117 
FXUS66 KOTX 061129
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
429 AM PDT Mon Sep 6 2021

.SYNOPSIS...
The region is expected to be dry and warm this Labor Day and
will continue through mid week. Locally breezy conditions are also 
expected today through the Cascade Gap valleys. Changes in the 
weather pattern are expected mid week with the potential for 
mountain showers, isolated thunderstorms, and breezy winds.

&&

.DISCUSSION...
Monday and Tuesday: 
Early morning water vapor satellite imagery
shows the shortwaves moving through British Columbia along the
WA/ID border sending mid and high clouds across northern
Washington and northern Idaho. The surface pressure gradient along
the Cascades remains tightly packed and as a result breezy to
gusty winds through the Cascade Gaps are still evident early this
morning. Expecting these winds to slowly subside through mid day.
As the ridge begins to build across the west coast, the drying and
warming trend will begin to enhance. The low-level moisture from
the marine layer that is spilling over the Cascades this morning
will quickly erode. Westerly flow aloft today will advect wildfire
smoke from the fires in the Cascades eastward, depending on the
fire activity. Skies will be mostly clear or see some high cirrus
streak across the region.

*Return of smoke to the region.

Tuesday as the ridge strengthens over the Great Basin, centered to
our south- southeast, the flow will turn more southwesterly. This
will act to warm temperatures to about 10-12F above seasonal
normal through Wednesday. The downside to this flow pattern is
this will draw up more wildfire smoke from the ongoing wildfires
in Oregon and California. Smoke models all advertise this
blanketing of total smoke Tuesday through late week, with some
clearing possible late Wednesday and again Thursday but returning
Friday. 

*Thunder potential

A shortwave will track along the Oregon coast late Tuesday and
bring increasing instability and moisture into the Cascades
through Wednesday. Models have continued to hint at this feature
moving north through the Cascades and into Canada bringing
moisture and limited instability. The more recent model guidance
is now hinting at a bit more instability and dynamics with this
wave. Lapse rates look a bit more healthy on the east side of the
Cascades with a bit more shear available. We have added thunder
chances to the forecast with the more recent model updates and
feel the potential is there, our confidence just remains a bit
low. Timing for precip and thunder chances will be overnight
Tuesday into the morning hours on Wednesday from about the
Kittitas Valley north through the Okanogan Valley. /Dewey

Wednesday through Sunday: Remnants of an upper level low off the 
California coast eject and pass over Eastern Washington and North 
Idaho in the provided southwest flow. Enough moisture and 
instability to keep a small mention of thunder over parts of the 
Cascades along with some showers. The southwest flow continues but 
flattens out some and is coupled with a cold front passage Thursday 
with its influence felt mostly by breezy/gusty westerly winds. 
Friday and on through the weekend the flow is more a flat 
progressive zonal type which may allow disturbance passage however 
efficient shadowing by the Cascades will limit any pops for minor 
light precip to the vicinity of the Cascade Crest and some parts of 
the Blue Mountains up into the Central Panhandle Mountains of North 
Idaho. Of particular concern with this weather pattern is how much 
smoke/haze may linger in and over the area. Have kept a strong 
wording of haze Wednesday and into part of Thursday but when upper 
level flow becomes less from the southwest and more zonal (westerly) 
it should lose potential to bring up smoke from fires in Northern 
California and Oregon so haze is not mentioned Thursday night night 
and over most of the weekend. Forecast temperatures show a general 
and gradual cooling trend yet remain on the warm side of climo. 
/Pelatti


&&

.AVIATION...
12Z TAFS: Main aviation concerns for Labor Day will be smoke from
area/regional wildfires. The dry and breezy weather pattern has 
perked up fire activity and smoke production in the Cascades, 
resulting in smoke being drawn into central and eastern 
Washington. This will occasionally reduce visibilities to MVFR 
thresholds. A shift in the weather pattern Monday night into 
Tuesday has the potential to allow a lot more smoke intrusion from
the south into the aviation area, resulting in more widespread 
haze and visibility reduction. /Dewey


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        82  51  87  54  87  55 /   0   0   0   0   0   0 
Coeur d'Alene  80  50  86  54  87  54 /   0   0   0   0   0   0 
Pullman        79  47  87  52  85  51 /   0   0   0   0   0   0 
Lewiston       88  56  94  61  93  61 /   0   0   0   0   0   0 
Colville       81  45  86  48  86  48 /   0   0   0   0   0   0 
Sandpoint      77  45  82  48  82  49 /   0   0   0   0   0   0 
Kellogg        78  55  85  59  84  58 /   0   0   0   0   0  10 
Moses Lake     83  49  89  56  89  53 /   0   0   0   0   0   0 
Wenatchee      84  59  88  65  87  61 /   0   0   0   0  10   0 
Omak           85  54  89  58  88  57 /   0   0   0   0  10   0 

&&

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

&&

$$