Area Forecast Discussion
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Issued by NWS
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209 FXUS64 KLUB 231716 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 1216 PM CDT Thu May 23 2024 ...New AVIATION... .SHORT TERM... (Today and tonight) Issued at 305 AM CDT Thu May 23 2024 Low clouds are rapidly expanding northwestward early this morning as southeasterly winds continue to transport better moisture into the forecast area. Unfortunately, this moisture won`t last long as a dryline is positioned across eastern New Mexico and far West Texas and will begin to spread eastward by mid-morning. This will lead to the quick dissipation of low-clouds across the forecast area from west to east with mostly sunny skies expected by early afternoon as drier downsloping winds move across the Caprock. These downsloping winds will help to boost temperatures back above normal into the low to mid 90s across the forecast area. This hot and dry airmass, combined with breezy southwest winds will lead to near-critical to critical fire weather conditions on the Caprock (see fire weather discussion below for additional details). The dryline is expected to stall across the eastern Rolling Plains this afternoon and serve as a surface forcing mechanism for thunderstorm development. While forcing for ascent aloft won`t be overly strong, a weak ripple in the southwest flow combined with the exit region of a 250 mb jet moving overhead should be more than sufficient for isolated thunderstorm development along the dryline. While most guidance has the dryline mixing to the edge of our forecast area, previous experience suggests that the dryline will end up farther west so have kept a slight chance mention for severe thunderstorms across our eastern most column of counties (Childress to Stonewall). East of the dryline MLCAPE around 3000 J/kg will be present thanks to a combination of steep mid-level lapse rates and surface dewpoints in the upper 60s to lower 70s. With the exit region of the jet moving overhead, effective bulk shear values of around 45 kts will also be present with nearly straight hodographs present. This would favor splitting supercells with the potential for large hail and damaging winds. Thunderstorm activity will quickly shift east and out of our forecast area this evening with dry weather persisting through the remainder of the night. A surface cold front will begin to move into the forecast area around sunrise Friday morning with breezy northerly winds developing in its wake. /WI && .LONG TERM... (Friday through Wednesday) Issued at 305 AM CDT Thu May 23 2024 The split-flow regime in the upper-levels will begin to phase on Friday as a negatively-tilted shortwave trough pivots over the far northern Great Plains and the apex of an anomalous ridge wobbles westward over the northeastern Pacific Ocean. Quasi-zonal flow will develop in response to this phasing of the 250 mb jet stream pattern as the large-scale gyre centered across the northern Rocky Mountains and west-central Canada finally begins to dissipate, and as the 594 dam ridge remains anchored over central Mexico. At the surface, a fast-moving cold front will arrive in the extreme southern TX PH prior to sunrise and weaken as it crosses into the northern Permian Basin. A brief period of strong gusts (30-40 mph) are forecast to accompany the front immediately following its passage given the moderate spike in pressure tendencies, and winds were raised from the NBM to account for this scenario. However, winds should quickly slacken by late morning as the front stalls and the southern periphery of a weak anticyclone located in the central Great Plains eclipses the region. High temperatures will also be 5-8 degrees cooler, though it will still be very warm area-wide. Return flow will become established once again on Friday night as a shortwave trough digs into the Great Basin, with the dryline forming east of the edge of the Mescalero Escarpment and quickly mixing into the Rolling Plains by Saturday afternoon. Deep, vertical mixing of the boundary-layer is expected as the dryline crosses east of the 100th meridian; however, the presence of a cirrus deck should temper the overall magnitude of mixing that has been observed in prior days (i.e., 500 mb) with forecast soundings indicating a theta-e bulge around 600 mb as a west-southwesterly, mid-level jet streak near 50 kt translates overhead. Strong, southwesterly winds between 20-30 mph will develop on the Caprock and into the Rolling Plains as cyclogenesis of a <=994 mb surface low continues in the central Great Plains. The magnitude of southwesterly winds, in addition to the hot surface temperatures, will facilitate the potential for elevated-to-critical fire weather conditions on Saturday afternoon. The dryline will remain east of the Rolling Plains on Sunday as a another shortwave trough emerges over the central Rocky Mountains, though winds may attain a west-northwesterly component due to the possibility of an outflow-reinforced, pre-frontal surface trough. High temperatures will be a few degrees lower than Saturday due to the weakness in adiabatic compression compared to a southwesterly fetch, and temperatures will range from the lower-to-upper 90s from west-to-east across the CWA, respectively. Winds were raised from the NBM for Sunday (50 percent weighting applied with the NBM 90th percentile) as renewed cyclogenesis of a 994-996 mb surface low occurs near the OK PH and the boundary-layer mixes above 700 mb in the afternoon. Elevated-to-critical fire weather conditions are, therefore, forecast to develop once again across portions of the Caprock on Sunday afternoon. A tertiary shortwave trough is forecast to eject into the north-central Great Plains on Sunday evening, which will generate another cold front (perhaps also reinforced by convective outflow from thunderstorms in the central Great Plains), with the cold front moving through the CWA early Monday morning. High temperatures on Monday may stay below 90 degrees for most of the CWA, with the trend continuing into the middle of the week. All suites of the global NWP guidance continue to indicate that the anomalous ridge originally positioned over the northeastern waters of the Pacific Ocean will shift inland and across the Intermountain West. However, there remains discrepancies in its amplitude and the geometry of the synoptic-scale flow. Regardless, presence of return flow at the surface and low-levels beneath a west or northwesterly component to the steering flow points towards favorable chances for thunderstorms across portions of the CWA from late Tuesday through Thursday, some of which could be severe. Sincavage && .AVIATION... (18Z TAFS) Issued at 1213 PM CDT Thu May 23 2024 Breezy southwest winds are expected through this afternoon before diminishing into the evening. Gusty northerly winds will develop Friday afternoon behind a cold front. VFR will continue. && .FIRE WEATHER... Issued at 305 AM CDT Thu May 23 2024 Clouds will quickly dissipate this morning as a dryline surges eastward. Behind this dryline, downsloping southwesterly winds will boost temperatures into the low to mid 90s and bring a much drier airmass into the South Plains and far southwestern Texas Panhandle. This drier air combined with the hot temperatures will drop afternoon relative humidity values into the lower to middle single digits across the far southwestern Texas Panhandle and South Plains. Southwest winds will also become breezy (sustained winds of 15-20 mph and gusts to 30 mph) across this same area with the strongest winds expected across the far southwestern Texas Panhandle and the southwestern South Plains where sustained winds of 20-25 mph and gusts up to 35 mph will be possible. The combination of breezy and dry conditions will lead to RFTI values of 4-6 across the Caprock. Therefore, a Red Flag Warning has been issued from 1 pm until 9 pm today for the far southwestern Texas Panhandle into the western South Plains. While a Fire Danger Statement is in effect for the remainder of the Caprock. Very poor relative humidity recoveries will be observed overnight on the Caprock only increasing into the mid to upper teens until a cold front arrives around sunrise on Friday bringing relative humidity values up to around 30 percent. Unfortunately, this front will also switch winds around to the north with sustained winds around 20 mph and gusts up to 35 mph behind it. && .LUB WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 9 PM CDT this evening for TXZ021-022-027- 028-033-039. && $$ SHORT TERM...58 LONG TERM....09 AVIATION...19