textproduct: Seattle/Tacoma

SYNOPSIS

Dry conditions will continue across Western Washington through Friday, with a gradual warming trend expected over the next few days. Clear skies and cool overnight temperatures will allow for frost to form across portions of the region both Wednesday and Thursday morning. Cooler temperatures and precipitation chances return this weekend. Unsettled conditions may continue into early next week.

SHORT TERM /TODAY THROUGH FRIDAY/

Temperatures as of 8AM show widespread frost conditions across much of the area, with areas in the Southwest Interior and the southern portions of the Olympic Peninsula just below freezing. Temperatures are on track to warm up quickly as the sun continues to rise.

A gradual warm up is expected through Friday, with Friday being the warmest day. High temperatures by Friday are expected to be in the low 60s along the coast, while along the interior temperatures are expected to peak in the upper 60s to low 70s. These temperatures will put portions of Western Washington under Minor HeatRisk for Thursday and Friday. Overnight temperatures are also expected to trend slightly warmer through Friday. There is another chance of frost development Thursday morning, but confidence is low as temperatures will be slightly warmer in the mid 30s. Current probabilities of seeing temperatures below 36 degrees are around 25-40%.

29/62

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

An upper level low offshore is expected to drop down from the Gulf of Alaska late on Friday. Models are still struggling to pinpoint the exact trajectory of the low. Some models have the center of the low going over Oregon, which would yield a wetter solution for Western Washington. Other models have the center of the low passing through northern California; this solution will still bring precipitation to the area but QPF values will be slightly lower. When looking at long-term ensemble guidance, it is favoring the latter solution, with the low passing over California.

Uncertainty continues into early next week, particularly Tuesday. Ensemble guidance seems to be in good agreement that an upper level ridge will build over the Pacific Northwest on Monday. Ensemble guidance suggests the next system may arrive on Tuesday, with the majority (68%) of ensemble members favoring this solution. However, a few members (31%) still have the upper level ridging over the area, suggesting there is a small chance that dry conditions may continue into Tuesday.

29

AVIATION

Northwesterly flow aloft will continue across Western Washington through the day with ridging situated offshore. Satellite imagery shows a few areas of fog across the south Sound and Chehalis River Valley this morning, which has mainly impacted KHQM, KOLM, and KPWT. Expect fog to scatter over the next few hours for a return to VFR conditions by mid-morning. Elsewhere, expect VFR conditions to prevail through the day with some FEW/SCT high clouds moving overhead at times. Another round of fog for the river valleys will be possible by Thursday morning. Otherwise, light winds this morning will increase to 5-10 kt from the N/NW this afternoon.

KSEA...VFR conditions through the TAF period. Light N winds mainly under 6 kts through 16/17Z will increase to 5-10 kts around midday and persist through the evening before easing again after 06Z.

JD/14

MARINE

Benign marine conditions expected to continue into early next week. Weak high pressure over the waters will keep northerly winds through Friday. High pressure will weaken late Friday as a weather system drops down from the Gulf of Alaska and will clip area waters as it moves southwards into California/Oregon. Northwesterly winds will increase slightly on Sunday, but at this time they are expected to remain below small craft thresholds. Current probabilities of exceeding 21 kt are at 10% or less. High pressure will rebuild on Monday over the waters briefly. The next frontal system is likely to move over area waters on Tuesday, with probabilities of 25-35% of seeing small craft winds over the coastal waters. Seas are expected to remain below 10 ft into early next week.

29

HYDROLOGY

No river flooding expected in the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory until 9 AM PDT this morning for Eastern Strait of Juan de Fuca-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- Foothills of the Western and Southern Olympic Peninsula- Lake Crescent Area Including US 101-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Olympia and Southern Puget Sound-Willapa and Black Hills.

PZ...None.