Area Forecast Discussion
Issued by NWS Spokane, WA

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FXUS66 KOTX 292143

Area Forecast Discussion
National Weather Service Spokane WA
243 PM PDT TUE JUL 29 2014

Sunny and hot weather will continue over the Inland Northwest
through at least Friday. A gradual increase in clouds over the
next few days may knock temperatures down a few degrees, but mid
90s to low 100s will be common through the work week. The threat
for thunderstorms should increase over the weekend which may
knock temperatures down a bit more.


Tonight...The region will remain under the control of a strong
upper level ridge. Any of the monsoonal moisture and instability
working slowly northward through northern Oregon/central Idaho
will generally remain south of our forecast area. However there is
a very small chance of a shower or thunderstorm early this evening
over the southern Idaho Panhandle or the extreme southeast corner
of Washington due to the greatest potential instability combined
with the weakest convective cap. After sunset most of the activity
will taper off rapidly. It will be a dry and mild night once again
with poor relative humidity recoveries for most locations. Clouds
will increase late tonight near the Oregon border as a pool of
mid-level instability and moisture surges slowly northward. We do
not expect any precipitation to occur...however there could be a
small field of ACCAS clouds and perhaps a sprinkle after sunrise.

Wednesday through Friday: It is tough to get too excited about
precipitation chances for the majority of the Inland Northwest
Wednesday, Thursday, or Friday. The morning runs of the weather
models keep the lion`s share of the mid-level moisture and
surface based instability for thunderstorms over Oregon and
southern Idaho for the second half of the work week. The models
are in good agreement that a weak upper level disturbance off the
coast of northern California will dent the formidable upper level
ridge on Wednesday shunting a bit of mid-level moisture into the
Panhandle. The NAM looks to be the most aggressive generating
convection over the Idaho Panhandle mountains Wednesday afternoon
and evening, but it is tough to forecast more than a 20 percent
chance of showers and thunderstorms, even following the "moist"
NAM. Another marginal push of mid-level moisture is suggested on
Friday, possibly into the Cascades and southeast Washington. Once
again, it is tough to forecast more than 20 percent chance of
mainly terrain based convection.

Raw model output is generally hotter than MOS guidance Wednesday
through Friday. Given the relatively limited amount of cloud cover
expected, temperatures have been trended a bit hotter. 850mb
temperatures do not trend down much the second half of the week,
so it looks like a continuation of mid 90s to near 100 degrees for
most of the region. /GKoch

Friday night through Tuesday...Very odd interval of the forecast.
Pops were raised as at least three ECMWF runs hint fairly hard
that some remnant moisture and energy from post-tropical storm
Hernan gets ejected up from the East Pacific and into the
southerly/southwesterly flow on the west side of the longwave
ridge axis over the Western US. This leaves a good part of the
interval with increase pops and the QPF is something to ponder a
good time over. Many are noting some similarity in this solution
to what Hurricane Fabio did back around this same time period back
in late July of 2012. Discussion of this similarity last night
with other forecasters noted that remnants of Fabio were
associated with dropping 1.76 inches on Omak back on July 20,2012
along with 1.70 inches on Chelan and 0.92 inches Mazama on July
20,2012. Locations further east such as Spokane received 0.25
inches on July 20, 2012. Nobody is saying that this scenario will
repeat exactly as Fabio did in 2012 but it is worth looking back
and noting how much rain did fall back then. With this in mind as
far as Friday night through Sunday goes pops were increased some
with uncertainty noted as it is usually problematic to model
solution run to run consistency anytime tropical energy gets
ejected up into the mid-latitudes. Expectation is any/all
disturbances that may be remotely associated with remnant Hernan
moisture/energy will be to the east of the area and the prevailing
Southwest flow on the west side of the persistent longwave ridge
may steer additional shortwaves through either from the East
Pacific or up from the south but current model runs are not
aggressive in doing so. As such Sunday night through Tuesday pops
show a decrease and are lower in comparison to those over the
weekend. /Pelatti


18Z TAFS: VFR conditions expected at all forecast sites during
this period as strong ridge remains over the region. There could
be a weak disturbance moving across the OR/WA border after 12z
which could deliver increasing mid and high level clouds...but
little else. fx


Spokane        68  97  68  96  67  93 /   0   0  10  10   0  10
Coeur d`Alene  64  95  63  94  62  92 /   0  10  10  10  10  10
Pullman        58  95  58  94  59  91 /   0  10  10  10  10  10
Lewiston       71 102  71 101  71  98 /  10  10  10  10  10  10
Colville       59 102  58 101  59  97 /   0  10  10  10  10  10
Sandpoint      55  93  55  92  54  91 /   0  10  10  10  10  10
Kellogg        63  93  61  93  62  90 /   0  10  20  10  10  10
Moses Lake     66 102  64 101  65  99 /   0  10   0   0  10  10
Wenatchee      71 100  70 100  72  99 /   0   0   0   0  10  10
Omak           66 101  65 100  66  99 /   0   0   0   0   0  10


ID...Heat Advisory until 8 PM PDT this evening for Lewiston Area.

WA...Heat Advisory until 8 PM PDT this evening for Lower Garfield and
     Asotin Counties-Moses Lake Area-Okanogan Valley-Upper
     Columbia Basin-Washington Palouse-Wenatchee Area.


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