043
FXUS66 KOTX 191731
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
1031 AM PDT Sat Oct 19 2024

.SYNOPSIS...
This weekend will feature above normal temperatures with rain
over the Cascades. Precipitation will spread west to east with a
cold front passage Sunday night into Monday. The front will also
bring cooler temperatures and breezy winds. Chilly overnight
temperatures with lows in the 20s expected to return next week.

&&

.DISCUSSION...
Quick update: Well into the warm sector. Temperatures running
about 8 to 15 degrees warmer than yesterday at this time. Adjusted
pops and qpf based on radar trends and high resolution models.
Precipitation should be focused along the northern Cascades crest
with a well defined rain shadow across central WA. Light showers
will brush across far northeast WA into north Idaho and over the
Blue mountains through the afternoon. Breezy westerly winds will
prevail across the Columbia Basin. /rfox

Today through Monday: A weak atmospheric river will be directed
into the Cascades today into tonight. A firehose of moisture will
deliver moderate to heavy rain at the Cascade crest with 1-3
inches anticipated. Downsloping on the lee side of the Cascades
will dry out the air mass quickly with a sharp gradient of
rainfall expected moving east to west along the east slopes of the
mountain range. The moisture will also be less so draped across
the northern mountains of northeast Washington and the Northern
Panhandle. Rainfall across these locations will pale in comparison
to what is expected across the Cascade crest with places like
Colville, Newport, Sandpoint, and Bonners Ferry generally expected
to pick up less than a tenth of an inch. A shortwave trough of
lower pressure will dig offshore in the eastern Pacific late
Saturday into Sunday. This will buckle the flow pattern northward
placing the atmospheric river over southern BC resulting in a
brief break in the rain over the Cascades Sunday morning into
early Sunday afternoon.

Break in the precipitation will last until the cold front pushes
across. The timing of the cold front passage will be Sunday
evening across western Washington to Sunday night across eastern
Washington and then reaching the Idaho Panhandle by the afternoon
on Monday. A pronounced rain shadow will generally keep the basin
dry aside from up to a few hundredths. Precipitation will then
pick up along the front across extreme eastern Washington and the
Idaho Panhandle where a focus will be from the Palouse into the
southern to central Idaho Panhandle where between a quarter of an
inch (on the Palouse) to around three-quarters of an inch (over
the Central Panhandle Mountains) is expected. Rainfall will be
beneficial and only help, at least in a small way, the ongoing
drought across the region.

Snow levels will also be lowering behind the cold front with a
transition to snow above 4,000 feet on Monday primarily just over
the Cascade crest. Snow accumulations will be light and likely
won`t accumulate over the mountain passes due to afternoon timing
and warm surface temperatures. Winds will be breezy over the
weekend. Saturday and Sunday will see pre-frontal south-southwest
winds of 10-20 mph with gusts up to around 25 mph on Saturday over
the exposed areas of the basin. Winds will be a little stronger
by a few mph on Sunday. Cold front passage will veer winds
westerly by Monday. The upper level jet isn`t particular strong
with winds less than 100 mph at 250 mb. This translates to around
25-30 mph at 850 mb. Wind magnitude at 850 mb is a good proxy of
what to expect for wind gusts at the surface.

Monday night through Saturday: The post-frontal air mass heading
into next week will be drier and colder. Lingering upslope
showers will continue over the Idaho Panhandle on Tuesday. These
showers will then cease heading into Wednesday. The main impact
going into the middle part of next week will be chilly overnight
temperatures. Wednesday morning looks to be coldest day of the
week with lows down into the 20s across much of the region. Cold
pockets in the northern mountain valleys will see the potential
for temperatures in the upper teens. This will be the first good
hard freeze of the fall. Make sure to take precautions to protect
irrigation equipment from lines from freezing up.

Models show the next low pressure system swinging through around
Friday of next week. There are timing differences and differences
on precipitation amounts resulting in low confidence on details.
Precipitation type will largely be rain in the valleys across the
region with some snow in the mountains, and particularly in the
Cascades where snow levels look to be between 4500-5500 feet or
so. This is low enough for snow at Washington Pass and Sherman
Pass, but may not be low enough for snow at Stevens Pass.
Overnight temperatures will moderate a bit with this weather
system Friday into Saturday. /SVH

&&

.AVIATION...
18Z TAFS: Mid and high level clouds will prevail across eastern WA
with a lower 4-6K ft deck across north ID. Precipitation will be
focused over the northern Cascades crest with lighter rain showers
over the mountains north of Deer Park and Sandpoint. VFR
conditions should be found in most areas. Breezy southwest to west
winds 10-15kt with gusts near 20kt will be found across the
Columbia Basin into the Spokane area, then winds should taper off
in the evening.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
High confidence for VFR conditions will be across the TAF sites through
the period. /rfox.

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

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        67  46  71  47  59  34 /  30  10  10  80  70  20
Coeur d`Alene  64  45  70  47  56  34 /  50  10  10  90  90  40
Pullman        65  42  70  45  54  34 /  20  10  10  60  90  30
Lewiston       72  49  77  53  63  41 /  10  10   0  40 100  30
Colville       63  36  68  37  59  24 /  50  20  30  80  70  40
Sandpoint      56  42  66  43  53  31 /  70  30  20  90  90  60
Kellogg        59  49  69  49  52  38 /  50  20  10  80 100  50
Moses Lake     70  44  72  46  63  31 /  10  10  10  60  40   0
Wenatchee      68  50  70  45  60  37 /  30  30  30  60  20  10
Omak           66  47  69  41  64  33 /  40  30  40  50  20  10

&&

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

$$