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000
FXUS66 KOTX 252127
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
227 PM PDT Sat May 25 2013

.SYNOPSIS...
Memorial Day Weekend is expected to be a little cooler than
average, and a series of weak upper level disturbances will bring
the potential for scattered showers through Monday. The moist,
showery weather pattern is expected to linger into late next week.

&&

.DISCUSSION...
Tonight and Sunday...After lingering showers die off this evening
mainly near the Cascades and northern mountains, attention will
then shift to a wave rotating around a closed low near the north
Washington coast. This wave will swing into western Oregon/southwest
Washington overnight tonight...then move slowly into the
Washington Cascades and southeast Washington during the day
Sunday. Models are in good agreement with this scenario.  As it
does so the closed low will open up into a weak negative tilt
trough. Increased diffluent southerly flow will increase the
chances for showers especially in the Cascades, as well as
southeast Washington, Lewiston area, Palouse, and Central
Panhandle Mountains where instability will be greatest. Uncapped
CAPE values of 200-500 J/KG could also spark a few thunderstorms
from the Blue Mountains in southeast Washington towards the
Central Panhandle Mountains in Idaho. Elsewhere less instability
and only weak lift will support a 20-30 percent chance of rain
showers. A weak thermal ridge lifts up into western Montana
clipping the North Idaho Panhandle Sunday afternoon which will
result in 6-10 degrees of warming compared to Saturday high temps.
JW

Sunday night through Tuesday...the upper low that has brought
several days of cool and unsettled weather to the region will
finally eject east into Montana Sunday night and Monday...but not
before dragging one last short wave through the southern fringes
of the low. This will result in continued showers across my east
and southeast zones Sunday evening. But don`t expect much of a
break in the weather. Enough moisture and instability will linger
through Monday for a chance of showers mainly tied to the higher
terrain outside of the Columbia Basin. No big changes in
temperatures are expected with highs remaining on the cool side of
normal.

The next weather system will move quickly into the region as an
occluded front late Monday and Tuesday. Moisture associated with the
warm front will stream into the region from the southwest. Not
much lift with the warm front but the large amount of moisture
that comes with it makes it prudent to keep the mention of
precipitation in the forecast for Monday afternoon and early
evening. The models are similar that the focus of the
precipitation will be with the cold front as it moves through the
region. The front looks to cross the Cascades from the west after
06z then slowly move east through the forecast area Tuesday
morning...before getting hung up across the eastern third of the
forecast area Tuesday afternoon. With the exception of the lower
east slopes and perhaps the deep basin just about all areas will
have a chance to pick up measurable precipitation...with the
northern and eastern mountains very likely to see a wetting rain.
The models are showing a negatively tilted trough just nosing into
southwest Washington Tuesday afternoon. It appears the best
instability will remain west of the Cascades for now and will hold
off on adding thunderstorms for now. /Tobin

Tuesday night through Saturday...cool and unsettled weather
associated with a negatively tilted trough will prevail for much of
the work week. The focus for precipitation will be eastern half of
the forecast area, and the northeast zones in particular, where a
boundary will stall. Draped from northwest to southeast, this
boundary will be a forcing mechanism along with favorable upslope
flow to bring a good chance of showers to the rising terrain north
and east of the Columbia Basin. As we get into next weekend, this
boundary will weaken as the upper low drifts off to the southeast.
This will allow drier and warmer conditions to push in from the west
and spread across the Inland Northwest for Friday into Saturday.

Beyond next weekend...Medium range models are hinting that an upper
level ridge may build over the eastern Pacific for the beginning of
next week, bringing warmer and drier weather for the first week of
June. /Kelch

&&

.AVIATION...
18Z TAFS: An upper level trough will remain over the Inland
Northwest over the next 24 hours.  Today showers will increase
mainly over the mountains but instability is marginal for
thunderstorms with none expected.  These showers will die off after
03z with the loss of daytime heating.  Another disturbance embedded
within this trough will spreading thickening cloud cover into the
region between after 14z Sunday especially KEAT/KMWH where a few
showers may develop.  The bulk of the showers should hold off til
after 18z Sunday.  JW


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        44  67  47  66  47  62 /  10  30  20  30  30  50
Coeur d`Alene  40  68  46  65  44  61 /  10  30  40  40  20  60
Pullman        40  64  45  66  45  60 /  10  50  40  20  30  50
Lewiston       46  69  50  73  51  67 /  10  50  40  20  30  50
Colville       39  73  46  70  45  68 /  20  20  20  50  20  50
Sandpoint      36  67  44  64  42  62 /  10  20  40  50  20  50
Kellogg        40  65  46  62  46  58 /  10  40  50  50  30  60
Moses Lake     44  68  49  72  50  70 /  10  30  20  10  30  30
Wenatchee      49  66  50  69  52  68 /  10  40  10  10  20  40
Omak           39  69  46  71  46  68 /  20  20  10  20  30  50

&&

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

$$