Area Forecast Discussion
Issued by NWS Amarillo, TX

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603
FXUS64 KAMA 301744
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1244 PM CDT TUE AUG 30 2016

.AVIATION...
For the 18z TAFs...moist easterly low-level flow will provide supply
of moisture and upslope flow this afternoon and tonight, especially
near AMA.  Higher instability expected to remain east of terminals,
limiting threat of thunder.  Will monitor convective developments
closely and add thunder in the very near term if direct impact to
terminals become more certain.  Otherwise, showery weather expected
to continue through the evening, with occasional mvfr conditions at
AMA, followed by prevailing mvfr conditions late tonight and
Wednesday morning.  At northern terminals, somewhat drier low-level
conditions should cause VFR conditions to prevail.

Cockrell

&&

.PREV DISCUSSION... /Issued 700 AM CDT TUE AUG 30 2016/

AVIATION...
For 12z TAFs...Some low level stratus along with showers in the
vicinity of all TAF sites this morning will lead to occasional
MVFR/IFR cigs/vsbys. This activity is moving slowly to the northwest
with a break in the activity along the eastern Panhandles. The break
in the east will not last long as showers and a few storms are
expected to redevelop in those areas over the next few hours. This
activity should continue moving northwest through the day. After
this morning cloud ceilings should lift some and VFR conditions
will be more prevalent except for occasional MVFR with showers
and storms. Kept PROB30 in for afternoon for all site this
afternoon.

Ward

PREV DISCUSSION... /Issued 452 AM CDT TUE AUG 30 2016/

SHORT TERM...Today
08z water vapor shows subtropical moisture continuing to stream into
West Texas on upper ridge over Ohio Valley and weak upper low over
Colorado. Showers and a thunderstorm or two continue to push
northwest across the Texas and OK panhandles. There is a break in
activity across the southeastern zones which is where redevelopment
of showers and storms will occur again later this morning or early
afternoon. High res models do suggest some elevated CAPE values
across the eastern zones this afternoon but very low LI.
This will lead to better chances for heavy rain producers in the
eastern zones. Also a possibility for patchy fog prior to 15z this
morning with very light surface winds and moist soil conditions.
Temperatures will be tricky with cloud cover and shower
activity...looks like most with get into the high 70s with a few low
80s in the eastern zones.

LONG TERM...Tonight through Monday
Much of the overall details of the forecast from tonight through the
end of the work week remain unchanged. Subtropical moisture continues
to stream into the Panhandles with an upper trough starting to lift
northward. A retrograding ridge will slide across Texas tonight but
will keep the Panhandles in southwest flow. Wednesday the upper flow
becomes more zonal while embedded shortwaves traverse the periphery
of the ridge. By Thursday, most medium range models (00Z NAM
excluded) show an elongated lobe of vorticity approaching the eastern
Panhandles. This vorticity lobe resides on the far western extent of
a cold front expected to drop across the Midwest and southeastern US
Thursday/Thursday evening. The combination of the surface front and
positive vorticity advection will help thunderstorms to redevelop and
move from the northeast to the southwest across the Panhandles.
Subtropical moisture will still be draped across the Panhandles
during this time as well to keep the chance for heavy downpours
possible.

Forecast models do differ greatly concerning the westward progression
of the above mentioned front which could make temperatures tricky
Thursday night. With that being said, medium range models are in
agreement that the Panhandles will quickly recover Friday with winds
returning to a southerly direction by the early afternoon at the
latest. Residual outflow boundaries and embedded shortwaves emanating
from New Mexico could give us one final shot at widespread rain
Friday afternoon/evening before our chances diminish over the
weekend.

We return to southwest flow aloft for the weekend however, we will be
lacking the deep subtropical moisture from earlier in the week.
Initially, embedded shortwaves will have to combat subsidence from
the exit region of an approaching upper jet early on Saturday. By
Saturday afternoon, the upper subsidence reduces as the exit region
of the jet moves into Nebraska/Missouri and will allow scattered
storms to develop across portions of the Panhandles. Southwest flow
persists into early next week to keep scattered afternoon convection
possible through the first half of next week.

HYDROLOGY...
Have expanded the Flood Watch to include Armstrong and Carson
Counties in the Texas Panhandle due to rainfall amounts over the past
several days. MRMS gauge corrected 24 hour radar estimates show
portions of both counties receiving between 2 to 4 inches of rain.
Soil conditions are likely becoming saturated when coupled with the
heavy rain from late last week. Have also extended the duration of
the watch until Wednesday evening to account for additional rounds of
heavy rain. Our PWATs remain in the climatological +2SD for this
time of year with slow forecast storm motions expected to continue
through Wednesday evening.

There is some concern that the watch duration may need to be extended
further out in time given the increasing chances for heavy rain
Thursday. With that being said, will hold off for now to see how the
models handle Thursday`s setup mentioned above.

&&

.AMA Watches/Warnings/Advisories...
TX...Flood Watch through Wednesday evening for the following zones:
     Armstrong...Carson...Collingsworth...Donley...Gray...
     Hansford...Hemphill...Hutchinson...Lipscomb...Ochiltree...
     Roberts...Wheeler.

OK...Flood Watch through Wednesday evening for the following zones:
     Beaver...Texas.


&&

$$

03/15



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