Scientific Forecaster Discussion
fxus64 kama 120547
Area forecast discussion
National Weather Service Amarillo Texas
1147 PM CST Wed Dec 11 2019
kdht and kguy should remain VFR through the 06z period. Kguy may
have some low level wind shear for the next hour until 07z. Kama will be MVFR with
possible periods of IFR for low cigs, from now until 12z, maybe
14z. After 14z conditions should dry out leaving all terminals
with VFR cigs. Winds continue to be strong out of the S to SW 15
to 20 kts with higher wind gusts up to 30 kts especially for kama.
Winds will gradually turn to the northwest and become less than
10 kts between 12z and 14z. By Thursday afternoon, winds will be
light and variable at times.
Previous discussion... /issued 524 PM CST Wed Dec 11 2019/
VFR conditions for all three terminals for the next nine hours or
so. After 09z kama will become MVFR with some low cigs and
possible fog. Have left out the fog and IFR conditions in the
tafs, as confidence is low at this time. Kdht and kguy should
stay VFR. Winds will continue to be gusty through the first half
of the period with gust between 25 and 30 kts. Then winds will become
calm between 12z and 18z. Also, kdht and kguy have a chance to
see some wind shear between 02z and 07z this evening.
Previous discussion... /issued 330 PM CST Wed Dec 11 2019/
Short term...today through tomorrow...
the residual low clouds and fog has finally burned off giving way
to mostly clear skies for the remainder of today. With these
mostly clear skies, temperatures are still expected to reach the
lower to mid 50s.
A rather potent short wave will be moving through the region later
this evening through the overnight. Although no precipitation is
expected with this h500 perturbation in the zonal flow, winds will
be quite gusty, especially along and downstream of the mid level trough
axis. Winds will be sustained 20-25 kts with higher gusts
possible, especially across the northeastern panhandles where the
steepest height gradient will occur with the progressing short
wave. Latest hi-res log-p diagrams and numerical data shows sct to
bkn mid to high lvl cloud coverage moving in to the region with
the disturbance. In-conjunction with a pronounced cap at 4-7 kft,
this should keep the strongest winds from reaching the surface.
Could not rule out a strong wind gust over 35 kts through early
tomorrow morning, if the low level jet erodes part of the cap, especially
in the northeastern panhandles. Winds should wane as the mid level
perturbation departs to the east of the region as we go past 1-2
am tomorrow morning.
Similar to this morning, areas of fog may develop around sunrise
tomorrow morning as temperature tonight reach the crossover
temperatures; in-conjunction with stagnant airmass remaining over
the region. Fog that does develop should burn off once again by
afternoon hours. High temperatures tomorrow will be a degree or
two warmer compared to today with highs in the mid 50s which is
slightly above average for mid December.
Long term...Friday through Tuesday...
Main focus for the extended forecast was on Saturday through
Monday, when models depict a 500mb trough digging southeast from
the pac northwest. Ahead of this trough, the panhandles will be under
northwest to zonal flow aloft as broad cyclonic flow lifts
out of the eastern Continental U.S.. minor surface troughs will move through
Friday and Saturday, keeping light to breezing northerly winds
with Max temperatures in the 60s. Temperatures will trend down
Saturday through Monday, with highs on Sunday and Monday in the
30s or 40s at best. Snow will also be possible, mainly Sunday and
Sunday night. Details to follow...
Flow aloft becomes more southwesterly Saturday into Sunday as
upper trough digs towards the Utah/Colorado rockies. Fairly strong 500mb
flow of 65 to 75 knots through Sunday night should help boost
moisture levels in the Southern Plains, especially mid and high
level moisture. Meanwhile, lift will increase as 250mb divergence
overspreads the area starting Saturday, but maximizing on Sunday
and Sunday night as right entrance region of upper jet traverses
the area. The main 500mb positive vorticity advection is progged to arrive Sunday night
behind as surface cold front and some weak upslope flow.
Forecast elements were not changed much from previous, and the
trend of going colder for high temperatures both Sunday and Monday
were kept. Winds were also nudged to fit more in line with the
gefs mean and ec, which better depict evolution of surface
features given upper level pattern. This supports a stronger
backdoor front on Sunday with another push of cold air Monday
(still not nearly cold enough if ec/can pan out). The GFS
solutions was largely ignored, as it is not only an outlier
compared to other raw models, it is also a major outlier to the
gefs members (both in terms of temperatures and moisture). It will
be Worth watching the GFS compared to other models starting
Saturday, as it depicts much drier air near surface moving with
dew points falling into the single digits. If this were to be
confirmed, then it will take longer to recover (especially
considering the GFS is further north with 500mb jet streak).
The ec/can/gefs mean all suggest moisture will be sufficient for
precipitation as lift overspreads the area Saturday night through
early Monday morning. Most of the precipitation will be light,
with upper lift and weak upslope flow being the main support.
However, will have to watch for some 850-700mb frontogenesis as
there are some hints that some decent baroclinicity may be
present. Thus, some bands of heavier precipitation can't be ruled
out mainly Sunday night. Current temperature profiles support
mostly snow for precipitation type, with some light accumulations
possible across most of the area. Some advisory level snow can't
be ruled out, especially in the northern half of the combined