000
FXUS66 KOTX 160915
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
215 AM PDT Sun Jun 16 2013

.SYNOPSIS...
The chance for showers and thunderstorms will begin today over
the Cascades...and gradually broaden out to encompass the entire
inland northwest by Monday and Tuesday. high temperatures will
peak today and begin a cooling trend on Monday. Downright wet and
cool conditions will arrive by Wednesday...with a drying and
warming trend late in the week.

&&

.DISCUSSION...
Today and tonight: The Inland Northwest will be in a southwest
flow between an offshore low and ridge axis shifting over the
northern Rockies and in the path of a couple shortwave
disturbances. The most subtle shortwave will be lifting through
this morning. However it has little instability to work with and
it will continue to weaken as it encounters the ridge. The primary
area with a semblance of elevated instability is near the
Cascades. A slight chance of showers will continue here. Otherwise
look for some middle to high clouds.

Currently pivoting across 130W on the southeast side of the
offshore low, a second and comparatively stronger shortwave comes
into the western Washington and the Cascades later this afternoon
and tonight. It is driven in on a 60-90kt jet, the nose of which
comes into the Inland Northwest this evening. This pushes the
ridge axis east to the Continental Divide and places the Inland
Northwest in diffluent northeast side of the low, which is more
favorable for lift.

The mean southwest flow through the day will also bring mild air
and increasing moisture to the region, with PWATs ranging from 80
to 140% of normal from the Camas Prairie to the Cascades. Also
going into the afternoon, surface-based instability increases
across the region. Model agreement places the best SBCAPE across
the Cascades and northern mountains, as well as secondarily across
the Blue Mountains through the central Idaho. That includes the
Spokane area and Palouse. Values between 100-250 J/kg are
depicted. However, outside of the mountains, this is largely
capped. The approaching shortwave does not appear to reach the
region in time to take advantage of this instability. So this
afternoon the primary shower/thunderstorm threat will lay across
the Cascades through northern mountains, including the Waterville
Plateau, and the Blue Mountains.

By tonight, however, there is lingering elevated instability.
Just how much is not agreed upon. Yet with the incoming shortwave
there is enough to keep a threat of nocturnal showers and
thunderstorms going across the region. What agreement there is
continues to place the best threat around the Cascades, which will
be closer to the best lift in the LFQ of the jet and passing
shortwave. However most areas will see a threat of at least
isolated showers or storms through the night. /J. Cote`

Monday and Monday Night: As the Low off the Pacific slowly
progresses inland, southerly flow will draw warm moist air into
the region. Rain showers with possible thunder will mainly be in
the Northern Mountains as virga from high based cells will affect
the Columbia Basin. With increasing moisture and warmer mid level
temperatures moving into the region throughout the period, nocturnal
thunderstorms for the region are possible as lapse rates in the
mid levels range for 7 to 8 degrees c per KM through the evening
hours. High Temperatures will be 5 to 10 degrees warmer than
normal. /JDC

Tuesday through Wednesday...The incoming upper low works into the
region during this period. Very moist southerly difluent flow on
Tuesday will promote an increasing chance of hit-and-miss showers
and thunderstorms during the day...indeed Tuesday will bring the
best chance of general thunderstorm activity for the forecast
period. All models suggest moisture and instability will be well
established by this time...and models are sensing a wave
disturbance rounding the base of the upper low and passing
through the forecast area from south to north Tuesday afternoon
and Tuesday evening. This wave should be adequate to kick off some
beefy thunderstorms across the forecast area during the afternoon
and evening hours. Overnight the wave may become a slow or
stationary deformation axis over which showers will become
widespread and perhaps even universal at least over the northern
and eastern reaches of the forecast area as the parent upper low
arrives. High temperatures on Tuesday will probably begin to
return to near normal readings as increased clouds filter the sun
and the surface thermal trough retrogrades eastward into Montana.

By Wednesday the here-to-fore hit and miss showery and thundery
pattern will evolve into a predominantly light rain or frequent
shower regime with a few thunderstorms continuing to prowl the
region as the upper level cool pool maintains instability despite
cooler surface temperatures. Temperatures on Wednesday are almost
certain to be much cooler if this precipitation forecast comes to
fruition...and given the model consistency and latest run`s
agreement...this wet pattern has become a fairly high confidence
forecast.

Wednesday night through Saturday...the offending upper low slowly
migrates through the region during this period as depicted by
both the latest GFS and ECMWF models. While Wednesday looks like
the best chance/most widespread precipitation period...wrap around
moisture hooking around the north edge of the low and returning
into the region from the west will probably be sufficient to
justify continued shower activity through Thursday and
Friday...but more focused over the orographically favorable
northern and eastern mountains. By Saturday this activity will be
diminishing but probably still present especially over the Idaho
Panhandle. High temperatures will begin to recover back to near
normal values by Saturday. /Fugazzi

&&

.AVIATION...
06Z TAFS: High based showers and thunderstorms have formed along a
mid-level front late this evening across north-central OR into
south-central WA. These showers will continue to form further north
later tonight are expected to impact KEAT and KMWH after 10Z.
Chances for thunderstorms with these showers will be low by this
time. A better chance for thunderstorms will be possible across the
Cascades Sunday afternoon as another shortwave trough of low
pressure swings into the region around a deep upper level low
pressure system circulating in the eastern Pacific. These
thunderstorms may begin to impact KEAT and KMWH late in the
afternoon into the evening hours; however, confidence is low at this
time for thunderstorms, but will see a good chance for some high
based showers into the western basin. /SVH



&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        84  56  81  55  75  50 /   0  20  20  30  30  80
Coeur d`Alene  83  54  81  54  78  50 /   0  20  20  30  30  70
Pullman        84  49  79  49  71  46 /   0  20  10  30  20  70
Lewiston       91  58  88  56  81  54 /   0  10  10  30  20  60
Colville       87  53  85  52  79  50 /  10  20  40  30  50  80
Sandpoint      82  50  81  52  81  48 /  10  20  30  40  30  70
Kellogg        80  55  79  54  80  50 /   0  20  30  30  40  70
Moses Lake     91  60  86  58  75  53 /  10  30  20  40  40  50
Wenatchee      88  62  85  60  74  55 /  20  20  10  30  50  50
Omak           87  54  85  54  77  52 /  30  30  20  40  60  60

&&

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

$$