Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 251159
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
459 AM PDT Mon Mar 25 2024

.SYNOPSIS...
Monday and Tuesday will feature seasonal temperatures with
periods of rain and snow showers. A wetter storm system arrives
Wednesday and Thursday delivering widespread precipitation before
warmer and drier weather returns next weekend.

&&

.DISCUSSION...

Today through Tuesday night: The Inland Northwest will be under a
northwest flow pattern to start the week. We will also be on the
conditionally unstable side of the upper level jet stream that will
be directed into northern California and Oregon over this period.
Infrared satellite imagery early this morning indicates a few clouds
over portions of the region, but plenty of sunshine to start out the
day will be replaced by a developing cumulus field reaching the
convective temperature between about 11AM-12PM today. CAPE will be
weak this afternoon of around 100 J/kg or so with cloud tops
reaching about 10-12 kft. This will result in weakly forced showers
due to differential heating. Showers will be favored over the
southeast portion of the region and especially the southern to
central portions of the Idaho Panhandle where instability and orographics
will be more favorable; but, much of the region will see at least
the potential for an isolated shower aside from directly in the
lee of the Cascades. Snow levels will generally be around 3,500
feet with snow reserved for the mountains and any accumulations
will be light. Orographics will keep shower activity going through
the night over the southern to central Idaho Panhandle.

Showers on Tuesday will then expand further west into eastern
Washington as the atmosphere destabilizes with surface heating. The
atmosphere will be a bit more unstable compared to today with the
potential for CAPE values near 150 J/kg. We will also see slightly
favorable dynamics aloft with a passing shortwave disturbance. All
this together will translate into more in the way of shower activity
for Tuesday afternoon. Convection will be a bit deeper as well with
cloud tops reaching 15-18 kft. This will result in more in the way
of graupel showers. Convection doesn`t appear to be deep enough
though for charge separation to generate thunderstorms. Snow levels
will remain around that 3,500 foot level; however, graupel will more
likely be able to reach lower elevations down to valley bottoms. The
passing shortwave will also tighten up the westerly pressure
gradient with more in the way of breezy winds for the afternoon.
Expect sustained winds of 12-18 mph with gusts up to around 25 mph.
Breeziest spots will be exposed areas in the lee of the Cascades out
across the Columbia Basin. /SVH

Wednesday through Sunday: Wet frontal zone associated with a warm
southwest flow juxtaposed between short lived negatively tilted
ridging exiting to the east and a digging upper level trof off the
coast allows for wet and unsettled Wednesday where the highest QPF
and mountain snow amounts (mainly above 4000 feet MSL) of the
forecast remain. By Thursday the frontal zone is well away to the
east and the upper level trof gains greater influence and increases
instability and potential for disturbances rotating counterclockwise
in and around the outer edges of it to trigger it. This portion
looks more convective with way less precipitable water to work with
in comparison to Wednesday thus QPF and snow amounts in the forecast
are much lower in comparison, with the addition of a mention of a
slight chance of Thursday afternoon and evening weak short lived low
topped pulse thunderstorms. The upper level low continues to dig
southward off the coast and a col/saddle point is in place over
Washington and North Idaho Friday and Saturday with the low still
within close enough proximity to keep some pops for light precip in
the form of light valley rain/mountain snow Friday that may segues
to a drier forecast Saturday. I added "may" because a col/saddle
point may be agitated by a disturbance dropping down from the
northwest Saturday so some minor pops remain for the terrain that
can utilize the resulting orographic effects with a disturbance
approaching from the Northwest, primarily North Idaho and the
extreme southeast portion of Washington. Ensembles suggest Northerly
flow remains ahead of positively titled ridging nosing in from the
west as the earlier mentioned upper level trof/low is by now well
too far south to have a direct influence on sensible weather over
Eastern Washington and North Idaho. Such a forecast supports the
gradual warming trend apparent in daytime highs with various dips
and drops of overnight lows near freezing. /Pelatti

&&

.AVIATION...
12Z TAFS: Low stratus will develop this morning resulting in MVFR
conditions over extreme eastern Washington and into the Idaho
Panhandle (KPUW-KGEG-KSFF-KCOE-KDEW-KCQV-KSZT). There is also
expected to be patchy fog in the valleys of the Central Panhandle
Mountains in the vicinity of KCOE. Low stratus will slowly lift
into a stratocumulus field for the afternoon with isolated to
scattered showers. Showers will be a mix of rain and graupel near
aforementioned airports.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: Confidence is high
for stratus producing ceilings between 2-4 kft agl and MVFR
conditions at the KPUW-KGEG-KSFF-KCOE terminals through at least
18Z today. /SVH

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

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        49  34  53  33  50  37 /  20  20  40  10  50 100
Coeur d`Alene  45  33  48  31  47  36 /  30  30  60  20  40  90
Pullman        47  34  48  31  50  37 /  50  50  70  10  50 100
Lewiston       54  38  55  36  56  41 /  50  50  50  10  40  90
Colville       50  30  52  29  48  35 /  20  20  40  20  60  90
Sandpoint      42  32  44  32  46  36 /  20  30  80  30  50 100
Kellogg        43  35  43  32  47  38 /  50  50  80  30  40 100
Moses Lake     58  35  59  35  53  37 /  10  10   0  10  70  60
Wenatchee      55  39  56  36  47  37 /  10  10   0  10  80  50
Omak           57  36  59  35  50  38 /  10  10  10   0  70  70

&&

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

$$


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