Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 272345
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
445 PM PDT WED MAY 27 2015

.SYNOPSIS...
Scattered showers and thunderstorms decrease through sunset
Wednesday night, but the threat returns for the afternoon hours
on Thursday and Friday. However they will be more focused around
the mountains. Expect a warming trend into the weekend, with highs
in the 80s, with a lingering threat of mainly mountain showers
and thunderstorms. By next Monday and Tuesday the next best chance
of showers and thunderstorms arrives, with the potential for some
stronger storms and the return of cooler temperatures.

&&

.DISCUSSION...

This evening and tonight: Showers and thunderstorms will continue
through sunset across a majority of southeastern WA and the lower
ID Panhandle as an area of low pressure slowly departs to the
south. Activity north of a line from Mullan to La Crosse will be
more isolated in nature and contend with increasing large scale
subsidence. We are seeing isolated cells busting through the CIN
layer near Loup Loup and another just north of Lake Wenatchee so
despite the lack of activity right now, a small threat will
remain in place through dark but the overall threat for heavy rain
on the burn scars is low. There are two satellite waves that will
enhance or produce small clusters of storms. One is diving south
into Adams County and will be out of our area soon. The second is
just entering far northeastern WA and could bring last gasp of
showers and storms across the NE Mtns and into the Upper Basin
through the evening.

The main threats with any storms will be brief heavy downpours...small
hail...and lightning strikes. Storms near the Blue Mtns and Camas
Prairie will be nearly stationary and more favored to produce
rainfall amounts that could lead to localized flood problems. On
the contrary, the lack of wind shear in this environment will also
mean less organization within the storm structure and quicker
collapse of initial updrafts.

Areas of fog possible again by morning, especially near rivers and
areas that receive appreciable rainfall this afternoon.
Temperatures will be near to slightly warmer compared to this
morning. /sb

Thursday through Saturday night...This period will be
characterized by a warming trend with plenty of sunshine over most
locations...but marred by the potential for afternoon and evening
showers and thunderstorms mainly over the high terrain surrounding
the basin. Overall...the upper level low currently circulating
over the region will move off to the east on Thursday and cease
to be a factor in convective initiation...however a second upper
low descending down the Canadian Pacific coast and ejecting inland
over British Columbia will prevent a strong ridge from moving over
the region. Instead this low will promote a more southwesterly low
aloft through Thursday and Friday...allowing a strong warm up to
well above normal temperatures...mainly in the 80s with a few low
90 readings in the deep basin by Saturday.

Adequate moisture to fuel thunderstorms will continue to prevail
over the region and assuming dew points remain elevated to near
current levels with expected high temperatures in general most
locations will achieve anywhere from a few hundreds to near 1000
Joules/Kg each afternoon. However...on Thursday dynamic support
will be absent so thunderstorms will be confined to the mountain
zones. On Friday the GFS and NAM models both sense a weak wave
crossing the region in the southwesterly flow aloft generating
some moderate dpva and jet divergence as well as weak cooling
aloft. This will likely allow another round of afternoon and
evening storms and the presence of this weak energy aloft may
allow storm initiation over the rising terrain of the eastern
basin and the Waterville Plateau...in addition to the mountain
zones.

By Saturday drier air finally invades the region effectively
suppressing any further thunderstorm threat except for a small
lingering chance over the Idaho Panhandle. The surface thermal
trough will remain over the basin and the drier air will heat more
efficiently resulting in the highest temperatures of the week for
a splendidly benign beginning for weekend outdoor activities.
/Fugazzi

Sunday through Wednesday...An active weather pattern will prevail
across the Inland Northwest during this time period as an upper
level trough takes aim at the region. Timing differences between
the GFS and ECMWF are starting to be resolved with the 12Z run
today. The GFS has shown better run-to-run consistency up to this
point and now the latest run of the EC is trending closer to the
GFS timing. With confidence increasing, I have increased PoPs and
thunderstorm coverage for Monday/Monday night time period. The
upper trough will track toward the PacNW coast Sunday, placing the
forecast area under warm and moist southwest flow. This will keep
temperatures above normal Sunday with some shower and thunderstorm
coverage possible across the southeast zones. As the trough swings
inland Sunday night into Monday it will take on a negative tilt.
This pattern is a favorable one for showers and thunderstorms
across the forecast area. A decent amount of shear and surface-
based CAPE values of 500 to 1000 J/kg Monday afternoon means that
some thunderstorms could become organized. A tap into a sub
tropical moisture fetch supports heavy rain as a threat as well.
Tuesday the upper low drifts over the Inland Northwest with the
threat of scattered showers and thunderstorms continuing in an
unstable atmosphere. By Wednesday the low starts to exit to the
east and thunderstorm coverage will be more focused on the eastern
zones. Daytime temperatures will be on a cooling trend as the
region comes under the influence of the upper low with associated
clouds and precipitation. Expect widespread 80s on Sunday to be
replaced by 70s for the first half of the work week. /Kelch

&&

.AVIATION...
00Z TAFS: Isold to sct -shra/-tsra will be possible across much
of the region, with the best chance before 03Z. Thereafter the
main threat will dissipate with the loss of daytime heating. There
may be some lingering showers chances into the early overnight
between MWH, GEG, SFF, COE with the potential for the left over
showers over the northern mountains to drift south, before
abating but confidence is low.  The threat of showers/t-storms
will be renewed Thursday afternoon, with the main chances closer
to the mountains/ID border, including near EAT, COE, PUW, LWS and
maybe SFF. Brief heavy rain, gusty/erratic winds and small hail
are possible, along with isolated lightning strikes. There will
also be a small window where patchy fog is possible, between 11Z
and 16Z around SFF/COE and perhaps LWS. Confidence leans toward
this not being much of issue and if any develops it should be
shallow and short-lived. /J. Cote`



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        52  79  57  82  59  85 /  20  10  10  20  10  10
Coeur d`Alene  49  78  54  82  56  83 /  30  20  20  30  20  20
Pullman        46  75  52  82  56  83 /  30  20  20  20  20  20
Lewiston       52  83  58  88  63  90 /  40  10  10  20  20  20
Colville       53  82  54  83  54  86 /  30  20  20  30  20  20
Sandpoint      50  78  51  81  52  80 /  30  20  20  30  20  20
Kellogg        47  76  49  81  53  81 /  40  40  40  30  30  20
Moses Lake     53  86  58  90  59  92 /  10  10  10  10  10  10
Wenatchee      59  86  64  89  63  90 /  10  10  10  10  10  10
Omak           51  86  56  87  54  90 /  20  10  10  20  20  10

&&

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

$$



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