Flash Flood and Hail in Texas, May 31, 2022

Area Forecast Discussion...CORRECTED
National Weather Service Lubbock TX
220 PM CDT Tue May 31 2022

.SHORT TERM...
18Z upper air analysis depicts a vertically stacked/occluding
cyclone over the southern Manitoba/Ontario border, with a trailing
mid-level cold front extending west-southwestward into the central
Great Plains and into the Great Basin as per 12Z 500 mb objective
maps and recent RAP analysis. A secondary cyclone, although less
amplified, was centered over the central Great Basin with a series
of smaller-scale shortwave perturbations detected on the latest
water vapory imagery that were rotating east-northeastward towards
the region. At the surface, a quasi-stationary front was anchored
from southwest-to-northeast across the CWA along a line from Denver
City to Tulia and extending towards the I-40 corridor as per recent
West Texas Mesonet data and the shallow cumulus field demarcating
its position. The dryline intersects the quasi-stationary front
across far southeastern New Mexico, and is not expected to propagate
eastward this afternoon as the airmass becomes increasingly
barotropic with southward extent from the front and as larger-scale
forcing for ascent remains displaced over the west-central Great
Plains region. West Texas Mesonet data and WSR-88D VWPs from KLBB
indicate that surface-to-low-level flow is parallel to the frontal
position across the moist sector, with winds shifting to the north
in wake of the front with speeds generally between 10-20 mph across
the post- and pre-frontal sectors with steady pressure tendencies.
This has resulted in weak convergence in vicinity of the stalled
front, evident by the shallow cu field despite the influx of strong,
diabatic heating.

The 12Z MAF RAOB sampled a very moist boundary-layer with dewpoints
in the upper 60s and a mean mixing ratio of 14.6 g/kg that was
advecting northward. South of the quasi-stationary front, a plume of
dewpoints ranging from the lower 60s across the Caprock and into the
middle-upper 60s in the Rolling Plains is present with temperatures
in the upper 80s to lower 90s, contributing to strong-extreme
thermal instability as MLCAPE nears 3,000 J/kg on the latest RAP
analysis. Confidence in this prognostication with respect to the
magnitude of MLCAPE across the moist sector is high based off the
observed morning sounding from WFO MAF. Effective bulk wind
differences (EBWDs) are modest as the CWA remains beneath the
glancing influence of the mid- and high-level jet streaks to the
north, with EBWDs near 40 kt in addition to the 850-500 mb wind
vectors remaining boundary-parallel. Isolated to widely-scattered
thunderstorms are forecast to form across the South Plains with mean
storm movement governed by advection, with storms quickly becoming
severe as the large, upward-directed accelerations accentuated by
wide updrafts offsets the modest shear. Significant/2"+ diameter
hail is expected to occur in addition to severe-caliber gusts as
cells move east-northeastward. Across the extreme southeastern Texas
Panhandle and into the northern Rolling Plains, scattered convection
is expected to develop mid-to-late afternoon as low-level
convergence maximizes while quickly becoming severe. Precipitable
water content is anomalously high, as per 12Z MAF RAOB and recent
GOES-East Total Blended Precipitable Water imagery. Initial storm
characteristics are expected to be multi- and supercellular, with
weak storm-relative flow throughout the LCL-EL layer which will
enhance precipitation-loading within the wide updrafts. Severe to
potentially significant-severe/65+ kt gusts are expected as
convection morphs into a Mesoscale Convective System (MCS) with
embedded mesocyclones. MCS movement will be slow, and dictated
largely by the combination of intense cold pools and the isolated to
widely-scattered cells to the southwest merging with it which will
augment the possibility of a forward-propagating MCS. A short-lived
tornado risk will accompany any storm merger or within any mesoscale
convective vortex that develops; however, the strong/cold downdrafts
and potential steeply-sloped outflow boundaries will eventually
undercut surface-based inflow parcel trajectories, ultimately
resulting in the demise of the MCS as theta-e advection weakens and
diabatic stabilization occurs. Severe convection should wane/exit
the northeastern zones altogether near 01/06Z.

The low-level jet will strengthen overnight with the stalled front
remaining positioned in vicinity of the TX PH and South/Rolling
Plains region, though the exact position of the front may be
affected by convective outflows from the decaying MCS. The airmass
is forecast to be in a similar state tomorrow ahead/south of the
front, with the center of the sub-tropical ridge retrograding over
Mexico along with a shortwave trough pivoting across the central
Great Plains, causing mid- and high-level flow to veer. The stalled
front will begin to transition into a cold front and move southward
across the CWA by the mid-afternoon hours, with scattered, severe
convection expected to develop with a few supercells possible across
the South Plains before cold pools merge as frontogenetical forcing
increases. Localized flash flooding will once again be possible, in
addition to the potential for severe-caliber hail (possibly 2"+) and
wind events.

Sincavage

.LONG TERM...
Precipitation chances will continue through the rest of the week
after Wednesday afternoon with additional heavy rain and severe
thunderstorm chances. The cold front will continue to push through
the rest of the area Wednesday evening with expected widespread
convection ongoing through the evening hours. The weather pattern
will look slightly different for the rest of the week after that.
Zonal flow will be overhead on Thursday with weak short wave ridging
moving over the area. Southeasterly low level upslope flow will
dominate the lower levels in the post frontal air mass. Furthermore,
a weak short wave moving through the flow with the above conditions
will promote higher terrain convection in eastern New Mexico.
However, convection may struggle to reach far into West Texas.
Better lift for convection will exist from the Permian Basin into
Far West Texas and the Big Bend as a stronger upper level jet streak
noses into that area. Additionally, instability will mostly be
elevated on Thursday with cool and cloudy conditions.

Severe chances may be better on Friday with upper flow slightly more
backed. Much better instability will be available with better low
level moisture and warmer surface temperatures. Additionally,
another weak short wave may be moving through the flow aloft
initiating thunderstorms again on the higher terrain of eastern New
Mexico. However, this convection would stand a better chance at
progressing farther across the South Plains for the aforementioned
reasons. CIPS analog guidance highlights Friday as a higher
probability day for severe weather over Thursday. A sloshing dryline
will return this weekend but convective chances are doubtful at the
moment with temperatures rising back well above seasonal averages.

&&

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

09/01

Hazardous Weather Outlook...UPDATED
National Weather Service Lubbock TX
1129 AM CDT Tue May 31 2022

TXZ021>044-011630-
Parmer-Castro-Swisher-Briscoe-Hall-Childress-Bailey-Lamb-Hale-Floyd-
Motley-Cottle-Cochran-Hockley-Lubbock-Crosby-Dickens-King-Yoakum-
Terry-Lynn-Garza-Kent-Stonewall-
1129 AM CDT Tue May 31 2022

This Hazardous Weather Outlook is for the South Plains, Rolling
Plains, and the far Southern Texas Panhandle.

.DAY ONE...This afternoon and tonight.

The potential for severe thunderstorms will increase late this
afternoon, especially across the extreme southeastern Texas Panhandle
and northern Rolling Plains. Chances for severe thunderstorms will
also increase across the South Plains late this afternoon, generally
near and east of the Interstate 27 corridor. Thunderstorms across the
region will be capable of producing damaging wind gusts up to 80 mph
and very large hail greater than two inches in diameter. A tornado
or two will be possible as well. Heavy rainfall will result in
localized flash flooding due to the slow movement of thunderstorms,
particularly across the extreme southeastern Texas Panhandle into the
evening.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorm chances will continue on Wednesday. Some storms may be
severe, capable of producing large hail and damaging wind gusts.
Localized flash flooding will be possible due to heavy rain.

Thunderstorms, some severe, will be possible again on Thursday and
Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed.