Brier Weather Station

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 Latitude N 47° 46' 49"    Longitude W 122° 16' 48"    Elevation 341 ft

184
FXUS66 KSEW 231126
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
325 AM PST Sat Feb 23 2019

.SYNOPSIS...A cool upper level trough will remain over the area
through the weekend keeping showers in the forecast with daytime
highs remaining well below normal. A system south of the area may
bring the potential for lowland snow to some locations late Sunday
night and Monday.

&&

.SHORT TERM /TODAY THROUGH TUESDAY/...Current satellite and obs
showing a relatively quiet early morning over W WA with temps in
most locations near or above freezing and low level clouds in place
to help keep them that way. Radar has some showers...mainly either
over the western half of the Olympic Peninsula or over the northern
two-thirds of the Cascades. Temps and snow levels with the western
batch of showers will be warm enough to keep precip mostly as rain
although some locations may see a little mixed precip through an
hour or two after sunrise. Activity over the Cascades will be enough
to keep inherited headline there going and statement will need to be
refreshed for the morning forecast package. Will continue to
monitor...but at this time activity there does not look like it will
warrant any temporal extension of said headline.

An upper level trough approaching the area will keep the chance for
showers in the forecast today...although POPs and coverage with this
system is fairly unimpressive. Snow levels will climb throughout the
day reaching their peak this evening right around 1500-1800 ft...so
any precip that falls is expected to be rain...aside from the
aforementioned mix early this morning. Snow levels will drop pretty
hard overnight...falling to near sea level by early Sunday morning
but by then...POPs start to fall off as well. Snow levels rebound
some...on average to between 700-1200 ft...Sunday afternoon and
evening...so once again...any precip that falls would likely be
liquid.

The big headache in the forecast comes with Sunday night and through
the day Monday as snow levels plunge again without much in the way
of recovery. Model solutions have been slightly schizophrenic when
it comes to precip...precip type...how far north it will reach
and...come to think of it...most forecast details. Prior solutions
maintained a somewhat consistent trend with precip remaining
generally well south of the Seattle Metro with the occasionally
trending wetter or drier...but no major deviations. That changed
with the 12Z ECMWF yesterday...apparently advertising the potential
for significant snowfall. Fortunately...the 00Z ECMWF has backed well
away from that solution...making it a significant aberration in the
forecast trend. As such...primary thinking this shift is to return
forecast to a state similar to 24 hours ago...ignoring that 12Z
solution...especially given that 00Z solutions are favoring those
pre-established trends. All that being said...there still is a
prospect for lowland snow during this time period but total
accumulations at this time look to be less than 2 inches for the
entire 24 hour period starting after midnight Sunday night through
midnight Monday night. As it is just coming in at the time of this
writing...the 06Z GFS has any precip being well south of the CWA for
this time period...turning the snowpocalypse advertised in the 12Z
ECMWF from yesterday into a big old nothing burger. The main reason
of pointing that out is to display the wide spectrum of solutions
out there. Until a consistent set of solutions present
themselves...persistence forecasting in the vein of the already
established trend of prior solutions seems to be the safest bet.

Tuesday looks to see a drying trend continue...even though current
ECMWF is in some disagreement...easing on POPs for the first half of
the day then bringing a slug of moisture for the evening and
overnight period. Snow levels would still allow for snow or mixed
precip during this time...but given that the models are struggling
with Monday...not sure if it would be proper to assign much
confidence to Tuesday either.  SMR

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Models agree on an upper
level low off the coast influencing the weather over W WA
Wednesday...they just disagree on how much moisture will be with
it...the GFS generally dry with some showers possible while the
ECMWF is rather juicy. Opted to split the difference. The good news
is that snow levels recover rather nicely...climbing back above 1000
ft and as such...any precip would be rain. The best part is that
they stay that way for most locations throughout the long term
forecast period...hopefully marking an end to the threat of lowland
snow for this winter season. Fingers crossed. This low pushes
through the area Thursday with rain expected. Getting into
Friday...models once again fall into disagreement...with the GFS
bringing a pretty sizable ridge over the Pacific and thus going for
dry conditions. The ECMWF on the other hand ends up retrograding the
aforementioned low...pushing it back out the Pacific and thus W WA
remains dry as this system reloads so it can bring rain back to the
area late in the weekend. To be honest...this solutions just looks
odd. Opted to lean more toward the GFS...but tipped my hat to the
Euro with weak POPs under 20 percent...just in case.  SMR

&&

.AVIATION...An upper level trough will continue to linger
over the area, keeping westerly flow through today. Moist airmass
will remain in place through this afternoon keeping a few spotty
showers around. Ceilings will mainly remain MVFR through through
midday. Localized areas of IFR/LIFR are possible during the morning
hours. Cigs will improve to VFR by afternoon into the evening hours.
Expect VFR to into Sunday morning. Surface winds will mainly be
southerly through today with a more southeasterly component by the
overnight hours. Winds generally under 10 knots.

KSEA...Current MVFR cigs will continue through midday before
transitioning to VFR during the afternoon. A shower or two is
possible during the day as the airmass will remain moist. Surface
winds will remain southerly through the afternoon. Southeasterly
component will develop during the evening hours (02z-04z) and become
more easterly into Sunday. Winds generally under 10 knots. JD

&&

.MARINE...Low level flow turning weak offshore today into Sunday
as a weak surface low offshore moves south to off the Oregon
coast. Fraser river outflow winds will develop tonight and continue
through Wednesday but will be mostly confined to the Northern
Inland Waters. Low level offshore flow Sunday will continue into
Wednesday with high pressure over British Columbia and lower
pressure to the south of Washington. Felton

&&

.HYDROLOGY...No river flooding expected in the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 6 AM PST early this morning for
     Cascades of Pierce and Lewis Counties-Cascades of Snohomish
     and King Counties-Cascades of Whatcom and Skagit Counties.

PZ...Small Craft Advisory for rough bar until 9 AM PST this morning
     for Grays Harbor Bar.

&&

$$

www.weather.gov/seattle

NWS SEW Office Area Forecast Discussion

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