Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 191128 AAA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
628 AM CDT Thu Oct 19 2017

For the 12Z TAFs, there is a minor threat of tstms tonight
at KDHT and KAMA. However, decided to omit mention of this
weather element due to low probability of occurrence and
corresponding low confidence at this time. Gusty south winds
are expected this afternoon at all TAF sites. Otherwise, VFR
conditions are anticipated at all terminal sites through 12Z



.PREV DISCUSSION... /Issued 503 AM CDT Thu Oct 19 2017/

Previous forecast is still on tap with few changes in this
forecast. The current upper level analysis shows split flow over
western CONUS as an amplifying trough moves into the PAC NW with
a weaker southern stream flow entering the desert SW. This pattern
has resulted in mostly zonal flow over the Panhandles of TX/OK and
dry mid level air per 00z KAMA sounding. Some very high cirrus can
be observed on infrared satellite, but otherwise the area is dry
with temperatures in the 50s.

A weak shortwave in the southern stream flow is currently being
sampled over southern NV. This features is expected to move
towards the southern plains today helping to bring some mid/upper
level moisture to the area with mid level clouds increasing from
southwest to northeast late this afternoon and overnight. Some
isolated showers and perhaps a weak/brief thunderstorm is possible
in the evening mainly over the western Texas Panhandle where
there will be better moisture/dynamics associated with the
shortwave combined with a lee side trough. Otherwise, breezy
southerly winds and slightly above average temperatures can be
expected before clouds invade the area this evening.

The PAC NW trough begins to advance southeast and merge with the
southern stream flow on Friday. This will result in stronger
southwest flow over the Panhandles along with surface
cyclogenesis over the Front Range Friday evening. A strengthening
pressure gradient and lee trough will result in breezy to windy
conditions across most of the Panhandles Friday afternoon and
evening. Surface moisture will also be on the increase for roughly
the eastern half of the outlook area with dew points nearing 60
degrees. This will lead to a more unstable environment with MUCAPE
values around 1000-2000 J/kg. However, being that the area will
be under at least weak mid/upper level subsidence on backside of
southern stream shortwave and a fairly strong cap, not expecting
much if any storm development. If low level theta-E advection can
overcome the cap and weak subsidence aloft, then a strong to
severe thunderstorm cannot be ruled out late Friday afternoon and
evening given veering wind profiles and developing LLJ over the
eastern Panhandles during the evening. Otherwise, winds will likely
stay gusty overnight especially for the northeastern zones as
deterministic guidance suggest and 50-60 knot 850mb jet will be in
place there.

Model guidance is then in decent agreement showing the surface low
over the front range advancing over southern NE with a seasonably
strong cold front in its wake. This front is expected to enter
our northern zones by Saturday morning and southern zones by late
afternoon. Strong to severe thunderstorms are expected to develop
mainly in western OK due to better moisture (instability) and
a weaker cap as the front moves through. Most of the Panhandles
should be "dry slotted" resulting in a dry frontal passage. The
one exception may be the southeastern Texas Panhandle, where a
pseudo dryline will be shifting east ahead of the cold front.
Otherwise, gusty north to northeast winds will be common behind
the front with cooler temperatures. Winds should decrease
considerable late Saturday into Sunday morning. Winds and clouds
should be low enough for frost concern in the cooler air mass
Sunday morning, mainly for the western zones as a weak surface
high develops over northeast NM. Temperatures will top out in the
60s for most of the area Sunday.

Flow aloft will become northwesterly as the open wave trough
shifts over the southeast states Sunday into early next week. A
brief warm up is expected Monday before another cold front moves
through Tuesday. Model differences exist for timing and strength
of the front on Tuesday with the GFS/Canadian being stronger and
faster compared to the Euro. This is mainly due to differences in
the upper level pattern, as models show a strong meridional 500mb
jet developing over the plains ahead of an amplifying ridge over
the western CONUS. The Euro has the mid level jet feature much
further east keeping the main surface front east of the
Panhandles. Will have to see how models trend with this feature
over the next few days, as the colder solutions could spell
freezing temperatures for portions of the area next Wed morning.
Otherwise, a dry and near average temperature forecast is expected
in the extended.



.AMA Watches/Warnings/Advisories...


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