Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 282144
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
244 PM PDT Fri Apr 28 2017

.SYNOPSIS...
Scattered showers will bring brief periods of rain and possibly
graupel to north Idaho and northeast Washington this afternoon and
evening. The majority of Saturday should be dry before a frontal
system brings the potential for rain Saturday night and gusty
winds for Sunday. The middle of next week will be warm with
afternoon temperatures in the 60s to near 70 degrees.

&&

.DISCUSSION...

Tonight: Scattered rain and graupel showers will produce brief
periods of precipitation this evening over the Idaho Panhandle and
northeast Washington. As of 230 PM, regional radar showed showers
under a 500mb cold pool (-27C to -28C) extending from Republic to
Davenport to Couer d`Alene to Sandpoint. RAP analysis suggests up
to 400 J/Kg of surface based CAPE over northeast Washington and
far north Idaho. There may be enough instability for a few
lightning strikes, but without a clearly defined shortwave kicker
to enhance lift, it is doubtful that any thunderstorms will become
very organized. By mid to late evening, upper level high pressure
will build over the Inland Northwest. The loss of surface heating
combined with warming aloft should cause most showers to
dissipate by 8 PM. It will be a chilly night with most areas
dropping into the 30s, under clearing skies and light winds.

Saturday: The majority of the Inland Northwest will be dry on
Saturday. The influx of moisture ahead of a frontal system will
bring increasing chances for showers to the northern Cascades in
the afternoon and evening, but the rest of our region will start
the day with some sunshine followed by increasing mid and high
clouds. Rain chances will likely peak after midnight Saturday. The
GFS, NAM and ECMWF are in good agreement that a cold front will
cross the Cascades overnight. The front will be accompanied by a
good deal of mid-level westerly flow which favors precipitation
over the Cascade Crest, the mountains of north Idaho and far
northeast Washington. The models suggest up to a quarter of an
inch in the Panhandle mountains with most of our region getting
less than a tenth. At this time, the Columbia Basin and Wenatchee
area look to get sprinkles at best.

Sunday and Monday: Sunday will be breezy behind Saturday night`s
cold front. Wenatchee to Mose Lake to Spokane and Pullman will
likely experience sustained west winds of 15 to 20 mph with gusts
to 30 mph for much of the day. Convective showers during the day
Sunday should be the most concentrated over the mountainous
terrain of the Idaho Panhandle and the Cascade Crest. Low chances
for showers have been included in places like Lewiston, Pullman,
Spokane, and Colville, but any showers in these lowland
communities should be brief. Monday will be less windy, but
chances for showers are in the forecast. The GFS, ECMWF, NAM, and
Canadian models depict a fast moving shortwave trough. Again,
mid-level westerlies should produce a rain shadow on Monday and
limit showers to the mountainous terrain of the Panhandle,
Northeast Washington, and the Cascade Crest. /GKoch

Monday Night through Friday: Northwest flow aloft is expected
Monday night as a weather disturbance moves across eastern WA and
north ID. Have increased our chance of precipitation during the
evening hours across the south central ID Panhandle. Kept a
mention of showers in the overnight hrs into Tuesday as the
disturbance exits. Tuesday night through Thursday will be be dry
as an upper level ridge builds into the area. 850 mb temperatures
warm to 15-16C late Thursday. Wednesday we will see temps 3-6
degrees above average, and Thursday 6-9 degrees above average.
Current forecast for Spokane next Thursday is 71. We haven`t seen
temps above 70 since last Sept 30th, when we were 75! Thursday
night onward there is very low confidence in the forecast. The
models all have differing solutions in how to break down the
ridge. Currently don`t doubt the breakdown of the ridge as this
spring`s weather patten has been progressive... However all models
have differing timing, strength and placement of a trough moving
into the Pac NW. Have kept mention of showers in for eastern WA
and north ID with a dry area across the Columbia Basin. Expect
this forecast to change as models hopefully come more in line with
the breakdown of the ridge. /Nisbet

&&

.AVIATION...
18Z TAFS: Afternoon destabilization will produce scattered showers
over northeast Washington and the Idaho Panhandle this afternoon
into this evening. For the Spokane and Coeur d`Alene airports, the
best shot for scattered showers will be in the 21-03z time frame.
Locally breezy winds are expected at Wenatchee in the 22z-04z time
frame as Cascade gap winds are enhanced in the late afternoon and
early evening. /GKoch


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        37  57  44  58  37  55 /  20   0  60  20  10  10
Coeur d`Alene  36  57  42  56  35  54 /  30  10  80  40  10  20
Pullman        38  59  45  58  37  55 /  20   0  70  40  10  10
Lewiston       41  65  49  64  42  60 /  10   0  40  40  10  10
Colville       36  58  42  60  37  56 /  20  10  30  20   0  30
Sandpoint      34  56  40  54  34  53 /  20  10  80  80  20  30
Kellogg        35  55  40  52  35  51 /  30  10  90  90  20  30
Moses Lake     37  63  47  66  40  63 /   0   0  10  10   0  10
Wenatchee      40  60  45  62  41  60 /   0   0  10  10   0  10
Omak           37  61  45  65  40  62 /  10   0  10  10   0  10

&&

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

$$


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