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Area forecast discussion 
National Weather Service Seattle Washington
910 am PDT Thu Oct 27 2016 upper level trough over the northeast Pacific will
keep showers over the area through this evening. Weak high pressure
building east of the Cascades on Friday will help dry conditions
out, especially over the interior. For the weekend and early next
week, a series of weather systems will keep unsettled weather over
the region, with brief periods of dry weather between systems.


Short term...radar and satellite imagery this morning showing
lingering showers, mainly over the coast and Olympics. A broad upper
level trough over the northeast Pacific and Gulf of Alaska will help
nudge an upper level trough over the offshore waters of Washington
and Oregon into British Columbia this afternoon and evening.
Mesoscale models consistently show this trough weakening as it lifts
into British Columbia, with showers brushing western Washington
rather than spreading through the entire area outright. The forecast
has been updated this morning to reflect this, keeping lightly
probabilities over the coast and north interior with lower chances
for showers over the southeast half of the forecast area today.

The upper level trough over the Gulf of Alaska will dig south along
140w Friday, allowing upper level heights to rise somewhat over
Washington and Oregon. In addition, weak high pressure will build
over eastern Washington on Friday as another weak frontal system
brushes the olympic peninsula. The expectation is that this will
impact mainly the coast, Olympics with light offshore pressure
gradients helping keep the interior dry.

Models continue to show moisture working north into the region
Saturday as the upper level low over the offshore waters begins to
shift east. Expect rain along the coast early Saturday morning then
spreading into the olympic peninsula and interior through the day.

Long term...from previous models all show a
split flow pattern dominating along the West Coast of the US from
Sunday through the middle of next week. A weather system on Sunday
will pass mainly to the south of the area with western Washington
seeing clouds and best rain chances south of Seattle. A weak
northern stream system moving through mainly British Columbia will
give a chance of rain on Monday and possibly into early Tuesday. A
ridge of high pressure aloft and low level offshore flow gives the
best chances for dry weather later Tuesday into possibly early
Wednesday. The weather will likely become increasingly active late
next week as the upper level flow consolidates along about 45n. The
only change to the forecast was to decrease pops a bit on Tuesday
with the passing upper ridge. Otherwise the previous long term
forecast looks good. Albrecht

&& upper trough embedded within moderate southwest
flow aloft will pass western Washington this evening, enhancing
shower later this afternoon and this evening. Expect MVFR cigs at
times within shower activity. On Friday, a brief period of upper
ridging will build into the area, and drying low-level easterly flow
will strengthen during the day. This will lead to more substantial
thinning and scattering of low-mid level cloud layers on Friday.

Ksea...little change in ceilings during daylight hours. A few
showers will start to develop after about 20z-21z. Shower coverage
will peak in the 03z-08z time frame tonight, as an upper disturbance
scoots by. Ceilings could drop briefly into the 020-030 range during
any heavier showers. Showers will move out and dissipate overnight.
Then the development of drying easterly low-level winds on Friday
morning will easily clean out low clouds, with significant thinning
and scattering of mid-level clouds on Friday. Haner


Marine...gradients will ease today as a low center dissipates over
northern Vancouver Island. In addition...swell over the coastal
waters will subside a bit more today. A weaker low will approach the
coast tonight and dissipate over the offshore waters Friday.
Another low will move into northern California Sunday. Haner


Sew watches/warnings/advisories...
Pz...Small Craft Advisory until 11 am PDT this morning for Admiralty
Inlet-coastal waters from Cape Flattery to James Island 10
to 60 nm-coastal waters from Cape Flattery to James Island
out 10 nm-coastal waters from James Island to Point
Grenville 10 to 60 nm-coastal waters from James Island to
Point Grenville out 10 nm-coastal waters from Point
Grenville to Cape Shoalwater 10 to 60 nm-coastal waters
from Point Grenville to Cape Shoalwater out 10 nm-East
Entrance U.S. Waters Strait of Juan de Fuca-northern inland
waters including the San Juan Islands.




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