Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 120442
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1042 PM CST Sat Nov 11 2017

.AVIATION...
For the 06z TAFs...
MVFR ceilings have reached GUY within the past hour.  Expect all
terminals to drop to LIFR by 08z Sunday as lower levels of cool
post-frontal surface ridge become saturated.  Have included low-
level wind shear at AMA for the early hours of this forecast,
based on 40 kt northeast winds being sampled by KAMA 88D.  Abrupt
loss of airspeed within 500 feet of surface during landing may be
encountered.

Ceilings expected to lift into MVFR range after sunrise at AMA and
GUY, with DHT expected to improve quickly to VFR at about the
same time.  AMA and GUY expected to return to VFR between 17z and
19z.

Light to moderate north surface winds will trend to east during
the day on Sunday, and then to southeast Sunday evening.  Expect
MVFR or IFR ceilings to make another appearance Sunday evening.

Cockrell

&&

.PREV DISCUSSION... /Issued 559 PM CST Sat Nov 11 2017/

UPDATE...
Have updated graphical forecasts, calling for areas of fog after
midnight, continuing into Sunday morning.  Cool surface high
pressure ridge building southward into forecast area tonight
expected to reach saturation over a fairly large area, and a fog
scenario is supported in recent high-resolution guidance.
Updated text products are being issued.

Cockrell

PREV DISCUSSION... /Issued 529 PM CST Sat Nov 11 2017/

AVIATION...
For the 00z TAFs...
Cold front has passed through all of our terminals.  Expecting
light north and northeast surface winds to prevail this evening
and overnight.  As lower levels drop to the point of saturation,
expecting LIFR ceilings and fog to develop around 06z or 07z
Sunday.  Expect that this fairly deep saturated layer will mix
out around 12z to 14z Sunday at northern terminals, and around
16z at AMA, marking the return of VFR conditions for the rest of
the day on Sunday.  Light to moderate northeast surface winds
expected to trend to east during the day on Sunday as post-frontal
surface high pressure ridge translates to the southeast.

Cockrell

PREV DISCUSSION... /Issued 346 PM CST Sat Nov 11 2017/

DISCUSSION...
A cold front continues to work across the Panhandles this
afternoon and evening. Some low clouds are expected to return
tonight and may linger through the day on Sunday. This will help
keep temperatures right around 60. Any cloud breaks that occur
will likely return Sunday evening, with some possible drizzle
Sunday night across the southeast Panhandles.

Clouds expected to clear out on Monday afternoon, with
temperatures in the mid to upper 60s across the Panhandles. The
eastern Panhandles may be on the cooler side, since it looks to be
the last area for the sky to clear.

Overall, high pressure remains suppressed to the south just east
of the Baja Peninsula, with several systems passing to the north.
As been stated in many earlier discussions, this will keep the
Panhandles mainly in a zonal flow for the coming week. Monday and
Tuesday will see a rebound in temperatures, but a fast moving
cold front Tuesday night/Wednesday morning will lower the highs
on Wednesday back into the 60s.

Right now highs on Thursday are set to be in the 70s with upper
50s to upper 60s on Friday, and this is set with the GFS solution.
If the ECMWF solution pans out, then we will be looking at Friday
being a very warm day, with a cold front later in the afternoon
and evening.

See Fire Weather Discussion for a breakdown of Thursday and
Friday.

Weber

AVIATION...
A cold front will move south across the region late this afternoon
and evening switching winds around to the north and northeast. Low
clouds in the IFR range are expected to develop behind this cold
front overnight at all sites. These IFR conditions should last
through the rest of the forecast. Visibilities may also drop in
fog, but confidence in fog formation is not high at this point.

FIRE WEATHER...
Thursday and Friday...Right now models continue to hint at
elevated Fire Weather conditions as strong west southwest winds
aloft could mix down to the surface. This will be followed by a
cold front from the north.

The issue is that the models are off by about 12 to 18 hours,
with one model suggesting this frontal system on Thursday night,
and another model holding off the front until Friday afternoon.

The (GFS) Thursday solution is not as favorable for elevated
conditions as winds may only mix up to about 800H and surface
gusts may only be in the mid 20mph range. Relative humidities look
like they would be in the mid 20 to lower 30 percent range. It`s a
day to keep an eye on, but the system will need to move through
earlier in the day for better mixing of the winds.

The (ECMWF) solution has a very strong 110kt 300H jet, with an
associated 70-90kt 500H jet, and a 60-70kt 700H jet over the
Panhandle during peak heating on Friday. This would suggest
elevated, and in some areas possibly critical Fire Weather
conditions. If the ECMWF is the right model, it will definitely be
a windy day on Friday, with a north wind shift late in the day as
the cold front moves through.

We`ll continue to monitor this system to see if the Fire Weather
threat changes.

Weber

&&

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

&&

$$

03/14



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