997
FXUS66 KOTX 032330
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
430 PM PDT Fri May 3 2024

.SYNOPSIS...
Temperatures on Saturday will be mild with highs in the 60s and
low 70s. Bands of rain will spread into central Washington on
Saturday. Widespread rain is expected on Sunday as a slow moving
low moves through the Pacific Northwest. As the low pulls out of
the region, look for cool, showery, and windy conditions Monday
and Tuesday. Warmer and drier weather will likely arrive late next
week.

&&

.DISCUSSION...

Tonight and Saturday: Clouds will be on the increase tonight into
Saturday as a slow moving low off the coast of Washington this
afternoon pushes into Oregon and northern California on Saturday.
Rain will be slow to spread east of the Cascades. Chances for
measurable rain will be less than 50 percent east of Omak,
Waterville and Moses Lake until late Saturday evening. Even though
Saturday will be mostly cloudy, temperatures will be mild. Morning
lows will range from the 40s in north Idaho and northeast
Washington to the low 50s in Moses Lake and Wenatchee. Highs are
expected to be in the 60s Saturday for the majority of the Inland
Northwest.

Sunday: There is decent model agreement that the most significant
precipitation with this slow moving low will occur south of
Washington and Idaho Saturday and Sunday with a foot or more of
snow for the high elevations of the Oregon Cascades and mountains
of northern California. However, this storm should deliver some
much needed rainfall to eastern Washington and north Idaho. Models
often struggle with wrap around precipitation, and we have seen
some variability in the ensembles the last few days with the
timing and location of the deformation band wrapping into the
Inland Northwest. The latest National Blend of Models (NBM)
generates the most significant band of rain Sunday and Sunday
night across the eastern third of Washington and over the north
Idaho Panhandle. The NBM deterministic output (most likely
scenario) has a swath of a quarter to half inch centered along the
WA/ID state line Sunday and Sunday night. The NBM 75th percentile
increases these amounts to localized amounts of two-thirds of an
inch while the 25th percentile knocks amounts in the rain band
down to a tenth to quarter of an inch. Rains across the Palouse
and West Plains will be welcomely received by dryland farmers
after a dry April. However, outdoor activities on Sunday will be
dampened by the rain and much below average temperatures. Places
that experience an all-day rain may struggle to get out of the 40s
Sunday afternoon including Spokane, Pullman, and the Idaho
Panhandle. Places like Omak and the Methow Valley may remain north
of the main rain band and have a good chance of topping out in the
60s.

Monday and Tuesday: The beginning of the work week will be cooler
than average, showery, and locally windy. As our deep weekend low
migrates eastward, a tight westerly pressure gradient will set up
across the Cascades on Monday. Then on Tuesday, a fast moving
shortwave descending from the Gulf of Alaska will dig into the
Pacific Northwest delivering another round of gusty west winds.
Guidance form the ECMWF ensembles suggest that wind gusts of 30 to
35 mph will be a good bet Monday with 70 percent of members
generating gusts of 35 mph or higher across the open country of
southeast and east central Washington on Monday and 50 percent of
members on Tuesday. Showers will be more widespread Monday with a
60 to 80 percent chance of measurable precipitation over the Idaho
Panhandle and the eastern third of Washington. Shower chances
should decrease on Tuesday as drier air accompanies the Gulf of
Alaska system, however snow levels will drop unseasonably low
Tuesday...as low as 3000 feet in the morning and again overnight
into Wednesday morning. If you haven`t gotten your fill of graupel
this spring, Tuesday will give you another shot at seeing our
"corn snow", "snow pellets", or (insert your favorite graupel
name).

Wednesday and Thursday: The medium range models are trending
toward a more amplified ridge/trough pattern over North America by
mid to late week. While there are some differences in where the
ridge axis will set up by Thursday and Friday of next week, the
majority of the ensemble members are forecasting above average
temperatures and dry weather Thursday and Friday. The NBM
advertises highs in the mid 60s to mid 70s Thursday and widespread
70s for Friday. /GKoch

&&

.AVIATION...
00Z TAFS: A low pressure system will move slowly onshore off of
the eastern Pacific tonight. This will spread mid to high level
clouds across the region. Light rain is expected across the
Cascades by the morning hours on Saturday with rain at KEAT by
14-16Z. Ceilings down to 3-4 kft with MVFR conditions possible.
South and easterly winds will pick up with the front approaching
through the day today into Saturday as well. KPUW-KGEG-KCOE will
see the potential for gusts up to 25 kts into Saturday morning
with the easterly pressure gradient tightening up.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence for
VFR conditions through Saturday afternoon except for at KEAT where
confidence is moderate. The HREF/NBM model guidance for KEAT
indicates a 50% chance ceilings lower down to between 2-3 kft
agl. and visibility down to 4-6 miles with rain by 15Z. /SVH

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

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        45  69  42  49  40  56 /   0  10  40  90  80  40
Coeur d`Alene  42  68  42  49  39  52 /   0  10  30  90  90  60
Pullman        46  65  39  45  38  52 /   0  10  80 100  80  60
Lewiston       47  73  46  54  44  59 /   0  10  90 100  80  60
Colville       40  68  42  57  38  60 /  10  20  20  90  80  70
Sandpoint      42  66  44  51  39  52 /   0  10  30  90  90  80
Kellogg        43  65  44  48  40  47 /   0  10  40 100  90  80
Moses Lake     53  71  44  58  42  63 /  10  40  60  80  30  10
Wenatchee      52  62  49  60  44  60 /  10  70  40  30  20  20
Omak           49  69  49  64  42  65 /  10  40  30  40  40  20

&&

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

$$