA. For the update, have issued a Heat Advisory for the entire CWA from 18z through 00z. Raised temperatures a degree across the board and tweaked dew point grids. PW values are over 2.00 inches over the eastern half of the CWA and convective temperatures are around 90 degrees so raised PoPs over mainly the eastern half of the CWA for this afternoon. Areas lucky enough to receive rainfall will probably remain below Heat Advisory criteria. 43 PREV DISCUSSION... /ISSUED 425 AM CDT Wed Aug 7 2019/ SHORT TERM [Today Through Thursday Night]... Isolated to widely scattered WAA-type showers developing across the coastal counties/nearshore waters at this time are expected to continue this trend through the late morning hours. Addition- al (mainly isolated) development is possible along and near the seabreeze later this afternoon. Otherwise, this could to be our last best chances for rain as the upper ridge settles more firm- ly over the region by Thur. Early looks at progged temperatures and dewpoints for tomorrow are indicating the decent likelihood of elevated heat index values (105F - 110F) for portions of the CWA. Locations along and south of the I-10 corridor may be most vulnerable. 41 LONG TERM [Friday Through Tuesday]... With the strong upper ridge ensconced across the Southern Plains through the weekend, rain chances will remain quite low/nil. The big forecast issue looks to be the high temperatures which could peak from 100F - 103F these next several days...especially areas around the Brazos River Valley. At this time, not expecting heat indicies to be too crazy high as a slightly drier mid-level flow helps to mix dewpoints down a bit. However, we'll have to keep a closer eye on things further south near the coast where moisture (and dewpoints) could be a touch higher. Looking further ahead, extended models are still keeping with the idea of a weak backdoor frontal boundary moving toward the region by the middle of next week. Given the time of year, not very con- fident of this happening, but progs of increasing PWs (2.3"-2.5") from the E/NE don't look too out of line at this point. As such.. did start with the slow re-introduction of low POPs for this time frame. 41 MARINE... Southerly winds will persist this coming week with and upper level ridge of high pressure limiting the chances for showers and thunderstorms and encouraging the development of the diurnal seabreeze pattern. The onshore flow of 5-15 knots will be the norm with stronger winds near 15 knots the next few nights over the Gulf waters. May even reach SCEC tonight and Thursday night for a few hours. 45 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 99 78 100 77 100 / 0 0 0 0 0 Houston (IAH) 97 79 98 79 100 / 20 10 10 0 0 Galveston (GLS) 93 83 91 82 92 / 20 10 0 0 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...Heat Advisory until 7 PM CDT this evening for the following zones: Austin...Brazoria Islands...Brazos...Burleson... Chambers...Coastal Brazoria...Coastal Galveston...Coastal Harris...Coastal Jackson...Coastal Matagorda...Colorado... Fort Bend...Galveston Island and Bolivar Peninsula... Grimes...Houston...Inland Brazoria...Inland Galveston... Inland Harris...Inland Jackson...Inland Matagorda... Madison...Matagorda Islands...Montgomery...Northern Liberty...Polk...San Jacinto...Southern Liberty...Trinity... Walker...Waller...Washington...Wharton. GM...NONE. && $$ Discussion...33 Aviation/Marine...43