Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 131141 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
541 AM CST Tue Feb 13 2018

.AVIATION...
For the 12Z TAFs, south to southwest winds will increase and
become gusty at the terminal sites by late this morning and
continue through the afternoon hours before diminishing near
sunset this evening. Periods of high level clouds are also
expected during this fcst cycle.

Andrade

&&

.PREV DISCUSSION... /Issued 417 AM CST Tue Feb 13 2018/

DISCUSSION...
Not much change from previous forecast. Water vapor imagery shows
upper trough sitting over central CA, with another wave advancing
towards the Pac NW. Southwest flow continues over the Southern
Great Plains with increasing mid/upper clouds as moisture feeds in
from the southern Baja region. At the surface, southeast winds are
expected to veer to the southwest through mid-morning in response
to a weak lee trough. Temperatures today will start out mostly in
the low 20s, but should warm into the 60s by afternoon as winds
increase to 10-15 knots. The warmest temperatures should be in the
northwest zones where better downslope warming is expected.

Model ensembles and deterministic guidance continue to build in a
ridge over the Gulf of Mexico, while the western CONUS low sits
over the central CA coast and even retrogrades offshore briefly.
However, the CA low is progged to get caught back up in the
southwest flow as the Pac NW wave digs south and eventually merge
as an pos tilt open wave crossing the Rockies on Wednesday.
During the merge of the two upper lows, a mid level jet streak
develops and moves over the Panhandles Wednesday through Thursday.
The stronger southwest flow aloft will support a more pronounced
surface low both Wednesday and Thursday near the Raton Mesa.
Moreover, not even considering mixing, the area should be on the
windy side due to a decent pressure gradient force across the
Panhandles (especially the western half). The downslope winds will
help warm the area well above average, especially Wednesday where
850mb temps are progged around 16-18 deg C. Mid and upper level
clouds should help limit warming and max windspeeds some, but
still expected highs in the low 70s on Wednesday. Fire weather
conditions are a concern on Wednesday (see discussion below).
Windy conditions should continue Thursday as the upper trough axis
approaches, but decreased 850mb temps and increasing surface dew
points as sub-tropical moisture feeds in should prevent fire
weather on Thursday.

Thursday evening a surface cold front switches winds to the
north. Wind speeds were increased towards MOS guidance behind the
cold front. Some guidance still hints at some precip developing as
the front collides with the increased low level moisture along
the southern Texas Panhandle. While this possibility can`t be
ruled out, for now still keeping mentionable pops out of forecast
as chances look much better further south where moisture is
increased. Friday will be much cooler behind the front, as the
upper trough axis finally crosses the Rockies. Northwest to zonal
flow is expected through Saturday as the next Pac NW upper trough
begins digging into the western CONUS. The latest ECMWF amplifies
the trough considerably more than the GFS and is much colder
going into next week with little to no precip on the horizon.

Ward

FIRE WEATHER...
Elevated fire weather conditions are expected today for the
northwest Texas Panhandle and far west Oklahoma Panhandle. A weak
lee trough will aid in 15 mph southwest winds and RH values
dipping into the 20 percent range.

Widespread elevated to near critical fire weather conditions are
possible Wednesday afternoon as a fairly strong 500mb jet streak
noses into the Panhandles. Clouds may limit mixing, but a strong
surface pressure gradient will still support windy conditions as
southwest twenty foot winds approach 18-23 mph with gusts around
30-35 mph. Min RH values are the biggest question, but it looks
likely that they will dip into the 14-16 percent range for most of
the area given the downslope flow and well above average
temperatures. These RH values could be lower if clouds are fairly
thin and warming/drying is enhanced.

Another round of elevated fire weather conditions looks possible
on Sunday afternoon.

Ward

&&

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

&&

$$



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