textproduct: Seattle/Tacoma

UPDATE

No changes made to the inherited forecast. The previous discussion remains below along with an updated marine/aviation section:

SYNOPSIS

A weak system will brush the area Tuesday with cooler temps and showers mainly to the coast, Olympic Peninsula and north interior. Conditions will trend dry and warmer Wednesday through Friday, followed by cooler and potentially showery weather for some areas over the weekend.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Temperatures running about 5 to 10 degrees warmer this afternoon over yesterday, but still near normal. A weak system remains on track to brush the area Tuesday morning, mainly clipping the northwestern third of the area with what looks to be another round of light rain for the coast, Olympic Peninsula and Whatcom County. NBM is showing a 15% chance of thunder over northern Whatcom County during the afternoon hours. For all other areas, expect little more than a chance of light rain or drizzle mainly during the morning and a bit more cloud cover into the afternoon hours.

Wednesday looks to be a transitional day, with morning stratus and afternoon sunshine. High temperatures will likely run a few degrees warmer than Tuesday, but remain pretty close to normal.

LONG TERM /THURSDAY THROUGH MONDAY/

Ensembles continue to highlight the persistent upstream tough and southwesterly flow aloft Thursday. Upper level heights will begin to creep up with highs Thursday in some spots along the foothills and Cascade valleys and areas south of Puget Sound warming into the lower 80s. Friday continues to look like the warmest with a 80-90% chance of highs at or above 80F over the interior lowlands from King County Southward. Even with the warmer temperatures, HeatRisk values are expected to remain Minor (yellow) for much of the area with impacts primarily to those individuals extremely sensitive to heat especially if outdoors without adequate cooling or hydration.

Ensembles settling on a cooler and potentially showery pattern for the weekend. The most likely scenario looks to be showers along the coast with widespread cloud cover and cooler temperatures over the interior. Highs will likely run near- to slightly cooler than normal.

AVIATION

Clouds currently still in place over the coast & much of the Olympic Peninsula. Therefore, coastal terminals (KHQM) under cloud cover may see periods of MVFR conditions this evening while the remainder of the CWA remains VFR. Cigs lowering overnight although most terminals expected to remain VFR, save for those west of PWT which are expected to dip down into MVFR. SEA remains borderline where forecast models trending either low-end VFR or right at the VFR/MVFR divide of 3000 ft, but potential impacts from MVFR conditions have warranted inclusion into inherited forecast.

Surface winds trending lighter this evening before gusts up to 15-20 kt increase into early Tuesday morning out of the south.

KSEA...VFR through tonight. Ceilings look to redevelop early Tuesday morning and may dip close to MVFR. There is a 20-25% chance of MVFR cigs from 12-19Z Tue, but potential impacts have warranted inclusion into TAF. Southwesterly wind 6 to 10 knots. Winds become more west after 02Z Tue before returning to southwesterly 6 to 10 kt overnight.

18/62/41

MARINE

The next front is on track to arrive on Tuesday, weakening as it does so. As a result, winds speeds will increase across the coastal waters however, the strongest winds look to prevail across portions of Puget Sound and Hood Canal, and into the Northern Inland Waters during the morning on Tuesday where gusts up to 20-25 kt will be possible. A relatively weak push down the Strait may follow behind the frontal system Tuesday afternoon.

Broad high pressure builds in behind the system on Wednesday and winds remain weak until we start to get stronger diurnal pushes down the Strait towards the end of the week. Another low pressure system looks to approach the area waters this weekend.

Seas remain 6 ft or less through the next week.

62/41

FIRE WEATHER

A weak system brushing the northwestern third of the area Tuesday will bring another round of potential wetting rains for the north coast and West Slopes of the Olympics. Both REFS and NBM showing a 50-60% chance of 0.25" or more through Tuesday afternoon. The NBM is showing a 15-18% chance of thunderstorms over northern Whatcom County Tuesday afternoon likely as the upper level trough brushes the area. While low, does indicate the chance of isolated thunder for a period of time during the afternoon. Drier and warmer conditions return Wednesday through Friday. Minimum RH values dip into the 30s Thursday and into the upper 20s Friday. Persistent low level onshore flow will help maintain good humidity recoveries in the overnight hours. The pattern looks to shift back to a cooler, potentially showery pattern through the weekend.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory from 5 AM to 1 PM PDT Tuesday for Northern Inland Waters Including The San Juan Islands- Puget Sound and Hood Canal.