textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low off the Northern Oregon coast will move southeast today ending up in Northern California late this afternoon. The low will not move much tonight through Thursday then weaken and move east Friday. An upper level trough moving out of the Gulf of Alaska just offshore Friday will move inland Saturday. A weaker trough will move through Sunday followed by some upper level ridging Monday.

SHORT TERM /TODAY THROUGH THURSDAY/

Satellite imagery shows clearing along the coast and Southwest Interior with mostly cloudy skies elsewhere. Doppler radar has a band of showers over the North Cascades foothills moving northwest towards Bellingham. Temperatures at 2 am/09z were in the 40s and lower 50s.

Upper level low off the North Oregon coast will move southeast today ending up over Northern California by late afternoon. This will pull the showers rotating around the low south of Western Washington by afternoon. Showers approaching Bellingham will be north of the border before sunrise. Air mass slightly unstable over the higher terrain this afternoon keeping a slight chance of showers over some of the mountains. Clearing skies over the South Puget Sound and Southwest Interior allowed fog to form early this morning. The layer is shallow and will dissipate by mid morning. Highs mostly in the lower to mid 60s.

Upper level low not moving much tonight and Wednesday keeping shower activity south of the area. Patchy fog possible in the fog prone locations like the Southwest Interior around sunrise otherwise partly cloudy skies tonight and mostly sunny skies Wednesday. Surface gradients going flat with southerly flow aloft pushing some warm air up into the area. Highs much warmer Wednesday, in the mid 60s to mid 70s. Lows tonight in the mid 40s to lower 50s.

Upper level low wobbling around over Northern and Central California Wednesday night into Thursday. Upper level trough exiting the Gulf of Alaska still well offshore Thursday but the combination of the two features will create diffluent flow over Western Washington Thursday afternoon. This plus daytime heating could kick off some convection over the Cascades in the afternoon. Another warm day over the interior with highs in the 70s. Highs along the coast in the mid and upper 60s. Lows Thursday morning in the upper 40s to mid 50s. Felton

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Upper level low to the south weakening and moving east Thursday night and Friday while the upper level trough offshore approaches the coast. Chance of showers over the eastern portion of the area. In the lower levels flow turning onshore Thursday night with onshore flow continuing through Friday. Much cooler Friday with highs near 60.

Models in good agreement with a couple of weak troughs moving through the area over the weekend. Not much in the way of moisture with the troughs but the low level flow will remain onshore. This will keep clouds in the forecast with highs in the lower to mid 60s Saturday and mid to upper 60s Sunday.

Upper level ridge building into the area Monday. Low level flow turning weakly offshore. This will warm daytime temperatures significantly with highs in the 70s to lower 80s.

Lows near 50 Friday morning. A little cooler Saturday, Sunday and Monday mornings with the colder locations getting down to near 40. Mid to upper 40s for the remainder of the area.

AVIATION

East to southeast flow aloft is expected much of Tuesday as a closed upper low along the Oregon coast gradually shifts southeastward. Remnant low level moisture in the wake of this system will lead to areas of MVFR ceilings and isolated pockets of IFR along with isolated showers into midday. Gradual improvement to VFR is expected across most of the region by around 00Z.

KSEA...Periods of MVFR ceilings are expected through midday before a general lifting to VFR is expected this afternoon and evening. Surface winds light southerly this morning will veer northwesterly 4 to 7 knots this afternoon then northerly 7 to 10 knots late this afternoon.

27

MARINE

A weak surface trough along the coast will shift southward and weaken with broad high pressure over the offshore waters expanding into the coastal waters tonight and Wednesday. This will lead to increasing northwesterly winds over the outer coastal waters. A system moving into British Columbia Thursday into Friday will increase onshore flow with westerlies approaching gale force in the central and east strait Thursday evening. Surface ridging builds into the coastal waters and interior this weekend for lighter winds.

Hazardous seas continue for the coastal waters into tonight. Seas will subside to around 10 feet Wednesday. Another longer period swell train around 10 feet is expected to arrive on Thursday.

27

HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...High Surf Advisory until noon PDT today for Grays Harbor County Coast-Northern Washington Coast.

PZ...Small Craft Advisory until 8 PM PDT this evening for Grays Harbor Bar.

Small Craft Advisory until 5 AM PDT early this morning for West Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory until 5 PM PDT this afternoon 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 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.