Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
FXUS66 KSEW 250454
Area Forecast Discussion
National Weather Service Seattle WA
854 PM PST Fri Feb 24 2017
.SYNOPSIS...Showers will taper off across the area tonight, making
way for sunny weather on Saturday. On Sunday, a low pressure
system will move down the coast bringing a chance for lowland
snow on higher terrain north and east of Seattle. A chance of
showers continues through much of next week, with snow levels
rising after Tuesday.
.SHORT TERM...Showers are winding down tonight as an upper level
low spins off the OR/CA border. KATX shows isolated coverage over
Western WA and remaining showers should taper off by midnight.
Saturday will be dry but cool with northerly flow aloft. Models
are showing clouds increasing in the afternoon as the next system
arrives from B.C. Morning lows will be chilly in the upper 20s to
mid 30s...with afternoon highs in the 40s.
Another cool upper level trough will bring showers to the area
Saturday night into Sunday. Lowland snow showers are possible,
especially Sunday morning with temperatures near freezing. Snow
accumulations look spotty and light for the most part...but cannot
rule out an inch on the higher hills. The air mass will remain
moist and unstable through Sunday afternoon with the low spinning
overhead. We may see a rain/snow showery mix or small hail
showers. But with afternoon highs reaching the lower to mid 40s we
should not see significant accumulations. Showers will decrease
Sunday night as this system shifts south and east of the area.
There is a chance of showers as we move into Monday with a broad
upper level trough over the West. Temperatures will continue to
trend a few degrees cooler than normal. 33
.LONG TERM...Previous Discussion...Northwesterly flow aloft with
some weak shortwave troughs keeps a good chance of showers in the
forecast through the end of next week. In the most recent runs,
both the ECMWF and GFS have been indicating somewhat wetter
conditions, with limited breaks in between showery periods. The
threat of lowland snow will diminish after Tuesday with snow
levels rising a couple hundred feet. JSmith
.AVIATION...Clouds over Western Washington tonight and Saturday
expected to be generally SCT to BKN...with any cigs that do develop
remaining in VFR range...as weak high pressure builds over the area.
Another weather system will arrive Saturday night and Sunday with
increasing moisture and showers as a low pressure area drops down
over the area.
KSEA...SCT mid-level clouds overnight tonight with variable winds
less than 5 kts. Clouds expected to increase to SCT-BKN by mid-
morning Saturday. SMR
.MARINE...Surface low pressure is moving south out of the area and
will be replaced with weak high pressure. Another low will drop
down from the B.C. coast Saturday night and move over Western WA
on Sunday. After that low departs there will be a period of
stronger northerly flow, especially over the coastal waters
starting around Sunday afternoon or evening. Next week could
see stronger southwest flow developing over the area around
.HYDROLOGY...No flooding is expected during the next week.
You can see an illustrated version of this discussion at