Area Forecast Discussion
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Issued by NWS
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727 FXUS64 KLUB 211055 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 555 AM CDT Sat Sep 21 2024 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 350 AM CDT Sat Sep 21 2024 Water vapor imagery currently shows the FA beneath the upper level ridge, with the center of the high pressure parked near the central Texas region. To our east, the upper level trough is currently positioned over southern desert southwest where it is expected to track into the Four Corners region by this afternoon. As the trough tracks closer to the FA the associated 50 to 60 knot jet streak will clip portions of the West Texas region. One more day of above normal hot temperatures is in store for the region as an incoming cold front shows us a slight glimpse of fall temperatures. A surface low to our north is expected to strengthen and begin tightening the pressure gradient across the region. This will lead to breezy southerly conditions this afternoon around 10 to 20 mph with gusts up to 30 mph. Given the breezy southerly flow and similar thickness values most of the region can expect similar temperatures as previous days in the 90s to lower 100s. However, some areas across the far southwestern Texas Panhandle and northern South Plains may see highs top out in the upper 80s as model guidance hints at FROPA entering our NW zones by early this afternoon. Therefore, if the front arrives before peak heating hours we could see a slight temperature gradient across the FA this afternoon. Meanwhile, southerly to southeasterly flow from the surface to H7 will continue to influence increased moisture being pumped into the FA from the Gulf of Mexico. Additionally, ample pacific moisture wrapping along the western side of the upper level ridge will track through most of the FA over the next 24 hours. As the upper level low begins to barrel closer to the region, we can expect increased chances for thunderstorms beginning as early as mid-morning into early afternoon depending on when convective Ts are met. An H7 theta- e ridge encompassing most of the South Plains and far central and southwestern Texas Panhandle is expected to develop this afternoon east of the dryline and ahead of the incoming front. This highlighted area, relatively west of the I-27 corridor will be primed with decent mid-level LR, MLCAPE up to 2000 J/kg, and effective bulk shear around 55 knots. All of which support strong to severe thunderstorms capable of producing damaging wind gusts and large hail. All hazards will be at play this afternoon with a tornado or two possible given 0-3km shear around 20 knots and veering winds with height although 0-1km shear remains unimpressive and relatively less than 5 knots. Regardless, the area to see an increased risk for tornadoes looks to be near the frontal boundary; which is expected to stall around the far southwestern TX Panhandle this afternoon. Storm motions are expected to be pretty fast, however given forecasted PWATs around 1.5" we could see localized flash flooding develop with stronger storm that develop. Thunderstorms are expected to continue into the overnight hours as they track from west to east into the Rolling Plains. Overnight lows are expected to be much cooler than previous nights for most as the front begins its surge southward with lows ranging from the upper 50s in our northwest counties to low 70s across our southeastern counties. As the front pushes southward we will see an additional round of thunderstorms track into the FA. For more information regarding precipitation chances heading into Sunday morning check out the long term discussion below. && .LONG TERM... (Sunday through Friday) Issued at 350 AM CDT Sat Sep 21 2024 Just in time for the first day of fall, a cold front Sunday morning will usher in below normal temperatures, breezy north winds and more importantly a decent shot at rain for those areas that miss out today and tonight. The surface map by daybreak Sunday should feature a cold front across our Panhandle counties accompanied by scattered to numerous showers and thunderstorms, mainly along and east of a low-level moist axis progged to bisect the forecast area from SW-NE. Other than frontal convergence, background ascent in the form of upper divergence and height falls looks pretty muted well south of an upper low lifting from CO into NE. Along with a faster FROPA, the highest PoPs will likely shift into the southern Rolling Plains by early afternoon as aggressive low-level drying and subsidence overspread the remainder of the CWA during this time. If convection can grow upscale Sunday afternoon in the southern Rolling Plains, then a greater heavy rain threat would be in the cards given anamolously high PWATs approaching two inches. NBM`s post-frontal PoPs from Sunday afternoon through the overnight were dialed lower to account for the overwhelmingly drier 00Z guidance which best fits this faster FROPA theme. Temps by early Monday morning over much of the Caprock now look to fall well into the 40s under clearing skies and diminishing N winds. Other than a few straggler showers in our far southeastern zones early Monday morning, mostly clear skies and dry conditions prevail as surface high pressure moves across the CWA underneath weakly cyclonic westerly flow. This flow aloft turns sharply cyclonic on Tuesday as a vigorous trough dives south from the CO Plateau before pinching off an upper low somewhere over West TX by Wednesday. Long range models are showing less spread with this low`s position by Wednesday as the ECMWF has trended closer to the GFS solution. Moist isentropic flow should ramp up late Monday night through Tuesday in advance of this trough/low resulting in a broad field of showers and some storms. Am not buying the unusually mild GFS/MEX temps in this otherwise cloudy and cool pattern for Tuesday, so have stuck to the NBM`s temps which are supported well by the ECM MOS. Heavy rain remains some concern in this pattern given the long residence time of saturated ascent with PWATs of 0.3 to 0.5" above normal, although unlike the convectively-driven heavy rains such as today and Sunday, Tuesday looks to be more of a prolonged/beneficial soaking rain. Rain chances gradually taper thereafter as ensembles build a modest rex block over the Great Plains with the upper low poised anywhere from the TX Panhandle to the Chihuahuan Desert. Oddly, the 00z GEFS is closer to the ECM and EPS regarding the upper low hanging closer to our neck of the woods on Thursday than the deterministic GFS, but this is too distant to justify making any changes to the mostly dry NBM. High temps slowly moderate by late week following a welcome fall cooldown. && .AVIATION... (12Z TAFS) Issued at 551 AM CDT Sat Sep 21 2024 Southeasterly winds will begin to pick up by mid-morning where they are expected to become breezy around 15 to 20 knots with gusts up to 30 knots. Thunderstorms are expected to develop this afternoon where they will track east into all TAF sites late this afternoon and evening which may threaten VFR conditions. Exact timing in storms remains a bit uncertain but regardless, gusty and erratic winds and locally heavy rainfall may be associated with stronger storms. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...12 LONG TERM....93 AVIATION...12