Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 272133
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
233 PM PDT FRI MAR 27 2015

.SYNOPSIS...
A fast moving cold front will arrive tonight bringing widespread
showers, gusty winds, and the potential for thunderstorms to
southeast Washington and portions of the Idaho Panhandle. Saturday
will be quite windy with gusts of 40 mph possible over Palouse,
West Plains, and Upper Columbia Basin. The weather Sunday and
Monday should be mild and relatively dry. Another fast moving
front on Tuesday will bring more showers and wind.

&&

.DISCUSSION...
Tonight and Sat...

Thunder and showers: We backed off the pcpn and thunder potential
through late afternoon to early evening as it looks like much of
the surface will remain capped. Showers and thunder will then
rapidly develop and spread NE across much of Ern and N Idaho as
the cold front and upper trough (currently just offshore) moves
inland. Convective mode: Shear and thermodynamic profiles show the
main threat will be very gusty winds, with any thunderstorm
outflow augmenting the already strong synoptic-scale pressure
gradient dry slot winds overnight. Severe gusts (gust to 58 mph)
is a possibility, but not likely with the strongest embedded
thunderstorms. Steering flow for these cells alone should be at
least 30-35 kts with this embedded thunder. Small hail is
possible. The challenge tonight will be how much thunder is
generated across Nrn Wa late tonight as the vort max (and
associated cold pool and steep mid-level lapse rates) translate
east rather quickly. If this was occurring during peak heating,
thunder would be a certainty.

Winds: We`ll issue a wind advisory with the passage of the cold
front this evening through midday Sat for especially the Palouse
area as a significant mid-level dry slot surges across Ern Wa.
Initially the heavy showers and thunder will help to mix stronger
winds aloft (35-40 kts) to the sfc, then strengthening pressure
gradients and cold advection overnight following fropa will help
to transfer 45-50kt winds aloft in a nearly unidirectional
westerly vertical wind profile.bz

Saturday night through Friday...A gulf of Alaska area of low
pressure juxtaposed against a weak ridge of high pressure with
axis placement generally to the east of Northern Idaho allows for
a persistent flux of moisture through an elongated baroclinic band
located between the low and the ridge. The placement of the
baroclinic band is far enough to the north through Monday so as to
allow for a dry forecast for most locations with the exception of
locations close to the British Columbia Border and the North
Cascade Crest. Another cold front wipes out the ridge Monday night
into Tuesday. As it does this is will spread precipitation from
west to east and allow for Windy Conditions during and after its
passage Tuesday. From about Tuesday night on Through Thursday the
jet stream straddles the forecast area along the southern Border
which allows for a conditionally unstable airmass and associated
cold pool aloft to overhang Eastern Washington and Northern Idaho
through most if not all of this interval which allows for a cool
forecast with mainly diurnally driven showers and the possibility
of some frost with more widespread temperatures just below
freezing Wednesday night. By Friday the trof aloft exits to the
east and leaves a more flat zonal flow with the jet stream in
closer proximity which would suggest a further decrease in pops
but perhaps a return of breezy conditions as the jet stream gets
positioned closer overhead of Eastern Washington and Northern
Idaho. /Pelatti

&&

.AVIATION...
18Z TAFS: A vigorous early spring cold front will collide with an
unseasonably warm and moist air mass tonight bringing widespread
showers and embedded thunderstorms to north Idaho and the eastern
third of Washington. Strong winds will also develop behind the
cold front after 07-09z and persist into Sunday afternoon. Gusts
of 30-38kts will be possible in Spokane, Coeur D`Alene, and
especially Pullman. bz

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        47  60  39  59  40  62 /  80  40   0  10  10  10
Coeur d`Alene  45  59  38  59  38  63 /  90  70   0  10  10  10
Pullman        46  58  40  58  41  64 /  90  40   0  10  10  10
Lewiston       51  64  41  63  42  68 /  90  20   0   0  10  10
Colville       44  63  39  60  39  63 /  70  60   0  10  10  10
Sandpoint      45  56  38  57  36  62 / 100  90   0  10  10  10
Kellogg        42  53  36  56  38  60 / 100 100   0  10  10  10
Moses Lake     48  65  40  65  39  67 /  10  10   0   0  10  10
Wenatchee      48  65  43  65  44  68 /  10  10   0  10  10  10
Omak           44  65  39  64  39  66 /  40  10  10  10  10  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 11 PM this evening to 11 AM PDT Saturday for
     Idaho Palouse.

WA...Wind Advisory from 11 PM this evening to 11 AM PDT Saturday for
     Lower Garfield and Asotin Counties-Washington Palouse.

&&

$$




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