357 FXUS64 KSJT 120222 AFDSJT Area Forecast Discussion National Weather Service San Angelo TX 922 PM CDT Mon Sep 11 2023 ...New MESOSCALE UPDATE... .MESOSCALE UPDATE FOR Thunderstorms... Issued at 922 PM CDT Mon Sep 11 2023 A west to east broken line of thunderstorms is currently located south of Interstate 20 and moving southward into the Concho Valley this evening. The east end of the line appears to have become more shear dominant as it pushes eastward into north central Texas. Meanwhile, the southward-moving part of the line appears to be outflow dominant. Also, IR satellite imagery is filling in with colder, higher cloud tops which indicates this activity should form into a solid line of convection over the next 2-3 hours. The threat for some localized severe wind gusts and perhaps some hail will continue as it moves southward into an airmass characterized by only 1000 J/kg of CAPE. Overall, this fits well with the latest hi-res model solutions and, as long as it remains outflow dominant, storms should transition into mainly a heavy rain threat by 2 or 3 AM. && .SHORT TERM... (This evening through Tuesday) Issued at 238 PM CDT Mon Sep 11 2023 As showers from this morning have weakened/dissipated, we are starting to see some patchy clearing across the area, allowing for temperatures to climb into the 90s. Overall hi-res models have backed off on the potential for activity in our area this afternoon, likely due to the slower degradation of cloud cover than expected. The main concern for severe activity will be with the arrival of the cold front this evening and through the overnight hours. Much of the area remains under a Slight Risk of severe storms in the latest SPC Day 1 Convective Outlook. Some discrete cells look to really start forming after 21-22Z in the Rolling Plains region of NW Texas where better clearing with allow for more rapid destabilization. With decent instability given MLCAPE values in the 1000-2000 J/kg range and a low amplitude shortwave bringing increased upper level winds leading to bulk shear in the 35-50 kt range, initial storm mode is expected to be more supercellular with large hail and damaging winds the primary factor. As the front pushes south and instability decreases with the loss of heating, the storms are expected to grow upscale into a more MCS type feature moving southeast through the Big Country and continuing into the Concho Valley and Heartland overnight tonight. Damaging winds would be the main concern at that point, especially with storms that can remain rooted along the frontal boundary. While overall severe threat is expected to decrease later during the overnight hours, a low level jet across the Concho Valley and Edwards Plateau may help to maintain intensity for longer. We're watching for the possibility of heavy rains leading to potential flooding concerns. With a moist atmospheric profile and pWAT values in the 1.5-2 inch range, storms that form will likely be efficient rain producers. While these storms are not expected to be slow moving, rain rates may prove to be of concern, with lots of runoff possible given how dry the West Central Texas region is. We are also watching for the potential of training showers and storms as activity behind the front in the higher elevations of eastern New Mexico are also expected to propagate southeast into the area behind the activity associated with the front. Current hi-res models show the highest QPF amounts generally between a Sweetwater to San Angelo line. General consensus is widespread 1-3 inches across the Concho Valley and Heartland north with between 1/2 and 1 inch possible as one moves south towards the I-10 corridor. Locally higher amounts should be expected with some locations potentially seeing 3-4+ inches before the activity gradually weakens through tomorrow. Rain will remain possible through the day tomorrow as shortwave impulses continue to pass overhead though it likely won't be as intense as what is expected tonight. Temperatures will cool fairly significantly behind the front as winds shift to the north. Temperatures for Tuesday will range from the mid 70s in the Big Country to the lower 90s along and south of I- 10. Overnight lows will be on the cooler side in the 60s thanks to cloud cover and rain cooled air. && .LONG TERM... (Tuesday night through next Monday) Issued at 240 PM CDT Mon Sep 11 2023 Wet period will continue as a broad upper trough brings zonal or slightly northwest flow to the Southern Plains. Uncapped air mass will continue in this regime, as a series of weak shortwaves allow a weak front to wash back and forth across the area for much of the week. Model blends continue with high POPs into the weekend, although best chances may end up Wednesday into Thursday with the next impulse after tonight's set to move across the area. Its certainly not going to rain every day into the weekend, but model uncertainty with mesoscale boundaries and weak shortwaves in is leading to broad high chance POPs for much of the period. As we get closer into the weekend, will likely see the POPs condense into a few higher likelihood periods while lowering many of the periods down a little. Finally, temperatures will generally be cooler with the cloud cover and precip. Highs will cool into the 80s and lower 90s, first time we have below normal temperatures for an extended period of time in several months. && .AVIATION... (00Z TAFS) Issued at 629 PM CDT Mon Sep 11 2023 Thunderstorms have developed to the northwest of our area, and will be impacting most sites later tonight. Have generally kept the timing of TEMPO groups from previous set of TAFs as CAMs have stayed fairly consistent in timing of these storms. Expect these storms to move through the area, with some lingering past 12Z tomorrow. After storms dissipate, the bulk of Tuesday should be characterized by MVFR CIGs for KABI, KSJT, and KBBD, while VFR ceilings are expected farther south, with a few light showers throughout the day. && .PRELIMINARY POINT TEMPS/POPS... Abilene 67 76 66 79 / 90 60 80 90 San Angelo 67 84 66 86 / 70 60 70 80 Junction 68 92 67 90 / 40 40 50 60 Brownwood 67 82 66 81 / 80 50 80 80 Sweetwater 67 75 66 80 / 80 60 80 80 Ozona 69 88 68 89 / 40 50 60 70 Brady 67 86 67 84 / 70 40 60 70 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...50 LONG TERM....07 AVIATION...20