Brier Weather Station
Latitude N 47° 46' 49" Longitude W 122° 16' 48" Elevation 341 ft
621
FXUS66 KSEW 271020
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
320 AM PDT Tue Oct 27 2026
.SYNOPSIS...
Upper level trough moving through the area today. Upper level
low moving south over British Columbia today and tonight will
veer southwest off Vancouver Island Wednesday. The low will
drift south Wednesday night and Thursday ending up off the
Washington coast Thursday night. The low will remain off the
coast Friday then weaken and move inland Saturday. Upper level
ridge building offshore Sunday moving over Western Washington
Monday.
&&
.SHORT TERM /TODAY THROUGH THURSDAY/...
If we are going to be dealing with slow moving upper level lows
into the first part of next year it is going to be a long
forecasting season.
Satellite imagery shows small circulation just off the North
Oregon coast early this morning. Doppler radar has showers
spinning around the low over the Central and Southern Coast
spreading into the Southwest Interior. With the cloud cover
temperatures in a narrow range at 3 AM/10Z, mid 40s to lower
50s.
Small upper level low opening up into a trough and moving mostly
into Northwest Oregon this morning with the highest pops over
the southern half of the area. Upper level low over Northern
British Columbia this morning moving south during the day. Vort
lobe spinning out of this feature over mainly the northern
portion of the area this afternoon producing more showers. Snow
levels in the 4500 to 5000 foot range confining snow showers to
the higher elevations. Highs in the lower to mid 50s.
Upper level low to the north moving over Vancouver Island by
late tonight. Showers rotating around the low moving through
the area overnight. Air mass cooling with snow levels lowering
to 3500 to 4000 feet. Up to 4 inches of new snow in the
Cascades overnight. Higher amounts possible from around Mount
Rainier southward. Lower snow totals in the Olympics, less than
2 inches. Lows in the upper 30s to mid 40s.
Upper level low not moving much Wednesday with showers rotating
around the low continuing to move through Western Washington.
Snow levels lowering slightly to 3000 to 3500 feet. Up to
another 4 inches of new snow in the Cascades with slightly
higher amounts possible again Mount Rainier southward. Highs in
the lower to mid 50s. Winter weather advisory for the Cascades
tonight and Wednesday looks good and will be continued with
this forecast package.
Little change in the forecast Wednesday night into Thursday as
the upper level low hangs out off the Washington coast. Flow
aloft becoming southwesterly ( versus westerly tonight and
Wednesday ) as the low drifts slowly south. This will reduce the
orographics over the mountains lowering the precipitation
amounts. The air mass will still cool with snow levels 2500 to
3500 feet so most of the passes will continue to see light snow
with another couple of inches of new snow. Lows mid 30s to lower
40s. Highs in the lower to mid 50s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Upper level low hanging out off the Washington coast through
Friday night will finally weaken and shift inland Saturday.
Pops slowly decreasing Friday and Friday night with just chance
to slight chance pops by Saturday. Snow levels remaining in the
2500 to 3500 foot range but precipitation amounts will only
produce another couple inches of new snow.
Upper level ridge building offshore Sunday moving inland Monday.
Atmospheric river on the backside of the ridge aimed at the
Central British Columbia coast. As the ridge moves inland warm
front may nick the coast Monday night.
Highs in the lower to mid 50s warming into the mid and upper 50s
Monday. Lows in the mid 30s to lower 40s dropping to the upper
20s and 30s Monday. Felton
&&
.AVIATION...
Northwesterly flow aloft as upper level troughiness remains in place
over the Pac NW. Surface winds mostly southwesterly with speeds less
than 5 kts with some areas of light and variable. More pronounced
southwesterlies expected by late morning/early afternoon for all
terminals with speeds generally increasing to 5-10 kts with some
terminals possibly seeing wind gusts up to 20 kts.
Wide selection of cigs in place this morning. Majority of obs show
VFR conditions, however some terminals in the south Sound area,
including Sea-Tac, are reporting MVFR to IFR conditions. Cigs will
continue to lower throughout the early morning with widespread MVFR
to IFR conditions expected by 12-14Z. Cigs begin to recover by late
morning/early afternoon with generally VFR conditions returning,
save for those terminals that favor lower cigs, where clouds may
only lift to high-end MVFR. Showers will remain a contributing
factor to lower cigs throughout the day, with scattered activity
expected in the morning becoming more widespread this evening. Will
begin to reflect increased chances of precip during this time frame
with 12Z issuance. As rainfall becomes more prominent, widespread
MVFR conditions expected to return by tonight.
KSEA...Conditions continue to deteriorate this morning with latest
special ob reporting high-end IFR conditions as opposed to model-
advertised low-end MVFR. Will likely favor the latter as the
dominant condition for 12Z update with TEMPO group reflecting the
former. As southwesterly winds increase to 4-8 kts by 12-14Z, this
should help cigs to lift a little bit more, nudging upward into low
to mid MVFR. As speeds reach their peak this afternoon and early
evening, generally ranging 8-12 kts with gusts up to 20 possible,
should see cigs return to low-end VFR. As rain becomes more
widespread tonight, cigs will droop again back to MVFR as wind
speeds lower slightly to 5-10 kts.
18
&&
.MARINE...
Onshore flow returns to the area waters today. Northwesterly winds
along the outer coastal waters will become breezy this morning and
linger into Wednesday, with wind gusts approaching 25 kt at times.
That said, inherited SCA looks good and will remain in place.
Another frontal system will move into the waters tonight into
Wednesday, increasing winds and seas across the area. Increasing
onshore flow will bring a brief push of small craft westerly winds
to the central and eastern Strait late this afternoon into this
evening. New SCA will cover this. Southerly winds will also pick up
along the Puget Sound waters tonight, with latest guidance
highlighting a 60-80% chance of gusts exceeding small craft
criteria. Even though the time frame for these gusts seems to be
pretty limited, will opt to cover with an additional headline here
as well.
Winds will ease again across the area waters on Wednesday as the
accompanying surface low drops into the area and tracks southward
along the coastal waters. This low will allow for flow to turn back
offshore, with offshore flow persisting the second part of the week.
Seas 4-6 ft this morning will increase to 6-8 ft by this afternoon
and will persist at this height into Wednesday. Conditions slowly
subsiding back to 4-6 ft on Thursday and remain that way into the
weekend.
18/14
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory from 5 PM this afternoon to 5 PM PDT
Wednesday for Cascades of Pierce and Lewis Counties-
Cascades of Snohomish and Northern King Counties-Cascades
of Southern King County-Cascades of Whatcom and Skagit
Counties.
PZ...Small Craft Advisory until 5 AM PDT Wednesday for Coastal
Waters From Cape Flattery To James Island 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville 10 To
60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater 10 To 60 Nm.
&&
$$
NWS SEW Office Area Forecast Discussion