Area Forecast Discussion

SYNOPSIS

Mostly warm and dry conditions will continue today ahead of a pattern change through mid-week that will bring cooler temperatures and increased chances for rain. Conditions are favored to dry out and warm up by the end of the week and into the weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Today will bring the last of unseasonably warm and dry conditions over the next several days. As a deep upper level low continues to meander southward along the Pacific coast, split flow will develop aloft today for very similar conditions to yesterday. Temperatures will peak in the low to mid 70s across the inland lowlands, with highs in the 60s along the coast.

The cutoff low will begin to shift inland over Oregon later tonight into Tuesday, advecting moisture northward into western Washington. Higher terrain south of the Puget Sound and areas along the Pacific coast may see light shower activity develop as a result later today, with light accumulations possible. After midnight, a stronger surge of moisture will lift northward, bringing widespread showers across western Washington through much of the day. Instability from the low to the south may also produce a few lightning strikes over the western Cascades Tuesday afternoon. Conditions will briefly dry out Tuesday evening ahead of another round of widespread precipitation as the low slowly progresses eastward towards the Intermountain West. Snow levels will remain above 5000-6000 feet as this system passes through, with minimal accumulating snow over the higher peaks. Through Wednesday, the region will see roughly a half an inch of rainfall or less, with the highest amounts concentrated over the Cascades. Temperatures will also cool considerably as this system passes over the Pacific Northwest, with highs peaking in the mid 50s on Wednesday.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Light shower activity will taper off over the Cascades Wednesday night, with conditions drying out and warming up heading into the weekend. Models continue to show good agreement over a sharp ridge of high pressure building offshore through Sunday, bringing dry conditions and near normal temperatures through the weekend. However, models continue to show disagreement over the strength of the ridge and how long conditions will remain dry before another pattern change.

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AVIATION

W WA still finds itself situation between an upper level ridge to the east and an upper level low out over the Pacific centered off the coasts of CA and OR. This will keep flow aloft mostly southerly with occasional shifts to southeasterly from time to time. Surface winds this early morning and into the late morning/early afternoon will remain light and variable for some terminals, northerly 4-8 kts for others. Terminals along the Sound will join in the northerly winds by late morning. All terminals will see a shift to south to southwesterly winds late this afternoon or early this evening with speeds generally remaining in that 4-8 kt range. HQM, OLM and SEA may see winds pick up this evening and early tonight, ranging 8-12 kts.

The aforementioned upper low will continue to churn moisture into the area, but nothing in the way of precip is expected during the TAF period...only high to mid clouds. As such, current VFR conditions are expected to persist.

KSEA...VFR through the period. Northerly winds with occasional shifting to the NE during the early morning then favoring NW late morning and afternoon. Speeds generally 4-8 kts. Wind shifting to the SW after 00Z and speeds increasing to 8-12 kts around 06Z. Models have these winds easing early Tuesday morning.

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MARINE

Low pressure will spin offshore, off OR/CA, with light offshore over western WA today. The low will shift inland and weaken Tuesday resulting in increased onshore flow. Highest winds will be through the Strait of Juan de Fuca, but should remain just under SCA criteria. Onshore flow will continue through Thursday with high pressure over the NE Pacific. Offshore flow may develop toward the end of the week as a thermal trough forms along the coast.

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HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES / WARNINGS / ADVISORIES

WA...None. PZ...None.