textproduct: Seattle/Tacoma

SYNOPSIS

A weak ridge of high pressure will bring warm and dry conditions to Western Washington into Tuesday. A weak frontal system will move through on Wednesday with cooler temperatures and a little rain for parts of the area. Onshore flow will keep temperatures near normal for the second half of the week with areas of night and morning clouds.

SHORT TERM /TODAY THROUGH WEDNESDAY/

A weak upper ridge axis is shifting inland early this morning with light northerly flow near the surface. Interior areas will see several degrees of warming today under mostly sunny skies. The ridge will begin to weaken tonight in response to an upper trough moving into the central British Columbia coast. This will induce a decent onshore push with marine air and some stratus filtering inland tonight. This will knock several degrees off high temperatures on Tuesday. A weakening front is still on track to arrive on Wednesday with further cooling and a chance of a little rain. Recent model runs are generally less enthused with rain chances and most of the meager precip this system stands to produce will be over the Olympic Peninsula and portions of the North Interior.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

The flow aloft turns more or less zonal on Thursday with weakening post-frontal low level onshore flow. This is a pretty good recipe for morning clouds, afternoon sun over interior areas, and high temperatures within a couple degrees or so of climo. Looking ahead to the remainder of the week, Western Washington remains locked in the struggle between upper ridging to our south and an upper trough over British Columbia. This keeps general onshore flow in place for night and morning clouds and seasonal temperatures. Another front tries to approach at the end of the week, but may ultimately result in little more than an uptick in onshore flow. There are signs at the tail end of the extended forecast period early next week that strong upper ridging anchored near the Four Corners region will begin to exert a little more influence on us...for warmer and drier conditions. And with mid-July approaching, that story checks out from a climatological perspective. 27

AVIATION

VFR conditions expected today, with the exception of terminals along the coast. There remains a 40-50% chance of MVFR cigs this morning and a 30% chance for IFR cigs. Improvement to VFR is likely after 18z. Guidance suggests MVFR cigs may return Monday night/Tuesday morning. Currently highest confidence is along the coast, with probabilities around 60-80%. As for the interior terminals, highest chances are along the Kitsap Peninsula and Southwest Interior at 40%. Variable to light NE winds early this morning will transition NW in the afternoon at 5-12 kt, with strongest winds along the coast. Breezy conditions expected along the Strait of Juan de Fuca this evening with gusts to 20 kt. Surface winds transition to SW late Monday/early Tuesday morning.

KSEA...VFR expected through the TAF period with a few high clouds at times. NE winds early this morning will transition NW this afternoon at 6-9 kt. Winds then shift SW early Tuesday morning after 08-09z.

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MARINE

Broad high pressure over area waters continues to weaken with a frontal system expected to move over area waters late Tuesday/early Wednesday. Later on Wednesday high pressure will rebuild in the wake of the front. Another front will move over area waters late in the week, weakening high pressure again. Onshore flow will continue through the Strait of Juan de Fuca throughout the week. Expect small craft winds through the central and east Strait this evening. Additionally, winds continue to trend downward for the coastal waters but seas look to linger around 7-8 ft today with a dominant period around 7-8 seconds, and thus have extended the advisory through this evening. Stronger high end small craft westerlies are likely (70-85% chance) Tuesday and Wednesday evenings. Guidance is starting to highlight the potential for low-end gales for both Tuesday and Wednesday evenings. Currently there is a 20-35% chance on Tuesday and a higher 40-65% chance on Wednesday. Additional small craft advisories are likely late in the week.

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FIRE WEATHER

Low-level onshore flow will continue through the week. This will keep good overnight relative humidity recoveries in the forecast and help subdue fire weather concerns despite somewhat warmer temperatures through Tuesday. In addition, a weakening front will move across the area Tuesday night into Wednesday, bringing the chance for light rain to portions of Western Washington.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 8 AM 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 until 8 AM PDT this morning for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.