Marine Weather and Tide Forecast for Onalaska, WA

SYNOPSIS
Dry and warm conditions will develop as an upper level ridge offshore moves inland midweek over a thermal trough along the coast. Winds will turn offshore at times, bringing smoke from fires in eastern Washington west into our region. Expect the thermal trough and ridge to both weaken and shift east as early as Thursday, with cooler temperatures by next weekend as a trough passes through dry.

SHORT TERM /TODAY THROUGH THURSDAY/
A ridge offshore in the Pacific is beginning to amplify a bit in between two upper level lows/troughs, one over the northern Great Plains/Upper Midwest, and the other over the north Pacific. Down at the surface, it's the opposite effect as MSLP has a thermally induced surface trough along the coast developing as conditions warm under the ridge. The combination of the two will lead to warmer temperatures, and drier conditions as the flow will turn offshore at times. This offshore flow is also expected to bring in smoke from fires in eastern WA over the next couple days. Soundings favor some of the smoke to mix down to the surface as temperatures warm at the surface, breaking the shallow inversion just aloft. For the most up to date smoke and air quality information in your area, please visit airnow.gov or your local air quality agency.
Besides smoke, heat will be the other factor to be aware of as the ridge/thermal trough set up in the area. While smoke may play a factor in holding temperatures during the day a few degrees cooler, high temperatures in the upper 80s/low to mid 90s in the interior, with lows in the upper 50s to low 60s will likely lead to a 2-3 day stretch of widespread Moderate (Orange)
HeatRisk across much of the interior. There is a 20-30% chance of south Puget Sound urban areas seeing Major (Red) HeatRisk Wednesday and Thursday. If planning to spend time outdoors next couple days, consider taking frequent breaks indoors in a cooled building as much as possible.

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
Ensembles favor keeping the warm pattern going through at least Thursday as the ridge and thermal trough begin to weaken and shift eastward. This will favor cooler temperatures going into the end of the week and into the weekend, with HeatRisk becoming predominately Minor (Yellow) by Saturday for the region. Highs will still reach the upper 70s to low 80s for most of the interior, but lows will likely improve into the mid and upper 50s. A trough will pass through next weekend, but there is no signs of moisture at this time as this trough will likely only produce a few clouds via weak onshore pushes. The smoke clearing out will be dependent on how quickly the onshore gradient strengthens with the trough following quickly behind the waining ridge.

HPR

AVIATION
Northwesterly flow aloft as upper level ridging continues offshore. VFR conditions will continue at all terminals early this morning and throughout much of the TAF period. Some terminals starting to see visibility impacted this morning due to smoke. Conditions are expected to gradually deteriorate this afternoon, with the visibility decreasing generally to 4-6 SM.
It is important to remember this smoke may limit both horizontal and slant- range visibilities, therefore, experienced vsbys may be less than what is being reported in observations. Otherwise, we will see SKC and VFR for all terminals and smoke/haze likely in most of the TAF sites, the exception likely being KHQM.

KSEA...Visibility impacts being reported at the terminal.
Expecting visibility to continue lowering this afternoon to generally 4-6 SM. Visibility may reduce further, depending on daytime mixing and how much smoke is mixed down to the surface.

Mazurkiewicz/29

MARINE
A strong area of high pressure will remain offshore through midweek as a thermally induced low pressure expands northward along the interior coast. Winds will decrease over the southern coastal waters early this morning, allowing for the small craft advisory to expire. Breezy conditions can be briefly expected this morning across Puget Sound, however winds should remain below small craft thresholds. A small craft advisory has been issued for all the coastal water zones this afternoon and evening due to choppy seas.

The aforementioned surface trough will shift eastward into Thursday, resulting in increased onshore flow across the area waters. Headlines likely throughout the Strait of Juan De Fuca as increased westerlies filter through. At this time this push likely will be small craft strength, but some guidance has been hinting at a 30-40% chance of some gale strength gusts at times.

Seas 4 to 6 feet this morning increasing slightly this afternoon to 6 to 8 feet, with the highest waves being in the outer coastal water zones. With a 7 to 8 second swell, seas will likely be choppy this afternoon and evening. Seas will remain under 10 feet through the week.

Mazurkiewicz

FIRE WEATHER
A ridge and thermal trough pattern remain on track to setup across the region this week into Thursday, with a few days of warm and dry conditions. Relative humidity (RH) values will likely drop to critical levels into the teens (and perhaps a few single digit values) as offshore flow helps dry things out. The driest locations are the Cascades, and south interior, with Wednesday and Thursday being the driest days. The good news with these low RH values is that wind values likely remain light, not leading to any critical fire weather conditions. However, the dry relative humidity values will be more than enough to aid in worsening fuels quality/conditions for fire starts. As the thermal trough moves inland with the ridge Thursday/Friday, there is some potential for increased instability in the atmosphere for fire growth (though confidence is low). Onshore increases by Friday, with another trough potentially passing through dry into next weekend.

Additionally, smoke from fires in eastern WA is expected to transit into our area, with some of it mixing down to the surface next couple of afternoons.

HPR

SEW WATCHES/WARNINGS/ADVISORIES
WA...Air Quality Alert until 5 PM PDT Wednesday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County- City of Seattle-Downtown Everett / Marysville Area- Eastern Kitsap County-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-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Pierce and Southern King Counties- Lowlands of Western Skagit and Northwestern Snohomish Counties-Northern Hood Canal-Olympia and Southern Puget Sound-Shoreline / Lynnwood / South Everett Area-Willapa and Black Hills.

PZ...Small Craft Advisory from noon today to 2 AM PDT Wednesday 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.