Area Forecast Discussion Issued by NWS Spokane, WA
000
FXUS66 KOTX 162141
AFDOTX
Area Forecast Discussion
National Weather Service Spokane WA
241 PM PDT Tue Apr 16 2024
.SYNOPSIS...
Anticipate cool, brisk, and somewhat showery weather as a low
pressure system aloft drops over the Inland NW and lingers
through Thursday. It will be chilly early in the morning with lows
dipping below freezing for many areas and the threat of frost.
The weather gradually warms and dries by Friday into the weekend
and continues into early next week with above normal temperatures.
&&
.DISCUSSION...
An amplified upper ridge centered off the coast near 135W will
result in a broad trough with north-northeast flow over the area
through Thursday. Colder air aloft associated with the trough
combined with daytime heating will help generate convective
showers each day, mainly in the afternoon and evening hours. The
coldest air aloft with 500mb temperatures in the -30 to -34C
range will be focused over NE Washington and the Idaho Panhandle
which is where the models are generating the highest focus of
showers. The cold atmosphere and drier low levels with dew points
in the teens and 20s will support higher cloud bases with the
convection that develops, with most of the CAPE layer composed of
ice. This will support mainly graupel showers, with thunderstorms
not expected although can not rule out a stray lightning strike.
This air mass will also favor cold overnight lows for this time of
the year. For tonight areas that have begun their climatological
growing season (Wenatchee and Moses Lake area, LC valley) will see
temperatures remaining above freezing. For tomorrow night the LC
Valley and Moses Lake area will be near freezing so will have to
keep a close eye on potential frost or freeze highlights. JW
Friday through Tuesday: Conditions look to dry out for Friday and
Saturday with daytime temps warming to near daily normals. Also
expect breezy northeasterly winds on Friday with local gusts of 25
to 35 mph, especially across the Columbia Basin. Enough instability
and moisture with a passing wave will lead to a chance for mountain
showers Sunday, but most locations will remain dry. The gradual
warming trend looks to continue Monday and Tuesday, with forecast
max temperatures ~5+ degrees above normal. /KD
&&
.AVIATION...
18Z TAFS: Afternoon heating combined with cooling aloft will
destabilize the atmosphere through the afternoon over the
northern mountains surrounding Winthrop, Colville, Republic,
Sandpoint, and Bonners Ferry. Yet with a dry boundary layer
showers that develop are expected to be isolated to scattered in
nature. Given the higher cloud bases and mainly light intensity to
the showers CIGS will remain VFR, except under localized moderate
showers where snow or graupel could reduce visibility to MVFR. As
the cold pool tracks into the Spokane/Coeur d`Alene area between
1-4z there is a 20-30% chance of a brief shower impacting these
TAF sites.
FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: There is high
confidence in VFR conditions through the TAF period, with one
exception. As the atmosphere destabilizes this afternoon into the
early evening, the HREF shows near a 10-20% chance of visibilities
dropping to MVFR under moderate showers consisting of snow or
graupel. 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 30 54 31 55 32 56 / 20 20 20 20 0 0
Coeur d`Alene 30 52 31 53 30 54 / 30 20 20 20 10 0
Pullman 29 50 30 54 31 57 / 20 10 10 10 0 0
Lewiston 37 56 34 61 35 63 / 10 10 0 0 0 0
Colville 32 55 32 55 29 57 / 20 30 20 20 10 0
Sandpoint 31 50 33 51 31 52 / 50 30 20 20 10 0
Kellogg 33 48 32 50 29 52 / 30 50 20 30 10 0
Moses Lake 34 60 33 62 36 63 / 0 0 0 0 0 0
Wenatchee 34 58 35 59 35 60 / 0 0 10 0 0 0
Omak 34 59 33 61 34 63 / 10 10 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$