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000
FXUS66 KOTX 192137
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
237 PM PDT Sun May 19 2013

.SYNOPSIS...
Evening showers will begin to wind down as the sun sets and a
ridge heads into the region. By Monday the ridge will become
firmly established over much of the region providing a dry and
warm day before a strong storm system enters the region on
Tuesday. Tuesday`s weather system will bring a good threat of showers
and thunderstorms followed by significantly cooler temperatures.
cool and showery weather will envelop the region from mid- week
into the holiday weekend.

&&

.DISCUSSION...
.Tonight and Monday...Elongated upper level trough remains fixed
over the eastern half of the forecast area late this afternoon
per the latest water vapor loops. The best moisture per satellite
looks like it extends east of a line from Omak to the Moses Lake.
This region correlates fairly well with the best region of
instability per the Rapid Refresh model which shows MLCape values
between 100-300 j/kg mainly over the NE corner of Washington and
extending across most of the Idaho Panhandle. Showers and even a
thunderstorm or two will likely continue into the early
evening...especially over the NE quarter of Washington and the
northern half of the Panhandle...however since there is very
little if any trigger in the mid/upper atmosphere evident on
satellite things should taper off rapidly during the evening.
After the threat wanes...the focus will turn to an upper level
ridge axis meandering into the region from the SW. Plenty of dry
air is evident across of much of Oregon and western Washington and
this will track into the region later tonight and Monday. The
decreasing moisture will contribute to a drier forecast while
increasing stability will also work against any convection. The
one exception could occur tomorrow afternoon near the
Montana/Idaho border where residual instability and moisture could
trigger a shower during the afternoon. Model soundings also
suggest a small possibility of thunderstorms...but better chances
will likely occur east of the border as the ridge works into Idaho
during the day. fx

Monday night through Wednesday: We will transition from a dry and
above average temperature regime to a very wet and below average
temperature regime.

Monday night through Tuesday morning: A very strong closed upper level
low pressure system will move south down the coast line out of the
Gulf of Alaska. This will put the Inland Northwest under southerly
flow ahead of the cold front. The forecast will remain dry with
the exception of the cascade crest where starting Tuesday
morning they may start to see rain. Temperatures will remain at or
above average.

Tuesday afternoon through Wednesday: The low will push inland and
the chances of widespread rain will spread from west to east
starting Tuesday afternoon. Tuesday afternoon there may be enough
instability for an isolated thunderstorm ahead of the front across
extreme eastern WA and north ID. The front will push through early
Wednesday morning. Widespread rain can be expected everywhere. Have
increased chance of precipitation as well as how much liquid
precipitation we are expecting. Temperatures will plummet from
Tuesday to Wednesday. A 10 degree drop in temps across the
Cascades and a 20 to 25 degree drop in temps across Eastern WA and
north ID can be anticipated. Winds will be breezy from the
southwest 10 to 15 mph with gusts around 20 mph. Snow levels will
lower to about 4k ft by Wed with snow expected in the mountains. /nisbet

Wednesday night through Sunday...Confidence is high that the region
will be under a very slow moving upper level low pressure center
that will bring an abundance of clouds, unseasonably cool daytime
temperatures along with a good chance of precipitation for the
Inland Northwest during the extended forecast period. If there were
to be any breaks in the overcast during daytime heating, and this is
fraught with uncertainty, some convection would be possible. For
now, confidence is too low to add thunder to the weather grids.
/Kelch

&&

.AVIATION...
18z TAFS: VFR conditions expected to affect all TAF sites through
the period...although brief MVFR cigs will be possible through 20z
at COE due to the presence of convective cloud bases just below
030. There will be a threat of -shra at PUW...COE...GEG...and SFF
however the limited coverage suggests that if an airport is hit
the wet weather would be brief. Do not believe there will be any
thunder at any of the sites as best instability will remain over
NE WA. Skies will clear overnight at all sites with the upper
level ridge moving overhead. fx



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        46  72  51  76  44  51 /  10   0   0  20  90  90
Coeur d`Alene  45  71  46  76  45  49 /  10   0   0  10  60  90
Pullman        42  71  48  75  42  50 /  10   0   0  10  70  60
Lewiston       48  79  52  81  49  57 /   0   0   0  10  60  60
Colville       44  78  45  77  46  55 /  20   0   0  40  90  80
Sandpoint      42  72  44  76  45  52 /  20  10   0  20  70  80
Kellogg        41  69  50  76  45  47 /  20  10   0  10  60  90
Moses Lake     48  80  51  73  47  60 /   0   0   0  40  50  30
Wenatchee      49  78  53  67  46  57 /   0   0   0  50  50  30
Omak           43  78  47  70  46  58 /   0   0   0  70  90  60

&&

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

$$