507
FXUS66 KOTX 300918
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
218 AM PDT Tue Apr 30 2024

.SYNOPSIS...
Scattered showers will continue through the week, along with a
warming trend through the weekend. Conditions will remain
unsettled with a weather system moving in from the west Thursday,
and another one over the weekend into next Monday.

&&

.DISCUSSION...

Today through Wednesday Night...For today, another shortwave is
expected to traverse the region, bringing back showers and
possibly graupel by the afternoon. There`s also a slight chance of
thunderstorms in southeast and northeast WA during the later part
of the day, accompanied by moderately breezy winds but not near
what the region has seen the last couple days. After sunset, the
threat of showers diminishes. Expect highs hovering around 50
today, with lows dropping into the 30s yet again tonight. Those
with sensitive plants should take precaution.

By Wednesday, the trough will move eastward, resulting in
slightly warmer temperatures but still remaining around 5 degrees
cooler than normal. Temperatures will warm into the upper 50s to
mid 60s. Showers will also return but will mainly impact the Idaho
Panhandle and far northeastern WA. With the increase in
temperatures, precipitation is expected to fall as rain rather
than a rain/graupel mix. Lows Wednesday will be slightly warmer
than tonight, but still remain in the mid to upper 30s. /KM

Thursday to Monday: The Inland NW remains in an active pattern,
with periodic chances of precipitation and a warming trend into at
least Saturday. Model agreement toward the weekend continues to
be much less than ideal to have high confidence in the forecast by
then. Ensembles are at least in slightly better agreement than
the deterministic.

First on Thursday another shortwave drops into the region, but
its track takes its center over the southwest half of WA into
Oregon, then into the southern half of ID. This will hold the
primary precipitation potential over the Cascades and southern
third of WA and the lower ID Panhandle in the morning. Then the
afternoon comes with steepening lapse rates and little bit of
instability, increasing the threat of showers over a larger
portion of the CWA. The higher potential will remain the mountain
zones and southeast WA/lower ID. While not in great abundance,
there is some convective instability and some isolated t-storms
are possible primarily closer to the mountains in the afternoon
too. The showers wane going into Thursday night with the loss of
daytime heating.

By Friday a weak ridge builds in. Some instability and orographic
lift will keep shower chances alive around northeast WA and ID
mountains in the afternoon, with a slight chance of t-storms.
Otherwise look for more sun.

Heading into the weekend: through Friday, low pressure (that is
now just coming into the Aleutians) approaches the Pacific coast.
How far south it tracks before moving onshore is where models
continue to disagree. Yesterday more solutions were holding the
low further south, with the EC the primary model that brought it
into our region. Today the EC track is slightly further south and
the other solutions are slightly further north. About 60% of the
ensembles track the low inland over Oregon and the other 40% take
it toward northern or central CA. While there is still some chance
of a drier weekend, the forecast leans on the ensembles with
favor toward the Oregon track with slightly higher than average
confidence in precipitation in the region this weekend. Snow
levels average at 5500 feet or higher, so mainly rain and higher
mountain snow are in the forecast. There is a little bit of
instability so a slight risk for t-storms will be in the forecast
for Sunday afternoon. Winds will a bit breezy with increased
mixing with the system, but with gusts near 15-20 mph mostly.

Going into Monday another low drops in and helps to carve out a
broader trough over the West, including our region. This will mean
overall higher confidence in precipitation. The higher risk will
be away from the lee of the Cascades and deeper Columbia Basin
and there could be some t-storms mixed in the afternoon, but
nothing too strong. Snow levels drop to around 4500-5500 feet by
this time, lowest near the Cascades. Thus some light snow may come
back toward places like Stevens Pass, but it is too early to have
confidence in precise amounts other than to say it is marginal
for snow and so the impacts may be limited. Winds still look
marginally breezy with gusts near 15-20 mph.

Temperatures will be trending warmer through at least Saturday,
then start to trend downward by at latest Monday. There remains a
modest spread in solutions in precise numbers by the transition
day, Sunday, when models show highs could be anywhere from near
50 to the lower 70s. Overall look for near to slightly above
normal temperatures into Saturday, then temperatures close to or
slightly below normal by Monday. Morning lows still remain in the
30s to near 40 on Thursday and Friday, meaning potential frost
lingering in some spots. /Solveig

&&

.AVIATION...
06Z TAFS: Following the showers that went through the Idaho
Panhandle this evening is a moist boundary layer. Expect
increasing areas of MVFR stratus between 9-15z Tuesday over the
Idaho Panhandle and southeast Washington as light upslope winds
continue which includes KCOE/KPUW. Drier air in Central
Washington has spilled into the Spokane area which leads to a
better chance for conditions remaining VFR at KGEG/KSFF. On
Tuesday another round of showers will develop as the atmosphere
destabilizes but less in coverage compared to today. Isolated
thunderstorms may also develop, but the main threat will be over
the higher terrain of SE Washington (Blue Mountains), and up over
NE Washington around Republic and Colville.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
The HREF is showing near a 60% chance of MVFR stratus expanding
over the Palouse into the Idaho Panhandle overnight, but keeping
probability closer to 20% for KGEG/KSFF. There is high confidence
in continued VFR conditions in Central Washington due to a much
drier boundary layer. There is a 20% chance of thunderstorms on
Tuesday mainly across southern Washington into the Lewiston area,
and up over the mountains of NE Washington. Confidence is any of
the TAF sites being impacted is too low to include in the TAF
forecast. 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        51  35  58  36  62  37 /  20  20  20  10  20  10
Coeur d`Alene  47  34  54  36  60  37 /  40  20  30  20  20  10
Pullman        46  31  53  34  59  36 /  50  30  30  20  30  10
Lewiston       54  37  60  38  65  42 /  50  30  20  20  30  10
Colville       52  29  60  33  64  34 /  30  20  20  10  30  10
Sandpoint      46  34  51  36  58  37 /  40  30  60  20  40  20
Kellogg        43  34  48  36  56  37 /  70  40  70  30  40  20
Moses Lake     56  34  65  35  67  39 /  10   0   0  10  20   0
Wenatchee      54  39  62  40  65  44 /  20  10   0  10  10   0
Omak           56  35  65  39  67  41 /  20  20   0  10  20  10

&&

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

$$