Lyman, Washington Weather Forecast Discussion

416
FXUS66 KSEW 122210
AFDSEW
Area Forecast Discussion
National Weather Service Seattle WA
310 PM PDT Fri Sep 12 2025
.SYNOPSIS...Weak high pressure over the region through Saturday.
A cold front will then move through Saturday night into Sunday,
with rain and showers. Warmer and drier conditions develop early
next week. Additional troughing towards the second half of next
week is possible.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY/...Transient ridging aloft as
the next incoming disturbance sits well offshore. Marine stratus
is gradually scattering this afternoon but widespread coverage
still remains with mostly cloudy skies prevalent for Puget Sound,
southwest interior and the coast. For tonight, the aforementioned
ridge axis will track directly overhead with mostly dry
conditions. Can`t rule out areas of drizzle squeezing out of
developing marine stratus and patchy fog. Overnight lows are to
bottom into the lower to mid 50s.
Upper-level progression will lead into Saturday as the ridge
cross east of the Cascades. Morning clouds will start the day yet
again but should give way to afternoon sunshine. However, high
clouds are slated to build overhead Saturday night as a precursor
of the next rain maker. A cold front will arrive at the coast by
early Sunday morning, spreading precipitation as the day progress.
Total rainfall amounts range from 0.25-0.50" along the mountains
to around 0.10-0.25" for the lowlands. The air mass will be
slightly unstable with a chance of thunderstorms too.
A few showers possible into Monday morning as a lingering
convergence zone fizzles out. Drier weather rebounds across the
region as ridging returns. Seasonal temperatures will cool down
Sunday into Monday and trend slightly below average for mid-
September.
.LONG TERM /TUESDAY THROUGH FRIDAY/...Drier weather is favored
to persist into Tuesday. Highs Tuesday and Wednesday will reach
the mid to upper 70s with a few low 80s possible. Critical fire
weather conditions remain low with higher humidities, particularly
into Tuesday as offshore looks to return briefly. A trough may
bring cooler and wetter conditions moving toward the end of the
week.
McMillian
&&
.AVIATION...An upper level ridge will pass over western WA today
into Saturday. The flow aloft will be weak, but will increase out of
the south late Saturday as a trough/cold front approach from the
west. MVFR cigs will continue to scatter between 21-23Z, with light
north winds increasing to 4-8 kt this afternoon`evening (some
terminals close to the Strait of Juan de Fuca may see 6-12 kt).
Light & variable winds tonight (along with the marine layer
returning tonight) has increased probabilities/likelihood of low
IFR/LIFR stratus and fog returning into a majority of terminals
tonight/Saturday morning. Highest confidence is coastal, south and
north interior terminals (with medium confidence that Puget Sound
terminals will see lower cigs and vis). Clearing will take place 18-
21Z with light southwest winds 4-8 kt Saturday.
KSEA...Satellite showing a scattering of MVFR cigs to the north of
the terminal continuing southward - this will likely upgrade
conditions to VFR by 22-23Z. Winds will continue to solidify to
northwest 4-8 kt and become light & variable out of the south
tonight with low stratus most likely arriving as early as 12-14Z
Saturday morning, and clearing by 18-21Z. Some low vis may accompany
the stratus at times. Clearing to take place 18-21Z, with winds
becoming southwest 4-6 kt by Saturday afternoon.
HPR
&&
.MARINE...Onshore flow will continue through Friday night with weak
high pressure remaining over the waters (and lower pressure inland).
A few areas may see fog tonight (especially in the coastal waters
and the Strait of Juan de Fuca). A cold front will approach the
coastal waters Saturday, and cross inland Sunday. Probabilities have
increased for a period of wind gusts exceeding 20 kt in the coastal
waters and Strait of Juan de Fuca Sunday - will continue to monitor
for a possible small craft advisory. Once the front passes, onshore
flow will return Tuesday, with some models indicating another
possible system midweek.
Seas will build to 6-8 ft through the weekend (with the period
dropping to 8-10 seconds on Sunday), but wave heights will decrease
down to 4-6 ft next week.
HPR
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...None.
&&
$$

NWS SEW Office Area Forecast Discussion