Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 151721 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
Issued by National Weather Service ALBUQUERQUE NM
1121 AM CST Wed Nov 15 2017

.AVIATION...
VFR conditions will prevail for the next 24 hours. Surface winds
will weaken and veer around to the northeast today, then
southeast this evening. Wind will ramp back up Thursday mid
morning from the south-southwest with gusts near 20-25kts
possible. Otherwise, scattered high clouds should move across
later today and overnight.

&&

.PREV DISCUSSION... /Issued 415 AM CST Wed Nov 15 2017/

DISCUSSION...
Water vapor imagery shows upper level shortwave traversing the
central plains with trailing cold front pushing through the
Panhandles. As of 800z the surface front was through the southern
Texas Panhandle with 12-18kt north winds behind it. A few stratus
clouds are showing up on infrared satellite in the far
southeastern Texas Panhandle along the leading edge of the front
where surface moisture is slightly better. However, dew points
are dropping quickly behind the front which should quickly
eliminate these clouds and keep the area mostly clear through the
day. Temperatures will be much cooler than yesterday, with lows
mostly in the 40s and highs in the 50s and 60s (near average).

High pressure spinning over Baja coastal region will keep zonal
flow with neutral or weakly rising heights going into Thursday as
a much more amplified Pac NW trough begins to dig south into the
Great Basin. Surface high pressure will slide into the plains just
east and northeast of the TX/OK Panhandles before shifting east.
This sfc high will help winds veer from northerly to
southwesterly by Thursday morning as a lee trough develops over
Front Range into the Raton Mesa. Deterministic models actually
show dew points increasing initially Thursday even with the
southwest winds. Still think as least the far northwest Texas
Panhandle and far western Oklahoma Panhandle could see a few hours
of elevated fire weather conditions as this area will see
warmest/driest surface conditions. All zones will see southwest
winds around 15-20 mph Thursday afternoon.

On Friday the well amplified northern stream trough begin its
advance over the central and southern Rockies as upper level high
pressure is suppressed well south of Texas leading to a break
down of the zonal flow. A strong mid/upper jet streak is expected
to move over the Panhandles Friday afternoon ahead of the trough
axis. Models are in fairly good agreement that 40-50kt 700mb jet,
a 70-80kt 500mb jet, and 100kt 300mb jet will traverse the area
Friday. A surface low is expected to develop off the Front Range
leading to tightening pressure gradient across the southern plains
ahead of a strong cold front. Moreover, southwest winds at the
surface are expected to be in the windy category Friday.
Probabilistic data brings winds well into advisory range for far
western zones Friday afternoon, but decided to nudge more towards
blend for now given uncertainly with high cloud cover off the
mountains which could limit mixing potential. However, if mixing
to 700mb occurs as GFS suggest, then 30kt winds with gusts over
40-45kts seems very possible. Blowing dust is also possible given
lack of any appreciable rainfall over the last month or so and
westerly winds which may carry dust from NM. Decided to keep
mention out of grids for now, but may want to consider in future
package. Temperatures will also be tricky depending on what
happens with high clouds, but record highs seem very possible
given 22-23 deg 850mb thermal ridge and downsloping winds. Of
course, all of these things spell fire weather concern, even
though the surface dew points given in the models are still
modestly dry across the area which keeps RH values around 20
percent. Given fairly strong downslope winds, Tds were reduced
some in grids which resulted in 16-18 percent min RH across most
of the Panhandles.

Models have continued their trend to slow the surface cold front
down as the trough axis shifts east with GFS still slightly faster
than the Euro/Canadian/NAM. At this point, GFS solution bringing
front through between roughly 05z and 10z makes most sense given
position of upper level trough, so nudged towards GFS which was
also higher on wind speeds. Strong CAA along and behind front will
allow for gusty winds as the front moves through overnight.

Northwest to zonal flow can be expected as the upper level trough
shifts east of the area into the weekend. Temperatures will be
around average with a dry forecast continuing through the
extended. Models do hint at a shortwave or two as split flow
begins to take shape again going into next week. Another front is
also expected by midweek.

Ward

FIRE WEATHER...
While there are a few uncertainties with this forecast, it does
appear that most if not all of the Panhandles will see at least
elevated fire weather conditions on Friday afternoon. Confidence
is high that twenty foot southwest winds over 20 mph will occur
for at least the western half of the TX/OK Panhandles. The main
question surrounds the level of dryness at the surface, as high
cirrus clouds could limit max temperatures and dry surface dew
points. That being said, even with high clouds it looks likely
that min RH values will fall as low as 18 percent especially for
the western zones given downsloping winds. If cirrus is fairly
thin, the elevated conditions could fall into the critical range
fairly easily. ERC values in the northern zones may be mitigated
some where snow fell last week, but southern zone ERC values
should be around if not slightly above average on Friday. Lastly,
winds will shift to the north Friday night as a strong cold front
moves through the area. 20-25kt winds can be expected behind the
front with gusts over 30kts likely.

Ward

&&

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

&&

$$

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