227 FXUS64 KBRO 230539 AAB AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 1239 AM CDT Thu Apr 23 2020 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...Satellite images and surface observations indicate low clouds to high level clouds moving across southeast portions of the CWA late tonight. Elsewhere...skies were mostly clear across the rest of deep south Texas. Ceilings were near 1200ft at KPIL to near 11000ft at KTXW. Expect MVFR conditions across the Rio Grande Valley the rest of tonight into early Thursday morning as low level moisture continues to pool along and ahead of a weak cold front across central Texas moving into deep south Texas Thurs morning. Haze will continue to restrict visibilities across the area Thursday. Otherwise...VFR conditions will prevail in the wake of the front Thurs afternoon. && .PREV DISCUSSION... /issued 653 PM CDT Wed Apr 22 2020/ DISCUSSION...Updated for latest aviation discussion below. AVIATION...Satellite imagery and surface observations show high clouds and haze across the Rio Grande Valley. VFR conditions are likely to prevail through the evening before ceilings lower. Expected MVFR/IFR conditions to develop after midnight with these lower ceilings and lower visibilities due to the haze and patchy fog. Thunderstorms may develop late tonight into early Thursday morning, with higher chances over the western valley, so have included PROB30 groups for KMFE. A weak cold front is expected to reach the Rio Grande Valley Thursday morning, shifting winds out of northwest. With drier air behind the front, VFR conditions are expected to return later in the morning. PREV DISCUSSION... /issued 335 PM CDT Wed Apr 22 2020/ SHORT TERM (Tonight through Thursday Night): Breezy to strong southerly winds, including gusts up to 35 to 40 mph, have occurred across the lower to mid-valley throughout midday as low pressure strengthens across north Texas and southern Oklahoma. A dryline/surface trough entering the far western portions of the CWA may allow for winds to gradually subside late this afternoon and into the evening. A very hot day otherwise has commenced with afternoon highs topping out in the mid to upper 90s for most, but a few locations could touch 100 degrees. The surface trough/dryline retreats westward back into Mexico early tonight. Trailing shortwave energy across Mexico associated with the storm system to the north will swing into the region overnight. Latest short-term model guidance (HRRR, NAMNEST, WRF-NSSL) indicates that this energy could be enough of a lifting mechanism with moisture sitting just above the capping inversion, for development of some elevated shower and thunderstorm activity. A strong cell or two couldn't be ruled out with locally heavy rain, gusty winds and perhaps small hail. Timing of this convection will be between generally 08Z and 14Z. Muggy conditions will otherwise occur featuring light and variable winds as a weak cold front is to gradually approach from the north. This could result in the formation of some patchy fog. The aforementioned weak cold front will advance across Deep South Texas throughout Thursday morning, shifting the winds out of the north-northwest and ushering much drier air into the region. This will lead to clearing skies by the afternoon. The front does not impact temperatures much but did drop the afternoon highs by a degree or two compared to the previous forecast. We will closely monitor for fire weather concerns due to the dry air but 20 foot winds speeds look to stay below thresholds at this time during Thursday afternoon. Thursday night will remain mild despite the overnight lows falling a few degrees lower than the forecast for tonight. LONG TERM (Friday through Wednesday): A series of 500 mb short waves will move across the south central Plains States on Fri pushing a weak cold front into the region. Overall moisture levels with this frontal boundary remain very limited and expect just some low dewpoints and lighter surface winds pushing into the region dropping temps down closer to climo. Additional 500 mb vortices will continue digging across the region carving out a broad closed low/trough axis over the eastern states/East Coast into early next week. Meanwhile, broad 500 mb ridging will prevail over the Rockies into northern Mexico throughout this weekend with the ridging gradually breaking down towards the end of the forecast period which will allow more seasonable temps prevailing through Wed and Thur. The heat spike potential for Friday looks pretty high due to the combination of S-SW low level winds and fairly low dewpoints across the area. Record high temps may be threatened especially for the MFE area on Fri. The overall high temps may edge up some towards the end of the forecast period allowing for some highs back near the 100 degree mark across Zapata County next Tues and Wed. The ECMWF and GFS 500 mb heights are in pretty good agreement through Days 7/8, so an overall long range model blend looks reasonable for both temps and pops. MARINE (Now through Thursday night): Breezy southerly winds gradually subside tonight as a weak cold front will gradually approach from the north. Winds on Thursday briefly shift out of the north behind the weak front before returning to an east- southeasterly flow on Thursday night. Otherwise, expect moderate seas to continue across the gulf waters. Small craft operators should continue to exercise caution into and through tonight. Friday through Monday Night: As the frontal boundary sags into the region later this week, the PGF will likely remain fairly weak and onshore throughout the longer range marine forecast period. Accordingly, expect fairly low to moderate winds and seas to prevail into the weekend. The PGF may tighten up enough next Mon, due to the formation of the pretty strong surface low over the south central Plains States, to push the marine conditions back up near SCA levels next Mon. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV 61/63