Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 312340
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
440 PM PDT MON AUG 31 2015

.SYNOPSIS...
Light rain in the northern mountains will slowly creep north
tonight. Tuesday will feature dry and breezy conditions. A weak
cold front brings a reinforcing shot of cooler air Wednesday
along with a chance for showers and gusty winds. A cooler and
showery weather pattern will linger over the region late week and
into the weekend.

&&

.DISCUSSION...

Tonight through Wednesday night:  A broad upper-level trough is
anchored over the Pac NW today and will remain in place through
this period. A corridor of rich mid and upper level moisture
currently coming inland along the base of the trough is sprawled
across the northern mountains. Over the next 12-24 hours, another
shortwave will dig into the backside of the trough and back
midlevel flow to the south. This will nudge the clouds and light
rain northward into southern BC and Tuesday will feature light to
locally breezy winds, warmer temperatures, and dry conditions. By
Tuesday night and Wednesday, the aforementioned shortwave dropping
into the trough will round the base and eject inland. This will
usher the next cold front through the Inland NW. The front will
pick up the lingering moisture over southern BC and bring it back
to the southeast. Some showers will get squeezed out along the
front but precipitation amounts will be rather light. The northern
and eastern mountains carry the highest threat for up to a tenth
of rainfall with most other locations getting between a trace and
few hundredths. The frontal boundary stalls somewhere between NW
Montana and NE Oregon keeping clouds and threat for showers in the
vicinity of far southeastern WA and the lower ID Panhandle.
Behind the front, the atmosphere will become increasingly unstable
increasing the threat for afternoon mountain showers. A majority
of this activity will be confined to the International Border and
Cascade Crest.

Temperatures will remain below normal with afternoon highs in the
60s and 70s. Overnight lows will be in the 40s and 50s tonight and
Tuesday night then cool Wednesday night. Isolated pockets in the
northern mountains could dip down in the mid 30s. /sb

Thursday through Friday night: The area of low pressure in the
northern portion of the Gulf of Alaska and in northern BC will
slowly drift south over the region. This will keep temperatures
below normal and keep the weather unsettled. Friday looks to have
the better chances for showers and thunderstorms across the
region. P-wats off of the models are only up half an inch. These
values are relatively low, which would mean that storms are not
expected to be proficient rain producers. However, the steering
flow will be weak, especially over the northwestern portion of the
forecast area. The atmosphere also does not look like it will be
too unstable, but there is a potential for some storm to achieve
deeper convection with heavy downpours possible. The time of day
for thunderstorm development would be in the afternoon. There is a
small chance that a thunderstorm may drift over a fresh burn scar
or burn scar from recent years; although chances are low, the
heavy rain may trigger some minor mud flows or debris flows or
possibly a flash flood if storms are nearly stationary. The risk
doesn`t look great at this point do to the lack of moisture
available, but will be a situation we will need to monitor as we
head through this week. Low temperatures may get a bit chilly
with some colder spots lowering into the mid 30s during the
overnight hours. Confidence is low as far as how cold we may get
since I do expect there will be some cloud cover over the region,
which would limit our radiational cooling potential. /SVH

Saturday through Monday: Models are agreeing that a Low will pass
South the region and bring precip to the region. The models differ
on the amount and location of this rainfall. The bast chances for
rainfall is expected to be in the Blue Mountains and Idaho
Panhandle through the weekend. The Cascades and Northern
Mountains could see some rain on Saturday. Temperatures are
expected to remain on the cool side of normal for this time of
year. /JDC

&&

.AVIATION...
00Z TAFS: Areas of light rain will continue across the Cascade
crest and far northern WA tonight but will not impact any TAF
site. Smoke models still bring some smoke from near Pomeroy
toward the KPUW- KLWS corridor and if this is the case, nocturnal
inversions could result in some reductions of VIS until morning.
Confidence is low due to uncertainty with burning behavior of that
NE Oregon wildfire. Some smoke is expected to settle into the
valleys of northern WA and northern panhandle of Idaho. Otherwise...
mid and high clouds will persist. Breezy early evening winds will
diminish overnight but will become breezy again Tuesday afternoon.
/EK

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        50  75  52  68  44  66 /  10  10  20  10  10  20
Coeur d`Alene  50  74  52  67  43  65 /  10  10  20  20  10  20
Pullman        47  76  50  68  42  66 /  10   0  20  30  10  20
Lewiston       55  83  58  73  49  71 /   0   0  10  20  10  20
Colville       49  74  50  70  40  68 /  20  10  20  30  10  30
Sandpoint      46  72  48  66  40  64 /  20  10  20  20  10  30
Kellogg        46  73  49  65  41  63 /  10   0  20  40  20  20
Moses Lake     53  77  53  73  47  71 /  10  10  10  10  10  10
Wenatchee      54  75  56  71  50  70 /  10  10  10  10  10  10
Omak           48  75  49  72  43  69 /  10  20  20  20  10  20

&&

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

$$


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