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Area forecast discussion 
National Weather Service Spokane Washington
433 am PDT Wednesday Jun 3 2015

Synopsis...

Cool and showery weather lingers over the inland northwest
through today, with the best chance for showers in the
mountainous regions of the Idaho Panhandle and northern
Washington. The main shower threat retreats to further into the
mountains Thursday. Much warmer weather is expected Friday into
the weekend as a high pressure ridge returns to the region.
Saturday, Sunday and Monday will feel like Summer, with afternoon
temperatures in the mid 80s to low 90s.



&&

Discussion...
today through thursday: the inland northwest will remain under a mushy
trough with some chance of showers and thunderstorms, especially
around the mountains in the afternoon. In general, however, most
of the period will be dry. But let's talk briefly about the
precipitation threat. In the southwest flow on the eastern side of
the trough a couple shortwave tracks by southeast Washington and Idaho this
morning and evening. A third shortwave pivots into the northern
Cascades tonight into Thursday morning, before swinging toward
northeast Washington and north Idaho Thursday afternoon. This evolution will
work with some pockets of mainly afternoon instability to bring a
shower and thunderstorm threat. For this afternoon the best threat
will be across the northern Washington and Idaho Panhandle mountains, as well
as from The Blues into the Camas Prairie. The Cascades, the
Columbia Basin into the Spokane/c'da area and Palouse/l-c valley
will only see a slight/isolated threat. For Thursday afternoon
the best threat will be across the northern Washington through northern
Panhandle mountains with that third shortwave, with smaller
chances lingering around The Blues and central Panhandle
mountains. Temperatures look to be similar this afternoon to
yesterday, or a degree or two warmer. Conditions continue to warm
a bit into Thursday. /J. Cote'

Thursday night through Sunday night...a significant transition will
begin during this period as the unstable trough of the past week
or so gives way to a strong upper level ridge. The trough which
covers most of the pacnw right now is expected to dig south into
Southern California by Thursday afternoon with a well defined
upper level ridge gradually folding over Washington and southern
British Columbia. This will deliver a significant warming and drying trend to
the region but the question is how quickly will things dry out.
There are some model differences on Friday with the GFS holding
onto some decent potential instability over the Cascades and all
the other models placing the instability over central Idaho. Model
soundings in these areas suggest it will be possible to see some
isolated convective activity, however the upper level support and
moisture for such activity is lacking, especially over the
Cascades. We will keep a small chance of thunderstorms in the
forecast however if we see more model runs in the future limiting
convection we can likely safely remove the mention from the
forecast. The threat will diminish even further on Saturday and
Sunday as the ridge gains strength and 500 mb temperatures climb
significantly putting an effective cap on deep convection.

The main story for this period won't be the chances of
precipitation, but rather that of very warm-hot temperatures. The
model guidance is rather consistent on warming the 850 mb
temperatures each day and by Sunday we will be faced with readings
in the 22-25c range, which is on par with Summer time temperatures
with highs in the 90s, and even some triple-digit heat possible
over the basin. The MOS guidance might not be going warm enough
based on a similar setup to June 2007. The last time the Spokane
area saw temperatures this warm this early in the year was on June
3, 2007. Model soundings on that day showed 850 mb temperatures on
par with if not slightly cooler than what is being currently
forecast. Consequently we went with the warmest guidance and that
may not be warm enough. . although these temperatures are hot,
they aren't record setting over most of the forecast area. The
exceptions might occur over the lower Columbia Basin, Wenatchee
area, and the Cascade valleys. The warming trend will then
continue into the work week. Fx

Monday through wednesday: the period will be dominated by a
stable ridge pattern. This will continue the dry, warm trend from
the weekend. The influence of the northern California low has decreased
from the previous runs and diminished the chance for the of precip
in the region. Temperatures are still expected to be above normal
with ranges of the mid 80s to low 90s expected. /Jdc

&&

Aviation...
12z tafs: upper low pressure and waves rounding it will bring
mostly cloudy to cloudy and generally VFR conditions. Some lower
level moisture spreading up through southeast Washington may briefly
produce some MVFR/IFR stratus this morning, but confidence leans
toward this not being a significant issue around taf sites.
Satellite will be monitored. Otherwise widely scattered to
isolated showers are possible. The main taf sites that may have
a risk will be around eat/mwh/Coe/puw/lws in the afternoon and
before sunset. Some thunder is also possible, with the best threat
across the northern and eastern mountains and taf-wise the best
threat will be near Coe/lws before sunset. /J. Cote'




&&

Preliminary point temps/pops...
Spokane 69 49 74 53 81 57 / 20 20 10 0 10 0
Coeur D'Alene 68 47 73 50 80 54 / 30 20 10 0 10 10
Pullman 67 44 71 48 78 51 / 20 20 10 0 10 0
Lewiston 74 51 78 54 84 58 / 40 20 10 0 10 10
Colville 70 47 76 50 83 53 / 50 30 30 10 10 0
Sandpoint 68 45 73 48 79 52 / 50 30 20 10 10 10
Kellogg 68 43 73 47 79 49 / 40 30 10 10 10 10
Moses Lake 75 50 79 53 87 59 / 20 10 10 0 0 0
Wenatchee 74 55 80 58 88 64 / 20 20 10 0 0 0
Omak 72 49 78 51 87 55 / 50 30 20 10 0 0

&&

Otx watches/warnings/advisories...
Idaho...none.
Washington...none.
&&

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