textproduct: Seattle/Tacoma

SYNOPSIS

Below normal temperatures and shower activity are expected through Friday. While mainly rain is expected in the lowlands, precipitation may occasionally become snow or a rain snow mix, particularly during the cooler overnight and early morning hours. Temperatures will increase slightly this weekend as active weather continues.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Scattered showers persist across western Washington this evening, with reports of some snow mixing in with the rain in the Bellingham area. The western slopes of the Olympics are also still favored for some snow mixing in throughout the night. Accumulations will be very limited. No other major updates have been made this evening, and an updated aviation discussion has been added. The rest of the previous discussion can be found below.

As we move into the evening and overnight hours, the potential for showers falling as a rain-snow mix or snow will increase. Based on the latest HREF and REFS guidance, the most likely areas to experience accumulating snow between now and mid-day Tuesday will be along the west slopes of the Olympics south to Grays Harbor, the Willapa Hills, and Hood Canal. A Winter Weather Advisory remains in effect here. Again, other locations may see a few flakes, but the potential for an inch or more of accumulation remains low.

The potential for accumulating snow will decrease Tuesday afternoon through Wednesday morning, but again, cannot be completely ruled out.

Regardless, overnight low temperatures are favored to fall below freezing in most areas Tuesday and Wednesday mornings.

LONG TERM /THURSDAY THROUGH MONDAY/

Probabilistic guidance does indicate increased probabilities for a rain-snow mix or light snow showers Wednesday night- Thursday morning and again Thursday night-Friday morning. The probability for measurable 6-hour snowfall remains below 50% for any individual 6-hour period, mainly due to the uncertainty in the precipitation itself. Overnight lows are favored to fall below freezing through at least Friday morning.

Temperatures are favored to increase at least a few degrees Saturday through Monday, reducing the overall risk of lowland snow. However, this change will also be accompanied by continued precipitation chances and increased winds. In other words, a return to more seasonable conditions. -Wolcott-

AVIATION

South to southwest flow aloft continues through Tuesday as a deep upper low drifts southwards offshore. A mix of VFR/MVFR cigs continues this evening with scattered showers. Showers will continue into Tuesday, with activity especially focused along the Olympic Peninsula. The threat of rain/snow mix exists in heavier showers. No significant accumulation is expected but impacts to visibility will be an issue in higher intensity showers. Otherwise, VFR/MVFR will continue through Tuesday, with localized IFR in heavier showers. Light S/SE winds into Tuesday.

KSEA...Cigs will fluctuate between VFR/MVFR through Tuesday as showers persist at times. A rain/snow mix may occur in heavier showers into Tuesday morning. However, no snowfall accumulation is expected. Impacts to visibility will be the main threat in showers. The threat for rain/snow mix will end Tuesday afternoon. S/SE winds into Tuesday. JD

MARINE

Successive frontal systems will track over the offshore waters throughout the week. Winds won't be a widespread issue but models are indicating a threat for Fraser River outflow developing Wed-Thurs for the Northern Inland waters. Otherwise, highs seas (10- 13 ft) are the main threat for the coastal waters here through midweek as a SCA remains in place. These waves may draw near Grays Harbor which will need monitoring. The pattern may remain active into early next week as well.

McMillian

HYDROLOGY

No river flooding is expected over the next 7 days.

SEW WATCHES/WARNINGS/ADVISORIES

WA...Winter Weather Advisory until noon PST Tuesday for Foothills of the Western and Southern Olympic Peninsula-Lake Crescent Area Including US 101-Lower Chehalis River Valley-Southern Hood Canal-Willapa and Black Hills.

PZ...Small Craft Advisory until 10 PM PST Tuesday for Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm-Grays Harbor Bar.

Small Craft Advisory until 4 AM PST Wednesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.