Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 172305
AFDAMA

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

.AVIATION...
00Z TAF Cycle

Showers and thunderstorms will be possible mainly at the Amarillo
and Guymon TAF sites through 02Z to 03Z Friday. Wind gusts to 40
to 45 knots can be expected at both TAF sites. VFR conditions can
be expected at all three TAF sites except for some MVFR conditions
in and near any thunderstorms. Southeast to south winds 15 to 25
knots with gusts near 30 knots at all three TAF sites through 00Z
Saturday.

Schneider

&&

.PREV DISCUSSION... /Issued 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

&&

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

&&

$$

11/11


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