FXUS64 KAMA 182101

Area Forecast Discussion
National Weather Service Amarillo TX
401 PM CDT Mon Mar 18 2019

A cold front will push south across the Panhandles on Tuesday. Some
rain showers may form along and behind the cold front in an area of
lift ahead of an upper level short wave trough moving south through
the Central High Plains. Highs should be cooler than normal behind
the front mainly from the Canadian River and points to the north,
with near normal temperatures to the south. North winds will
increase behind the front into the 15 to 25 mph range with higher



General Overview: Forecast elements continue to favor more active
period beginning Tuesday and into next weekend. The upper level
pattern is progged to become more amplified with some semblance
of an Omega Block. The main 500mb ridge is progged to be over the
Great basin Monday into Tuesday. The first system of interest will
move south out of Saskatchewan/Alberta on the downstream side of
the ridge, and will help push a front into the area Tuesday
afternoon into Wednesday morning. The front will help generate a
band of showers and perhaps a few snowflakes mainly Tuesday night
into Wednesday morning. The second more vigorous system will move
off the West Coast behind the ridge, then become a cutoff low
underneath the ridge. There is still uncertainty with the timing
and track of this system due to the fact that it won't start being
sampled well until Wednesday as it comes onshore. As of now
models have trended slower and slightly weaker, so onset of precip
has been pushed back to Thursday night, and thunderstorms chances
do not look quite as high Friday, but may be better Saturday. A
third system may try to come in on the backside of the second,
bringing yet another chance for precipitation Sunday into Monday.

In the Weeds: The first quick moving and increasingly positive tilt
shortwave is expected to move south on the downstream side of the
ridge Monday night into Tuesday night, and may bring some showers to
the area in association with a low level baroclinic zone aided by
weak low level upslope flow Tuesday night into Wednesday morning.
Most of the mid/upper level dynamics are offset to our east, but
there is a brief period of weak 500-300mb Q-vector divergence early
Wednesday morning ahead of trough axis. The exact track of this wave
could be augmented slightly by the southern stream flow and
increasing height rises as an upstream trough off west coast helps
kick high amplitude ridge further east. Latest numerical guidance
has come into better agreement with the position of the best
frontegentical forcing which maximizes generally between 00z and
12z Wednesday. The enhanced convergence noted at 700mb-600mb is
supported by negative omega values in Bufkit soundings maximizing
nearly along I-40. Would not be surprised to see around 0.25" to
0.5" rain amounts within the main band. It should also be noted
that raw models show enough low level cold air advection to
support some light snow mixing in with rain Wednesday morning
mainly in the northwestern zones. Will keep rain with slight
chance snow in forecast at this time and expand slightly east
based on similar thermal profiles, but snow accumulations not
expected as surface wet bulb temperature stays above freezing for
most of the event. Colder temperatures are possible in the far
northwestern zones, but precipitation chances are lower there due
to drier air moving in more quickly. Most guidance suggest main
lift and precip with this system should come to an end by
Wednesday mid morning as transient ridge crosses the Panhandles.

The next more vigorous system moves onshore Wednesday afternoon and
slowly advances east across the Four Corners region as a cutoff low
Thursday into Saturday. Latest guidance has slowed the system
considerably and weakened the kinematic fields enough that severe
storms are looking more questionable. The latest timing suggest
better lift and instability may be more on Saturday as a surface
low develops with some better frontal forcing. Deep layer shear is
looking more marginal as 500mb jet streak does not look strong.
Up to that point, Theta-E advection will begin to increase across
the western zones Thursday night as southwest flow aloft becomes
more prevalent. An axis of 40s dew points will sharpen in the
west going into Friday along lee trough, and minor shortwaves
ahead of the main low will help promote showers within the better
theta-E field. Moisture will expand eastward going into Saturday
as the low track east then northeast. Will maintain healthy pops
Friday through Saturday, with slight chance for thunderstorms on
Friday and Friday night given marginal instability. As surface
features sharpen Saturday, models are hinting at axis of better
instability across the eastern Panhandles, but this will largely
depend on insolation and strength of mid level cooling. Will also
have to watch for some possible flood concerns given the fairly
slow system speed and modest PWAT values. The big questions that
remain are with extent of cloud cover limiting insolation and
timing and placement of all of the features. Long term guidance is
in decent agreement right now, but as mentioned before the system
will not be sampled well until Wednesday.

The pattern will continue to support unsettled weather in the
extended forecast with additional waves progged to move into the
Southern Plains going into Sunday and Monday.



Amarillo TX 35 61 34 55 34 / 0 20 70 10 0
Beaver OK 40 58 33 58 31 / 0 30 20 0 0
Boise City OK 32 53 29 55 29 / 0 20 30 5 5
Borger TX 38 61 37 57 35 / 0 20 60 5 0
Boys Ranch TX 35 61 33 56 34 / 0 20 70 10 0
Canyon TX 34 63 34 55 34 / 0 10 50 10 0
Clarendon TX 35 67 38 57 35 / 0 10 50 10 0
Dalhart TX 31 56 32 55 30 / 0 20 50 5 5
Guymon OK 37 56 32 57 31 / 0 30 30 5 0
Hereford TX 32 64 34 54 33 / 0 20 40 10 5
Lipscomb TX 40 59 34 58 35 / 0 30 50 5 0
Pampa TX 37 60 34 56 33 / 0 20 70 5 0
Shamrock TX 35 67 38 58 35 / 0 20 70 5 0
Wellington TX 35 69 40 58 36 / 0 10 50 5 0


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