textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge over the area today weakening tonight through Tuesday. Thermally induced surface trough over the interior will shift east of the Cascades tonight. Record high temperatures today inland. Increasing low level onshore flow tonight with much cooler weather Tuesday. Low level onshore flow pattern continuing through Wednesday. Upper level ridge rebuilding Thursday with weak low level onshore flow. Little change in the pattern Friday through the weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Satellite imagery shows weather system moving inland over British Columbia well north of Western Washington. High clouds associated with the system beginning to move over the northern portion of the area. Clear skies elsewhere. Temperatures at 3 am/10z were in the mid 50s to near 70.

Thermally induced surface trough over the interior today for one more round of record high temperatures. Highs along the coast peaking midday as afternoon seabreezes kick in with the thermal trough inland. System moving by well to the north will spread high clouds over the area. Highs over the interior in the 80s to mid 90s. Highs along the coast in the 70s and lower 80s.

Thermally induced surface trough moving east of the Cascades tonight with the low level flow going onshore. This will eventually bring cooler marine air into the interior by Tuesday morning. Because of this the heat advisory will come to an end at 5 am/12z Tuesday morning. Stratus developing along the coast overnight getting as far inland as the South Puget Sound by sunrise. Lows tonight in the mid 50s to lower 60s.

Much cooler Tuesday as the upper level ridge overhead weakens with low level onshore flow. Surface analysis has ridge axis to the south of the area. This is an indicator of a stronger marine push cooling high temperatures as much as 20 degrees versus the highs Monday. Highs in the mid 60s to mid 70s.

Little change in the pattern Tuesday night into Wednesday. Low level onshore flow continuing with a flat upper level ridge over the area. Stratus along the coast moving inland overnight getting close to the Puget Sound by morning before retreating back to the coastline. Lows in the upper 40s to mid 50s. Highs in the 60s on the coast and upper 60s to upper 70s inland. Felton

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Upper level ridge rebuilding slightly Wednesday night into Friday with weakening low level onshore flow. Highs a little warmer Thursday, in the upper 60s to mid 70s coast and 70s to lower 80s inland. Slight warming trend continuing Friday highs in the 70s to mid 80s over the interior. Afternoon seabreezes along the coast keeping highs there in the 60s and lower 70s.

Flat upper level ridge over the area for the weekend. A few more ensemble solutions indicating stronger onshore flow then the current blend forecast is showing. Will stay with the idea of highs in the mid 70s to lower 80s for the interior and 60s on the coast both days of the weekend. If the model trends continue look for the forecast highs inland to be cooler in future forecast packages.

AVIATION

High pressure centered offshore in the Pacific will allow for dry conditions to continue across western Washington. High level clouds can be seen on infrared satellite imagery moving in from British Columbia; these clouds will be in place through the morning and afternoon hours before clearing out this evening. VFR conditions persist through the TAF period. Northerly winds will be less than 5 kts today, shifting to becoming northeast/east and increasing to around 5 to 10 kts this evening and into Tuesday.

KSEA...VFR conditions prevail through the TAF period with high clouds expected throughout the day. Northerly winds around 5 kts ease to be calm this morning. Winds then pick up again from the east around 10 kts late this evening into early Tuesday morning.

MARINE

A thermal trough continues to shift inland this morning, which will allow for onshore flow to begin later this afternoon and evening. A strong marine push will occur for the central and eastern portions of the Strait of Juan de Fuca tonight through Tuesday night. West winds will increase this afternoon and evening to 15 to 25 kt, then then further increase on Tuesday for a period of gale force winds Tuesday afternoon and evening with gusts up to 40 kts. Winds begin to decrease through the Strait late Tuesday.

Northwesterly winds will increase through the coastal waters beginning Tuesday and lasting through the rest of the week for an extended period of Small Craft Advisory conditions. Seas will also become locally wind-driven and become very steep. Waves will increase Tuesday night into Wednesday up to 10 to 12 ft with a dominant wave period of around 9 to 10 seconds.

FIRE WEATHER

Record high temperatures with dry conditions in the lower levels today. Daytime minimum relative humidity values below 20% across much of Southwest Washington and the Southern Cascades and below 30% elsewhere. Even though fine fuels have not reached critical thresholds, this dry of an air mass will create elevated fire concerns especially for dry grassy areas, as well as piles of dead fuels. Relative humidities improve with the return of onshore flow tonight into Tuesday easing fire weather concerns into the middle of the week. Conditions dry out a bit again Thursday and Friday with minimum relative humidity values dropping into the 25-35% range despite no low level offshore flow. Fuels will continue to slowly dry with no precipitation forecast through the weekend. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 5 AM PDT Tuesday for City of Seattle- Downtown Everett / Marysville Area-Eastern Kitsap County- Eastern Strait of Juan de Fuca-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Island County-Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties- Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Port Townsend Area-San Juan County-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Willapa and Black Hills.

PZ...Small Craft Advisory from 1 PM this afternoon to 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 11 PM this evening to 11 PM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 2 PM to 11 PM PDT Tuesday for Admiralty Inlet.