textproduct: Seattle/Tacoma

SYNOPSIS

A dissipating frontal system will spread some clouds across Western Washington today along with cooler temperatures. High pressure briefly rebuilds into the region on Friday before an area of low pressure brings a chance of rain to the area over the weekend into early next week. Dry conditions return areawide by the middle of next week.

SHORT TERM /TODAY THROUGH SATURDAY/

No major updates have been made to the forecast. Please see below for an update to the aviation and marine sections of the discussion.

A weak front will fall apart as it comes ashore today. We'll see a few clouds and cooler temperatures today, but that'll be about the extent of it. High pressure briefly rebuilds into the area on Friday for a little more in the way of sunshine, but cooler temperatures (really, just more seasonal) will remain in place.

Forecast uncertainty starts to ramp later Saturday and beyond. Anomalously strong upper ridging building into southeastern Alaska over the weekend will aid in cutting off an upper low sliding southward down the British Columbia coast. And the models continue to really struggle with the path of the low. In a general sense, the ECMWF suite of ensembles are more aggressive with bringing some precip to the area and the GFS less so. The NBM is something of a compromise and spreads at least a chance of rain to the northwest half of the CWA by Saturday evening.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Most of the forecast area retains at least chance PoPs Sunday into Monday as the models keep an upper trough over the region before eventually kicking it eastward. Beyond that, eerily quiet conditions are slated to return. Ensemble 500 millibar height plots from the Euro, GFS, and Canadian at days 6 through 8 keep anomalously strong upper ridging over the Gulf of Alaska and broad troughing just offshore of California. That's a recipe for a pretty quiet period of weather here in Western Washington.

27

AVIATION

Areas of IFR to LIFR this morning in lingering fog, with some areas along the central Puget Sound maintaining VFR conditions out of the low stratus and fog. A weak frontal system will bring light showers to the region this morning, with persisting northerly winds 10 kt or less. Conditions will likely improve by the afternoon today after the weak frontal passage, with all terminals expected to return to VFR between 18z-21z. Models suggest MVFR to low end VFR ceilings may linger south and east of the Puget Sound this afternoon, though confidence is low with dry northerly flow. Calm conditions overnight will likely result in another round of MVFR to IFR/localized LIFR in low stratus and fog development early Friday morning. Surface winds early Friday morning expected to shift southeasterly, switching back to northerly Friday afternoon.

KSEA...VFR with a FEW002 cloud deck floating near the terminal. Conditions are expected to remain VFR this morning and into the afternoon. Low end VFR ceilings (4000-5000 feet) may linger after the passage of a weak frontal system this afternoon, though with dry northerly flow, this may not materialize. Surface winds generally northerly around 10 kt today, lightening overnight and switching southeasterly early Friday morning. Fog potential remains low early Friday morning with VFR conditions favored for now.

15

MARINE

Wind and seas will both increase today as a front moves inland. Highest wind and seas will be over the Coastal Waters where a Small Craft Advisory remains in effect. Expect building seas to 10-15 ft Thursday night. An eye will need to be kept on the western two- thirds of the Strait, as speeds there may get close to SCA criteria, but expecting that they will remain just under. Also for monitoring, seas at Grays Harbor Bar may also get close to rough, however forecast keeps waves peaking in the 7-9 ft range, again, just shy of criteria.

Winds and seas will ease and subside on Friday. The flow will turn offshore this weekend as a deeper surface low spins south over the offshore waters. The low will weaken as it moves inland early next week.

18/33

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 8 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 until 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.