261
FXUS66 KOTX 300456
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
956 PM PDT Wed May 29 2024

.SYNOPSIS...
Areas of near or below freezing temperatures are expected Thursday
morning and again for Friday morning. Drier weather is expected
Thursday and Friday. A chance of mountain showers returns on
Saturday followed by widespread rain late Sunday and Monday next
week. There is increasing confidence for above normal temperatures
for the latter half of next week.

&&

.DISCUSSION...
Today through Friday: The main threat for today is widespread
gusty showers with isolated wind gusts up to 50 mph. Thanks to a
cold upper trough and surface heating from this morning,
widespread shower activity has sparked in the entire Inland NW. As
daytime heating wears off, the pressure gradient that is
delivering gusty winds will also relax. MOS guidance is still
hinting at sub- freezing temperatures in the northeast Washington
valleys, so I upgraded the freeze watch to a freeze warning. I
also issued a broader frost advisory for the Idaho Panhandle,
parts of the Columbia Basin/Spokane area, Palouse, and Methow
Valley but this carries lower confidence. There is a 30-50% chance
of temperatures cooler than 35 degrees in the frost advisory and
a 60-80% chance of temperatures cooler than 33 degrees in the
freeze warning. Currently the freeze warning encompasses through
Friday morning as there is moderate confidence for 2 nights of
freeze potential while the frost advisory only covers tonight. The
temperatures appear to be warmer tomorrow night in the frost
advisory area, lowering the risk. This will be reevaluated based
on how tonight goes and if the models change.

Tomorrow appears much drier but models still have a few weak
showers over northeastern Washington and north Idaho. High
temperatures will reach into the 60s despite a cold start in the
30s and low 40s tonight. Friday also looks dry and mild with highs
in the upper 60s to upper 70s. /Butler

Saturday and Sunday: A weak trough will move across the region
Saturday with a quick broad shortwave ridge for Sunday. Showers
and thunderstorms will occur mainly in the afternoon and evening
hours across the mountainous areas of eastern WA and most of the
Idaho Panhandle. Temperatures Saturday will be in the 70s, which
is near average. Sunday we cool several degrees as thick dense
clouds move in during the afternoon preventing additional heating.

...Beneficial rains for the Inland Northwest Monday...

Sunday night through Wednesday: A large tap of Pacific moisture
moving along the base of a strong low pressure system will move
into the region beginning Sunday and continue through Monday.
190-200% of normal precipitable water values will be widepsread
across the region. Precipitation chances will begin to increase
late Sunday afternoon and evening and continue through Monday.
Widespread rains are expected. We are still several days out, but
precipitation amounts are looking to be near a tenth of an inch to
a quarter of an inch in the valleys and lower elevations of
central WA; 0.40 to 0.80 for the valleys of eastern WA and north
ID; and over an inch along the crest of the Cascades, and the
mountains of extreme northeast WA and the ID Panhandle. These
rains will be beneficial to the region, creating rises on local
creeks, streams and rivers. Some ponding of water is possible for
areas that do not have proper drainage.

Temperatures will remain on the cool side with highs in the 60s to
around 70 through Tuesday. Monday there will be some breezy to
gusty southwest to west winds as a trough passes. There is a
50-60% chance of gusts over 30 mph across the Waterville Plateau
and onto portions of the Columbia Basin.

Showers remain in the forecast for Tuesday as 57% of the
ensembles support the parent low remaining to the northwest
providing west or southwest flow and potential additional waves
moving into the region.

Wednesday onward a ridge will build somewhere over the western US.
There are some discrepancies of where the ridge sets up, which
will directly impact how hot we will get. For now, plan on warming
conditions. 60% of the ensembles support a ridge with temperatures
around 90 in the Columbia Basin and 80s for the valleys. /Nisbet

&&

.AVIATION...
06Z TAFS: Convection is winding down with the loss of daytime
heating with just a few residual showers left in north Idaho and
down around the Blue Mountains. The showers moistened the boundary
layer over N Idaho Panhandle and around Spokane Felts Field with
the relative humidity already at 85-100% at some locations. While
the models are showing very little chances for fog, current RH,
clearing skies, and light winds does support as least some patchy
fog development. Given drier air above the boundary layer with NW
winds, confidence in coverage is low, but did indicate a TEMPO
group for IFR conditions at KSFF/KCOE. Thursday will not be as
unstable, but afternoon heating will trigger scattered to broken
flat cumulus over much of Eastern Washington and North Idaho
especially over the higher terrain. Slightly greater instability
over the North Idaho Panhandle will lead to a 20 percent chance
of a shower or thunderstorm at Sandpoint between 21z Thu-02z Fri.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS:
Convection is high for VFR conditions at KGEG/KLWS/KEAT/KMWH.
Confidence is lowest for KSFF/KCOE where a moist boundary layer
left over from recent showers could lead to fog development
overnight. Fog has the potential to impact Bonners Ferry,
Sandpoint, Coeur d`Alene, and Kellogg as well. 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        37  65  35  71  49  73 /  50   0   0   0   0  10
Coeur d`Alene  36  62  37  69  46  70 /  70   0   0   0   0  10
Pullman        35  61  37  68  47  69 /  60   0   0   0   0  10
Lewiston       42  69  44  77  53  79 /  50   0   0   0   0  10
Colville       32  65  34  71  42  69 /  60   0   0   0   0  30
Sandpoint      36  61  37  67  44  68 /  80  20   0   0   0  20
Kellogg        38  59  39  66  49  67 /  80  10   0   0   0  20
Moses Lake     36  71  38  76  51  79 /  10   0   0   0   0   0
Wenatchee      41  69  44  75  57  74 /  10   0   0   0   0   0
Omak           36  71  39  75  51  75 /  10   0   0   0   0  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Frost Advisory from 2 AM to 8 AM PDT Thursday for Central
     Panhandle Mountains-Idaho Palouse-Northern Panhandle.

WA...Frost Advisory from 2 AM to 8 AM PDT Thursday for Spokane Area-
     Upper Columbia Basin-Washington Palouse-Western Okanogan
     County.

     Freeze Warning from 2 AM Thursday to 8 AM PDT Friday for
     Northeast Mountains-Okanogan Highlands.

&&

$$