Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 240954
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
254 AM PDT TUE MAY 24 2016

.SYNOPSIS...
Precipitation will become more showery today over the Idaho
Panhandle as low pressure slowly moves out of the region.
Wednesday will be the warmest day of the week with temperatures
in the 70s and the potential for thunderstorms in Idaho and
northeast Washington. The Memorial Day weekend will likely be
chilly and showery with the arrival of another slow moving low.

&&

.DISCUSSION...

Today through Wednesday night...General longwave trof remains in
place over the forecast area through this time interval. Significant
synoptic scale features have residing in the trof and contributing
to the prolonged interval of wet weather or Eastern Washington and
Northern Idaho. These synoptic features include a low pressure
system centered over Southern Central Canada which has been been
very slow to exit to the east and away from the area. Instead the
low has remained in close proximity and disturbances and moisture
rotating around its backside have kept the weather over a good
portion of Northeast Washington and Northern Idaho wet. Consensus is
that on Wednesday night low should be far enough to the east and
away from the area to not be an influencer of sensible weather for
the forecast area. Until that time the forecast continues to have
some mention of unsettled weather, some in the form of
thunderstorms, today through Wednesday evening. It should be noted
further that the expected storm motion for today is rather slow with
storms moving south at 5 mph or less. This is a concern because a
slow moving shower or thunderstorm has a higher likelihood of
producing localized heavy rainfall. With this slow storm motion in
mind the forecast text wording notes the hazard that some
thunderstorms may produce heavy rainfall. /Pelatti

Thursday: The broad longwave trough over the Western U.S. will
reload Thursday and Friday as another upper low dives down the
coast of British Columbia and settles over Washington on Friday.
Thursday could be the driest day of the week for the Idaho
Panhandle which has been soaked in recent days. Much of Bonner and
Boundary counties and parts of Shoshone county received 1 to 3
inches of rain since Saturday. Widely scattered showers may still
be possible on Thursday over the mountains of the Panhandle, but
precipitation chances will become more focused over British
Columbia and northwest Washington Thursday with low pressure
moving down the B.C. coast. Increasing onshore flow on Thursday
will produce breezy conditions along the East Slopes of the
Cascade as cooler air spills through the Wenatchee and Kittitas
Valleys as well as Lake Chelan and the Methow. Gusty winds will
likely peak early in the evening with localized gusts in the 25 to
35 mph range.

Friday: It looks like a return to showery and cool weather Friday.
The evening runs of the GFS and ECMWF are in good agreement that
the 500mb low will be squarely over Washington Friday afternoon.
If these model runs verify, the most concentrated shower activity
will occur over the mountainous regions of north central and
northeast Washington. The air mass will be quite chilly with 500mb
temperatures dipping to roughly -25C. An air mass that cool won`t
support high precipitable water values, but locally heavy rain may
still be a concern. Friday won`t be a text book heavy rain
scenario for burn scar flooding, but it will be a day to keep an
eye on. It looks like there will be ample instability for
convective showers, and cell motion has the potential to be slow
given the lack of mid-level flow under the heart of the upper
low. The abundance of clouds and showers under the cold core low
will make for a damp and chilly day with many areas in northeast
and north central Washington struggling to get out of the 50s
Friday afternoon. Snow levels will be as low as 4500 to 5000 feet
with brief slushy accumulations possible in the high Cascades and
possibly around Sherman Pass.

Memorial Day Weekend: Mother Nature is not going to cooperate with
the unofficial kick-off of summer. Residents of the Inland
Northwest have experienced many chilly and showery Memorial Day
weekends, and 2016 looks to serve up another one. If you have
plans to camp or spend time at the lake this weekend, bring the
rain gear. At this time, Saturday has a good chance of showers
especially over the mountainous portions of the Panhandle and
northeast Washington. Sunday doesn`t look much better with the low
languishing over the region. Hopefully, we can salvage Monday. The
GFS is more optimistic than the ECMWF for less shower activity
Monday. /GKoch

&&

.AVIATION...
06Z TAFS: An upper level low pressure system will remain nearly
stationary over southern Saskatchewan through Tuesday afternoon
with moisture continuing to wrap around into the region. Lingering
showers will continue to develop over the Northeast Mtns and over
the ID Panhandle tonight. A brief period of stratus is expected
in the morning at KGEG, KSFF and KCOE. Showers will expand in
coverage during the day on Tuesday as the atmosphere destabilizes
with afternoon heating. Embedded thunderstorms will be possible,
but coverage will be isolated and may impact the KGEG, KSFF, KCOE
and KPUW TAF sites, but confidence is very low. /SVH


&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        66  49  70  48  67  44 /  50  40  30  20  10  10
Coeur d`Alene  63  47  68  48  66  44 /  70  60  40  30  10  10
Pullman        63  46  66  45  64  43 /  40  30  50  20  10  10
Lewiston       69  52  73  51  70  48 /  30  30  30  10  10  10
Colville       69  46  73  46  70  45 /  60  50  50  30  20  30
Sandpoint      62  44  67  47  64  43 /  70  50  50  40  20  20
Kellogg        59  43  63  44  59  40 /  80  60  60  40  20  20
Moses Lake     74  49  77  49  74  47 /  10  10  10  10  10  10
Wenatchee      72  53  76  52  72  49 /  10  10   0  10  10  10
Omak           73  50  76  49  74  47 /  30  20  10  10  20  30

&&

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

$$


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