Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 032318

Area Forecast Discussion
National Weather Service Spokane WA
417 PM PDT SUN MAY 3 2015


Warm and dry conditions will persist through Monday with
widespread 70s returning to the region. A strong cold front is
expected Monday night and will likely return our temperatures into
the 60s Tuesday. Cooler and breezy weather is in the forecast for
Tuesday. Spotty showers will be possible Tuesday and Wednesday
followed by the potential for gusty northeast winds Thursday and


Tonight and Monday: Shortwave upper level ridge will continue to
build across the Inland Northwest through Monday. Clear skies are
expected tonight with temperatures right around average for this
time of the year. Monday the upper level low currently in the
eastern Pacific will approach Vancouver Island. Sunny skies in the
morning will give way to some mid and high level clouds in the
afternoon across the Cascades. Light and variable winds tonight
will become a more pronounced southerly wind 5 to 10 mph in the
afternoon. Given the sunny skies and high pressure
dominating...temperatures will be about 10 to 14 degrees above
average Monday. A beautiful day expected with widespread
temperatures in the 70s, around 80 in the Columbia Basin and LC
Valley. /Nisbet

Monday night through Wednesday...The arrival of the tightly wound
closed low visible on satellite approaching the Pacific Coast will
drive the weather through this period. Latest model runs are in
decent agreement in handling the evolution of this arrival. The
upper low will bring a weak outriding wave through the Idaho
Panhandle Monday night with a small chance of showers and possibly
a random evening thunderstorm...but confidence is quite low for
this possibility given only weak and shallow instability and a dry
surface layer. More confidence accrues to the passage of a
moderate to strong surface cold front during the night which will
promote breezy and gusty conditions along with the likelihood of
much cooler temperatures on Tuesday.

The precipitation field Tuesday and Wednesday will probably favor
the western zones...the deep basin and Cascades for a change. The
upper low is expected to dig southward into Oregon by Wednesday
with a dry slot existing over the eastern zones and Idaho
Panhandle. Precipitation probabilities will be highest under the
cold pool aloft and dynamic support region under the track of the
center of the low as it drops south. Instability should be
sufficient for a few thunderstorms interspersed among scattered
valley/basin rain and mountain snow showers (with snow levels in
the Cascades running 3500 to 4000 feet). Wednesday
model confidence begins to decrease and if the low track is
slightly off by then...then the entire region...including the
eastern zones and panhandle could see at least isolated
showers...warranting slight chance pops over the entire forecast
area. /Fugazzi

Wednesday night through Sunday: A complex weather pattern is setting
up for the end of the week as three areas of low pressure
potentially influence the Northwest. Overall, models are in decent
agreement that these features will exist but continue to struggle
resolving how these features will or will not interact. The most
influential system will be the area of low pressure arriving
early this week (Tuesday). This low starts off near the WA/OR
border Wednesday night and begins to branch off from the mean
flow...migrating southward into CA/NV. Moisture within a
deformation axis on northeastern periphery of this low will likely
influence the region`s weather bringing periods of light
precipitation. Exactly where is up to debate. Forecast preferred
the GEM/ECMWF guidance which keeps most of the region dry under
breezy N/NE winds. Southeastern WA and the lower ID Panhandle will
carry the highest probability to be influenced by the deformation
precipitation. By the weekend, confidence continues to degrade as
an area of low pressure migrates toward the WA Coast and another
wave drops south down the Canadian Plains. Some model guidance
suggest there could be some phasing between the southern and
western systems, some suggest phasing of the southern and
northern, and others, no phasing at all. Loose agreement would
suggest the Pacific trof will be the most dominate leading to incr
southerly flow, warming temperatures. Precipitation chances carry
much lower confidence. /sb


00Z TAFS: Dry westerly flow aloft will keep the region mainly
cloud-free with VFR conditions at all TAF sites through 00Z
Tuesday. Winds will start to increase and become gusty late Monday
afternoon for the Cascade gap valleys and Columbia Basin ahead of
the next cold front. Isolated showers may affect the NE Blue Mts
south of KLWS Monday afternoon but confidence is low that any
showers will affect the KLWS terminal. /EK


Spokane        46  76  44  60  36  59 /   0   0  10  10  10  20
Coeur d`Alene  42  75  42  60  35  61 /   0   0  10  20  10  20
Pullman        38  74  41  58  34  58 /   0   0  20  20  10  30
Lewiston       45  81  49  66  39  64 /   0   0  20  20  20  30
Colville       34  78  45  65  37  65 /   0   0  10  20  20  30
Sandpoint      32  73  41  61  33  62 /   0   0  10  20  10  20
Kellogg        38  75  41  58  34  60 /   0   0  40  30  10  20
Moses Lake     41  80  44  66  37  65 /   0   0  10  10  30  20
Wenatchee      48  79  47  64  42  65 /   0   0  10  20  30  40
Omak           46  78  39  66  36  66 /   0   0  10  20  30  40


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