318 FXUS64 KBRO 240052 AAA AFDBRO Area Forecast Discussion...UPDATED National Weather Service Brownsville TX 752 PM CDT Sat May 23 2020 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...Conv firing off to the west of the RGV is leaving behind plenty of cirrus blow off over the region moving off to the ESE. Meanwhile, vsbl satl imagery shows some SCT-BKN low clds moving in off of the Gulf waters. Expect these MVFR ceilings to become a little more widespread and lower later this evening and tonight for all 3 RGV airports. The latest 88D mosaic across the western areas of the EWX CWA extending down south into north central Mex. A single large hail producing t-storm is firing about 115 NM WSW of the KBRO radar. This single cell is drifting slowly SE and is not much threat to the RGV at this time. The HRRR conv guidance seems to be initializing pretty well on this ongoing conv. This model generally keeps the RGV clear of the conv until closer to sunrise Sun. So for now will leave out any mention of conv for the current TAF issuance until the later sections of the TAFs where will include some PROB30 remarks. && .PREV DISCUSSION... /issued 309 PM CDT Sat May 23 2020/ SHORT TERM (Now through Sunday Night): Satellite imagery and surface observations continue to indicate some fair weather CU and moderate to gusty winds across deep south Texas this afternoon. Temperatures this afternoon generally range from the low to mid 90s inland and mid to upper 90s near Falcon Lake. Adjusted high temperatures a couple of degrees warmer for the rest of the afternoon due to current trends. Brownsville radar currently shows some convection across the higher terrain of northeast Mexico. Latest satellite imagery indicates convection developing in associated with a 500 mb shortwave moving over northern Mexico and the Texas Big Bend region. This mid to upper level feature will strengthen over central Texas through the day on Sunday. A weak trough axis and vorticity will swing over south Texas tonight. However, most CAMs models develop storms far west late tonight before weakening as the convection approaches the CWA. However, low confidence continues for rain chances for tonight and Sunday due to differences in the model guidance. Brownsville upper air data this morning indicate a PWAT value of 1.62 inches. PWATs will increase tonight to between 1.8 to 2.0 inches and remain high through Sunday night. Another stronger mid- level support is expected to arrive Sunday night. Any convective would likely contain locally heavy rainfall, with minor flooding possible, especially in low lying and poorly draining areas. SPC Day 2 convective outlook has the entire CWA outlined in a marginal risk for severe weather Sunday and Sunday night. Also, WPC has most of the CWA into a slight risk for excessive rainfall Sunday into Sunday night. The best rain chances and potential of heavy rainfall appears to be Sunday night into Sunrise Monday as the mid level energy passes overhead. LONG TERM (Monday through Saturday): The long term period continues to look wet and unsettled. A deep mid to upper level trough will dig into the Central Plains on Monday. As it continues to deepen into the Southern Plains, a mid level cutoff low will form at its base, effectively detaching itself from the mid level westerly flow. This will allow the cutoff low to camp-out over the state of Texas through the end of the period. With ample surface moisture streaming in from the Gulf over the region and conditional instability in place, the nature of the convection that forms will depend primarily on the timing and location of mesoscale interactions...namely, the vort maxes that circulate around the low as well as any surface features including convective outflows. While there is generally good agreement between the models on the wet forecast through the period because of this general pattern, the exact onset, location, and duration of the showers and thunderstorms that may develop is very hard to forecast at this time. The Weather Prediction Center (WPC) has included all of Deep South Texas and the Rio Grande Valley in a marginal risk for excessive rainfall on Monday and Monday night as the first round of mesoscale features interact in the long term, but the potential for local areas to receive flash flooding conditions will likely continue through Wednesday morning. The better rain chances look like they will be concentrated mostly to our north through the period, but WPC's Day 1-7 QPF shows most of Deep South Texas receiving 2.50" to 3.0" of total rainfall through 7 AM CDT next Saturday, but locally higher amounts are possible. This is likely to change as we get a better understanding of the mesoscale features driving the convection through the period. The best rain chances for our area look to be on Monday through Tuesday and again late in the week, but at least slight chance PoPs will continue through the entire period at this point. The potential for isolated strong to severe thunderstorms continues for Monday through Tuesday night when instability is the greatest for our area, but remains a low probability at this point. The Storm Prediction Center's Day 3 Severe Weather Outlook only has Deep South Texas in a general thunderstorm risk. Temperatures next week will continue to depend on the cloud cover and any rain and thunderstorm development, areal coverage and longevity. MARINE: Now through Sunday Night...Buoy 42020 reported east- southeast winds around 14 knots gusting to around 18 knots with seas slightly under 4.9 feet with a period of 7 seconds at 1420 CDT/1920 UTC. The pressure gradient is expected to weaken as broad high pressure across the Gulf moves further northeast. Moderate southeast winds and moderate seas will prevail through the period. Small Craft Caution conditions are likely across the bay Sunday afternoon due to winds. Small Craft Caution to low end Small Craft Advisory conditions are possible across the Gulf of Mexico waters due to elevated winds and swell through Sunday night. Monday through Saturday...Elevated seas of 3 to 5 feet will start off the week and generally subside through the period to 1 to 3 feet. Showers and thunderstorms will be possible on and off through next week, and localized winds and seas will be affected by any outflows produced by any strong storms that may develop. && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV Short Term/Aviation...60 Long Term/Upper Air...65