239
FXUS66 KOTX 222307
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
407 PM PDT Wed May 22 2024

.SYNOPSIS...
Thursday will feature scattered afternoon showers and
thunderstorms mainly across north Idaho as well as north central
and northeast Washington. Friday, Saturday and Sunday will cool
with highs in the 60s and low 70s with chances for afternoon and
evening showers and thunderstorms. Memorial Day will be the
warmest and driest day of the holiday weekend with afternoon
temperatures well into the 70s.

&&

.DISCUSSION...

Tonight: Showers will become less numerous along the Canadian
border this evening with the loss of afternoon destabilization. By
8 or 9 PM, most shower activity around Republic, Northport, and
Metaline will dissipate. As daytime convection weakens, we should
see a band of rain wrapping around our departing upper low.
Through the night, the upper low and it`s associated band of rain
will migrate south bringing an additional tenth to quarter inch of
rain to Lookout Pass and the mountains of southern Shoshone
county. Less than a tenth is advertised by the National Blend of
Models (NBM) for Kellogg, Coeur d`Alene, St Joe, and Craigmont.

It will be a chilly night for our northern valleys including
places like Priest Lake, Metaline, Colville, and Republic. Mid and
high clouds will follow our departing low. Valley locations that
don`t fog in overnight will drop into the mid to upper 30s with
some patchy frost. The rest of central/eastern Washington as well
as the Idaho Panhandle will experience lows in the upper 30s to
mid 40s.

Thursday: There is good model agreement that an upper level
disturbance embedded within our weak upper trough will aid in the
development of showers thunderstorms along the Canadian border by
late morning Thursday. Cells will move to the southeast between
20-25 mph during the afternoon and into the evening hours. With
dewpoints in the 40s, surface based instability will be relatively
weak. High Resolution Ensemble Forecast mean CAPE values are
generally less than 200 J/Kg. With limited shear, thunderstorms
that form should not be particularly strong. Chances for
measureable precipitation from the NBM ranges from 50 to 70
percent in places like Republic, Colville, and Bonners Ferry to 20
to 30 percent in Omak, Winthrop, Grand Coulee, Davenport, Spokane
and Coeur d`Alene. Moses Lake, Wenatchee, Ritzville, and Lewiston
have a less than 10 percent chance for showers Thursday.

Friday: The Inland Northwest will be in between systems on
Friday...at least during the day. Afternoon and evening showers
should be limited to mountainous terrain in the absence of any
significant upper level support. Afternoon temperatures will range
from the mid 60s in north Idaho and northeast Washington to the
low 70s in the Columbia Basin, Okanogan Valley, and the L-C
Valley. /GKoch


Friday afternoon through Sunday: Models are in excellent agreement
for an unsettled Memorial Day weekend for the Inland Northwest.
The first wave Friday afternoon will bring the potential for weak
thunderstorms in the Blue Mountains and Camas Prairie/Northern
Panhandle. The second and stronger wave Saturday will bring
additional chances for thunder in the northern mountains
Saturday afternoon. The best chances (40-70%) for a wetting rain
(0.10 or greater) Friday afternoon through Saturday afternoon are
in the northern mountains, the eastern third of Washington, the
Cascade Crest, Blue Mountains, and the ID Panhandle. Temperatures
Friday and Saturday will be in the 60s and 70s. Sunday looks
mostly dry except zonal flow aloft will promote weak shower
development in the ID Panhandle mountains and near the Cascade
crest. Temperatures Sunday will still be in the 60s and 70s.

Monday through Wednesday: Models are also in excellent agreement
of a substantial pattern change to warmer and drier weather
Monday. Height rises downstream a deep Gulf of Alaska trough will
send our high temperatures into the 70s and 80s early next week.
There is a 10-20% chance of temperatures 90 degrees or greater in
the deeper Columbia Basin southeast of Moses Lake by Tuesday if
the ridge axis stays in the region. 60% of models briefly cool us
off Tuesday with a shortwave. /Butler

&&

.AVIATION...
.AVIATION...
00Z TAFS: Afternoon instability showers will decrease through the
evening in areas along the Canadian border. A band of rain
organizing in west central Montana that is wrapping around low
pressure dropping southward through the night will produce periods
of rain over the central and southern Idaho Panhandle. The COE,
LWS, and PUW TAFs have mention of light rain in the 05-11z time
frame as this band sinks south. Moisture associated with this
precipitation will likely result in 1500-2500ft ceilings across
southeast Washington and the southern/central Idaho Panhandle
where the HREF gives Pullman an 80 percent chance 2000ft ceilings
between 12-18z.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
HREF probabilities for 2000-3000ft ceilings at Coeur d`Alene and
Spokane are about 50 percent Thursday morning. There will be a
good deal of dry northerly winds in the mid and upper levels
suggesting clearing in the morning. Since GFS MOS produces a
stratocumulus deck at Coeur d`Alene, and NAM/GFS soundings support
that idea a BKN025 deck has been included. It wouldn`t be
surprising to see similar conditions at SFF and GEG, and may need
to be added later TAFs. /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        40  64  45  68  46  63 /  20  20  20  10  20  30
Coeur d`Alene  40  60  44  67  45  60 /  40  30  20  10  30  50
Pullman        39  59  40  65  44  58 /  30  10   0  10  40  30
Lewiston       47  66  45  73  51  66 /  40  10   0  10  40  30
Colville       35  64  39  67  41  64 /  40  60  50  30  40  60
Sandpoint      38  58  43  64  44  58 /  70  50  60  40  40  60
Kellogg        42  57  44  64  47  56 /  70  30  40  30  50  60
Moses Lake     42  72  44  73  47  71 /  20   0   0  10  10  10
Wenatchee      47  71  47  71  49  67 /  20  10   0  10  10  10
Omak           43  72  44  72  46  70 /  50  30  10  10  20  20

&&

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

$$