Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 231754
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1254 PM CDT Wed May 23 2018

.AVIATION...18Z TAFs

Shower and storm chances are reasonably high at the TAF sites late
this afternoon/early this evening. Went ahead with tempo groups at
all the sites for TSRA as short term models seem to be narrowing
in on a pretty good window for storms. Could be a bit of low cloud
cover at KGUY tomorrow if rain materializes this evening, but
confidence was too low to prevail any IFR or MVFR cigs. Winds will
generally be southerly through the period.

Simpson
&&

.PREV DISCUSSION... /Issued 510 AM CDT Wed May 23 2018/

DISCUSSION...
Main items of interest for this forecast is the potential for
thunderstorms late this afternoon through tonight and the hot
forecast for the Memorial Day weekend. Latest water vapor imagery
shows upper level low moving north towards western Idaho amidst broad
cyclonic flow over the Desert SW. The TX/OK Panhandles remain
under weak southwest flow aloft. Subtle shortwaves in the flow
have once again produced convection over the high terrain of NM
and moved into our far western zones. This is mostly beneficial
rain (Boise City mesonet reported over an inch so far and a
Schoolnet site in Texline reported 2.53 inches). Some small hail
can`t be ruled out with the stronger pulse updrafts. Elevated CAPE
of around 500 J/kg is present based on the latest mesoanalysis,
but short term models suggest these storms will rapidly decrease
in coverage as they slowly move east. Will keep chance pops into
the central Panhandles through 12z this morning.

A more robust shortwave shows up in the southwest flow later this
afternoon and overnight tonight which should lead to another round
of showers and thunderstorms with highest chances again for the
western half of the outlook area. However, there is some concern
that the environment in the western Panhandles may take a while to
recover from current ongoing convection. Short and medium range
guidance suggest the area will destabilize with daytime heating in
an environment with PWATs approaching daily max values. Low low
level moisture is not terribly impressive with 50s dew points in
the west and low 60s in the east, but it should be sufficient for
1500 to 2500 J/kg MLCAPE with highest values in the west and very
little to no MLCIN. A few short term models are suggesting an axis
of increased low level moisture / theta-e advection over the
eastern New Mexico plains and far western Panhandles, resulting in
MLCAPE over 3000 J/kg this afternoon, dropping off rapidly
further east into the central Panhandles. These values will all
depend on if the environment is able to recover, which will depend
on how long the current convection lasts. Also, this is all in a
low shear environment given the weak mid and upper level flow
fields. However, there is just enough veering in the lowest 500mb
to support multicell structures, especially as the low level jet
gets going this evening. Moreover, severe weather looks
conditional with activity this evening, but if progged CAPE values
are achieved, large hail (perhaps golf ball to hen egg) and
strong winds would be possible with the strongest updrafts.
Convection may grow upscale into the evening as the low level jet
kick in, so kept pops through 12z Thursday.

A warming trend is expected through the weekend as a ridge begins
building over the Rockies and shifts over the Panhandles. This
will lead to a brief period of weak northwest flow late Thursday
through Friday. During this time, moisture shifts east with much
drier air invading the western Panhandles. A few thunderstorms
can`t be ruled out east of a pseudo-dryline on Thursday and
Friday, mainly in the eastern Panhandles. However, chances are low
given the proximity of the ridge axis and a more robust capping
inversion setting in. Another upper level low is progged to move
into the Great Basin while high pressure strengthens over northern
Mexico. This amplifies the ridge some as the axis moves over the
Panhandles on Saturday. This will lead to subsidence and very warm
850mb temperatures around 30-32 degrees Saturday afternoon. This
will keep thunderstorm chances very low while temperatures rise
into the upper 90s to near 100 for a large portion of the area
Saturday. The Palo Duro Canyon floor could approach the 102 to
104 range, or even higher if southwest winds are more breezy than
currently forecast.

Sunday looks a little more uncertain for high temperatures, even
though it still looks to be hot. Current medium/long range
guidance suggest ridge will begin to break down Sunday as upper
low moves further east. The increasing southwest flow may tap into
enough moisture off the Pacific to increase high level cirrus
Sunday and especially Monday, which may keep temperatures down
some (but still well into the 90s). Elevated fire weather can`t be
ruled out Sunday as the ridge breaks down, mainly for the western
Panhandles.

Ward

&&

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

&&

$$

9/24



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