Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 290701
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1050 PM PST Fri Feb 28 2020

.SYNOPSIS...

Today will bring generally sunny skies with mild temperatures
with highs in the 50s for most towns. The arrival of a frontal
system tonight will push temperatures down closer to average for
the weekend. Breezy and showery conditions are also expected
Saturday. A dry break period is expected on on Sunday. Unsettled
breezy and showery conditions arrive Monday and lasts through
much of next week.


&&

.DISCUSSION...
Update for tonight...The cold front has moved into the Cascades and
was swiftly tracking eastward. Widespread precipitation has become
firmly established at the Cascade Crest with moderate snow
currently falling per webcams at Stevens Pass. Meanwhile not much
was going on just east of the crest with warmer temperatures in the
valleys and thus rain at locations such as Coles Corner. Just a bit
farther east, clearing skies were noted at locations such as
Leavenworth, Wenatchee, and Winthrop. As the front pushes toward the
WA/ID border spotty showers are expected, but most should occur near
the Canadian Border. Pops have been adjusted accordingly. The other
change was to raise the winds just a bit in the vicinity of the cold
front and behind it. We have gotten a few reports of wind gusts 25
to 40 mph across much of the Columbia Basin, Okanogan Valley, and
Wenatchee area.

.Previous Tonight through Saturday discussion: It`s a very mild day
across the Inland Northwest as an upper ridge traverses across the
Western US. The combination of rising thicknesses and warm advection
from southwest winds has resulted in warm afternoon temperatures. As
of this writing, widespread 50s can be found across the lowlands,
with lower 60s now being reported in the lower elevations of Spokane
and the Lewis-Clark Valley.

This warm spell will be short-lived. Looking just upstream, a
cold frontal system is rapidly making its way toward the coast.
Much of central WA and parts of eastern WA will be precipitation-
shadowed with this event: the best precipitation chances will
remain along the Cascade crest and across the Idaho Panhandle. 5
to 10 inches of snow will be possible toward Stevens Pass, with a
couple of inches possible at Lookout Pass. Elsewhere, west to
southwest winds will be picking up this evening, and especially
after the cold frontal passage early Saturday morning. The
strongest winds aloft occur overnight, mitigating some of the
downward mixing potential. Breezy winds should continue into
Saturday, with local gusts up to 35 mph possible.

Showery weather will be possible as the cold pool aloft arrives
on Saturday. Instability progs show the potential for a few
hundred J/kg of CAPE Saturday afternoon across eastern WA and
north ID. Forcing isn`t the best however, and low level moisture
appears limited. HREF members do show the potential for a few
heavier showers, so will continue to mention a slight chance of
Saturday afternoon thunderstorms.

Generally drier weather with more seasonal temperatures are
expected Sunday with an upper ridge nosing into the Pacific
Northwest. With north to northwesterly flow aloft, we can`t
completely rule out a few light snow showers mainly over the
higher Idaho terrain.
Dang

Monday through Friday: Following a break on Sunday, active weather
returns Monday as moist zonal flow from the northwest brings the
chance for more precipitation and near seasonal temperatures.
There may be little, if any, precipitation in the Columbia Basin.
Most of the shower activity throughout the week will remain in the
mountains falling as snow. As a parade of surface lows marches
through southern Canada, it will keep little day to day change
with a slow snow accumulation in the Cascades and Panhandle
mountains. Through Wednesday, models are showing little, if any,
precipitation making it into the lower elevations at this moment.
Later into the week and weekend, conditions are beginning to look
more unsettled as models are hinting at an approaching trough.
However, still too soon with many differences and still much time
to come. Relatively strong pressure gradients are favoring breezy
days early Tuesday into Wednesday. The stronger and widespread
winds will be in the Columbia Basin, Palouse, and West Plains.
Temperatures will be near seasonal and slowly warming as the week
progresses. Early week temperatures will start off in the upper
40s and 50s with low temperatures in the 30s. JS

&&

.AVIATION...
06Z TAFS: VFR conditions are expected for all sites through most of
this period. Through the overnight hours the main focus will revolve
around an eastward moving cold front. This front will push through
the GEG-SFF-COE and PUW-LWS area between 07z-12z. There is a small
chance the front will trigger a shower especially for the northern
TAF sites, but odds were not great enough to make it a prevailing
condition. Winds have increased all sites which has considerably
lessened the threat of LLWS. As for the latter periods of the
forecast, we are looking at an unstable air mass and the possibility
of hit or miss showers during the afternoon. We suspect graupel will
be the primary weather type if a shower happens to hit an airport
but VFR conditions will prevail during the overwhelming majority of
the time. There will also be a very small chance of thunderstorms
during the afternoon over extreme eastern WA into the ID Panhandle
but it was too small to include in any of the forecast sites. fx


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  46  25  44  29  47 /   0  20  10   0  10  10
Coeur d`Alene  33  44  25  42  29  44 /  20  30  20   0   0  20
Pullman        33  43  27  41  29  46 /  20  30  30   0   0  20
Lewiston       39  50  31  47  32  51 /  10  20  30   0   0  10
Colville       29  47  23  46  26  48 /  20  20   0   0   0  10
Sandpoint      32  41  23  40  28  41 /  40  70  20   0  10  50
Kellogg        32  38  24  38  27  39 /  50  70  40   0  10  60
Moses Lake     32  52  27  51  30  55 /   0   0   0   0   0   0
Wenatchee      33  47  27  47  31  51 /  10  10   0   0  10  10
Omak           30  47  26  46  28  49 /  10  10   0   0   0   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Winter Weather Advisory from 7 PM this evening to 4 PM PST
     Saturday for the cascade crest including highway 2 between
     coles corner and stevens pass for East Slopes Northern
     Cascades.


&&

$$


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