Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Seattle Washington
338 PM PDT sun Jul 13 2014
Synopsis...a low pressure system off the Oregon coast will move
across the area overnight. Expect this system to be over eastern
Washington Monday afternoon...with high pressure aloft building in
its wake. High pressure aloft will then prevail over the region
through midweek. Temperatures will continue to run above normal
across much of the area.
showers and thunderstorms were moving into the far southern part of the
County Warning Area at this time. Look for this activity to continue moving
north through this evening.
Increased cloud cover ahead of the upper low off the Oregon coast
served to prevent temperatures from reaching their potential across the
southern part of the County Warning Area. In fact...most places were cooler than
what they were yesterday. Thus the heat advisory was cancelled.
Look for the upper low off the Oregon coast to move across the
area overnight and then east of the Cascades by midday Monday. Expect
the shower and thunderstorm threat to diminish late tonight across much of
the County Warning Area. By Monday morning...the risk of thunderstorms will become confined
to the Cascades. Onshore flow will prevail on Monday. It is possible
that the forecast temperatures might be a little on the warm side.
An upper ridge will rebuild over the region Monday afternoon and
remain over the Pacific northwest through Wednesday...although it will
gradually weaken with time. Low level onshore flow will also
persist. Expect daytime temperatures to rebound on Tuesday and then cool
slightly on Wednesday. Overall...temperatures will remain normal during this
the medium range solutions continued to advertise an upper trough
developing over the Pacific northwest during this period. The
main differences were in the details. Have continued with the
idea of temperatures approaching near normal during this period. There
is a chance that the forecast temperatures for day 7 might be too warm.
Aviation...southerly flow will become northwest on Monday as a weather
disturbance moves through the area. The air is unstable and a patch
of moisture over northwest Oregon will move north through western Washington tonight
for a chance of thunderstorms over western Washington. Marine layer fog and low
clouds along the coast will also push inland overnight...but mainly
in the Strait and Chehalis gap.
Ksea...northwest surface winds will switch to SW this evening. Middle and high
clouds will increase from the scattered thunderstorms that have been
over northwest Oregon today. There is a chance that a thunderstorm may pass
over Seattle this evening.
Marine...high pressure offshore and lower pressure inland will
continue to produce Small Craft Advisory level winds each evening in
the Strait of Juan Delaware fuca. The stratus layer on the coast will
bring fog and low clouds down the Strait again tonight. There is a
weather disturbance that has been triggering thunderstorms over northwest
Oregon today...that will move north through western Washington this evening.
Fire weather... hunderstorms associated with the upper level low
moving inland this evening causes a bit of a forecast problem. For
most locations in western Washington...the element of concern have
a hard time lining up. Not much to worry about on the olympic
peninsula and along the coast...as fuels remain too moist to meet
red flag criteria. Moving inland toward the Puget Sound sound lowlands...
here fuels are ready...but thunderstorm coverage is expected to be
mainly isolated. In the Cascades...fuels are borderline...but on
the moist side...and coverage is expected to be scattered. While
certainly cannot rule out that some areas on the west slopes of
the Cascades may have fuels dry enough to ignite should they be
struck by lightning...at this time do not expect that dryness to
be widespread...so have opted to not Post any additional fire
weather products for those zones at this time. The only place the
elements line up...dry fuels that meet red flag erc criteria and
scattered lightning threat...is in fire weather zone
662...including the eastern part of North Cascades National Park
and the Lake Chelan National recreational area. The thunderstorm
threat is expected to occur mainly in the evening and through the
overnight hours...but zone 662 may see some activity in the
morning as the low continues to move eastward.
Washington...red flag warning in effect until 8 am Monday for the east
portion of the North Cascades National Park/Lake Chelan
National recreational area.
Pz...Small Craft Advisory in effect until 7 am Monday for the
central and eastern Strait of Juan Delaware fuca.
For the graphical afd...visit