Area Forecast Discussion

SYNOPSIS

Mostly dry and mild conditions will continue into early next week, before chances for precipitation increase across western Washington through the middle of the week. Drying and warming conditions are favored to return by next weekend.

SHORT TERM /TODAY THROUGH TUESDAY/

Forecast is on track for the morning update with minor changes to the aviation/marine discussions below. -HPR

Southerly flow aloft will develop over western Washington today as a low pressure system drops southward along the Pacific Coast. This will allow for temperatures to continue on a warming trend, warming several degrees from yesterday. Most lowland locations away from water will see highs in the low to mid 70s, with some areas along the Cascade Foothills nearing 80 degrees.

By Monday, split flow will develop aloft as the low pressure system moves southward towards the California Coast. This will allow for steady conditions on Monday across western Washington, with temperatures once again peaking in the low to mid 70s across much of the lowlands and in the 60s along coastlines. As the low begins to push inland, wrap around moisture may generate light shower activity over the western Cascades late monday.

The upper level low will begin to shift inland overnight Monday into Tuesday, which will bring increasing chances for rain across western Washington, particularly for areas south and west of the Puget Sound. As moisture continues to be advected northward, chances for widespread rain increase across the region. Unstable conditions may produce a few lightning strikes over the Cascades on Tuesday, with cooler temperatures peaking in the upper 50s to low 60s.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Chances for widespread precipitation continue on Wednesday as the low pressure system to the south slowly moves inland. By Thursday, the system will be over the Intermountain West, pulling most of the associated moisture west of the Cascades. Ensembles and operational models remain in good agreement on Friday and heading into the weekend, with potential for warm and dry conditions to return.

15

AVIATION

A ridge of high pressure will continue to shift eastward today as an upper level low remains off the coast, sinking south. This will result in southerly flow aloft with occasional shifting to the southeast this afternoon and evening. Surface winds at most terminals have become light and variable and will remain that way into the early morning. Obs showing winds with a consistent direction are mostly northerly. As winds increase to 4-8 kts by mid-morning, most terminals will remain north to northeasterly.

VFR conditions area-wide this early morning and expected to remain that way. The aforementioned low pressure off the coast will keep high level clouds in place overhead, but should not have any significant impact.

KSEA...VFR conditions will continue throughout the TAF period. Northerly winds 4-8 kts for much of the forecast although some shifts to the northeast are expected, especially this evening and tonight.

MARINE

Low pressure will track south over the offshore waters today with offshore flow over western WA into Monday. Onshore flow resumes on Tuesday as the low weakens further then shifts inland. Seas generally 4-6 ft for much of the day, building slightly to 5-7 ft tonight. A more significant increase to seas is expected Wednesday, where waves will build to over 10 ft in the outer coastal waters.

HYDROLOGY

River flooding is not expected over the next 7 days.

SEW WATCHES / WARNINGS / ADVISORIES

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