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
515 FXUS64 KLUB 050757 AFDLUB Area Forecast Discussion National Weather Service Lubbock TX 257 AM CDT Fri Jul 5 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (Today and tonight) Issued at 257 AM CDT Fri Jul 5 2024 06Z upper air analysis reveals a shortwave trough pivoting over the Corn Belt with its mid-level closed low rotating east of the Minnesota River Valley beneath an amplified, cyclonically-curved, 250 mb jet streak approaching 100 kt as per the 05/00Z objectively analyzed map data. Farther west, amplification of a subtropical ridge across the Pacific coast continues via interaction with a baroclinic cyclone rotating over the northern Pacific Ocean and as the broadly cyclonic flow is maintained across the eastern half of the Lower 48. The CWA is positioned to the south of the base of this mid/upper-level trough, with the right entrance-region to the 250 mb jet streak translating over the TX PH as per recent water-vapor imagery amidst a broad area of difluent flow in the mid-levels that stretches across the southern Great Plains. This corridor of deformed flow at the inflection point of the mean troughing and barotropic airmass has resulted in the maintenance of a Mesoscale Convective Vortex (MCV) evident on KMAF WSR-88D imagery, where a narrow shield of showers and thunderstorms continues across the southern Rolling Plains. At the surface, a slow-moving cold front was drawn along a line from TCC-HOB and into the I-20 corridor as per recent METAR and West Texas Mesonet (WTM) data. Pressure tendencies over the last hour have been as high as -3 mb nearest the remnant MCV in the southern South Plains, and the resultant mesoscale high temporarily muddled the more-brisk, northeasterly winds in wake of the cold front across the rest of the South Plains as the 1020 mb anticyclone builds in from the north. The movement and position of the stalling front was also governed by the more-widespread convection from last evening, and the cold front will remain stalled to the west and south of the CWA through the remainder of the period (06/12Z or 7 AM CDT Saturday). Convective contamination of the surface wind pattern should erode entirely by sunrise, with northeasterly winds gradually veering eastward throughout the day as the aforementioned surface high rotates into central Kansas. Genesis of a low stratus deck should occur across the portions of the South Plains and persist throughout the mid-morning and afternoon hours as the low-level isentropic surfaces remain moistened via the component of upslope flow along the southern periphery of the surface high and to the north of the stalled front. High temperatures for today were lowered from the NBM to align with the 00Z raw statistical guidance as dense overcast and adiabatic expansion from the easterly fetch restricts diabatic heating. To the north of the CWA, a convergence zone situated beneath the belt of deformed, mid-level flow exists along the I-40 corridor. This, combined with northeasterly, upslope flow, has generated scattered, elevated thunderstorms across northeastern NM eastward across the TX PH and into western OK; and it is possible that these cells drift into the extreme southern TX PH by sunrise. The best potential appears to be across the extreme southeastern TX PH and Rolling Plains; however, flow throughout the steering layer is oriented from the west near 15 kt while 850-300 mb flow is less than 10 kt and slightly more-backed to the southwest. Thus, as evident on KAMA WSR-88D data, the mean storm motion with these multi-cellular clusters is east-southeast at 10 mph or less across northeastern NM to a more-southeastward direction in western OK. The 05/00Z RAOBs from WFOs AMA and MAF also observed precipitable water (PWAT) content of 108 and 139 percent above normal, respectively; with PWAT values of 1.11" and 1.57", respectively. RAP-derived PWATs exceeded 1.50" across the Rolling Plains, and localized flooding may occur through the morning hours as the multi-cellular clusters across western OK merge into a MCC and potentially clip portions of the Rolling Plains. The forecast for this afternoon is even more complex, and a broad area of chance PoPs has been delineated across all locations west of the edge of the Caprock Escarpment while lesser potential for storms exists across the Rolling Plains. The 05/00Z RAOB from WFO ABQ observed superadiabatic lapse rates throughout the low-levels and a plume of mid-level lapse rates in excess of 8.0 deg C/km, which was advecting eastward at the time the data was observed. Convective overturning, perhaps further enhanced by the morning MCC forming in western OK, in addition to the restriction of diabatic heating from overcast, should temper storm potential across the eastern zones this afternoon and evening even in the presence of residual outflow boundaries owing to the poor lapse rates. However, across the Caprock Escarpment, and particularly near the TX/NM state line, evolution of a more-mixed boundary-layer will be possible, facilitating the potential for heavy thunderstorms once again this afternoon into tonight compared to areas farther east into the Rolling Plains. The potential for severe-caliber gusts will be contingent on the erosion of the stratus deck and how much vertical mixing can occur to facilitate downburst potential via the formation of Inverted-V profiles beneath cloud base. However, this scenario appears to be more-probable towards the evening hours as any breaks in clouds would enhance localized areas of differential heating and mixing occur beneath MLCAPE values in excess of 1,000 J/kg. Similar to yesterday, a wet-microburst potential will exist particularly with cells that remain isolated across portions of the South Plains this late-afternoon and evening. Localized enhancements of isentropic ascent may occur via merging cold pools with storms propagating southeastward heading into tonight which would serve as the foci for localized flooding, and the highest PoPs are delineated across the southern South Plains by this time before storm chances wane heading into Saturday morning. Sincavage && .LONG TERM... (Saturday through Thursday) Issued at 257 AM CDT Fri Jul 5 2024 The overall pattern for the extended has an upper ridge to our west across California building slowly eastward into the Great Basin region towards the end of next week. Meanwhile, troughing will persist across the Plains and into the Mid-Atlantic as a subtropical ridge builds into the GoM behind Hurricane Beryl. Given this, the flow aloft will be mostly northwesterly through the extended forecast period. A few elevated weak showers and storms may linger Saturday morning from Friday night`s activity across portions of the South Plains and Rolling Plains; however, the bulk of the activity will be to the south. Lingering morning clouds, along with an increase of cumulus clouds and chances for thunderstorms during the afternoon hours may help to limit daytime heating. Temperatures are expected to remain slightly below normal in the upper 80s to lower 90s. South southeast surface winds will help to pump in low level moisture with dewpoints in the lower to mid 60s. Afternoon diurnal convection along the higher terrain of New Mexico is likely. Additionally, a shortwave aloft may help to kick off and drive some showers and storms across the forecast area Saturday afternoon and evening. Temperatures should warm enough to the break any morning capping inversion with MLCAPE values around 500-1000 J/kg and effective shear of 30 to 35 knots, which is capable of supporting a few strong to potentially severe storms. Main threats with the storms would be damaging wind gusts with steep low level lapse rates, but large hail up cannot be ruled out either. With the mean flow aloft being west northwesterly and increasing slightly with the shortwave, storm motion will be east southeast and concerns of flooding due to slow moving storms remains low at this time. However, heavy rainfall with localized flooding cannot be ruled out. Sunday, clearing skies with a more south southwesterly downsloping surface wind will give way to a return of hot temperatures in the mid to upper 90s, with a few areas approaching triple digits. Another shortwave aloft Sunday evening may introduce a few showers and storms to the far southeast Texas Panhandle and Rolling Plains. In addition, a surface low across northeast New Mexico will slide southward late Sunday night with a passing cold front early Monday morning. Showers and storms may develop along the frontal passage with ample moist surface convergence. Modest elevated instability will be present and supportive of a strong storm or two. Post frontal precipitation chances and low clouds will support cooler below normal temperatures for Monday ranging from the upper 70s to upper 80s. Heading into the middle and end of next week, temperatures will remain mild in the upper 80s to lower 90s, which is slightly cooler than normal. Afternoon diurnal convection across the higher terrain in New Mexico may occur each afternoon and with embedded shortwaves in the northwest flow aloft, the chances for late afternoon and evening thunderstorms across portions of the area remains possible each day. && .AVIATION... (06Z TAFS) Issued at 1223 AM CDT Fri Jul 5 2024 A cold front will continue to move southward across the region throughout the overnight hours, with northeasterly winds expected for the TAF period. CIGs will lower into at least MVFR towards sunrise at KCDS, KLBB, and KPVW; and chances for TSRA will follow at KCDS later this morning, too. Overcast CIGs will return to VFR by this afternoon. The potential for convection affecting KLBB and KPVW this afternoon remains unclear, and will be assessed further for the 12Z issuance. The complex of thunderstorms currently to the southeast of KLBB will gradually dissipate over the next couple of hours. Sincavage && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...09 LONG TERM....11 AVIATION...09