Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/01/21

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
745 PM CST Sun Feb 28 2021 .UPDATE... Very minor updates to the ongoing forecast package. Did retrend hourly temperatures/winds to reflect the current position of the front and make some slight chances to the PoP forecast given the quiet radar at this hour, the expected showers along the front later this evening, and the anticipated thunderstorms forming across the Rio Grande and moving eastward later tonight. Looking at the brand new 00z Sounding out of KDRT there is a 2-3 Degree C inversion just above 950 mb with southwesterly wind bringing in some weak air advection at that lay. It is important to note that the front was north of KDRT at the time of the sounding. Decent shear of over 70 knots and Surface CAPE values near 100 J/kg were reported. A 700mb-500mb low crawling across Southern Arizona and New Mexico (evident on GOES-EAST/WEST Water Vapor) will come into play later this evening. The cold front is currently extending from a Rocksprings to Kerrville to Lago Vista to Taylor line as it continues to move to the south and east. Earlier in the evening a few elevated showers developed across Llano county, but these quickly died out behind the front. Additional light showers have formed to the northeast of the area near Cameron and Caldwell, and a thin line of isolated showers is show in many of the mesoscale and high resolution models forming along the front later this evening. Some aircraft soundings out of AUS and SAT still show a weak capping inversion which may work against these showers. The main show will be with the approach of the low pressure to the west. Ahead of it, as it moves into southeastern New Mexico and the Texas Panhandle later tonight the low and mid-level winds will strengthen ahead of it. This will move more air in the mid and upper atmosphere out of the way, causing air at the low levels to fill that void there-by creating lift. With the front already through the area and based on the notes about the 00z DRT sounding, any convection that does form will be elevated. With enough instability, shear, and moisture in the area a few elevated supercells remain possible. The HRRR remains consistent in showing a few developing between 10pm and midnight across Val Verde County. The 12z ARW and NMM high resolution models also supported this solution while the NSSL WRF was the least bullish, and the NAM Nest somewhere in the middle with isolated storms across the Hill Country. Even if the CAP wins out and the severe risk is conditional, the lift from the upper low should produce scattered showers and thunderstorms across the Rio Grande Plains into the Hill Country through the early morning hours, spreading eastward towards the I-35 corridor. SPC maintained their marginal risk of severe weather in their 01z update to the Convective outlook, noting that if strong to severe storms do form that hail remains the primary threat. We will monitor the trends of the 00z High Resolution models and provide further updates this evening in NWSChat and on Social Media. Rain chances continue with cool temperatures on Monday. What a change in just a few weeks...from snow/sleet/thunder sleet to the chance of strong to severe storms! && .PREV DISCUSSION... /ISSUED 523 PM CST Sun Feb 28 2021/ AVIATION... The cold front that will be the main driver of the TAF through the period is already pushing into the Hill Country producing a few showers between KAQO (Llano) and KBMQ (Burnet). Ahead of the front, the prefrontal trough have already turned winds out of the north along the I-35 corridor. Winds will pick up out of the north and be gusty once the front arrives at all terminals between 03z and 05z. Showers will be possible with ceilings dropping to MVFR as the front arrives and moves through with thunderstorm chances, at least in the vicinity, increasing between 09z at AUS and DRT and 11z at SAT/SSF. Chances for thunderstorms will linger into the mid-morning Monday with gusty north winds continuing. Rain showers, MVFR cigs, and gusty north winds will continue through much of tomorrow, before finally beginning to clear late in the day. Timing of the clearing will be the focus of future TAFs, while this set focuses on the precipitation chances. PREV DISCUSSION... /ISSUED 236 PM CST Sun Feb 28 2021/ SHORT TERM (Tonight through Monday Night)... Afternoon surface observations show a warm and moist air mass in place with current temperatures in the upper 60s to lower 80s. Dewpoint temperatures are impressive for this time of year and range from the upper 50s in the Hill Country to the upper 60s in the coastal plains. For the remainder of this afternoon, we could see a few light showers develop across portions of the Hill Country and along and east of the I-35/I-37 corridors. In addition, a cold front will move in from the north and could help generate isolated thunderstorms across portions of Burnet and Llano counties. As the above mentioned front continues to move southward this evening, a line of showers and thunderstorms is expected to develop along and especially behind the cold front. These storms will be elevated in nature, that is they will not be rooted in the flow near the surface. Favorable MUCAPE and shear should result if some strong to possibly severe thunderstorm development during the mid-evening into the overnight hours across a good portion of south central Texas. The current SPC Day 1 outlook has most of our counties in a Marginal risk (Level 1 out of 5) for severe weather. Given most storms should occur behind the boundary, the main concern with these thunderstorms will be the potential for hail up to around 1" in diameter. Mesoscale models generally agree the best chance for storm development will be from the Hill Country into the I-35 corridor. We have noted the fairly consistent trend from the HRRR model in showing some activity developing over the Serranias del Burro mountains of Mexico. Should this occur, this activity would likely remain intact as it moves into the Rio Grande plains and southern Edwards Plateau. With this in mind, we did raise precipitation chances slightly across the above mentioned areas this evening. For tomorrow morning, we should see decent coverage of post-frontal showers and thunderstorms across a good portion of south central Texas. Temperatures will also be much cooler and we have opted to trend toward the cooler guidance numbers with the expected precipitation, cloud cover and cold air advection behind the front. Highs are expected to range from the mid 40s in the Hill Country to the upper 50s in the Rio Grande and coastal plains. It will be blustery behind the front on Monday with northerly winds of 15 gusting to near 25 mph across a good portion of the region. Wind speeds will not be in any rush to decrease Monday evening, but should begin a slow, downward trend through the overnight hours. Rain chances will also be on the decrease from west to east Monday night. LONG TERM (Tuesday through Sunday)... The long term periods are looking less eventful as the deterministic models have been trending with a slower and weaker storm system to pass through the Southern Plains late in the week. The result of this trend leaves a lower amount of cloud cover for Tuesday into Wednesday and a more gradual mid-week return of southerly flow. This means wider diurnal ranges and less available moisture in advance of the late week storm system. MOS guidance trends have arrived much drier over the past 24 hours in regards to the rain chances for Friday and have all but removed any thoughts of potential rain for late Thursday. The weaker trends of the late week disturbance also signals a weaker cold air advection pattern and milder temperature trends for next weekend. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 80 48 50 42 62 / 30 70 70 30 10 Austin Bergstrom Intl Airport 81 48 51 42 63 / 30 70 70 30 10 New Braunfels Muni Airport 81 51 52 44 65 / 20 70 60 30 10 Burnet Muni Airport 78 44 48 40 60 / 30 60 70 20 10 Del Rio Intl Airport 83 52 59 41 66 / 0 40 20 - - Georgetown Muni Airport 79 46 49 42 60 / 40 70 80 30 10 Hondo Muni Airport 81 49 55 41 67 / - 60 50 20 10 San Marcos Muni Airport 80 49 51 42 63 / 20 70 60 30 10 La Grange - Fayette Regional 82 51 53 45 61 / 20 70 70 40 20 San Antonio Intl Airport 80 51 53 43 64 / 20 60 60 20 10 Stinson Muni Airport 80 51 54 43 64 / 10 60 50 20 10 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Treadway Long-Term...YB