textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will build into the Northwest tomorrow through early next week for another round of hot temperatures and dry conditions. Dry conditions will elevate fire weather concerns west of the crest through Wednesday. High pressure begins to weaken in the second half of next week, with the next chance for precipitation occurring late next week into the weekend.

SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/

All areas, with the exception of the coast, have cleared up this afternoon for mostly sunny skies. High pressure will build more beginning tomorrow and lasting through the middle of the week. Tomorrow, expect another round of marine stratus clouds impacting parts of the Puget Sound region, breaking out in the late morning to early afternoon. Highs will generally be in the upper 70s to low 80s with 60s along the coast. Thermal troughing developing just east of the immediate coast will help bring about a sharper increase in the temperatures come Monday due to a period of offshore flow, with highs expected to get into the upper 80s to 90s in warmer locations. Heat advisories have been posted for much of western Washington, beginning late Monday morning. This level of heat corresponds to Moderate Heat Risk. Given the location of the thermal trough and temperature expectations along the immediate coast, this area was left out of the Heat Advisory.

LONG TERM /TUESDAY THROUGH SATURDAY/

Offshore flow continues into Tuesday morning, transitioning to a more northerly flow during the rest of the day. Temperatures jump to their peak for this heat event, with low 90s expected throughout much of the Puget Sound region south of Everett, and climb into the mid 90s for areas south of Olympia. Widespread Moderate Heat Risk continues, with a 20 to 40% chance of Major Heat Risk occurring in the urban heat islands.

Warm conditions prevail into Wednesday, though several degrees cooler than Tuesday in the upper 80s. More appreciable cooling sets in from Thursday into the rest of the week as the ridge weakens and potential for rain enters the forecast by late next week and weekend. If Tuesday was much too warm, consider that the forecast for Friday is back into the upper 60s with chances for rain. Rain would be welcome to at least temporarily quell some fire danger.

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AVIATION

Widespread VFR conditions over much of W WA this evening except for along the coastline and locations immediately inland, as marine stratus has already begun its incursion. Persistent onshore flow at the lower levels will help push these stratus further inland, with widespread MVFR conditions expected by 12Z...although latest model guidance suggests BLI may remain outside of this, remaining VFR for the TAF period. South to southwesterly winds easing this evening before shifting northerly by Sunday afternoon.

KSEA...VFR conditions at the terminal will persist into the overnight hours. Another round of marine stratus is likely to occur at the terminal around 12Z tomorrow morning. Probabilities for cigs of 2000 feet or less by 12Z are around 30 to 40%, with generally clearing skies by 18Z. Southwesterly winds 6-12 kts this evening before easing to generally 5 kts or less tonight and remaining that way overnight and Sunday morning. Speeds increase again with the aforementioned northerly shift, ranging 5-10 kts.

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MARINE

High pressure will build over the regional waters, lending toward periods of stronger northwesterly flow over the outer coastal waters and diurnal westerly pushes through the Strait of Juan de Fuca. Latest guidance suggests that the best chances for for small craft winds will be Wednesday and Thursday. On Wednesday there is a 65-85% chance for small craft winds and a slight chance (25-35%) of gales. The push on Thursday will be slightly weaker, but there is moderate to high confidence for small craft winds. Seas build to 10-12 feet over the outer coastal waters on Wednesday, but the ridge begins to weaken late in the week and allow for a weather system to move through into the weekend.

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FIRE WEATHER

Hot and dry weather returns in earnest for the first half of next week, with minimum relative humidity values dropping into the 20 percent range or less through Tuesday in the south interior and Cascade valleys. A thermal trough developing slightly inland from the immediate coast on Monday and Tuesday lends itself to a conditionally unstable atmosphere early in the week. Area fuels are getting much closer to critical levels as additional waves of hot and dry weather continues. Grasses are curing expeditiously and have already contributed to a number of roadside brush fires in recent days. Please continue to exercise caution with ignition sources.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory from 11 AM Monday to 11 PM PDT Tuesday for Eastern Strait of Juan de Fuca-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-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston 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- Southern Hood Canal-Willapa and Black Hills.

Heat Advisory from 11 AM Monday to 11 PM PDT Wednesday for 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-Lowlands of Pierce and Southern King Counties-Shoreline / Lynnwood / South Everett Area.

PZ...Small Craft Advisory until 11 PM PDT this evening 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.