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Area forecast discussion 
National Weather Service Spokane Washington
453 am PST Monday Feb 8 2016

Synopsis...
strong high pressure will develop today and persist into
Wednesday. Dry and mild conditions are expected for the first half
of the week. A more progressive and unsettled pattern will return
late this week bringing a chance of light rain Thursday in the
Cascades and over the rest of the region Friday through the
weekend.

&&

Discussion...
today through Tuesday night...an extremely strong upper level
ridge will continue to influence the weather through this period.
Weather anomaly charts continue to show this setup as an extreme
event both in terms of 850, 700, 500, and 200 mb heights as well
as temperatures at 850 and 700 mbs. 500 mb heights are expected to
near 586 dm which and more typical of heights seen at the
beginning of may. Also if we see The Heights exceed 580 dm it will
be definitely be the highest reading we have seen at the beginning of
February and if we exceed 580.2 dm it will be the highest in the
history of the month for Spokane. Upper air records for Spokane go
back to 1948! So while this data is fascinating for a
meteorologist, what does it mean for our weather today? It
translates to more fair and dry weather, but it also suggests we
will see inversions growing stronger than yesterday. Eventually
this will translate to fog and stratus in the valleys, but as of
215 am, we have yet to see any blossoming on the fog product. We
suspect the fog will be rather patchy today, but if it were to
form, the best chances will occur over the northern valleys based
on the lowest winds and the highest relative humidity levels.
Temperatures will be a little milder than yesterday over most
locations however with the stronger inversions expected today,
that warming may not be realized everywhere. For the most part we
expect to see high temperatures in the upper 30s and 40s in the
valleys, with some lower 50s possible over the lower Columbia
Basin and Lewiston area.

For tonight and into Tuesday night the upper ridge is forecast to
shift east of the Cascades with even stronger subsidence
inversions expected. Based on the low-level wind forecast combined
with a trend toward increased saturation in the boundary layer we
expect to see increased fog and stratus trapped in the valleys. We
should still see a light east wind pattern over most of the inland
northwest which would tend to concentrate the best chances for fog
and stratus over the western Columbia Basin toward the Cascades
and over the northern valleys. However it should be noted that
forecasting fog is tricky since the models often handle the
boundary layer moisture and temperature profiles quite poorly
under strong inversions. We are also getting closer to the time of
year where fog just doesn't stick around through the entire day.
However if and fog forms and persists through the entire day,
high temperatures could easily remain fixed in the 30s. We aren't
going to forecast that cool though and have most valleys warming
into the 40s with low to mid 50s again possible over the lc
valley. Fx

Wednesday through Sunday...models are in general agreement through
Friday then begin to diverge quite a bit in the details. An upper
trough off the coast will provide a mild southwest flow aloft
through Friday. Moisture is limited in this flow...except for a
couple of weak waves that track through Wednesday night into early
Thursday and then again Thursday night into early Friday. Main
impact from these will be an increase in mid and high with
possible sprinkles. The east slopes of the Cascades, Okanogan
Valley, and Okanogan Highlands stand the best chance of receiving
light measurable precipitation with snow levels of 6000 to 7000
feet. The Methow Valley may be just cold enough during the
overnight and early morning hours for freezing rain but confidence
in this is low. Models then struggle with how the upper trough
moves into the region over the weekend. The GFS stretches it apart
significantly leaving little to no precip for the area. The European model (ecmwf)
shows no split with a consolidated system and cold front passage
Friday night into Saturday. With the Canadian model agreeing with
the European model (ecmwf)...will lean this way which is not a major change from
previous thinking. Snow levels come down behind the cold front and
could see some snow showers in the mountains. The European model (ecmwf) and
Canadian models then show another mild system arriving Sunday into
early next week. Initially however snow is possible briefly in the
northern valleys and near the Cascades if the Saturday cold front
passage pans out. Jw

&&

Aviation... 12z tafs: a strong upper level ridge will persist over
the forecast sites during this period. Confidence is fairly high
that VFR conditions will prevail at all sites through the day,
however we could see some patchy fog form near sff and geg early
this morning. If it does form it won't last long as it will likely
be quite shallow. As of 445 am there was nothing detected by the fog
product. While confidence is fairly high during the today portion of
the forecast, that confidence drops steadily overnight for all sites
except lws and puw. The reason is the low-level inversions grow
stronger overnight and moisten suggesting a good potential for fog
and stratus. Just how widespread it will be, when it will form and
how bad flight conditions will get are hard questions to answer. If
it forms, we'd expect most of it to form after 06z tonight. Fx



&&

Preliminary point temps/pops...
Spokane 44 31 44 31 46 35 / 0 0 0 0 0 10
Coeur D'Alene 46 31 48 31 47 32 / 0 0 0 0 0 10
Pullman 49 34 53 35 53 38 / 0 0 0 0 0 10
Lewiston 51 36 55 38 55 39 / 0 0 0 0 0 10
Colville 42 29 42 31 43 33 / 0 0 0 0 0 10
Sandpoint 40 30 44 31 44 31 / 0 0 0 0 10 10
Kellogg 43 30 50 31 46 33 / 0 0 0 0 0 10
Moses Lake 45 30 46 31 46 36 / 0 0 0 0 0 10
Wenatchee 40 31 42 32 44 36 / 0 0 0 0 0 10
Omak 37 28 38 30 40 34 / 0 0 0 0 0 10

&&

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

$$

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