970
FXUS66 KOTX 012224
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
324 PM PDT Wed May 1 2024

.SYNOPSIS...
Tonight will be chilly with the majority of the Inland Northwest
falling into the 30s. Scattered afternoon showers will develop
over north Idaho and northeast Washington on Thursday and Friday.
A slow moving low pressure system will likely bring widespread
precipitation over the weekend. Next week looks cooler than
average and showery.

&&

.DISCUSSION...

Tonight: As of 3 PM, spring showers were detected by radar across
northeast Washington and north Idaho. The most concentrated shower
activity was over the northern and central Idaho Panhandle where
the best combination of low level moisture and orographic lift was
present. Surface dewpoints in north Idaho were mainly in the 30s
while low to mid 20s were more common across central and eastern
Washington. Ongoing shower activity will dissipate early in the
evening with the loss of afternoon warming and the continued
advancement of dry air into north Idaho. Clearing skies, dry air,
and decreasing winds overnight will allow temperatures to tumble
into the 30s by morning. Some of protected valley communities like
Republic, Springdale, Deer Park, and Colville may dip into the
20s. A Freeze Warning has been issued for Spokane, Coeur d`Alene,
Moses Lake, and the Upper Columbia Basin including Ritzville,
Wilbur, and Davenport. Climatologically, these communities are in
their growing season and there will be pockets of subfreezing
temperatures in these zones tonight.

Thursday: Our chilly upper level trough won`t move much by
tomorrow afternoon, so we can expect another day of spring showers
over north Idaho and northeast Washington as well as the high
terrain of north central Washington. Similar to today, a handful
of lightning strikes will be possible with the strongest cells in
Bonner, Boundary, Pend Oreille, Stevens and Ferry counties. Pea
hail and wind gusts to 30 mph will also accompany afternoon
showers Thursday. High temperatures will trend a couple degrees
warmer ranging from the upper 50s in north Idaho to the mid to
upper 60s along the lowlands of central Washington. Aside from
outflow from afternoon showers, there will be less wind Thursday
so that bump in temperatures will be noticeable.

Friday: Frost on Friday morning won`t be as widespread with the
majority of the Inland Northwest experiencing lows ranging from
the mid 30s to the low 40s. Mostly clear skies and light winds in
the morning will give way to increasing mid and high clouds in the
afternoon. South winds will also increase up the Okanogan Valley
and on the Waterville Plateau to 15 to 25 mph in response to an
approaching cold front. Afternoon temperatures will be above
average with highs in the 60s. Omak, Moses Lake, and Lewiston will
flirt with 70. Rain spreading east of the Cascades overnight will
be the beginning of what looks to be a wetter and cooler weekend.
/GKoch

Saturday through Tuesday: A deep upper-level low is on track to
approach the WA/OR coast Saturday, gifting all of us here in the
Inland Northwest an abundance of weekend rain. The low will move
inland rather slowly, and rain will crawl in along with it through
the day on Saturday. Temperatures will generally be in the 60s.

By Sunday, the low will be entirely over land and rain will be in
full swing across the region. Cloud cover and evaporative cooling
from the rainfall will send temperatures plummeting into the 40s on
Sunday for many locations, and for a few spots, highs may not even
break out of the 30s. Pullman has an 80 percent chance of seeing a
high temperature below 50 degrees, and a 30 percent chance of a high
temperature below 40 degrees. That`s cold for early May! The chance
of a high below 50 degrees in Spokane is sitting at 65%, and for
Coeur d`Alene, 40%.

Exactly how much rain will fall over the Saturday-Sunday timeframe
will be dependent on where the deformation band to the north of the
low sets up. There are still wide variations among model solutions
as to where that band of heavier rainfall will be located. Southeast
WA and the central ID Panhandle have a 40 to 50 percent chance of
receiving at least 0.5 inches of rain, while the Spokane and Coeur
d`Alene areas are looking at a 30 to 40 percent chance of the same.
Despite uncertainties in precipitation amounts, confidence is high
that Sunday will be at least somewhat wet for nearly all of the
region. Should make for great running weather. ;)

Temperatures will rebound a little on Monday and Tuesday as the low
works its way east of us, but we`ll still remain under the influence
of a broader trough which will keep us cool with intermittent
showers.

Despite the large fluctuations in daytime high temperatures,
overnight lows will be consistently in the upper 30s to low 40s
through the period. Winds will be breezy Saturday through Tuesday
with gusts of 20 to 30 mph. Some of our windier spots including the
Palouse and exposed areas of the Basin may see a few gusts to 35 or
40 mph. /Fewkes

&&

.AVIATION...
18Z TAFS: The 500 to 1500 ft stratus that developed locally around
Spokane and Coeur d`Alene shortly after sunrise will lift into
scattered to broken cumulus deck over north Idaho by 20z as our
temperatures warm. While the majority of central and eastern
Washington will advect enough dry air through the day to inhibit
convective showers, north Idaho will have a 30 to 50 percent
chance of showers with the highest concentration of showers
between 20z and 02z. /GKoch

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
There is a 10 to 20 percent chance of lightning over the
mountainous terrain of north Idaho between 20-02z. A few of the
strongest cells may produce pea hail or graupel as well. Given the
limited instability and wind shear, cells that become strong
enough to produce lightning or pea hail probably won`t last longer
than 15 minutes before collapsing. The probability of fog or low
clouds Thursday morning will be quite low...less than 10 percent
for GEG, SFF, and PUW. The probability for fog/low clouds at our
other TAF sites will be near zero probability. /GKoch

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

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        33  62  37  65  46  67 /  10  10   0   0  10  30
Coeur d`Alene  33  59  37  64  43  66 /  10  20  20   0   0  20
Pullman        30  58  35  63  46  64 /   0   0  10   0  10  40
Lewiston       35  65  40  71  47  68 /   0   0   0   0  10  30
Colville       30  64  34  66  41  67 /  10  20  20  10  10  30
Sandpoint      35  58  38  63  42  65 /  30  40  30  20   0  20
Kellogg        35  55  38  63  44  64 /  20  40  30  20   0  30
Moses Lake     32  67  37  71  52  67 /   0   0   0   0  20  50
Wenatchee      38  66  43  67  51  58 /   0   0   0   0  30  60
Omak           37  67  40  70  49  66 /  10  10   0   0  20  50

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Freeze Warning from midnight tonight to 9 AM PDT Thursday for
     Coeur d`Alene Area.

WA...Freeze Warning from midnight tonight to 9 AM PDT Thursday for
     Moses Lake Area-Spokane Area-Upper Columbia Basin.

&&

$$