Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 292239

Area Forecast Discussion
National Weather Service Spokane WA
238 PM PST THU JAN 29 2015

Areas of low clouds and fog will persist across portions of
Inland Northwest as high pressure remains in place. The ridge of
high pressure will begin breaking down Sunday. This will result in
and increased chance for valley rain and mountain snow through
the middle of next week.


Tonight through Friday night...An upper level ridge will persist
allowing for a continuation of fog and stratus in the valleys.
With boundary layer winds becoming light this evening...fog and
stratus will expand and include all valleys overnight. Fog will be
more favored tonight in the Upper Columbia Basin, Spokane/Coeur
D`Alene area, North Idaho Panhandle, and the palouse where breaks
in the stratus are occurring this afternoon which will allow for
radiational cooling this evening. Patchy dense fog is also
likely in these areas and its possible that advisories may be
needed. Freezing fog will also be a concern as temperatures
fall below freezing and fog freezes onto surfaces including
roadways. Meanwhile around Moses Lake, Wenatchee, Omak, and
Colville stratus will be more favored with limited if any fog
development due to limited cooling potential tonight with stratus
locked in place. Friday afternoon the stratus deck will lift
slightly but with light winds most valleys will stay cloudy
through the day. Friday night the NAM, ECMWF, and GEM models are
showing the potential for light drizzle, freezing drizzle, or
flurries out of the stratus layer as weak low level isentropic
lift develops ahead of a weak weather system over southern BC. JW

Saturday and Saturday evening...High pressure will continue to
dominate the weather...while an upper level disturbance slides by
along the Continental divide. This will put the region in a mainly
northwest-northerly flow. Little change in the weather as
fog/stratus will continue over the region. Temperatures will not
change much as well with high mainly in the 30s to lower 40s.

Saturday night through Thursday...The ridge will begin to bend
down Saturday night and Sunday. This will open the door for a
frontal system to pass through the region on Sunday/Sunday night.
Westerly flow will tap into Pacific moisture and bring a chance
for precipitation to the region. There looks to be a break in the
weather Tuesday and Tuesday night. Then another...slightly
stronger warm front is expected Wednesday and Thursday.

*Precipitation: Confidence in light precipitation is fairly high
 outside of the basin Sunday through Monday. The flow will become
 southwest and tap into deeper moisture off the Pacific. PWAT`s
 increase to between .60 - .70 which is 200% of normal or more. It
 will not take much lift to wring precipitation out of a saturated
 atmosphere. A weak cold front will track across the region
 Tuesday and Tuesday night for a drying trend. The exception will
 be the along the crest of the Cascades and the orographically
 favored Panhandle mountains. The we start the process all over
 again Wednesday and Thursday.

*Precipitation amounts: Not as much confidence with this portion of
 the forecast...but the thinking at the time is that all areas
 will see measurable precipitation. Sunday-Monday storm totals
 will range form around .10 in the deep basin to .35-.55 for the
 mountains. Wednesday and Thursday is where the confidence in
 amounts is much lower but still there will be plenty.

*Precipitation type: Snow levels will begin around 3k feet across
 the south and 1500-2000 feet across the north...but are expected
 to slowly rise Monday. So rain across the southern zones and
 starting as snow down to valley floors Sunday morning near
 Highway 2 northward...then the rain/snow line will push north
 Sunday night and Monday. There will be a limited amount of snow
 in the valleys and 3-6 inches in the mountains through Monday
 afternoon...locally higher amounts above 5000 feet. Partial
 clearing on Tuesday night will allow snow levels to lower for the
 beginning of the precip on Wednesday but the warm air advection
 appears to be much stronger with the second system and snow
 levels should rapidly rise through the day on Wednesday.

*Temperatures: No big changes to the temperatures. Highs will
 range from the mid 30s across the north to lower 40s across the
 south. Lows mid 20s to mid 30s...and a bit cooler through the
 Purcell trench Thursday morning. Tobin


00Z TAFS: Tonight as the ridge builds and inversions strengthen
and boundary layer winds being light...fog and stratus will expand
to include all valleys. Areas that are seeing some clearing this
afternoon will have a better chance of dense fog development
tonight including KGEG/KSFF/KCOE/KPUW and possibly KLWS. Stratus
is expected to persist into Friday afternoon due to light winds
although some lifting of the stratus should help improve
visibilities. With stratus locked in place at KEAT/KMWH only minor
fluctuations in CIGS are expected through Friday afternoon. JW


Spokane        29  36  30  37  30  36 /   0   0  10  10  10  50
Coeur d`Alene  30  39  31  39  30  37 /   0   0  10  10  10  60
Pullman        31  39  31  44  34  43 /   0   0   0  10  10  50
Lewiston       32  42  33  47  35  46 /   0   0   0  10  10  40
Colville       32  40  32  36  30  35 /   0   0  10  10  20  60
Sandpoint      29  36  30  36  28  34 /   0   0  10  10  20  70
Kellogg        28  39  30  39  30  36 /   0   0  10  10  10  70
Moses Lake     32  39  32  40  32  39 /   0   0  10  10  10  20
Wenatchee      32  39  32  39  32  40 /   0   0  10  10  20  30
Omak           31  36  32  36  31  38 /   0   0  10  10  10  30



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