Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 010545
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
945 PM PST SAT FEB 28 2015

.SYNOPSIS...
Dry, seasonal conditions will found across the Inland Northwest
this weekend. A weather system will pass through Monday into early
Tuesday with the potential for light snow, especially for the
Idaho Panhandle, with breezy conditions. Much colder air moves in
behind this system, with temperatures well below average for the
middle of next week. A dry period, with moderating temperature
will follow for the end of next week.

&&

.DISCUSSION...
Tonight through Sunday night: A dry continental air mass will
reside over the region delivering mostly clear skies and seasonal
temperatures. The region remains under broad northwest flow aloft
with one disturbance well to the south and another tracking across
through the Gulf of Alaska. Consequently, shortwave ridging will
be the dominate weather feature through the remainder of the
weekend. Winds are currently at their peak and will continue to
wane this evening and overnight. Dew points are extremely dry
with many locations reporting teens to single digits. As winds
calm overnight, look for temperatures to rapidly cool with
readings Sunday morning into the teens to lower 20s. Without
sufficient mixing (i.e. winds) returning Sunday, temperatures
will remain cool but should recover back into the 40s...very close
to March 1st normals. The aforementioned disturbance in the Gulf
of AK will track into Northwestern WA late Sunday night with the
potential for light snow reaching the Cascade Crest by early
Monday morning. Amounts through this period will be light with the
potential for a few tenths after midnight but before sunrise. /sb

Monday through Saturday: The next system drops across the Pacific
Northwest early in the week, with some snow threat and another
shot of cold air, before milder and relatively drier conditions
return.  Between Monday and Tuesday night a couple mid-level
shortwave dives across western Canada and the northwest United
States. Models have been consistently in disagreement over the
past few days over the evolution of the second wave, however this
morning the wetter ECMWF trended toward the other drier guidance.
One shortwave will be sliding south along the WA/OR coastline
early Monday, bringing some shower chances to the Cascades early.
A second shortwave slips by northeast WA/north ID and MT Monday
afternoon into Monday night. This will ramp up precipitation
chances across the eastern third of WA and north ID, especially
during the afternoon and evening. Overnight into Tuesday drier air
comes in on the a north-northwest flow, with a weakening surface
trough/deformation axis. There will be a lingering shower threat
across the central Panhandle and Camas Prairie, as well as about
the mtns of northeast WA and north ID, but by this time the threat
of significant precipitation will be ending.

As for precipitation-type, snow looks predominant. However during
the afternoon hours surface temperatures warming above freezing
will limit the potential for accumulation outside of the
mountains. Overall it still looks like about 1 to 2 inches in the
eastern mountains and less than an inch in the valleys, if
anything accumulates at all in the valleys that is.

Behind the precipitation threat comes increased winds and that
next push of cold air. In general, however, look for increasing
northerly winds between Monday afternoon and Tuesday. The speeds
abate through the Tuesday night. Tuesday afternoon temperatures
are expected to be below normal by 5 to 10 degrees, followed by
lows dropping some 10 to 15 degrees below normal Tuesday night in
an atmosphere more conducive to good rational cooling (i.e. dry,
with few clouds and lighter winds). This means lows in the singles
digits and teens Tuesday night/Wednesday morning.

Between Wednesday and Saturday the rebounded ridge is eventually
dampened again by another shortwave trough moving in from the
west. The primary wave stays north of the Canadian border, but
some weaker ripples do skim in on an the westerly flow. For the
most part the forecast is dry, but a few isolated showers cannot
be ruled out near the immediate Canadian border toward the end of
the work week. The rebounding ridge is also accompanied by some
milder air, so look for temperatures to moderate back toward
normal and, by Friday, slightly above normal again. /J. Cote`


&&

.AVIATION...
06Z TAFS: VFR conditions can be expected at all TAF sites through
Sunday. Thin high clouds will move in from the north overnight and
lower slightly and thicken some by Sunday afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        18  42  26  41  21  33 /   0   0   0  20  20  10
Coeur d`Alene  17  44  24  40  18  33 /   0   0   0  30  30  10
Pullman        20  44  27  40  22  33 /   0   0   0  30  20  10
Lewiston       24  47  28  44  26  38 /   0   0   0  20  20  10
Colville       19  47  26  44  22  37 /   0   0  10  20  20  10
Sandpoint      16  41  23  38  17  31 /   0   0  10  60  60  10
Kellogg        16  41  24  37  17  29 /   0   0   0  60  60  20
Moses Lake     23  48  29  49  26  42 /   0   0  10  10   0   0
Wenatchee      26  49  29  49  25  42 /   0   0  10  10   0   0
Omak           23  51  27  49  23  43 /   0   0  10  10   0   0

&&

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



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