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000
FXUS66 KOTX 122149
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
249 PM PDT Wed Jun 12 2013

.SYNOPSIS...
The rest of the work week will be cooler than normal with the
threat of showers. Thursday will likely be the most active day for
showers and thunderstorms as an area of low pressure tracks slowly
over the region. Drier and warmer weather can be anticipated by
this weekend...with more unsettled conditions returning early next
week.

&&

.DISCUSSION...
Tonight in Thursday morning: The Inland Northwest will be under the
influence of southwest flow aloft as an upper level low spins over
northwest Washington. Daytime heating and low level instability has
led to a widespread cumulus field across the region. Radar does
show isolated showers over the higher terrain and this will
continue through early evening. Meanwhile, a mid level moisture
band coupled with a low level thetae ridge will slide
northeastward overnight, crossing extreme eastern Washington and
into central Idaho. Mid level instability will be lacking for any
nocturnal thunder but would see isolated to scattered showers along
and east of a line from Lewiston to Pullman to Coeur d`Alene overnight
into early Thursday morning.

Thursday afternoon through Friday...The main concern with this
portion of the forecast will be the chances for showers and
thunderstorms both Thursday and Friday afternoons. The trough
currently sitting off the pacific coast will move inland Thursday,
with more widespread showers and thunderstorms possible during the
afternoon. Precipitation is possible almost anywhere as the cold
pool aloft spreads east, but we are having a hard time going too
high on chances outside of the higher elevations in northern
Washington and the Idaho panhandle. Most forcing associated with
the trough of low pressure will be pushing east into Montana. The
best instability remains over the Idaho panhandle and the northern
Washington mountains, and this is where the highest chances will
be. Not a ton of moisture to work with, so not expecting high
totals, although slower movement to any storm may allow isolated
higher totals.

Chances begin dwindling from west to east Friday as the trough
slowly moves east. Kept higher chances over the Idaho panhandle
and adjacent areas of eastern Washington as colder temperatures
aloft should trigger new development Friday afternoon.

Concerning Father`s Day weekend, expect a warm up to above normal
temperatures. Ridging aloft will suppress any potential
thunderstorm activity both Saturday and Sunday, with perhaps some
increasing cloud cover near the Cascades late Sunday. ty

Sunday night through Wednesday...Models are continuing to support that
this could be a rather wet and unsettled period. The culprit in
this case will be a slow moving upper level low currently seen
near 50n/158w. Between now and Monday morning confidence is fairly
high that the low will drift from its current position to
somewhere just off the NW Oregon coast. Initially the positioning
of the low will allow moisture and subsequent instability to track
northward along the Cascade Crest and through the western Columbia
Basin. Precipitable water values are expected to surge above 150
percent of normal in the southerly flow ahead of the low as early
as Monday morning and spread across the remainder of the Inland NW
through the afternoon. The combination of the increasing
atmospheric moisture and cooling temperatures aloft will result in
deep instability which will likely set the stage for showers and
thunderstorms. If the GFS is correct...MUCAPE values should surge
into the 1000-1500 j/kg range from the northern Cascades to the
northern tip of the Idaho Panhandle with little if any CIN.
Similar values will also be seen along a SW-NE boundary extending
from the Blue Mountains to the Clearwater Mountains. Meanwhile
this instability will be paired with 0-6km shear values of
30-40kt. These values hint that some of the thunderstorms could be
on the strong side. However that`s providing the GFS verifies
these instability parameters. Also with no well-defined upper
level shortwave trough moving through this is far from a confident
event. The same parameters from the ECMWF are much less
impressive, but easily sufficient for thunderstorms. At this point
confidence is high that we will see showers and thunderstorms but
not confident enough yet to advertise a chance of strong
thunderstorms. Another point of confidence is a chance of moderate
to heavy rainfall with the showers and storms given the
introduction of significant moisture from the south.

For Tuesday and Wednesday...the low is forecast to continue its
slow easterly drift. By Tuesday afternoon the center of the upper
level low is forecast to lie over the Columbia Basin per the GFS
or a much slower solution near Astoria per the Canadian and ECMWF.
By Wednesday confidence begins to falter a bit more as the GFS
takes the low into southern Alberta while the Canadian and EC
solutions keep it closer to the Inland NW. Given the strength of
the downstream ridge over central North America and better
consensus from the ensemble means, the fast solution is not the
one to follow. This means most of the region will be subject to a
good chance of showers and thunderstorms each day. We will trend
the pops upward through the period...and go with numbers higher
than climatology for all periods. For simplicity sake...pops will
generally be in the chance category for most of the Inland
NW...but if model consistency holds...we`d be better suited going
with widespread likely pops. The chances for strong thunderstorms
will likely wane through the period as the shear weakens
considerably with the low migrating over our forecast area. Given
all the moisture and the considerable cloud cover to go with it,
temperatures will likely struggle to reach the climatological
normals. fx

&&

.AVIATION...
18Z TAFS: Best chance for afternoon showers will be over the
ridges around KOMK to KCQV through 03z. A mid level cloud band
will linger from KLWS-KPUW-KCOE and eastward into north Idaho
through the afternoon, but after 06z anticipate isolated to
scattered showers to develop with embedded thunderstorms.
Meanwhile expect scatted cumulus build ups through the day. Local
gustiness will develop with speeds up to 20 mph. /rfox.


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        47  67  45  68  47  76 /  10  40  30  20  10  10
Coeur d`Alene  47  66  45  67  44  74 /  10  40  30  20  10  10
Pullman        43  65  42  67  44  77 /  20  30  30  20  10  10
Lewiston       51  71  48  75  49  85 /  20  30  30  20  10   0
Colville       46  71  45  73  45  81 /  10  40  40  20  10  10
Sandpoint      44  65  43  65  41  75 /  20  50  40  30  10  10
Kellogg        46  61  43  64  44  72 /  30  50  40  30  20  10
Moses Lake     48  73  48  76  49  83 /  10  20  10  10   0   0
Wenatchee      51  71  51  73  54  82 /  10  20  10   0  10   0
Omak           47  72  47  74  48  81 /  10  30  20  10  10  10

&&

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

$$