Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 201230
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
430 AM PST Tue Feb 20 2018
.SYNOPSIS...
Cold and generally dry conditions will persist throughout the
week outside some passing light snow showers at times. A stronger
storm system will impact the region this weekend bringing the
next chance for appreciable snow.

&&

.DISCUSSION...
Today through Wednesday...
A deep trough is located over the western US leading to record
cold temperatures in the west and record warm temperatures in the
east. The arctic airmass is bringing the coldest temperatures of
the season with widespread single digits while some wind and
cloud free locations are reaching negative temperatures. The
slight surprise of the morning is a 5000 foot stratus deck that
has developed over eastern WA and portions of northern ID. Under
this deck of clouds, temperatures are moderating a bit. For
example we watched the temperature drop to -5 F at the office here
west of Spokane. Shortly after the clouds developed, the
temperature climbed back up to +6 F. Meanwhile at Spokane Intl the
clouds developed earlier and kept temperatures above the record
of 2 degrees. The clouds have not made it into Coeur d`Alene where
temperatures are currently -9. The NAM does the best of capturing
this increased moisture in the low to mid levels...keeping it
around through the morning hours.

A weak disturbance currently over western BC is making its way
south toward WA this morning. This feature will bring increased
moisture in the form of clouds and the slight chance of flurries
this afternoon and evening. On the back side of the weak
disturbance, winds will turn northerly again albeit much weaker
than the Sunday night winds. Skies will also gradually clear out
by Wednesday resulting in a cool but overall pleasant day. Temperatures
will slowly moderate through the week...each day "warming" by a
few degrees. /AB

Wednesday night through Monday: The cold keeps its grip over the
Inland NW into early next week as a deep northerly flow persists
aloft. Shortwaves in the flow will bring occasional flurries or
light snow to the region. One of these features arrives Wednesday
night into Thursday with a band of mid to high level moisture
within an elongated trough. As instability increases, the air mass
will be quite dry with Pwats not even exceeding 0.25". The
limited moisture may bring light snow chances to the higher
terrain, while the lower elevations may just see flurries as it
passes. Drier air and a reinforcing shot of northerly winds
arrives Thursday into Thursday night while temperatures slowly
moderate. After the passage of a shortwave ridge aloft Thursday
night into Friday, the next clipper system drops in from BC. A
warm front brushes along the Canadian border by Friday evening
followed by a weak surface low on Saturday. Isentropic lift
increases with a renewed chance of precipitation. Snow levels will
stay remain low with snow being the likely precipitation type.
Afternoon temperatures warm enough to bring a rain snow mix to the
lower Basin and the LC Valley Saturday afternoon. This features
exits Saturday night with a decrease in precipitation. A
progressive NW flow prevails aloft, although 00z models are
grasping on timing of the features. As the GFS leans toward the
passage of another weak system early Sunday, the ECMWF shows a
slower but stronger wave arriving late Sunday into Monday.
Unsettled conditions will continue into early next week.
Meanwhile, temperatures continue their slow climb each day,
although remaining below normal through the period. /rfox.

&&

.AVIATION...
12Z TAFS: A stratus deck at about 5000 feet continued to develop
overnight over far eastern WA and northern ID. Indications are
that this deck will remain through the early morning hours before
dissipating and being replaced by more mid level clouds. An
approaching weak system will bring widespread ceilings at 10k feet
with the chance of flurries over the northern mountains of WA and
ID through the late afternoon and evening hours. Overall
anticipate VFR through the next 36 hours with the exception of
isolated MVFR in flurries. By Wednesday afternoon, expect skies
again to clear out and widespread VFR conditions to prevail. /AB

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        23   8  26  11  28  12 /   0   0   0  10  10  10
Coeur d`Alene  22   3  26  10  27  11 /   0  10   0  10  10  10
Pullman        21   8  26  13  27  14 /   0  10   0  10  10  10
Lewiston       27  16  33  19  31  20 /   0  10   0  10  10  10
Colville       23   5  27   9  30  11 /   0  20   0  10  10   0
Sandpoint      20   6  24   8  27  12 /  10  20   0  10  10  10
Kellogg        19   3  24   8  26   9 /   0  10   0  10  20  10
Moses Lake     32  14  34  17  36  18 /   0   0   0  10  10   0
Wenatchee      30  14  31  16  35  18 /   0  20   0  10  10  10
Omak           25   8  28  12  33  14 /   0  10   0  10  10   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.

&&

$$



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