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Area forecast discussion 
National Weather Service Seattle Washington 
240 PM PDT sun Mar 26 2017 


Synopsis...a front (pic1) will move inland this evening with the 
rain turning to scattered showers. A trough will keep showers in 
the forecast Monday. A warm front will reach the area Tuesday 
for more rain. A vigorous low pressure system and front will 
move through the area on Wednesday. A trough will keep showers 
in the forecast Thursday. Dry weather is expected Friday. 


&& 


Short term...rain from a front will break up to showers tonight 
and the showers should become more scattered on Monday. The Winter 
Weather Advisory for portions of the Cascades has been cancelled, 
snowfall tonight will be between 2 and 5 inches above the snow 
level, unremarkable. Tuesday will see a warm front arrive and that 
system fizzles out over the area Tuesday evening. Another frontal 
wave, this time a stronger system, will move through western 
Washington on Wednesday. The 12z GFS took a deepening 999mb low 
into Vancouver Island midday, with a decent southerly gradient 
giving windy conditions over the area. 


Long term...the push of onshore blustery weather behind the system 
on Wednesday will settle down Wednesday night and Thursday. An upper 
trough moves inland and surface high pressure builds across 
the region. An upper ridge will be in place Friday for a dry day 
with some sunshine. Clouds will likely increase Friday night with 
a chance of rain by Saturday as a warm front pushes into the ridge. 


&& 


Aviation...an upper level trough off the coast (pic10) is forecast 
to move onshore into western Washington Monday. (Pic11) SW flow 
aloft over Washington tonight becoming northwest behind the trough. At the 
surface, a frontal system was moving onshore this afternoon (pic12) 
and will continue inland this evening. Onshore flow behind the 
front. Air mass becoming somewhat unstable behind the front for 
showers into Monday. 


MVFR ceilings in the vicinity of the front. Showers with a mix of 
breaks in the cloud cover tonight into Monday morning will offer a 
mix of MVFR and VFR conditions. Mountains to remain obscured in 
clouds and precipitation through at least Monday morning. 


Ksea...the terminal is likely to have primarily upper end of MVFR 
ceilings both with the front late this afternoon and evening, and 
through the night into Monday morning with passing showers and cloud 
cover. Improving VFR conditions likely Monday afternoon. Southerly 
winds around 10 kt should kick in with the front and continue 
through Monday morning. Buehner 


&& 


Marine...an occluded front was moving onshore this afternoon 
(pic12) and will continue inland tonight. Low level onshore flow 
with and in the wake of the front. Will change the gale warnings to 
small craft advisories that will only last until this evening. 


A surface trough is expected to move onshore Monday (pic13) with a 
showery weather regime and then higher pres building behind it 
Monday night. (Pic14) the next weak Pacific frontal system is 
expected to arrive Tuesday. (Pic15) 


A low is expected to develop and intensify as it tracks from well 
off Cape Blanco northeast into central Vancouver Island Wednesday 
(pic16) with potential gale force winds at least for the coast. The 
associated cold front to move onshore late Wednesday with moderate 
onshore flow. Higher pres to build onshore Thursday into Friday. 
(Pic17) buehner 


&& 


Hydrology...river flooding is not expected for the next 7 days 
with the exception of possibly the flood prone Skokomish River in 
Mason County, where heavier rain in the Olympics Tuesday night 
and Wednesday could be enough to get the river above flood stage 
Wednesday. 


&& 




Sew watches/warnings/advisories... 
Washington...none. 
Pz...Small Craft Advisory near shore coast, Strait of Juan de Fuca, 
northern inland waters and Admiralty Inlet until this evening. 


&& 


$$ 






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