Severe Thunderstorm Warning 57, NWS Amarillo, TX

Area Forecast Discussion
National Weather Service Amarillo TX
401 PM CDT Thu May 17 2018

.DISCUSSION...
Latest water vapor channel reveals shortwave emanating from
upstream trough over central NV, as ridge axis continues to shift
east into western OK. At the surface, a dryline is sharpening with
50s dew points from Clovis to Dalhart and increasingly backed
winds east of dryline. Storms are initiating in the western South
Plains where a bulge in the dryline exist, with a few radar
returns showing up in the far western Texas Panhandle. An 18z
KAMA sounding showed SBCAPE around 2600 J/kg with a relatively
weak CAP. MLCAPE was sampled at 1300 J/kg with a lot more CIN (160
J/kg) mainly due to the EML in place. LCL heights of 2000m along
the dryline may decrease to around 1500m during the evening. The
combination of stronger mid-level southwest flow overspreading
the area and a 30-40kt low level jet increasing during the evening
will result in 10 to 20 knots of 0-1 km shear. Effective deep
layer shear of around 40-50kts is expected during the late
afternoon and early evening. Moreover, supercells with very large
hail and strong winds should be the primary threat through early
evening. Any supercell that can remain discrete into the evening
will have some potential to produce an isolated tornado. This
will depend on whether or not there is sufficient moisture and
cooling to at least locally reduce LCL heights, while storms
remain surface based to ingest low level SRH. Given the high based
nature of most storms today and DCAPE values upwards of 1500 J/kg
along with steep low/mid level lapse rates, strong downburst
winds can't be ruled out, especially if storms become more linear
in the evening. Storms should be out of the area by 02z to 04z.
However, some redevelopment is possible overnight where theta-e
advection stays stronger in the eastern Panhandles. Severe weather
is not currently expected with any redevelopment overnight.

The upper low continues its track east on Friday then begins to
stall as an open wave over the Rocky Mountains. The dryline is
progged to push further east with a stronger cap being suggested
in the guidance. Storm initiation looks less widespread compared
to Thursday, but did include slight pops for the eastern
Panhandles. Any storm would again have plenty of instability and
modest shear to work with, so an isolated severe storm is
possible. A cold front is progged to move through the area
Saturday. Model to model consistency is reasonable based on the
12z runs today, which suggest the front will move through most of
the area by Saturday evening. That being said, being that the
synoptic push for this is limited to a developing shortwave over
the central Plains, not completely convinced that this front won't
stall in the area providing forcing for additional storms over
the weekend. Storm chances continue next week with return flow
being maintained as broad cyclonic flow remains in place over the
western CONUS.

Ward

&&

.FIRE WEATHER...
Elevated to critical fire weather conditions are possible Friday
afternoon for the far western Panhandles with drier conditions and
breezy southwest winds. Haines index of 5 to 6 can also be
expected.

Ward

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                90  61  90  57  87 /  60  50  20   5  20
Beaver OK                  91  61  90  59  83 /  30  60  20  20  10
Boise City OK              92  51  87  53  76 /  30  10   5   5  20
Borger TX                  91  60  93  59  87 /  50  60  20  10  20
Boys Ranch TX              95  59  93  56  87 /  50  30  10   5  10
Canyon TX                  91  57  92  55  88 /  60  50  10   5  20
Clarendon TX               89  61  92  60  89 /  40  60  20  10  20
Dalhart TX                 93  54  89  53  81 /  30  10   5   5  10
Guymon OK                  92  57  90  56  80 /  60  50  20  10  10
Hereford TX                93  58  92  54  88 /  50  30  10   5  20
Lipscomb TX                90  63  90  60  87 /  30  50  20  20  20
Pampa TX                   87  61  91  58  86 /  40  60  20  10  20
Shamrock TX                89  60  92  62  89 /  30  50  20  20  30
Wellington TX              90  62  94  64  92 /  30  50  20  20  30

&&

.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.

&&

99/99

Hazardous Weather Outlook
National Weather Service Amarillo TX
416 AM CDT Thu May 17 2018

OKZ001>003-TXZ001>020-317-172130-
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-
416 AM CDT Thu May 17 2018

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

.DAY ONE...Today and Tonight.

Thunderstorms are expected across much of the area. Some storms
that develop will have the potential to become strong to severe,
especially this afternoon and evening. The main threats will be
hail up to the size of golf balls and winds up to around 65 MPH.
Heavy rains can also be expected with the stronger storms,
possibly leading to localized flooding or flash flooding.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Thunderstorms will be possible Friday through Wednesday across
much of the Oklahoma and Texas Panhandles. Some storms that
develop will have the potential to become strong to severe,
with the main hazards being large hail and strong winds.

Elevated fire weather conditions are expected today across the
far western parts of the Panhandles. Elevated to critical fire
weather conditions may develop on Friday across the western half
of the Panhandles.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

Area fire managers and emergency officials should be alert for
elevated fire weather conditions today across the far western
parts of the Panhandles, and for elevated to critical fire
weather conditions on Friday across the western half of the
Panhandles.

Cockrell

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AMARILLO TX
1204 PM CDT THU MAY 17 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1200 PM     HAIL             4 ESE SLAPOUT           36.60N 100.05W
05/17/2018  M0.75 INCH       BEAVER             OK   TRAINED SPOTTER

&&

EVENT NUMBER AMA1800070

15

Special Weather Statement
National Weather Service Amarillo TX
359 PM CDT THU MAY 17 2018

TXZ016-172130-
Deaf Smith TX-
359 PM CDT THU MAY 17 2018

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN DEAF SMITH COUNTY
UNTIL 430 PM CDT...

At 358 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles northwest of Summerfield, or 10 miles west of Hereford, moving
northeast at 25 mph.

Nickel size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Hereford.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3475 10280 3501 10272 3489 10225 3475 10238
TIME...MOT...LOC 2058Z 222DEG 21KT 3485 10258

Simpson