FXUS64 KAMA 181200
Area Forecast Discussion
National Weather Service Amarillo TX
600 AM CST Fri Jan 18 2019
12z TAF Cycle:
VFR conditions are expected through the afternoon with gusty winds
from the southwest to west ahead of a cold front. Winds will veer
to the northwest then north as the cold front moves through this
afternoon. Southwest winds will be strongest at KAMA ahead of the
front from mid morning through early afternoon. A rogue gusts
near 40 knots can't be ruled out after 15z this morning. North
winds will become strong at all terminal sites behind the front
with gusts over 40 knots likely between 00z and 06z at all
terminal sites. A rogue gust approaching 50 knots can't be ruled
out during this time. Showers or even a stray thunderstorm will be
possible mainly at KDHT and KAMA along the front this afternoon.
Showers behind the front are expected to switch over to light snow
this evening, with precip ending after 06z. MVFR or even some IFR
cigs/vsbys will be possible mainly between 00z and 06z. Expect VFR
to become prevalent going into the next TAF cycle.
.PREV DISCUSSION... /Issued 349 AM CST Fri Jan 18 2019/
SHORT TERM...Today through Tonight...
The main focus continues to be on the strong winds later today
through tonight, the possibility for some light rain turning to snow
tonight, and now the possibility of a thunderstorm in the southern
and central Texas Panhandle this afternoon.
An upper trough is currently digging into Great Basin region as
evident on latest water vapor imagery. This feature is expected to
continue digging south as it crosses the Rocky Mountains later
today, with decent model agreement with the overall mid/upper level
pattern. While there have been some minor shifts in run to run
output, the overall trend has been to keep this wave progressive and
open as it crosses the south/central plains through tonight.
Meridional flow on the backside of the mid/upper trough will briefly
phase with the upstream portion of an eastern Canadian low, which
will aid in sending a strong cold front through the area today. The
pressure gradient will strengthen as a surface low develops near
Raton Mesa and shift southeast ahead of the cold front. Strong
southwest winds are expected on the south side of the low. The track
of the low will largely determine where the stronger downslope winds
will setup this afternoon. Kept the Wind Advisory for Deaf Smith Co
where the stronger winds are expected. Otherwise, winds will
increase area wide behind the front late in the afternoon through
tonight. The strongest winds behind the front are expected in the
southeastern Texas Panhandle due to the track of the low, thus a
wind advisory was also issued for this area for the overnight period
when the low level jet increases on the backside of the low. It
should be noted that a 50 to 60 knot jet is expected in the 800mb to
700mb layer. Current wind gusts are just below warning criteria, as
the strongest winds should be limited by frontal inversion. However,
a few rogue 50 knot gusts will be possible in the central and
eastern Panhandles mainly during the evening. Winds will gradually
decrease through the day Saturday.
Steepening lapse rates and just enough mid/upper level moisture may
support a thunderstorm or two along the front this afternoon, mainly
confined to the southern Texas Panhandle given high based SBCAPE
values of 200-400 J/kg. Lift will overspread the area due to
positive vorticity advection in the mid/upper levels, while the
surface cold front provides some low level lift. Lack of low level
moisture ahead of the front should keep precip amounts limited with
afternoon activity. 700mb Frontogenetical forcing is maximized
between 00z and 06z Saturday, and this is when snow chances are
maximized as cold polar air filters in. There is some uncertainty
with exactly when precip will switch over to snow. Currently, most
precipitation after 03z is expected to be snow. The short duration
expected should keep snow amounts limited to less than one inch.
However, if snow switches over more quickly, or if the 700mb low is
stronger, some locations could get more than one inch. The NAM and
NAMNEST have hinted at some higher amounts. This should be monitored
closely. Either way, any period of snow with the strong winds could
lead to reduced visibility. Snow Precip should quickly come to an
end after 06z.
LONG TERM...Saturday through Thursday...
As the upper level low begins to move off to the east, winds start
to relax and will turn back to the south overnight Saturday into
Sunday. Sunday will see a return to upper 50s and lower 60s as lee
side troughing builds in as upper level ridging fills in the western
CONUS. By Monday, the Panhandle will see mid-level northwest flow
turn southwest as the next long wave trough approaches the area.
This downsloping will bring the warmest temps of the week to the
Panhandles. Clouds will return Monday evening along with a chance
for precip in the north. At this point, the precip looks to mostly
be snow starting near midnight Tuesday and should be out of here by
midday. Clouds look to linger along with breezy north winds, which
will lead Tuesday to be the coldest day of the week. Models are not
in the greatest of agreement with this system. The ECMWF tries to
close off the low and is faster than the other models. The GFS and
Canadian keep the system as an open wave and the Canadian is the
slowest model. Long range models do agree that the latter half of
the work week should be dry and generally cool with highs in the 40s
to low 50s.
While minimum RH values are expected to stay in the 30 percent
range today given temperatures and cloud cover, winds will be
strong enough to warrant some concern with spotty elevated fire
weather conditions this afternoon. Southwest winds will be gusty
in the far southwestern Texas Panhandle this afternoon at 25 to
35 mph with gusts over 50 mph possible. A cold front will sweep
through the area during the afternoon with north winds 25 to 35
mph with gusts again over 50 mph possible through tonight.
TX...Wind Advisory from 6 PM this evening to 6 AM CST Saturday for
the following zones: Collingsworth...Donley...Wheeler.
Wind Advisory from 11 AM this morning to 7 PM CST this evening
for the following zones: Deaf Smith.
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