Heavy Snow in Oklahoma, December 12 to 13, 2020

Area Forecast Discussion
National Weather Service Amarillo TX
154 PM CST Sat Dec 12 2020

.SHORT TERM...Today through Tomorrow...

The system is now over Idaho/Montana/Wyoming area and set to dive
southeasterly down the Rockies and aim for the southern Plains.
Models are in fairly good agreement on placement of the center of
the upper low and tracking it across LUB's area. Short range and
hi-res models are disagreeing slightly with the exact placement of
the surface low which should cross our area. Precip is expected to
start filtering into the northwest FA after 6 PM today. The precip
will start of north of the area and push southward, filling in
across the Panhandles. The models with a hint of slightly more
northward placement will put the band of highest snow totals just
north of the area into southeast CO and southwest KS. This is due
to how the moisture is being wrapped around the low and should be
located with good lift through the column. The OK Panhandle looks
to be just on the edge of this heavier band. So a small southward
movement by the surface low may mean another couple inches in our
area. 50 to 100 miles will be the difference of several inches.

Soundings show the dendritic growth zone nicely filled with
moisture and during periods where the lift is maximized, snow
ratios will bring wet, heavy snowfall. Models also indicate a
deformation zone will try to set up stretching from Boys Ranch
northeastward through Beaver and into KS. This will aid in larger
snowfall totals, particularly in the northeast where the better
lift and moisture are located. This deformation zone looks to
shift southward on Sunday as the system moves eastward. It will
combine with the upslope flow in the Canadian River Valley to
create some higher snowfall totals across that area as well. A
tight pressure gradient brought on by the low will bring winds of
20-30 mph with higher gusts. During the "down" periods when things
don't line up as well to be all co-located for the wet snow
ratios, we may see a lighter snow that can be blown around more
easily. Therefore, have included patchy blowing snow to the area.
The blowing snow in the north combined with the higher snowfall
rates is expected to cause visibility to reduce at times to 1/2
mile or less and cause significant impacts to the area. Therefore
have gone ahead and upgraded the Winter Weather Advisory to a
Winter Storm Warning across the remainder of the OK Panhandle.

Snow will begin to end Sunday morning from northwest to southeast
as the system pushes out to the east. For most, the snow will end
in the late morning hours and the southeast corner will see the
snow exit in the early afternoon. High pressure will filter in
behind and cut off the moisture and create downward motion. With
the high pressure, we will also see the pressure gradient relax
and winds ease by Sunday evening.

Beat

&&

.LONG TERM...Sunday Night through Friday...

A progressive upper level flow will continue into the extended. A
transient 500mb ridge will cross the area Monday ahead of the next
relatively quick moving 500mb wave. Very cold temperatures
(teens) are expected to occur Sunday night into early Monday
morning given snow cover and surface high moving into the area.
Wind chills could be a factor in the northwest zones as surface
high quickly shifts southeast with pressure falls occurring over
the Raton Mesa ahead of next system. However, the downslope winds
could actually increase the temperatures some after 06z Monday, so
right now it looks like the coldest wind chills will occur
between about 9PM and midnight when temperatures are coldest and
winds start picking up. Wind chills below zero are possible in the
northwest zones during this time. Other areas will see wind
chills generally in the single digits through early Monday
morning.

The latest models and ensembles show this next wave taking a path
slightly further north compared to the previous one. Height
anomalies showing up in the EC ensemble members along with the
deterministic EC suggests this next system may be a bit stronger
than Sunday's system. However, being on the tail of Sunday's
system, it may not have as much moisture to wrap around as the low
tries to close off Tuesday morning (GEFS mean/GFS keep open wave,
NAM/EC/EC ensemble mean close off low near Panhandles). Based on
the current track, the best chances for snow are in the northeast
zones during the day Tuesday as this is where the best overlap of
large scale ascent and potential deformation with 850-700mb low
occur. Will have to watch trends closely over the next few days,
would not be surprised if this system follows previous trends and
ends up further south and slightly slower the current model
output suggest.

Beyond Tuesday, long term models and ensembles hint at another
period of ridging, with another potential system towards next
weekend. Thus, after cold days with highs in the 30s and 40s and
lows in the teens and 20s Monday through Wednesday, some warming
should occur with mostly dry weather Thursday (possibly into
Friday depending on timing of next system).

Ward

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                28  33  18  45  23 /  70  90   0   0   5
Beaver OK                  26  34  12  37  21 /  90  90   0   0  10
Boise City OK              23  31  13  40  20 /  90  90   0   0  10
Borger TX                  30  35  18  46  25 /  80  90   0   0   5
Boys Ranch TX              28  36  16  47  22 /  70  90   0   0   5
Canyon TX                  28  34  17  47  22 /  50  70   0   0   5
Clarendon TX               31  34  20  44  25 /  80  90   0   0   0
Dalhart TX                 24  37  14  44  20 /  90  90   0   0   5
Guymon OK                  25  33  13  41  21 /  90  90   0   0  10
Hereford TX                28  34  18  49  23 /  40  60   0   0   0
Lipscomb TX                27  32  14  39  23 /  90  90   0   0   5
Pampa TX                   28  28  17  42  24 /  80  90   0   0   5
Shamrock TX                31  34  19  42  25 /  90  90   0   0   0
Wellington TX              31  35  19  44  26 /  70  90   0   0   0

&&

.AMA Watches/Warnings/Advisories...
TX...Winter Weather Advisory from 6 PM this evening to 6 PM CST
     Sunday for the following zones: Armstrong...Carson...
     Collingsworth...Dallam...Donley...Gray...Hansford...
     Hartley...Hemphill...Hutchinson...Moore...Ochiltree...
     Oldham...Palo Duro Canyon...Potter...Randall...Roberts...
     Sherman...Wheeler.

     Winter Storm Warning from 6 PM this evening to 6 PM CST Sunday
     for the following zones: Lipscomb.

OK...Winter Storm Warning from 6 PM this evening to 6 PM CST Sunday
     for the following zones: Beaver...Cimarron...Texas.

&&

16/7

Hazardous Weather Outlook
National Weather Service Amarillo TX
152 PM CST Sat Dec 12 2020

OKZ001>003-TXZ001>020-317-131000-
Cimarron-Texas-Beaver-Dallam-Sherman-Hansford-Ochiltree-Lipscomb-
Hartley-Moore-Hutchinson-Roberts-Hemphill-Oldham-Potter-Carson-
Gray-Wheeler-Deaf Smith-Randall-Armstrong-Donley-Collingsworth-
Palo Duro Canyon-
152 PM CST Sat Dec 12 2020

This Hazardous Weather Outlook is for the Texas and Oklahoma
Panhandles.

.DAY ONE...This Afternoon and Tonight.

Snow is expected to start tonight. A Winter Storm Warning is in
effect for the Oklahoma Panhandle and Lipscomb County. A Winter
Weather Advisory is in effect for all remaining counties in the
Texas Panhandle except Deaf Smith County. Accumulating snowfall
is likely tonight, especially in the northern combined Panhandles.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Snow is expected Sunday. A Winter Storm Warning is in
effect for the Oklahoma Panhandle and Lipscomb County. A Winter
Weather Advisory is in effect for all remaining counties in the
Texas Panhandle except Deaf Smith County.  Accumulating snow is
expected on Sunday.

Snow is also possible on Tuesday for parts of the Panhandles.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated at this time.