Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 221747
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1247 PM CDT Tue May 22 2018

.AVIATION...
For the 18z TAFs...
VFR conditions expected for the next 24 hours, with brief MVFR
visibilities possible in isolated to scattered thunderstorms
between 21z and 03z Wednesday.  Certainty at this time of a
direct impact from thunderstorms at any of our terminals remains
too low to include mention other than Thunderstorm in Vicinity.
Southerly surface winds today become more southeast this evening,
with return to south-southwest after sunrise.  Variable and gusty
winds possible near thunderstorms.

Cockrell

&&

.PREV DISCUSSION... /Issued 638 AM CDT Tue May 22 2018/

AVIATION...
12Z TAFs will be primarily VFR, however there is a 30 percent
chance of isolated thunderstorms starting at 21Z Tuesday for all
three TAF sites. Winds will be light until Tuesday afternoon when
winds will pick up to 18 kts gusting up to 28 kts at times out of
the south. By 03Z on Wednesday the winds will become SE at 10 kts.
There will be a few clouds 7-10 kft with possibly more with
isolated thunderstorms. Thunderstorms can cause outflow winds
which may require local amendments. KDHT is experiencing gusty winds
from rain which will last up to an hour from the time of
issuance.

Hoffeditz/Ward

PREV DISCUSSION... /Issued 435 AM CDT Tue May 22 2018/

DISCUSSION...
Split flow continues to dominate the overall upper level pattern
as southwest flow aloft continues over the southern Rockies and
adjacent plains. This is the result of a slow moving cutoff low
currently centered over southern NV. An embedded shortwave ahead
of the main low has resulted in a broken line of showers and
thunderstorms which are slowly propagating eastward over the far
western Texas Panhandle. The lightning activity has decreased
substantially over the last few hours as MUCAPE has become more
limited through the morning. The main question is how far east is
the rain going to advance before forcing becomes to weak too
overcome the increasing CIN. At this time, it does still look like
the combination of forcing with the shortwave along with parcel
lifting along outflow boundaries in weak upslope flow will support
chance pops as far east as Canyon and Amarillo through the early
morning hours. This activity should be decreasing in coverage
substantially through about 06z. Radar reflectivity did indicate a
possible MCV in the stratiform region of this activity which
moved up towards the western Oklahoma Panhandle. This feature,
along with remnant outflow boundaries may be the focal point for
thunderstorms initiation later this afternoon with very little CIN
expected. Southwest flow will be maintained with decent low level
theta-e advection in the afternoon. Dew points in the 50s and
modestly steep mid-level lapse rates will result in MLCAPE around
1000-1500 J/kg as storms get going. Shear will be lacking given
only 25-35 knots of mid-level flow. However, some veering in the
lowest 3km will result in effective shear perhaps as high as 30
knots (highest further west closer to jet streak associated with
cutoff low). Thus, some isolated strong to low end severe storms
can`t be ruled out with penny to quarter size hail and 50 to 60
mph winds being the main threat. Expected highs in the 80s with
southerly winds in the breezy category.

Models are in decent agreement going into Wednesday, with fairly
weak southwest flow being maintained as the upper low shifts
northeast over western WY. Probabilistic and deterministic
guidance suggest another embedded shortwave will move over the
area Wednesday afternoon/evening, bringing a round of showers and
thunderstorms with the best chances over the western half of the
Panhandles. Mesoscale conditions should be similar to Tuesday,
except slightly better theta-e advection along a lee trough/pseudo
dryline and better instability, resulting in a high CAPE low
shear day. Multicells with strong updrafts could result in large
hail and strong winds. Storms may become more linear in the
evening mainly driven by the upper wave and a modest low level
jet.

A low amplitude upper ridge begins building over the Rockies on
Thursday resulting in weak northwest flow late Thursday through
Friday. Kept pops minimal during the time frame for now given
proximity of ridge axis, questionable moisture availability and
more robust CAP. Going into the weekend, the ridge amplifies some
as medium/long range models bring another upper low out of the
Pacific and into the western CONUS. The ridge axis is currently
progged to be over the Panhandles on Saturday, resulting in
subsidence and plenty of sunshine. Fairly good consensus on very
warm 850mb temps with 28-32 deg C being advertised in GFS/Euro/Canadian
both Saturday and Sunday before the ridge breaks down and
southwest flow returns. Thus, bumped up temperatures for those
days, especially for our typical warm spots in this pattern (e.g.
Palo Duro Canyon floor). Precip chances looks slim during this
timeframe with a capping inversion being the main limitation.
Precip chances should return early next week as return flow
increases, shifting dryline further west.

Ward

&&

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

&&

$$

03/24


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