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000
FXUS66 KOTX 121121
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
421 AM PDT Fri Apr 12 2024

.SYNOPSIS...
The upcoming weather moving into the weekend will feature a few
chances of mostly mountain showers along with a warming trend.
There will be a small chance for thunderstorms near the Lewiston-
Clarkston Valley Friday and Saturday afternoons. High
temperatures for much of the area will climb into the 70s over
the weekend. A cold front will bring a return of cooler and
showery weather early next week. Cold front passage will bring
breezy to windy conditions Sunday afternoon through Monday.

&&

.DISCUSSION...
Today through Saturday Night: A large closed low 450 miles west
of the southern OR coast as of 2 AM will continue to sag south and
then east, eventually tracking over San Francisco, CA Saturday
Night. For this morning a decaying mid level front will continue
to produce an abundance of mid and high clouds over the region. A
ribbon of elevated instability from the Blue Mountains into the
Central Panhandle Mountains will continue to produce bands of
showers into the early morning. The majority of the CAM`s models
show this activity diminishing after sunrise. Attention will then
turn to surface based convection that will fire over NE Oregon
this afternoon. SB CAPE of 500-1000 J/KG and 0-6 km Shear values
of 50-60 kts will support the potential for strong storms. The
CAMS models suggest this activity will most likely weaken when
coming off the higher terrain into SE Washington, the Camas
Prairie, and LC Valley. But storms will still be capable of
producing wind gusts in excess of 35 MPH, small hail, and
lightning. Also with precipitable water values near 200% of normal
brief downpours can also be expected. CAM`s models suggest the
most likely time of thunderstorms will be between 4-8 PM PDT.

On Saturday as the low continues to move south most of the region
will see more sunshine and warmer temperatures with highs in the
low to mid 70s, which is 10-15 degrees above normal. Continued
southerly flow will keep the instability in place over the Blue
Mountains and Camas Prairie with SB CAPE again around 1000 J/KG.
With the low further south of the region and lack of large scale
lift any storms that develop will likely be isolated in nature.
Gusty outflow winds and brief downpours will again be a concern if
storms develop. JW

Sunday through Friday: Over the course of the day on Sunday, a
trough will drop down from British Columbia, marking the beginning
of a shift from a dry zonal flow pattern to a wetter, more active
pattern. Temperatures will be warm and skies clear through the
first half of the day Sunday before cloud cover and mountain
precip begin to creep back in. High temperatures Sunday are
expected to range from the upper 60s to mid 70s, which is 10 to 15
degrees above typical highs for early April.

Monday will be a different story. The trough out of the north will
send a fairly strong cold front through the Inland Northwest, which
will drop temperatures by 10+ degrees. Accompanying the temperature
drop will be an increase in winds regionwide. Most of the region
will see gusts into the 30s, and gusts upward of 40 mph will be
possible for some of our windier spots including the Waterville
Plateau east to Spokane Intl. and down to the Palouse. The Cascade
Crest and higher terrain of the Idaho Panhandle will take the brunt
of the precipitation with this system. Moderate snow showers will be
possible at times on Monday for the Cascades if the Puget Sound
Convergence Zone sets up as expected.

Behind the cold front, snow levels will plummet, introducing chances
for light snow down to valley floors Tuesday morning. Little to no
lowland accumulations are anticipated, and even for the mountains
the risk of significant snowfall is low. Stevens Pass has a 40%
chance of seeing at least 3 inches, and Snoqualmie has a 70% chance
of 3 inches. If the convergence zone sets up over a pass, heavier
snowfall rates may lead to minor travel disruptions, but generally
roads will be warm enough to mitigate impacts.

Winds on Sunday night into Monday in combination with dry air moving
in from the north will increase grass fire and blowing dust
concerns, particularly for the Waterville Plateau and Columbia Basin.

After the initial cooldown with the system coming in Monday, cooler
conditions will persist through the week with brisk winds out of the
north and occassional chances (20-40%) for showers. /Fewkes

&&

.AVIATION...
06Z TAFS: A band of decaying showers over SE Washington into North
Idaho will exit the area this morning. CIGS are expected to remain
mainly VFR but these showers did moisten the boundary layer
sufficiently where local MVFR conditions can not be ruled out.
Attention turns to thunderstorms that are forecast to develop over
NE Oregon this afternoon. There is a 20% chance of thunderstorms
coming off the mountains into KLWS. There is moderate confidence
of a gust front from weakening convection impacting KLWS between
1-4z but low confidence with timing so for now including this in
PROB30 group. JW

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high
confidence of continued VFR conditions over Central and Northeast
Washington into North Idaho thorugh 12z Saturday. VFR conditions
are favored for Lewiston and Pullman as well despite the rain that
fell overnight, with HREF showing a 10-20% chance of CIGS
dropping to MVFR. Thunderstorms over NE Oregon are expected to
weaken as they approach KLWS between 1-4z. If storms maintain
intensity longer, then KLWS could be impacted by a thunderstorm,
along with stronger gusts than are currently forecast in the TAF.
This scenario could also result in a gust front reaching KPUW this
evening but also carries low confidence. JW

-----------------------

Confidence descriptors:
Low - Less than a 30 percent chance
Moderate - 30 to 70 percent chance
High - Greater than a 70 percent chance

For additional probabilistic information for NWS Spokane airports,
please refer to the Aviation Dashboard on our webpage:
https://www.weather.gov/otx/avndashboard

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        65  45  72  45  72  41 /  10  10   0   0  10   0
Coeur d`Alene  64  43  71  43  71  42 /  10  10   0   0  10  10
Pullman        64  44  71  45  69  42 /  20  40   0   0  20  20
Lewiston       70  50  77  50  75  47 /  20  40   0   0  30  20
Colville       65  39  72  41  74  40 /  10   0   0   0   0   0
Sandpoint      62  40  68  40  69  42 /  10  10   0   0  10  10
Kellogg        63  45  69  47  71  43 /  30  20   0   0  20  20
Moses Lake     67  42  76  45  78  44 /  10   0   0   0   0   0
Wenatchee      65  46  74  49  74  45 /   0   0   0   0   0   0
Omak           66  41  74  44  73  42 /  10   0   0   0   0   0

&&

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

$$