Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 262147
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
247 PM PDT Tue Jul 26 2016

.SYNOPSIS...
Thunderstorms will develop over northern Washington and the Idaho
Panhandle today and again on Wednesday. Locally heavy rain and
cloud to ground lightning will be likely with these storms. Dry
and hot weather is expected Thursday and Friday. A cold front is
expected to arrive this weekend bringing breezy conditions and
cooler weather for the start of next week.

&&

.DISCUSSION...

Tonight: Thunderstorms will keep us busy this evening. Our
atmosphere is quite moist and unstable for this time of year.
Surface dewpoints in the upper 40s to mid 50s are common
throughout the Inland Northwest this afternoon. The moisture is
more than just "skin deep" with decent humidity extending to 700mb
and precipitable water values around an inch. Cooler air aloft
along the Canadian border is contributing to surface based CAPE
values in excess of 1000 J/KG over the mountains along the
Canadian border. Afternoon heating over the high terrain has
caused scattered storms over the northern Cascades into the
Okanogan Valley. Hail may occur with some of the strongest cells
through early evening, but excessive rain will be the biggest
concern. Storm steering flow is weak, and as of 2 PM cells
northwest of Omak have exhibited the tendency to be anchored to
the terrain, moving very little. Through mid evening we will be
watching storms closely. At this time, we expect the greatest
thunderstorm coverage to be close to the Canadian border, north of
the burn scars of Okanogan, Chelan, and Stevens counties. However,
it is not out of the question that a rouge cell could cause burn
scar issues this evening.

Precipitation chances through the night have been increased along
and north of Highway 2. Last night, we had scattered convection
continue overnight into the morning. The GFS and NAM suggest that
we will once again have steep mid level lapse rates and sufficient
mid-level moisture for a chance of late night and early morning
showers and thunderstorms over our counties bordering Canada.

Wednesday: It will be another warm day with highs in the upper 80s
to mid 90s. We will continue to have a good supply of low level
moisture with dewpoints in the upper 40s and low 50s. The GFS and
NAM suggest that our mid-levels will warm a bit with 500mb
temperatures rising to -9c to -11c compared to the -12c to -13c
we have today. We should have fewer afternoon thunderstorms
tomorrow, but those that do form over the high terrain along the
Canadian border will once again be slow moving and capable of
heavy rain. /GKoch

Thursday and Friday:
A weak ridge pattern will be in place over the region. This will
be keep a mostly cloud free warming trend for the period. The
main concern with the region will be the high temperatures
expected. Moses Lake, Ephrata, and Lewiston areas could see triple
digit temperatures. The rest of the Columbia Basin can expect
temperatures in the 90s. The overnight Lows will be in the 60s to
low 70s range. /JDC

Saturday through Tuesday: Upper level trough will approach the Pac
NW from the north on Saturday. There are still some big
differences btwn the GFS and ECMWF. The EC now keeps the low
further north into Canada and brings a stronger trough through
Sunday night/Monday. The GFS pushes the front through Sat
night/early sunday with another trough for Monday night/Tuesday.
Needless to say am not very confident in the extended forecast
until the models can start to show some agreement. Saturday still
looks to be slightly cooler than Friday, but still above normal
temperatures with valley temps generally in the 90s. Winds will
pick up Saturday morning and will continue through Monday morning
with the gustiest winds occurring late Saturday afternoon through
Sunday evening. The strongest winds will be across the Cascade
gaps into the Columbia Basin, Palouse and Spokane area as well as
down the Okanogan Valley. These winds combined with daytime
relative humidities in the upper teens to lower 20s will make for
potentially dangerous fire weather conditions both Saturday and
Sunday. The dry cold front will push through Saturday night/Sunday
and bring about 8-10 degrees of cooling on Sunday. These cooler
temperatures (valleys in the 80s, or about 3-6 degrees below
average) will continue Monday and Tuesday as well. For now have
kept Tuesday a dry forecast until models can better agree on a
possible trough passage. /Nisbet

&&

.AVIATION...
18Z TAFS: High based showers and thunderstorms in the vicinity of
the Spokane metro are expected to drift to the northeast in the
19-21z time frame. Additional showers and thunderstorms are
expected to develop over the high terrain of northern Washington
and north Idaho around 20z. This convection will likely be deeper
and stronger capable of producing locally heavy rain, small hail,
and frequent cloud to ground lightning. Airports that may be
impacted by these afternoon and evening thunderstorms are Omak,
Republic, Methow, Colville, Priest Lake, Bonners Ferry, and others
near the Canadian border. /GKoch


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        64  90  65  92  67  94 /  20  10  10   0   0   0
Coeur d`Alene  61  90  60  91  63  93 /  20  10  10   0   0   0
Pullman        55  90  54  92  57  93 /  10   0  10   0   0   0
Lewiston       67  98  68  99  69 100 /  10   0  10   0   0   0
Colville       58  90  57  94  59  95 /  30  20  20   0   0   0
Sandpoint      56  86  54  88  56  89 /  30  20  20   0   0   0
Kellogg        56  88  55  88  57  90 /  20  10  10   0   0   0
Moses Lake     64  97  65  98  65 100 /  10   0   0   0   0   0
Wenatchee      69  96  69  98  70  98 /  10   0   0   0   0   0
Omak           67  95  67  97  68  99 /  30  10  10   0   0   0

&&

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

$$


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