Area Forecast Discussion
Issued by NWS Spokane, WA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
550
FXUS66 KOTX 242345
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
345 PM PST Fri Nov 24 2017

.SYNOPSIS...
Isolated showers will linger in the mountains tonight, otherwise
there will be a brief break in the weather. More wet and unsettled
weather will move back into the region late Saturday into Sunday
with another weather disturbance moving in early next week.


&&

.DISCUSSION...
Tonight: Very broad flat ridge will persist over the region this
evening into Saturday. This will keep conditions mostly dry except
for some very isolated showers along the Cascade crest and
mountains of N ID. Clouds will thin and partially dissipate this
evening as drier air from the south begins to move in. Forecast
challenge for tonight will be the extent of stratus and/or fog.
Models are showing some boundary layer moisture across the north
as well as down into the Columbia Basin by about midnight, then
towards morning that moisture gets pushed into the Cascades. Have
adjusted our fog forecast to show the progression of the growing
patchy fog towards morning.

Saturday and Saturday Night: A trough will move south out of the
Gulf of Alaska Saturday morning and approach the west coast. By
afternoon the next warm front will begin to push in from the
south. The main impact will be an increase in clouds. By late
afternoon precipitation will move in from the south, and during
the evening most locations will see rain or high mountain snow.
The front is fast moving and have decreased our chance of precip
across the south overnight while keeping chance of precip high
across northern WA and ID. Snow levels will rise through the night
with snow levels in the north ranging from 4000-5000+ ft. Snow
amounts will be quite light across NE WA and N ID with an inch or
two possible. The Cascades will see more snow as they will have
good upslope flow into the east slopes. Generally 1-3 inches of
snow with locally up to 5 or 7 inches will be possible along the
higher peaks and crest. Temperatures will be about 4-10 degrees
above average for this time of the year. /Nisbet

Sunday through Friday...General agreement exists between the
latest GFS...ECMWF and Canadian models regarding the overall
field of motion through most of the upcoming week. A series of
troughs will bring periods of enhanced precipitation chances with
weak short wave ridge patterns bringing quiet interregnums with
scattered mountain snow showers.

Sunday will be a wet period with another subtropical origin
moisture feed enhancing along a transiting cold front. Snow levels
will remain high and only begin dropping after the FROPA...which
will also feature breezy and gusty winds but not as bad as
yesterdays frontal passage.

Monday and Monday night will be a dry break period followed by
deteriorating conditions on Tuesday as the next trough enters the
region. This wave will arrive on a more northwesterly trajectory
and snow levels will be noticeably lower...around 3000 feet during
the day but may drop to valley floors and the higher basin floor
Tuesday night. The focus of precipitation will be mainly over the
Idaho Panhandle but snow showers may backfill into the eastern
basin as the axis passes through.

Wednesday will be another break day...with a dry Canadian polar
air mass infiltrating the region promoting a cooling trend back
toward normal for the rest of the upcoming week.

For Thursday and Friday model agreement begins to
deteriorate...especially for timing the next wave of moisture
as early as Thursday for the ECMWF and as late as Friday for the
GFS.

It does appear that the Tuesday night system may herald a pattern
shift for the region from a mild and moist maritime regime to
more of a normal continental polar regime with lower snow levels
during passing disturbances and cooler temperatures more
seasonably characteristic for late November. /Fugazzi

&&

.AVIATION...
00Z TAFS: Westerly flow will be over the region tonight with
transient mid level clouds and high cirrus. Some valley fg and
IFR ceiling stratus are possible between 11Z and 17Z mainly at
the KMWH and KEAT TAF sites where a weak low level easterly
gradient will bank deeper moist boundary layer air against the
Cascades. After any morning fg or stratus breaks up...VFR
conditions expected at all TAF sites...but with lowering ceilings
as a moist storm system approaches the region from the southwest.
Any precipitation and MVFR conditions should hold off until after
00Z Sunday. /MJF


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        32  44  39  52  34  41 /   0   0  80  70  60  10
Coeur d`Alene  32  45  37  51  34  41 /   0   0  80  50  90  20
Pullman        34  47  42  54  35  43 /   0   0  60  50  90  10
Lewiston       35  51  42  57  38  48 /   0  10  30  30  70  10
Colville       33  42  35  46  32  42 /  10   0  80  80  70  10
Sandpoint      32  41  35  46  34  40 /  10   0  80  60 100  20
Kellogg        31  43  36  49  33  38 /  10   0  70  60  90  40
Moses Lake     31  45  35  50  31  46 /   0  20  60  50  40  10
Wenatchee      32  41  35  46  32  43 /   0  30  80  60  20  10
Omak           33  42  36  45  32  42 /  10  10  70  80  50   0

&&

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

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.