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wa discuss


Office: SEW

FXUS66 KSEW 162218
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
315 PM PDT Tue Oct 16 2018

.SYNOPSIS...High pressure will keep the region dry through the
weekend. Fair skies will be the rule, but areas of late night and
morning fog and low clouds are likely to increase through the end
of the work week. The upper ridge will break down next week--Monday
should be dry but then the weather pattern will change to wet and
blustery around the middle of next week.

&&

.SHORT TERM...An upper ridge over the area will flatten Wednesday
as a short wave passes to the north and then the ridge should
rebuild over the area for Friday and Saturday. There might be some
high clouds at times and a switch to a little light onshore flow,
so that should result in increasing fog or low clouds in the night
and morning hours--at least near the water and for the lowest
elevations. The mountains should remain clear. I have pushed the
forecasts and grids in that direction, but have limited the fog
and low clouds to just a very shallow marine layer that burns off
each day--and is mainly near the water at the lowest elevations.

.LONG TERM...The strong upper ridge over the area on Friday will
gradually weaken and shift inland over the weekend. A front will
approach from the west on Monday but rain should hold off until
Tuesday--and the front looks pretty weak and could break up. A
stronger front looks like it will reach us Wednesday night or
Thursday--but that is outside of the forecast--but it looks strong,
the ECMWF takes a 949mb low into the offshore waters on Wednesday,
so it seems worth mentioning that a rapid switch to blustery
fall weather is likely for the middle of next week. The GFS isn't
as deep--but it still has a storm in the 960s heading into Haida
Gwaii next Thursday.

&&

.AVIATION...Upper level high pressure remains in control with
light northerly flow aloft. At the surface, offshore flow
continues. Some patchy fog again Wednesday morning in the usual
river valley locations.

KSEA...Clear skies. Northerly winds under 10 kts. CEO

&&

.MARINE...High pressure remains in control with offshore flow at
the surface through Wednesday morning. The high will weaken
Wednesday and Thursday with surface flow becoming light onshore.
Northwesterly onshore flow pattern will continue into the weekend.
CEO

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&

$$

www.weather.gov/seattle



Office: OTX FXUS66 KOTX 162320 AFDOTX Area Forecast Discussion National Weather Service Spokane WA 420 PM PDT Tue Oct 16 2018 .SYNOPSIS... A ridge of high pressure will persist over the Inland Northwest through the week and into the weekend. This will bring mainly clear skies, light winds with chilly morning temperatures and mild afternoons highs. The next chance of precipitation looks like it could arrive by the middle of next week. && .DISCUSSION... Tonight through Tuesday: The Northwest will be under the influence of a blocking high pressure ridge. A weak upper level wave will brush across and flatten the ridge a little bit on Thursday. This will bring some high clouds to the region, but its impact will not translate down to the surface. The ridge will rebound and actually become stronger with 500 mb heights of 587 decameters over northern OR. This will result in strong subsidence and 850 mb temperatures warming up to around 14 degrees Celsius. Nights will be cold with strong inversions setting up. Inversions will not break with poor mixing expected through the day. A prolonged period of poor ventilation will increase the potential for pollutants to build up near the surface. The next two days will give us a better idea of how bad pollutants may build up over the weekend with an Air Stagnation Advisory potentially needed at the end of the work week. The earliest this ridge may break down appears to be Tuesday of next week. The first front that pushes into ridge usually weakens to the point that we don't see much precipitation. It will provide the best potential for some wind and mix out any pollutant buildup near the surface. A wetter frontal system is more likely toward the middle of next week. /SVH && .AVIATION... 00Z TAFS: High pressure will produce dry, VFR conditions at TAF sites with light winds. Patchy fog may impact conditions in the Cascade valleys and northern valleys, away from TAF sites, overnight/early Wednesday. /Cote' && .PRELIMINARY POINT TEMPS/POPS... Spokane 36 64 38 63 40 65 / 0 0 0 0 0 0 Coeur d'Alene 33 66 36 64 37 66 / 0 0 0 0 0 0 Pullman 34 66 35 65 41 67 / 0 0 0 0 0 0 Lewiston 39 69 40 69 44 71 / 0 0 0 0 0 0 Colville 31 66 35 64 36 66 / 0 0 0 0 0 0 Sandpoint 31 63 33 61 33 63 / 0 0 0 0 0 0 Kellogg 34 64 37 63 36 64 / 0 0 0 0 0 0 Moses Lake 30 67 32 66 36 68 / 0 0 0 0 0 0 Wenatchee 38 65 40 66 43 67 / 0 0 0 0 0 0 Omak 35 67 35 66 41 68 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$