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000
FXUS66 KOTX 302112
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
212 PM PDT Thu Mar 30 2023

.SYNOPSIS...
Expect seasonal late March weather today with a mix of clouds and
sun, light showers with afternoon temperatures in the 50s. More
clouds, wetter and cooler weather arrives by Friday and spans into
the weekend as a series of weather systems move through the
region, each with rounds of rain and snow. A return to drier and
more seasonal weather arrives by middle of next week.

&&

.DISCUSSION...

Tonight through Sunday night: Brief interval of upper level
shortwave ridging dropping down from the northwest and moving in the
wake of a departing low moving away to the southeast will allow for
minor pops to linger on over the higher terrain of the Cascade Crest
and North Idaho with a general broad rain-shadow positioned in
between overnight and into Friday morning. Ensembles suggest
moisture plume feeding into the baroclinic band associated with
another low pressure system approaching from the northwest starts to
influence the Cascade Crest by 18Z Friday and then better positioned
to enhance snowfall over North Idaho near 6Z Saturday which are good
times to start enhanced snowfall at those locations with lower
elevation rain or a rain non accumulating snow mix. As this moisture
feed traverses through the conditionally unstable airmass contained
in the larger trof dropping down gains influence. The result will be
lowering of snow levels. Small scale triggers utilizing the
instability to produce enhanced convection will may result in
enhanced snowfall rates over Stevens Pass in Washington on US2 and
Lookout Pass along I90 in North Idaho over the weekend. The
instability may help to provide an infrequent short lived shallow
weak thunderstorm or two as well possibly Saturday afternoon and
evening with a very quick storm motion from southwest to northeast
at 30 to 35 mph. Current guidance suggest that 48 hour of snowfall
between 5 pm Friday and 5 PM Sunday greater than 12 inches running
near or over 80 percent for Stevens Pass and Lookout Pass. For
greater than 18 inches of snow the probabilities are 46 percent for
Stevens and 27 percent for lookout pass. Most, if not all, of the
snow shower activity is expected to decrease substantially in
intensity, if not end, Sunday night. As such winter weather watches
have, or soon will be, issued to address this snowfall at those
mountain passes. In addition to the snowfall it is expected to be
windy and gusty with the most problematic winds blowing from the
southwest with some wind gusts as high as 45 mph not out of the
question. /Pelatti

Monday through Thursday: Models are coming into agreement on
another trough moving inland on Monday just south of us along the
southern Oregon/northern California coast. The trough will deepen
and dig into the southwest US through Monday and Tuesday, allowing
a cold, unstable airmass from the north to spill into the Inland
Northwest. As a result, Monday and Tuesday will be slightly cooler
than the rest of the week ahead. Highs will generally be in the
40s and lows will be in the 20s across the region.

In addition, the instability of the airmass will likely give rise
to convective showers on Monday with highest chances in the
northeastern Washington and the northern Idaho Panhandle. Graupel
and a few isolated lightning strikes not out of the question.

Northerly flow accompanied by dry conditions and mostly clear
skies will be the main story Wednesday and Thursday as a ridge of
high pressure approaches. After Wednesday there is a high amount
of uncertainty among model guidance. Some models are hinting at us
staying in a ridging pattern through the end of the week, while
others suggest the ridge will be more transient and another trough
will be quick to move in behind it. /Fewkes

&&

.AVIATION...
18Z TAFS: LIFR/IFR ceilings mostly for low stratus clouds but some
fog is there as well but less of a presence. By 20Z today any of
those low ceilings should show a tendency to rise/erode with IFR
likely to prevail in the afternoon and overnight. West-southwest
winds are to increase overnight and Friday. /Pelatti

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        33  48  37  48  30  45 /  10  10  90  90  40  80
Coeur d`Alene  33  46  35  45  28  43 /  20  20 100 100  50  70
Pullman        33  46  36  45  29  44 /  20  10  90 100  60  90
Lewiston       37  54  41  54  35  51 /  20   0  80  90  50  60
Colville       30  48  35  48  25  46 /  10  20  90  90  20  60
Sandpoint      33  43  36  43  28  40 /  10  60 100 100  60  80
Kellogg        34  42  35  40  30  40 /  30  60 100 100  80  90
Moses Lake     31  54  39  55  31  53 /   0  10  60  30  10  40
Wenatchee      33  51  37  50  30  48 /   0  10  60  30  10  40
Omak           32  50  35  52  28  49 /   0  10  70  40   0  30

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Watch from Friday evening through Saturday evening
     for Central Panhandle Mountains.

WA...Winter Storm Warning from 11 PM Friday to 5 PM PDT Sunday for
     Northeast Blue Mountains.

     Winter Storm Warning from 5 PM Friday to 11 PM PDT Saturday for
     Western Chelan County.

&&

$$