061 
FXUS64 KLUB 021926
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
226 PM CDT Fri Jul 2 2021

.SHORT TERM...
Synoptic analysis this afternoon reveals a continued dynamic upper 
flow pattern over much of North America, with a large trough 
centered over the eastern Great Lakes and low-amplitude troughing 
over the northwestern CONUS. West Texas remains under northwesterly 
flow aloft with a rather high-amplitude ridge axis over the northern 
Great Plains and an upper high over the Desert Southwest. Water 
vapor imagery depicts robust mid and upper level moisture rotating 
around the periphery of the high, with 12z AMA and MAF soundings 
sampling PWATs of 1.44" and 1.42", respectively. At the surface, the 
frontal boundary which entered the CWA early this morning has begun 
to wash out as it stalls across southern portions of the CWA.

Overall, the synoptic pattern will not change significantly 
throughout the Short Term period, with the upper high only forecast 
to shift very slightly westward. Consequently, upper steering flow 
and shear will remain weak, meaning that convection currently 
observed over eastern New Mexico will have a hard time organizing 
and is unlikely to make it into the CWA this evening. Therefore, 
precipitation chances this afternoon into tomorrow will rely on 
whether convection can initiate locally. Hi-res guidance seems to 
want to develop additional convection this afternoon, mainly within 
our southern tier of counties. With the stalled frontal boundary and 
the abundant moisture in place, this is certainly plausible. But, 
with a rather elongated and weak CAPE profile and a lack of any 
obvious upper level impulses upstream, precipitation this afternoon 
and evening will likely be in the form of scattered showers with 
perhaps a few embedded thunderstorms. Again, given the abundant 
moisture present, locally heavy rain will be the main concern. Will 
keep PoPs in the chance category as overall shower coverage remains 
uncertain.

Tonight into Saturday will be a similar setup as this afternoon, 
with the stalled boundary situated roughly near or just south of our 
southern CWA border. Chances for showers and and a few thunderstorms 
will therefore persist, with the best chances across the southern 
South Plains and southern Rolling Plains. At this time, it appears 
that precipitation will remain scattered, as West Texas will be 
underneath the outer edge of the upper high and there still does not 
appear to be any notable inbound upper impulses. Considerable 
cloudiness should also keep temperatures below average, helping to 
limit instability. However, it should be noted that with the surface 
boundary in place, only subtle upper impulses would be necessary to 
enhance convection. Furthermore, since guidance can have trouble 
resolving these features, there is a chance that precip could be 
more widespread than currently forecast. However, at this time 
confidence in widespread coverage of precip is low. As such, mainly 
chance PoPs were retained through the period. Given the moisture and 
the forecasted elongated CAPE profiles, however, heavy rain and 
efficient rainfall are possible within the showers and thunderstorms 
that do form. /DWK

.LONG TERM...
The mid/upper-level ridge will continue to expand over the southern 
and southwestern CONUS this weekend, with the axis centering across 
the Intermountain West and through the Four Corners region as it 
amplifies to around 594 dam by Sunday. A strong mid-level shortwave 
perturbation is forecast to rotate about the ridge top, with a small 
tranche of the shortwave splitting off and rotating southward along 
the eastern periphery of the ridge, crossing the 35th parallel late 
Sunday. The airmass across the CWA will also be similar to the last 
several days as the quasi-stationary front all but dissipates by 
this time, with the boundary-layer characterized by lower 100 mb 
mean mixing ratios around 14-16 g/kg and precipitable water (PWAT)
content near the 99th percentile as per 05/00Z sounding climatology
from the AMA RAOB site. Northwesterly 250-500 mb flow will result
in sufficient cold air advection aloft, enough to enlarge the size
and depth of the EML with MUCAPE values around 2,500 J/kg, surmounted
by increasing southeasterly low- level flow as a surface trough 
develops across the western High Plains.

Increasing convergence in vicinity of the surface trough late Sunday
as the aforementioned shortwave trough arrives, combined with strong,
diabatic surface heating as temperatures climb into the upper 80s,
should result in the initiation of thunderstorms near the Raton Mesa,
southeastern Colorado, and the northwestern Texas and Oklahoma 
Panhandles. Multi-cellular convection is expected to be the initial
storm mode, though as precipitation-loading increases from weak 
mid-level storm-relative winds and high PWAT content, convective 
clusters may very well become cold-pool-driven with the possibility
of a few bows developing as cells surge southeastward into the CWA
near sunset Sunday. The primary hazard of concern is the potential
for localized flash flooding, especially given the recent, soaking
rainfall over the last week across the forecast area. As of today
(July 2nd), NASA SPoRT 0-40 cm soil moisture content has reached 
the 99th percentile across nearly half of the CWA, particularly 
in the extreme southern Texas Panhandle and northern South Plains.
West Texas Mesonet data also indicates a broad area of water content
near 0.50" at a depth of 5-20 cm this afternoon as well, confirming
the satellite estimates. 

Negligible drying is expected between now and Sunday night, and the 
potential for excessive runoff will be exacerbated by high rain rates
per hour within the deepest cores. Though, a more significant flash
flood threat should be offset by the fast storm motions (current 
prognosis of around 330/40 kt). Nevertheless, a heavy rain event 
is forecast across portions of the extreme southern Texas Panhandle,
and the northern South and Rolling Plains, where a swath of 1-3" of
rain with locally higher amounts will be possible. A few localized
wet-microburst situations will be possible as well, with strong gusts
around 50-60 mph in the most intense cores or if a rear-inflow jet
becomes well-established.

Additional chances for precipitation exist into the middle of next 
week, though uncertainty exists as to when and where convection may 
occur owing to limited predictability. However, with poleward flow 
persisting over the CWA, any shortwave troughs that rotate along the 
downstream portion of the ridge axis may result in the potential for 
convection before the mid/upper-level high shifts back to the east 
and centers over the southern CONUS, eroding chances for rain by the 
end of next week.

Sincavage

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

30/09