Crystal Mountain

000
FXUS66 KSEW 211551
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
851 AM PDT Wed Oct 21 2026

.SYNOPSIS...
Upper level trough offshore today and tonight will move inland
Thursday with not much moisture associated with the trough.
Temporary ridge over the area Friday. Lots of uncertainty in the
weekend forecast with a chance of a system moving through
Western Washington. Trailing upper level low could still be
around Monday before an upper level ridge builds Monday night
and Tuesday.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
Satellite imagery shows fog in the Snoqualmie and Snohomish
river valleys with some low clouds and fog near the water in
Whatcom, Skagit and Snohomish county. Mostly clear skies over
the remainder of the area. Temperatures at 3 AM/10Z were in the
mid 30s to mid 40s.

Low level offshore flow this morning will not be strong enough
to prevent a little more fog and low clouds from forming near
the Puget Sound in the next couple of hours. The layer will be
shallow with sunny skies across the area by mid morning. The
offshore flow will add a couple of degrees to the highs with
most places in the 60s. Not expecting any records but this time
of year highs in the upper 60s can be records. The forecast high
of 65 in Seattle would be the 10th warmest October 21st in 82 
years of records. 

Low level flow turning light tonight and remaining light into 
Thursday. Upper level trough offshore reaching the coast late 
Thursday increasing the cloud cover over the area Thursday 
afternoon but not producing any shower activity. Lows tonight in
the mid 30s to mid 40s. Cooler Thursday with highs in the mid 
50s to lower 60s. 

Upper level trough moving through Thursday night perhaps giving
the Cascades a shower or two. Mostly cloudy skies in the evening
thinning out a little overnight. Lows in the lower 30s to lower
40s.

Weak temporary upper level ridge moving through Friday for
another dry day. Light onshore flow in the lower levels with
morning low clouds becoming at least partly sunny in the
afternoon. Highs in the mid 50s to lower 60s. Felton

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Upper level ridge weakening and moving east Friday night. 
Models continuing to have trouble coming to a consistent 
solution for the weekend. The ensembles favor a weak system 
moving through later Saturday into Sunday morning. Ensemble 
mean pops are slowly getting lower in the last three runs with 
now just chance pops for everywhere but the north coast. Upper 
level low associated with the front hanging around later Sunday 
into Sunday night keeping chance/slight chance pops in the 
forecast. There is better consensus with an upper level ridge 
building Monday or Monday night for a dry Tuesday. Highs in the 
50s through the period. If the ridge does build later Monday 
good chance we see some lows in the 20s Tuesday morning. Felton

As we head into the last third of October here are some current
October rainfall totals in the west. You don't see this very
often. Seattle 0.08 inches, Los Angeles 0.23 inches, San Diego 
1.04 inches, Palm Springs 1.17 inches, Las Vegas 1.19 inches, 
Phoenix 0.42 inches. Felton

&&

.AVIATION...
An upper level low continues to spin off CA with dry and stable
conditions across western WA. The flow aloft remains southwesterly.
Light and variable winds in place for all terminals this early 
morning except for HQM, where easterly winds ranging 5-10 kts 
are expected to remain in place into at least late morning/early
afternoon. Widespread north to northwesterly winds expected by 
noon today although speeds expected to generally remain less 
than 5 or 6 kts for the remainder of the TAF period. HQM may 
start the afternoon ranging 4-8 kts but winds there will also 
ease to around 5 kts by this evening.

Low stratus and fog in the interior this morning for IFR to LIFR
conditions. Low clouds will scatter by 18-20Z time frame. VFR 
conditions return for the remainder of the TAF period.

KSEA...Shallow/patchy fog this morning with VFR returning by
18-20z. Light and variable winds this morning before becoming 
more NW this afternoon with speeds around 5 kt. Winds will shift
northerly this evening while speeds remain the same. 

33/18

&&

.MARINE...
Weak high pressure will lead to generally light winds over the 
waters again today. Onshore flow will increase on Thursday as a 
cold front moves inland. Seas will build to 10-15 ft Thursday 
night then gradually subside under 10 ft on Friday. Since both 
winds and waves will meet SCA criteria for the coastal waters 
Thursday, went ahead and issued the headline with good level of 
confidence as models have been advertising this for some time. 
The flow will turn offshore this weekend as a thermal trough 
forms along the coast. Low pressure will weaken over the 
offshore waters early next week. 33/18

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory from 2 PM Thursday to 11 AM PDT Friday 
     for Coastal Waters From Cape Flattery To James Island Out 
     10 Nm-Coastal Waters From James Island To Point Grenville 
     Out 10 Nm-Coastal Waters From Point Grenville To Cape 
     Shoalwater Out 10 Nm.

     Small Craft Advisory from 8 AM Thursday to 5 PM PDT Friday 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.

&&

$$