Area Forecast Discussion
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Issued by NWS
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390 FXUS64 KLUB 202011 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 311 PM CDT Fri Sep 20 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Saturday) Issued at 257 PM CDT Fri Sep 20 2024 The upper ridge near the Texas and Mexico border will slide into southeast Texas by tomorrow as the upper low currently over southern Cali swings towards the Four Corners. Continuous weak shower and thunderstorm activity persists this afternoon across eastern New Mexico with ample mid-level moisture in the southwesterly flow of the approaching jet aloft. The main line of mid-level moisture and precipitation is expected to remain to our west and north. There is a very small potential for some of the precipitation activity to clip the far southwest Texas Panhandle this evening, but with dewpoints in the 40s and LCLs above 3000m, any precipitation is likely to evaporate before reaching the surface. If a storm were to push through the far northwest corner of the forecast area, the main threat would be a strong wind gust or two. Tonight, high clouds will continue across much of the area with the increasing mid-level moisture ahead of the approaching trough axis. Temperatures will dip into the 60s and lower 70s tonight. Tomorrow, the 40-50 knot 500mb jet streak will fill into West Texas as the bowling ball upper low approaches the Four Corners. The main jet streak will remain just west of the forecast area across New Mexico. Shower and thunderstorm activity is expected to continue through the morning hours tomorrow west and north of the forecast area. Surface ridging across the southeast CONUS will give way to increased low-level GoM moisture with south-southeast winds. Dewpoints will range in the lower to mid 60s by the afternoon hours with temperatures warming into the 80s along the Caprock to mid 90s off the Caprock. Breezy southerly surface winds will exist with height falls as a surface low strengthens with the approaching trough. Most of the models have the cold front nearing the far southwest Texas Panhandle during the late afternoon hours tomorrow. An axis of increased 700mb theta-e will setup across eastern New Mexico and into the western portions of the South Plains, ahead of the front and in the moist sector of the dryline. The aforementioned area will be where instability is the greatest through the afternoon hours with MLCAPE values nearing 1500-2000 J/kg and bulk shear of 50- 60 knots. Afternoon storms will develop across eastern New Mexico and push east-northeast through the early evening hours with strong to severe storms capable of producing large hail and damaging wind gusts. Low-level shear profiles have decent backing winds near the surface and surface-3km shear of around 20-30 knots, which could support a tornado or two. Depending on where the cold front is placed by the afternoon hours, if a storm or two latches to the boundary then there could be an increased risk for tornadoes. PWATs are near 1.5" to 1.75" and storms will be capable of heavy rainfall with localized flooding. The bulk of the activity will persist into tomorrow night and more details will be covered on this in the long term discussion below. && .LONG TERM... (Saturday night through next Thursday) Issued at 257 PM CDT Fri Sep 20 2024 Potential for severe storms and heavy rain will continue Saturday night through early Sunday as large-scale forcing courtesy of a broad mid/upper level jet streak increases as the potent upper low approaches from the west. Synoptic and hi-res guidance remains in good agreement depicting numerous showers and storms shifting eastward into West Texas on Saturday evening as a cold front slowly descends southward through the TX Panhandle. Strong forcing for ascent overspreading steep midlevel lapse rates, impressive deep-layer bulk shear magnitudes of 40-60kt, and robust low level theta-e advection will continue to support an environment favorable for severe storms into the evening over the far southwestern TX Panhandle and western portions of the South Plains. All severe hazards will be possible in this area, with a low but non-zero tornado risk as mentioned above. The severe weather threat is generally expected to decrease with eastward extent and with time as instability wanes, with the primary hazard shifting more towards heavy rain overnight as impressive northward low-level moisture flux continues. Most models still keep the axis of heaviest rainfall on Saturday night over the southwestern TX Panhandle into northern portions of the South Plains where an inch to perhaps several inches of rainfall are possible, but much will depend on how far south the front progresses overnight. Sunday will feature a continuation of active weather as the cold front over the southern TX Panhandle advances further southward. Additional thunderstorms are expected to develop and persist along the front, with the lingering upper jet streak maintaining large- scale lift through most of the day. The axis of rainfall on Sunday currently looks to be smaller than on Saturday night with storms concentrated along the front which may favor our southern and eastern zones, but for now will maintain broad PoPs area-wide until this becomes more clear-cut. Severe weather potential on Sunday also looks limited due to a cooler and more stable airmass, but robust focused ascent and a very moist airmass with PWATs in the 1.5-2.0" range will support a continued threat for heavy rain. Monday will feature a return of dry conditions as surface ridging builds into the region in the wake of the departing upper low. Many locations on the Caprock will see lows in the 40s to lower 50s on Monday morning, with below average temperatures continuing into the afternoon. Rain chances return to the entire region on Tuesday as most guidance depicts broad upper troughing deepening over the central CONUS. Models diverge on the amplitude and positioning of this troughing, but enough continuity is still present to maintain high chance to likely PoPs Tuesday through Wednesday. Beyond this, model spread supports keeping the blended forecast as-is with temperatures warming back near normal and PoPs generally below mentionable levels. && .AVIATION... (18Z TAFS) Issued at 1222 PM CDT Fri Sep 20 2024 VFR conditions are expected through the period at all three TAF sites. Breezy southerly winds around 10 to 15 knots will persist through this evening before diminishing during the overnight hours. Winds will begin to ramp up again through the morning hours tomorrow. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...11 LONG TERM....30 AVIATION...11