606
FXUS66 KOTX 192147
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
247 PM PDT Thu Sep 19 2024

.SYNOPSIS...

Weather will trend drier toward the end of the work week, then
light rain chances mainly for the mountains Sunday into Monday.
Chilly temperatures with frosty conditions is expected in the
mornings over the weekend. Colder pockets in the northern mountain
valleys will see a greater than 50 percent chance of reaching the
freezing mark. A warming trend with above normal temperatures by
mid week is expected after this weekend.

&&

.DISCUSSION...

Tonight through Sunday: A shortwave trough of lower pressure
moving across southern BC will bring enhanced westerly to
northwesterly winds through Friday. Winds will pick up through the
Cascade gaps this evening with gusts up to around 25-30 mph,
especially on the higher benches around Wenatchee to Chelan. The
pressure gradient then becomes more northerly into Friday with
similar magnitude winds down the Okanogan Valley. Funneling
effects late in the morning into the early afternoon hours will
increase the potential for wind gusts to around 35 mph between
Oroville to Coulee City. The northerly gradient will draw down a
polar continental air mass with dew points plunging into the lower
to mid 20s. Winds will relax Friday night with mostly clear
skies. This will set up the potential for strong radiational
cooling with chilly overnight temperatures expected. Model Output
Statistics (MOS) guidance tends to do the best for these strong
radiational cooling patterns when temperatures can get quite cold
right near the surface. Cold pockets across the northern mountain
valleys will see the potential of dropping down into the upper
twenties. This includes locations such as Republic, Colville,
Chewelah, Deer Park, Priest River, and near Priest Lake.
Surrounding areas, including up the Methow Valley, northern
Columbia Basin, Palouse, Central Panhandle Mountains will see a
greater than 50 percent chance for frost. Higher clouds will begin
to stream across the Cascades Saturday night. This will help
counteract radiational cooling effects for the next night, but it
doesn`t look like it will be enough to prevent northeast
Washington into the Idaho Panhandle from dropping back down to
near freezing. A freeze watch is in effect for Friday night
through Sunday morning and covers the risk for freeze damage to
sensitive vegetation Friday night into Saturday morning and again
Saturday night into Sunday morning. Temperatures will warm back up
next week, so there is opportunity to squeeze out a little more
growing potential if precautions are taken to protect sensitive
vegetation over the weekend.

Sunday night through Thursday: A shortwave disturbance drops
across the northern portion of the region Sunday night followed by
a warm front into Monday. Dynamics will be lacking with these
disturbances and there is just a 25-50 percent chance for light
rain mainly over the mountains from the Cascades over the Idaho
Panhandle. It will be so dry at lower levels that moisture will
have a hard time making its way all the way to the surface before
evaporating as virga showers. Expect clouds to increas and thicken
up, but little in the way of appreciable rainfall.

Warm air advection with the warm front will pump up a ridge of
higher pressure for Tuesday. Temperatures will warm up
significantly above normal with highs in the upper 70s to low 80s.
Warming trend continues into at least Wednesday with another
couple of degrees of warming as many valley locations look to be
in the 80s. There is uncertainty in timing and how this ridge will
evolve. A minority of the ensemble members indicate a quicker
break down with a stronger cold front passage that would bring
more in the way of westerly winds. This could begin as early as
Wednesday afternoon near the Cascades, and then breezy conditions
potential spreading further east and continuing into Thursday. The
greater consensus is fore a more gradual weakening and flattening
of the ridge that would result in less wind. The concern for the
former (less likely) scenario will be for elevated to critical
fire weather conditions if all ingredients of winds and dry
conditions line up. This scenario will be monitored with the
forecast adjusted accordingly as next week approaches. /SVH

&&

.AVIATION...
18Z TAFS: VFR conditions will prevail. A weather system passing
to the north will increase westerly winds this afternoon across
the Wenatchee area, Columbia Basin. Wind gusts to near 20 kts are
forecast but could be locally stronger especially around KEAT.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
for VFR conditions to continue for the TAF sites.

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        46  71  37  71  41  72 /   0   0   0   0   0  10
Coeur d`Alene  45  68  38  69  40  71 /   0   0   0   0   0  10
Pullman        44  65  38  68  37  69 /   0   0   0   0   0  10
Lewiston       53  72  46  75  46  76 /   0   0   0   0   0   0
Colville       35  69  32  71  32  70 /   0   0   0   0   0  20
Sandpoint      42  66  35  67  35  67 /   0   0   0   0   0  20
Kellogg        46  65  38  67  41  67 /   0   0   0   0   0  10
Moses Lake     46  72  40  73  40  75 /   0   0   0   0   0  10
Wenatchee      54  72  46  74  49  74 /   0   0   0   0   0  10
Omak           47  73  42  76  46  74 /   0   0   0   0   0  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Freeze Watch from late Friday night through Sunday morning for
     Northern Panhandle.

WA...Freeze Watch from late Friday night through Sunday morning for
     Northeast Mountains-Okanogan Highlands.

&&

$$