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Area forecast discussion 
National Weather Service Spokane Washington
451 am PDT Wednesday Aug 27 2014

Synopsis...
a dry and warm conditions are expected through the work week. The
next storm system is forecast to arrive for the upcoming Holiday
weekend. This will result in breezy to windy conditions along with
an increased chances for showers and temperatures dropping below
normal.

&&

Discussion...

Today through thursday: weather pattern for the short term looks
rather benign as the region remains under the influence of a Flat
Ridge ahead of the next system. A minor impulse passes this
afternoon, but with limited moisture to work with, increased
clouds will likely be the end result. Models do advertise some
surface based cape and high levels total totals show some life,
but the mentioned lack of moisture and dry lower levels should
prohibit significant cumulus build ups along with any moisture
reaching the surface. The main feature of note will be the
increased winds especially in the Cascade gaps and also along the
ridgetops. Gap winds will reach breezy to windy conditions as the
cross Cascade gradient tightens throughout the day. Critical fire
weather thresholds do not appear to be reached this afternoon, but
the breezy winds would easily make fires more difficult to
manage. Tomorrow evening and overnight the lower valleys will
decouple from the flow aloft leading to less wind overnight for
these areas. The ridges will remain above the inversion allowing
for breezy conditions to continue throughout the overnight hours.

Moving into Thursday we will have another more significant wave
approach the region within the zonal flow pattern. The wave does
not look to reach our Cascades until the afternoon allowing for
calm morning conditions region wide. The afternoon is when we
start to see more moisture funnel into the area allowing for
increased clouds. For this forecast issuance I added slight chance
pops to the northern Cascades as enough moisture and forcing from
the wave should allow for some isolated showers in the afternoon.
Moisture remains rather shallow from examining soundings, so
significant convection at this point looks unlikely. Winds once
again pick up for the region as the low levels mix out and the
surface gradient tightens.

Temperatures peak today with good daytime incoming solar
radiation pushing highs into the mid 80s to lower 90s for most
valleys. Cloud cover brings temps back down tomorrow, but they still
remain slightly above normal. The next few days look to be the
last of the widespread 80s throughout the next week, so be sure to
get out and enjoy them. /Fliehman

Thursday night through Monday...models are consistent and in
general agreement in depicting a pattern shift during this period
from our current weak ridge with dry conditions and Summer-like
temperatures to a more unsettled...cooler and breezy pattern just
in time for the Holiday weekend. Thursday night and Friday look
dry and benign...although a weak transient system may bring an
increase in clouds with a ghost of a chance of showers over the
mountains near the Canadian border.

From Saturday Onward things become more active with a stronger
transient trough scheduled by both the GFS and European model (ecmwf) to move
through the region on Saturday...with the GFS bringing another
wave through on Monday...although the ec model has not bought off
on this scenario yet. Thus the forecast for Saturday and Sunday
promote reasonable confidence of a noticeably cooler and breezy
period with at least scattered showers and a few thunderstorms
mainly concentrated over the orographically favorable mountain
zones. There are no coherent frontal complexes or organized low
pressure systems that would suggest a rainy weekend anywhere...but
may locations outside of the deep basin will be under threat of at
least a brief shower mainly on Saturday...and on Sunday over the
Idaho Panhandle.

Monday presents the period of maximum forecast uncertainty with
the latest GFS advertising a more robust and showery trough
arrival...while the European model (ecmwf) suggests a fairly dry northwest flow
regime. Consistency over previous runs suggest the ec solution is
more reliable than the GFS...but this is getting awfully far out
in the forecast period to hang a hat on either solution at this
time. Thus small to middling chances for showers will remain over
the northern and eastern zones through Monday. Uncertainty
persists into the new work week with the GFS continuing a train
of weak trough passages while the ec suggests a dryer more zonal
flow regime.

The Main Point of forecast confidence for the Holiday weekend is
cooler than normal temperatures...breezy conditions and a chance
of showers especially on Saturday. /Fugazzi

&&

Aviation...
12z tafs: flat high pressure will result in mostly clear
conditions over all taf sites through 06z Thursday. Winds will be
light through 18z and then increasing afternoon mixing and a
system clipping the area will create locally gusty winds. Gusts in
the 15-20kt range are expected at kgeg, kcoe and kmwh between 19z
Wed and 03z Thu, and at keat 00z-12z Thu. /Fliehman

&&

Preliminary point temps/pops...
Spokane 87 60 82 58 83 59 / 0 0 0 0 0 10
Coeur D'Alene 87 56 82 56 83 58 / 0 0 0 0 0 10
Pullman 87 54 82 52 85 53 / 0 0 0 0 0 10
Lewiston 93 64 91 61 91 64 / 0 0 0 0 0 10
Colville 90 57 87 53 84 55 / 0 0 0 10 0 10
Sandpoint 83 52 82 52 80 53 / 0 0 0 10 0 10
Kellogg 83 57 80 55 80 56 / 0 0 0 10 0 10
Moses Lake 93 59 89 54 87 56 / 0 0 0 0 0 0
Wenatchee 92 64 87 60 86 61 / 0 0 0 0 0 10
Omak 93 57 86 59 85 59 / 0 0 0 0 0 10

&&

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

$$

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