Area Forecast Discussion
Issued by NWS
Issued by NWS
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
178 FXUS64 KLUB 181930 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 230 PM CDT Wed Sep 18 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Thursday) Issued at 224 PM CDT Wed Sep 18 2024 The upper level pattern remains relatively benign across West Texas early this afternoon, with water vapor channel imagery depicting a belt of modest southwest flow aloft locally as a pair of upper lows remains over the northwestern CONUS. At the surface, a diffuse trough axis / pseudo-dryline is oriented roughly NE-SW across the TX Panhandle and South Plains with dewpoints in the mid/upper 60s off the Caprock at 19z with a drier, more well-mixed airmass further west. Regarding today`s rain chances, a stubborn zone of midlevel lift and associated elevated showers has lifted out of the Permian Basin into southern portions of the Rolling Plains, and have expanded low PoPs eastward off the Caprock through the rest of this afternoon with this activity expected to persist. Further west, uncertainty is much higher on whether any additional convection will fire this afternoon. Large-scale forcing for ascent is essentially non-existent, but model soundings do continue to indicate an erosion of capping along the I-27 corridor by late afternoon which may result in a few isolated storms firing in this area. However, the absence of any cumulus field at 19z and only very weak low level confluence adds some skepticism on the degree of convective development we will see today, and recent hi-res model runs have begun to back off on storm coverage. Will keep PoPs as-is from the previous forecast for now, especially given a conditional threat for a strong storm or two if cells are indeed able to develop; an isolated damaging wind gust of instance of hail to quarter size will still be possible within any storms that do develop, but overall this threat currently looks to be limited. Broad upper ridging to our south will expand slightly northward on Thursday, with a slight increase in layer thicknesses resulting in highs a couple of degrees warmer area-wide compared to today. Most guidance suggests a weak surface boundary will linger over our region with a few hi-res solutions suggesting isolated weak convection will develop on Thursday afternoon. Still not particularly impressed by this setup given a continued lack of broader forcing and only very weak low-level confluence. This combined with even warmer midlevel temperatures compared to today suggest that any convection that attempts to develop tomorrow will struggle, and will therefore keep PoPs sub-mentionable area-wide on Thursday at this time. && .LONG TERM... (Thursday night through next Tuesday) Issued at 224 PM CDT Wed Sep 18 2024 A brief period of active weather is expected this weekend with the weather pattern representing more of a spring like characterization. This active period will stem from a strong closed low moving across the southwestern US. This will begin on Friday as the closed low moves eastward across southern California into western Arizona. Upper ridging will remain over Texas but slight height falls aloft will begin to occur from eastern New Mexico into the South Plains. Large scale ascent on Friday afternoon will not be terribly strong this far from the center of the upper low but broad upper level wind divergence overhead will bring some weak ascent. However, lower levels of the atmosphere will see broad, moist upslope flow in the afternoon. Convective activity in New Mexico is likely but there is high uncertainty in this convection reaching the South Plains. Greater attention will then turn to Saturday as the upper low moves northeastward from Arizona over the four-corners and into eastern Colorado by the evening. An upper level jet streak around 100kt or so will be positioned from central New Mexico into southeastern Colorado and western Kansas on Saturday afternoon. The strongest ascent with this system will again be to the north of the area, mostly in Colorado closer to the upper level jet but will extend southward into West Texas. At the same time, a weak short wave around 700mb with a separate wind max will be moving more overhead than the upper level features on Saturday. Timing on the trough will be optimal for peak heating convection as the base of the trough will not move over the area until Saturday evening. At lower levels of the atmosphere, surface cyclogenesis will be stronger compared to Friday as the upper trough approaches. A dryline is expected to considerably tighten up and not mix very far eastward during the day. Very strong low level theta-e advection will persist through the day preceding convective initiation. This will result in strong instability values in an uncapped atmosphere which is likely to bring at least isolated to scattered convection with some possibility of severe. As the system pulls away from the area on Sunday a cold front will be sent down into the area but there are differences in model timing on the front. This may ultimately bring some additional convective chances on Sunday afternoon primarily off the caprock if the slower solutions were to verify. The front will bring down temperatures back to or below seasonal averages from Sunday and beyond. Another short wave trough will be diving southward around Tuesday of next week potentially bringing additional rain and thunder chances. && .AVIATION... (18Z TAFS) Issued at 1227 PM CDT Wed Sep 18 2024 VFR expected to prevail through this TAF period. Potential still exists for some iso-sct TSRA to develop during the mid to late afternoon hours mainly north of a line from LBB to CDS, but confidence in eventual areal coverage of this convection remains too low to include TS mention in any TAF at this time. Strong and erratic downburst winds should be expected in the vicinity of any TS, with convection diminishing after sunset and VFR continuing overnight through Thursday. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...30 LONG TERM....01 AVIATION...30