Hail and Damaging Winds in Texas, May 10, 2023

Area Forecast Discussion
National Weather Service Amarillo TX
709 PM CDT Wed May 10 2023

...New AVIATION...

.MESOSCALE UPDATE FOR WIND, HAIL, AND A LOW TORNADO THREAT FOR
THIS AFTERNOON THROUGH TONIGHT...
Issued at 241 PM CDT Wed May 10 2023

* Synoptic Overview: The latest 10/18z RAP H500 analysis shows a
  negatively tilted trough located over the Desert Southwest and
  is continuing to move east/northeast early this afternoon. Out
  ahead of this feature, southerly winds continue to advect
  theta-e at H700 across mainly an axis along west TX and east NM.
  This can be seen in the mid level water vapor satellite band and
  with some cumulus clouds developing across northeastern NM.
  Moisture return would be greater across the area if low pressure
  was not located to our southeast along with ongoing convection
  in east and southeast TX. A subtle weak shortwave out ahead of
  the main low pressure system is moving across north central NM
  early this afternoon. Current expectation is that this weak
  disturbance will aid in convective initiation across far
  northeastern NM, as already seen by a thunderstorm developing
  across the higher terrain in NM. The main event so to speak, is
  expected to be during the late evening into the overnight hours
  as the main upper level wave approaches the Panhandles and
  provides stronger PVA. This may generate a secondary round of
  thunderstorms, some of which could be severe, during the
  overnight hours and could continue into early Thursday morning.

* Mesoscale: Latest 18z surface analysis shows dew points are
  continuing to slowly decrease across the Southern High Plains as
  daytime mixing is bringing down drier air from aloft to the
  surface. A surface dry line continues to sharpen across eastern
  NM and is expected to be the surface lifting mechanism to get
  convection started this afternoon. This is already apparent as
  of 1845z, with a shower/storm beginning to develop south of
  Raton, NM. The 10/18z RAP mesoanalysis shows that there may be
  a small area along the dry line that is uncapped at this time,
  with MLCAPE around 1000 J/kg. This is located in the vicinity of
  where the initial storm is beginning to develop. CIN will
  continue to decrease through the daytime hours, but surface
  moisture will also decrease which will lead to lower CAPE
  values. Given the weak upper level flow aloft, any storms that
  form during the afternoon into the early evening hours are not
  expected to be fast moving. With that being said, effective
  shear will be quite weak and may inhibit some of the severe
  weather threat. As thunderstorms move into the western
  Panhandles later this afternoon, the more aggressive models
  suggest that 1000-1500 J/kg of MLCAPE may remain over the area
  along with slowly increasing effective shear as southerly H850
  winds increase to near 30 kts. The better chance of storms being
  surface based looks to be in the northwest based on the more
  aggressive soundings from models that have a higher moisture
  bias. This initial round of storms, which looks to become linear
  based on CAMs and the relatively marginal shear, may continue
  across the west and potentially the central Panhandles til
  midnight. A secondary line of linear storms may develop over
  portions of west TX as the main upper level wave comes across
  during the overnight hours. The first round of convection may
  hinder how far north this secondary line is able to develop as
  portions of the Panhandles could be worked over and may limit
  further thunderstorm development. In any case, low level
  moisture will be on the increase and surface dew points may
  approach the mid to upper 50s, with low 60s further east. As
  moisture increases throughout the column, long skinny CAPE
  profiles look possible with CAPE values around 1000 J/kg. Cannot
  rule out some of these storms potentially becoming surface
  based, which would lead to a low end tornado threat given the
  long low level forecast hodographs. A QLCS may develop as 0-3km
  shear values are near 30 kts along and behind where the line is
  forecast to develop. Several CAMs are depicting that this
  scenario is possible and a brief tornado spin-up looks plausible
  during the overnight hours. Will need to continue to monitor
  the potential for this threat, especially since it is during the
  overnight period.

* Threats: The main threats with any severe thunderstorms this
  afternoon through this evening will be large hail (up to ping pong
  ball) and damaging wind gusts (up to 65 mph). Given the lack of
  moisture this afternoon, especially across the west, CAPE values
  combined with weak shear are not overly supportive of a very large
  hail threat. Even though moisture and shear will increase through
  the overnight hours, as mentioned above, long skinny CAPE profiles
  are possible and are not the most supportive of very large hail.
  Storms are expected to become mainly elevated after sunset tonight
  as we lose daytime heating and capping in the low levels becomes
  prevalent. This will decrease the damaging wind threat, but if a
  QLCS is able to form, some gusty winds could mix down to the
  surface. The low end tornado threat is highly conditional and will
  depend upon the low to mid levels cooling as the upper level wave
  approaches the Panhandles. Cannot rule out a quick spin-up or two
  during the overnight hours. Will need to carefully monitor the
  trends through the overnight hours.

* Timing & Location: Two rounds of thunderstorms are expected over
  the next 12 to 18 hours. The first round is forecast to move in
  across the western Panhandles around 5 to 7 PM Central. A line
  of storms may move across portions of the western Panhandles
  through early evening. A secondary round of thunderstorms may
  develop across portions of west TX during the overnight hours
  (around 11 PM through 1 AM) and is expected to trek east. The
  highest chance at seeing these storms overnight would be across
  the central and/or southern TX Panhandle. These storms are
  expected to be east of the area near sunrise on Thursday.

Muscha

&&

.SHORT TERM ...
(This evening through Thursday night)
Issued at 241 PM CDT Wed May 10 2023

For the severe weather threat this afternoon through early
Thursday morning, refer to the Mesoscale Discussion above.

As this event gets going later this afternoon/evening, the best
chance for initial storms would be in the NW TX and OK Panhandle,
but confidence is low on storms being that far east from 21-00z.
For this reason, have slightly lowered and trimmed back NBM POPs
for that time frame. Otherwise NBM POPs looked reasonable for
tonight and were left in as they were. Some ongoing storms may
linger in the east/northeast combined Panhandles Thursday morning
into the afternoon but should generally exit the CWA by 18z so
have lowered and confined POPs to the northeast OK Panhandle after
18z.

Low clouds associated with tonight's system as well as breezy
southeast winds will limit radiational cooling overnight and keep
low temperatures Thursday morning in the 50s across the area. As
the upper level disturbance moves east, the pressure gradient will
tighten from a sfc low and increase winds out of the southwest.
Drier air will set in from west to east as these downsloping winds
and clear skies help most of the area warm into the 80s. A cold
front will move in behind the sfc trough Thursday night as it
moves east, bringing cooler temps and northwest winds to the
Panhandles. As a result, lows will dip to the mid 40s in the NW to
low 50s in the SE.

Harrel

&&

.LONG TERM ...
(Friday through next Tuesday)
Issued at 241 PM CDT Wed May 10 2023

Friday will be a transition day as the first disturbance moves
away from the area and the next disturbance approaches. This
should result in a mostly non-eventful day as a cool front
moves through during the daytime period. Chances for
thunderstorms will be on the increase Friday night into Saturday
as moisture attempts to surge back into the area ahead of a sub-
tropical disturbance. The question with this concerns how far
south the aforementioned front advances before it stalls. If it
stalls further south (say in Lubbock's area), storms will be less
likely in the area until Saturday morning. If it stalls further
north, then storms would be possible (a few severe given CAPE and
marginal shear also possible) in the southern zones by Friday
evening. Right now only about 20 to 30 percent of the total NBM
membership is showing more than 400 J/kg before midnight, and only
about 10 to 15% show 1000 J/kg or more which suggests the front
may slip too far south.

Beyond Friday night through early next week, the 500mb
disturbance advances from the Big Bend region of Texas almost due
north in a weak flow regime (very reminiscent of mid to late
Summer). There are differences in exactly where the low will
track, but most ensemble members bring it right across the
combined Panhandles, if not slightly west which puts the area in
really good shape for persistent moisture advection over a long
period and synoptic lift (along with theta-E advection /
isentropic ascent). The deterministic GFS brings the wave
slightly east which is not as favorable as it brings down drier
air from the north, especially for our western zones. The good
news is that the GFS is an outlier, even to its own ensemble
suite. The GEFS mean 24 hour QPF ending Sunday morning paints a
50% to 80% chance for 1/2" across all but part the northwest
zones (which are more around 20% to 40%). PWAT values may approach
daily max values with ensemble means suggesting periods over 200%
of normal, and with the weak flow aloft storms may be slow moving
and thus a flood/flash flood risk will exist. The models continue
to pump moisture into the area early next week on the backside of
the system, so solid chances for rain continue at least through
Monday. When it's all said and done, a good chunk of the area may
see well over 1 inch of rainfall this weekend into next week (as
long the the GFS doesn't verify).

Ward

&&

.AVIATION...
(00Z TAFS)
Issued at 648 PM CDT Wed May 10 2023

For the 00Z TAFs, an upper level storm system will impact the
forecast area tonight and will bring a threat for showers and
thunderstorms to the terminal sites. KDHT will likely be affected
by showers and storms this evening, followed by KGUY and KAMA late
tonight. All precipitation should be east of the TAF sites by
around 10Z Thursday. A brief period of MVFR cigs is expected to
develop at KGUY and KAMA late tonight into Thursday. Southwest
winds will then increase and become gusty at the terminal sites by
around mid to late Thursday morning and continue through Thursday
afternoon.

02

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                57  85  52  87 /  50  10   0   0
Beaver OK                  59  84  52  86 /  30  50  10   0
Boise City OK              52  79  46  80 /  70  20   0   0
Borger TX                  60  88  54  90 /  50  10   0   0
Boys Ranch TX              57  86  50  89 /  50  10   0   0
Canyon TX                  55  84  51  89 /  60  10   0   0
Clarendon TX               59  85  54  89 /  50  20   0  10
Dalhart TX                 51  81  45  83 /  60  10   0   0
Guymon OK                  57  83  50  84 /  60  20   0   0
Hereford TX                53  85  49  89 /  50   0   0   0
Lipscomb TX                58  85  52  89 /  20  40   0   0
Pampa TX                   58  85  53  87 /  40  10   0   0
Shamrock TX                59  86  54  90 /  30  30   0  10
Wellington TX              60  87  54  90 /  40  30   0  10

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&

SHORT TERM...38
LONG TERM....07
AVIATION...02

Hazardous Weather Outlook...UPDATED
National Weather Service Amarillo TX
441 PM CDT Wed May 10 2023

OKZ001>003-TXZ001>020-317-111100-
Cimarron-Texas-Beaver-Dallam-Sherman-Hansford-Ochiltree-Lipscomb-
Hartley-Moore-Hutchinson-Roberts-Hemphill-Oldham-Potter-Carson-
Gray-Wheeler-Deaf Smith-Randall-Armstrong-Donley-Collingsworth-
Palo Duro Canyon-
441 PM CDT Wed May 10 2023

This Hazardous Weather Outlook is for the Texas and Oklahoma
Panhandles.

.DAY ONE...Tonight.

Strong to severe thunderstorms will be possible across the
combined Panhandles through tonight. If severe thunderstorms
develop, large hail and damaging winds would be the primary
hazards. Additionally, a tornado or two cannot be ruled out. A
Severe Thunderstorm Watch is in effect for the western Oklahoma
Panhandle and the western Texas Panhandle until 11 PM CDT this
evening.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

The probability of widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed after 6 PM this evening.