Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 050918
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
218 AM PDT WED AUG 5 2015

.SYNOPSIS....
Cooler temperatures, continued breezy conditions, along with a
chance of showers and a few thunderstorms over the northern
mountains are expected through Thursday in the wake of a cold
front. Another threat of showers and thunderstorms arrives this
weekend, as yet another low pressure system is expected to move
into the region.

&&

.DISCUSSION...
Today through Thursday: A cold upper level low pressure system
will nudge further south across BC today. Satellite imagery shows
moisture about to move into northwest WA. This moisture will push
into the Cascades up across the northern mountains through this
afternoon. This will also result in an increasing chance for
showers across these areas. Best chances will be along the Cascade
crest. Chances will become much less along the lee side of the
Cascades where westerly flow will result in downsloping and drier
conditions.

Cooler and more moist air will funnel through the Cascade gaps.
This will act to strengthen the cross Cascade pressure gradient
with winds becoming increasingly more gusty through the day. These
winds will also funnel out across the interior basin. Winds will
be strongest along the lee slopes of the Cascades. The Wenatchee
Area and Waterville Plateau could see gusts as strong as 30-35
mph. Wind gusts closer to 25 mph are expected across the basin.
Although we will see moisture increasing across the Cascades
today, it is not expected advect much across the basin. This will
result in yet another day of breezy winds with dry conditions, and
will be a potential problem for rapid spread of any new or ongoing
fires.

The upper level low will eject more quickly east of the region on
Thursday. A lingering upper level cold pool aloft will keep the
Northeast Mtns and Northern Panhandle weakly unstable, but,
overall, a decreasing trend in showers and cloud cover can be
expected. Both Wednesday and Thursday will be relatively cool
compared to the hot conditions that have been experienced for much
of the summer season. Expect temperatures near to or slightly
below normal with highs ranging from the mid 70s to mid 80s. /SVH

Thursday night through Wednesday...Through this period of the
forecast we will see the exit of one upper level low for a brief
warming and drying trend...followed by another closed low that
will affect the weather through the weekend and well into next
week. Model guidance is similar through Tuesday...before showing
some differences Tuesday and Wednesday.

Thursday night through early Saturday...high pressure will track
through the region ahead of the next upper low approaching the
eastern Pacific. This will result in a 24-36 hour period of a
warming and drying trend. Temperatures will rebound quickly with
highs right around normal. Winds will be light and terrain driven.

Saturday afternoon through Monday...An upper level low will move
out of the gulf of Alaska and take up position off the Washington
coast...then linger in that area through the weekend. Several
waves will eject off the parent low and track through the region.
Moisture associated with these weak waves will be focused across
the north Cascades and along the northern mountains near the
Canadian border. None of these waves look particularly robust or
carry much in the way of deep moisture. But Showers with embedded
thunderstorms will be possible through the weekend. Each of these
waves will also increase southwesterly winds for breezy conditions
at times.

A secondary wave was progged to move through Oregon and clip the
southeast zones through the weekend. That wave now looks to to
take a more southerly route. As such the chance for showers and
embedded thunderstorms were pushed back to Sunday and Monday as
the main low begins to move inland.

Tuesday and Wednesday...Enough differences begin to show up in
the model guidance for only low confidence in this portion of the
forecast. The upper level low is expected to split with the
northern track opening into a wave and tracking northeast with
various solutions. The southern wave is expected to close off and
linger somewhere between about 130w off the Cal coast and in the
vicinity of Lake Tahoe. The solution will be somewhere in between.
The forecast has some lingering, mainly mountains showers with
temperatures remaining near normal. Tobin

&&

.AVIATION...
06Z TAFS: For tonight a few sprinkles or light showers are
possible near KLWS with the best chance of thunderstorms over the
Clearwaters southeast of KLWS as a weather disturbance tracks into
Central Idaho. Then an upper level low will skirt the Canadian
border on Wednesday with a chance of showers and isolated
thunderstorms over the northern mountains. An associated cold
front will result in breezy conditions after 18z Wed across the
region with windy conditions through the Cascade gaps and western
Columbia Basin (KEAT, KMWH TAF sites) with gusts up to 30-35 kts.
The strongest gusts are expected between 21z Wed- 03z Thu. VFR
conditions should continue at all TAF sites through 06Z Thursday.
JW

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        81  58  77  56  84  60 /   0  10  10   0   0  10
Coeur d`Alene  80  56  78  53  85  56 /   0  10  10   0   0  10
Pullman        80  53  76  49  84  54 /   0   0   0   0   0  10
Lewiston       88  62  85  59  91  65 /   0   0  10   0   0  10
Colville       81  55  80  53  87  55 /  10  30  20   0  10  10
Sandpoint      80  51  75  46  82  49 /   0  30  30  10  10  10
Kellogg        78  53  75  51  84  53 /   0  10  10   0  10  10
Moses Lake     86  57  83  55  88  59 /   0   0   0   0   0  10
Wenatchee      83  64  85  63  90  67 /   0  10  10   0   0  10
Omak           83  56  85  55  89  59 /  10  20  10  10   0  10

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...Red Flag Warning until 9 PM PDT this evening for East Washington
     Central Cascade Valleys (Zone 677)-East Washington Northern
     Columbia Basin (Zone 673)-East Washington Palouse and
     Spokane Area (Zone 674).

&&

$$


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