textproduct: Seattle/Tacoma

SYNOPSIS

Onshore flow will maintain cooler temperatures and cloudy skies through Thursday, with some drizzle tonight into Wednesday. A stronger system will bring showers across western Washington Thursday morning, with more widespread rain later Tuesday into Friday morning. Cooler and unsettled conditions will continue through the weekend, with additional chances for precipitation into next week.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

Broad upper level troughing will maintain southwest flow aloft and onshore flow at the surface over the next few days, with little change between today and tomorrow. Most of the low stratus from this morning has eroded under partly cloudy skies, with highs on track to peak in the mid to upper 60s for most areas. A weak disturbance in the upper level flow will bring increased clouds and some sprinkles alongside another marine push. This will bring low clouds and light showers inland tonight into early Wednesday morning. Conditions will improve by the afternoon, with cloudy skies lingering and highs once again generally in the mid to upper 60s.

A warm front will lift northward across the region Thursday morning, bringing light showers to the region. Forecast models show some differences in the timing, but a cold front will follow, bringing in widespread precipitation by the evening.

LONG TERM /FRIDAY THROUGH TUESDAY/

Widespread precipitation will move inland through Friday morning, with most lowland areas seeing roughly half an inch of rainfall and amounts closer to an inch over the mountains. With snow levels dropping to 6000-7000 feet on Friday, some of the higher peaks will even see the first dusting of snow of the season. Showers will likely continue throughout the day Friday as the upper level trough axis shifts east of the Cascades.

Forecast models continue to hone in on weak ridging building in behind on Saturday, which will temporarily bring drier conditions to western Washington. However, ensembles maintain chances across the region for more precipitation on Sunday and into early next week, with cooler-than-normal temperatures staying in place. Some uncertainty remains in model solutions early next week, with some breaking apart a frontal system as it reaches the coast. Regardless, additional rainfall is on the way, with more fall-like weather settling into place.

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AVIATION

Conditions continue to improve towards VFR this afternoon as cloud cover continues to scatter across western WA. A weak frontal system moving into western WA late tonight into early Wednesday will bring another round of lowering ceilings to the area by Wednesday morning. Most guidance suggests ceilings will range between low-end VFR to MVFR, though cannot rule out some localized IFR conditions developing. Light showers will be possible as this system moves into the area, most likely for terminals along the coast (KHQM) and Strait (KCLM). KBLI and KOLM may also see some light shower activity, but overall expect much of the interior terminals to remain dry as the front breaks up as it moves inland. Southwesterly winds between 5-10 kt will persist for the majority of the terminals through this evening before winds ease and become light overnight.

KSEA...VFR conditions are expected to prevail. Ceilings will lower again on Wednesday morning as a front approaches the terminal, however guidance continues to keep conditions VFR with the lowest ceilings remaining around 4000 ft. South to southwest winds will persist at 5-10 kt into Wednesday.

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MARINE

A weak front will move across the area late tonight into Wednesday with little to no impact expected across the area waters. Onshore flow will continue with another, weaker push of westerly winds expected along the Strait of Juan de Fuca this afternoon and evening. At this time, wind gusts largely look to remain below 20 kt for the majority of the Strait.

A stronger frontal system will then move through the area waters Thursday into Friday, bringing an increased likelihood of small craft winds to the coastal waters and along the Strait of Juan de Fuca. A third system may approach the waters over the weekend, but latest guidance shows the system breaking up as it approaches, so do not expect much in the way of hazardous winds or seas at this time.

Seas will primarily persist between 5-8 ft through Thursday before building towards 9-10 ft on Friday in the wake of frontal system. Seas will then subside towards 4-6 ft over the weekend.

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SEW WATCHES/WARNINGS/ADVISORIES

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