000 FXUS64 KHGX 190457 AFDHGX Area Forecast Discussion National Weather Service Houston/Galveston TX 1157 PM CDT Tue Jun 18 2019 .DISCUSSION... Updated for the 06Z TAF issuance. && .AVIATION... VFR conditions continue across all TAF sites. Previous TAF forecast continues on track, no significant changes were made. && .PREV DISCUSSION... /ISSUED 716 PM CDT Tue Jun 18 2019/ DISCUSSION... Updated for the 00Z TAF issuance. AVIATION... VFR conditions expected to continue this evening as surface high pressure moves eastward. Cloudiness will continue to dissipate during the next few hours and winds will decrease and become variable. Patchy fog may develop mainly east of I-45 late tonight into early Wednesday morning and could result in periods of MVFR/IFR cigs/vis. The local pressure gradient is expected to tighten across the region Wednesday, strengthening the southerly wind flow. Winds of 10-15 knots with occasional gusts of around 20 knots are forecast for most of the local TAF sites through Wednesday evening. Low level clouds expected to develop during the late morning and afternoon hours, with a chance of isolated showers/thunderstorms Wednesday evening across the northernmost sites as a shortwave trough moves across North Texas. PREV DISCUSSION... /ISSUED 341 PM CDT Tue Jun 18 2019/ SHORT TERM [Tonight Through Wednesday]... Surface high pressure over the region has kept skies partially cloudy, breezes light and allowed most interior ambient temperatures to warm into the lower 90s at 3 PM. Feedback from this has been drier mid level air more efficiently mixing to the surface and lowering dew points into the upper 60s to lower 70s. This has maintained upper 90 to near 100 F heat indices. A sea breeze boundary is beginning to lift off the coast. Thus, there are low end probabilities of late afternoon into early evening southern third CWA isolated showers/storm that may develop along or behind the sea breeze boundary. Also, higher moisture behind the breeze will also briefly spike heat indices to around or above 106 F. Quiet overnight with a decent chance for low clouds to develop past midnight over the west central forecast area. A shortwave trough passage across the Central Plains tomorrow afternoon will likely spark north to northeastern Texas convection. Outflow from this activity entering an unstable and humid mid-day northern county air mass will increase late day into evening shower and storm chances primarily north of a Brenham to Huntsville to Livingston line. 31 LONG TERM... A fast moving short wave will move across East Texas Wednesday night. The short wave will bring a chance of showers and thunderstorms to mainly the northern third of the region. Mid level forcing and jet dynamics are not too impressive so it'll probably be just a glancing blow. Upper level ridging will try amplify over the western Gulf and 500 heights build to around 590 dm which isn't all that impressive, but temperatures at 850 mb increase rather significantly. The warmer 850 mb temps translate to surface temperatures in the upper 90's to around 100 degrees. Fcst soundings show some mid level dry air which should mix to the surface so not expecting precip and sfc dew points should also mix out in the afternoon. Heat index values should remain below 108 degrees over most of the area but have some concern that dew pts could shoot up in the wake of the sea breeze during the late afternoon. Will need to watch trends but a Heat Advisory might be needed for Thursday afternoon for areas along and east of I-69. 850 mb temperatures cool on Friday as 850 winds back from the southwest to the south. The zonal flow aloft will transition to the southwest as an upper level trough moves toward the great basin. A series of upper level disturbances embedded in the upper flow will traverse the region over the weekend into early next week. Models diverge with the strength of an upper level ridge over the Gulf of Mexico but the strength of the upper high will determine whether the short wave energy will move up the Texas coast or be shunted further west and move over West/Central Texas. Will maintain slight chance/chance PoPs for now and hope that the global models will become in better agreement. For now, just split the difference between the wetter ECMWF and the drier GFS. 43 MARINE... A couple of quiet days over the maritime until the onshore pressure gradient tightens up late Thursday into Friday. Southwest to south winds will generally remain at Caution levels from Thursday through Saturday with brief jumps to Advisory criteria. Very low western Texas pressures in relation to high eastern Gulf pressure will create a tight enough onshore gradient to produce more persistent Advisory level winds on Sunday through Monday. Current 2 to 3 foot Gulf seas will lift to average 4 to 6 feet by the weekend...topping out in the 6 to 8 foot range across the western Gulf early next week. Of course, early next week's strong onshore fetch will introduce greater than 3 foot high tide nearshore sea heights increasing the coastal run up threat. The rip current will also likely restrengthen to Advisory levels by Sunday. 31 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 75 96 78 98 78 / 0 10 10 10 0 Houston (IAH) 77 95 80 97 80 / 0 10 0 10 0 Galveston (GLS) 82 89 83 91 83 / 0 10 0 10 0 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ Discussion...45 Aviation/Marine...24