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Area forecast discussion 
National Weather Service Spokane Washington
243 am PDT sun Sep 21 2014

Synopsis...
strong high pressure will provide a generally clear...warm and
dry rest of the weekend for the inland northwest. The new work
week will start out with continued above normal temperatures...but
a weak cold front will bring a chance of showers starting Monday
night. From mid-week Onward an approaching deep trough will
increase the probability of rain with cooler temperatures.

&&

Discussion...
today through monday: a ridge of high pressure will keep the
weather over the inland northwest unseasonably warm and dry.
Temperatures running about 2 to 5 degrees warmer than yesterday,
making it the warmest day of the week. North and east winds will
become lighter by afternoon and evening. By tonight, the upper
ridge axis shifts east and allows a stream of high level moisture
to creep northward from Oregon. This moisture should reach the
Cascades by Monday morning as a weak shortwave ripples through the
flow. This will be the start of the upper ridge breakdown. Expect
a slight chance of showers to develop over the Cascades Monday
morning as the moisture profile deepen and then the chance of
showers shifts across the northern mountains through the day and
evening. Instability looks to be capped so will keep mainly
showers in across the area. The exception would be across
southeast Washington into the central Idaho Panhandle where there
could be the potential of lightning. It will continue to be mild
with the low level thermal ridge lying over the area. Low level
winds will shift to southwesterly by Monday afternoon as the
shortwave passes. /Rfox.

Mon nt through thur nt: with a weak wave still over the area Mon
nt, we kept a small chance of rain showers for mainly the Idaho
Panhandle. Confidence is low that this short- wave will be an
efficient pcpn producer, but model guidance does show a decent
signal for the possibility of high- based convective pcpn tues
morning. The European model (ecmwf) has been the wettest with this feature
compared to previous NAM and GFS runs. However, the latter models
have trended wetter. A slow- moving cold front is expected to
make landfall tues nt and Wed morning along the Pacific NW coast.
As it does, the low level flow backs to the southeast and helps to drive
an ill-defined warm front north... which puts southeast WA and the cntrl
Idaho Panhandle in the warm sector south of the front by late
tues. This will keep the fcst warm and sunny. We've been favoring
a slower trend of the cold front as far as its ewd progression
based on model trends and pattern recognition applied to the
north-south shearing offshore trough. The downstream effects of
this shearing will be a more meridional steering flow over ern WA
and north Idaho, leading to a more persistent thermal ridge and warm,
dry wx likely extending into Wed for all of north Idaho and far ern
WA. Confidence is increasing that this stalled front will not make
much eastward progress... likely not reaching the Idaho Panhandle
until thurs. It's not until thurs that we see the front become
more progressive, leading to a more widespread pcpn threat for
all of ern WA and north Idaho. Even with the slight chance of thunder
for thurs, pcpn amnts should only be a few hundredths for lower
elevation towns. Bz

Friday through sunday: a slow moving trough will be pushing
through the region during this period. It is expected to begin
Friday afternoon and exit by Sunday morning. The moisture
associated with system is fairly light. Most of the region could
see some amount of precip. Temperatures will be on an up swing
during this period. The highs will be around the upper 60s for
Friday and near mid 70s by Sunday. /Jdc

&&

Aviation...
06z tafs: high pressure will promote dry and VFR conditions at
taf sites, with light diurnal winds. /J. Cote'

&&

Preliminary point temps/pops...
Spokane 88 57 85 58 82 56 / 0 0 10 20 10 0
Coeur D'Alene 87 53 85 55 81 55 / 0 0 0 20 10 0
Pullman 89 52 84 55 83 55 / 0 0 10 20 10 0
Lewiston 92 61 90 61 88 61 / 0 0 10 20 10 0
Colville 88 49 87 52 83 52 / 0 0 10 30 10 10
Sandpoint 83 46 80 50 78 50 / 0 0 0 20 20 10
Kellogg 85 54 81 55 80 55 / 0 0 0 20 20 10
Moses Lake 91 56 90 56 83 58 / 0 0 10 10 0 10
Wenatchee 91 64 88 61 81 61 / 0 0 10 20 10 20
Omak 91 55 87 56 82 57 / 0 0 10 20 10 20

&&

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

$$

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