textproduct: Seattle/Tacoma

SYNOPSIS

Drier conditions with seasonable temperatures through the weekend. High pressure builds over Western Washington next week bringing continued dry weather and well- above average temperatures through at least midweek.

SHORT TERM /TONIGHT THROUGH SUNDAY/

Clouds continue to clear for most areas this afternoon with temperatures in the 60s and 70s. The upper low remains positioned offshore of Cape Flattery and will slowly progress northeastward into British Columbia through Saturday. This will result in another round of morning stratus across Western Washington Saturday AM. Temperatures will remain seasonable again on Saturday with highs in the 60s along the coast, and 70s for the interior. High pressure slowly begins to build over the Pacific Northwest Sunday, resulting in less morning cloud cover, and temperatures warming into the 80s for some locations by the afternoon.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Upper level ridging further builds into Western Washington Monday through midweek. This will result in a more significant warming trend, with temperatures rising into the 80s and low 90s during this period. Widespread Moderate HeatRisk is expected for interior locations, with a 20 to 50% probability of Major HeatRisk for Cascade Valleys and portions of central Puget Sound Tuesday and Wednesday. Uncertainty begins to increase in ensembles in regards to potential weak troughing offshore of the west coast by late Wednesday/Thursday. At this time, a slight cooling trend may begin on Thursday and continue into Friday. Another aspect of the forecast that will be further monitored is the existence of any monsoonal moisture around the Thursday period which could result in POP chances, at least for the Cascades and Olympics. NBM POPs at this time remain low (around 10 to 20%), but will be dependent on the vicinity to troughing offshore. JD

AVIATION

An upper level low will continue to move northeastward today with south to southwest flow aloft as the trough transits inland. Satellite this afternoon continues to show scattering and lifting of ceilings, with most terminals reporting VFR with broken or scattered decks between 3,000 and 5,000 ft. A few MVFR areas remain along the north Olympics. Models still have the marine push bringing stratus in Saturday morning, but have decreased probabilities for non-VFR ceilings for the majority of the main Puget Sound terminals (KSEA and KBFI dropped to 20-40% chance of MVFR Saturday morning). The higher likelihoods of MVFR (and also IFR/LIFR) is from KPAE west through the Strait of Juan de Fuca, and from KOLM westward where the Pacific Coast/Strait of Juan de Fuca coasts have 40-60% chance of ceilings down to LIFR overnight. Winds will remain out of the southwest around 5-10 kt, with some north winds at times in the afternoons from KPAE down through Puget Sound to KSEA/KBFI.

KSEA...Scattering/VFR ceilings this afternoon, with a 20-40% chance of MVFR ceilings developing between 11Z-17Z Saturday. Winds 5-10 kt out of the southwest - diminishing to 6 kt or less after 03Z with winds switching briefly to the northwest/north through 10Z. Winds flip back to the southwest between 10Z-21Z before switching to the northwest again.

HPR

MARINE

A low/trough offshore will continue to move inland today with high pressure rebuilding offshore. There will also be a thermal trough building under a ridge going into next week. While flow does not appear to go offshore completely, there will be varying degrees of onshore pushes through the Strait of Juan de Fuca, as well as some north/northwest winds in the coastal waters early next week. The next potential for winds over 20 kt is a 40-60% chance of gusts over this threshold in the Strait of Juan de Fuca Saturday evening. Potential for these winds next week remains low at this time.

Seas of 3-6 ft will increase to 6-9 ft early next week, with seas potentially becoming choppy as periods decrease to around 8 seconds Sunday into Monday. Seas decrease back down to 4-6 ft the remainder of next week.

HPR

FIRE WEATHER

Fire weather concerns will linger throughout the forecast period as a hotter and drier pattern returns quickly over Western Washington, especially Monday through much of next week. This has the potential for increasing fire activity from any new lightning starts from Thursday's convection.

SEW WATCHES/WARNINGS/ADVISORIES

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