Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 031728

Area Forecast Discussion
National Weather Service Spokane WA
1028 AM PDT WED JUN 3 2015


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.


Today through Thursday: The Inland NW 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 WA and ID this
morning and evening. A third shortwave pivots into the northern
Cascades tonight into Thursday morning, before swinging toward
northeast WA and north ID 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 WA and ID 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 WA 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
BC. 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 CA 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


18Z TAFS: Upper low pressure and waves rounding it will bring
mostly cloudy skies with generally VFR conditions through 18z
Thu. Although enough boundary layer moisture remains across
southeast WA into the Idaho Panhandle that local MVFR CIGS will
persist through 20z including KPUW and possibly KCOE. The low
pressure system will also bring showers to the region as well as a
slight chance of thunderstorms. Most of these will be diurnally
driven with the best chances over the northern mountains. With
only isolated shower coverage around the TAF sites used VCSH. JW


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



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