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 MORNING/

As of 135 pm radar indicated scattered showers across western Washington. While most of this precipitation has fallen as rain, webcam observations along US 101 west of Lake Crescent and near Humptulips have shown periods of snow. mPing reports near Olympia also indicate some mixed precipitation this afternoon. 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 /WEDNESDAY NIGHT 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

Mainly southwesterly flow aloft through much of the TAF period. Variable ceilings (VFR-IFR) this afternoon with the trend continuing overnight into Tuesday. The threat for rain/snow mix must also be mentioned, especially during the early morning hours when temps are coolest. No significant accumulation is expected but impacts to visibility may be an issue if showers track directly overhead area terminals. The rain/snow mix threat will abate into Tuesday afternoon but shower activity is favored to persist with impacts to cigs/vis being the main concern.

KSEA...Variable cigs this afternoon under shower activity. Cigs will continue to vary between VFR-IFR through the evening as showers persist. A rain/snow mix is possible overnight into the early morning hours on Tuesday when temps are the coldest. Impacts to visibility is the main threat during this time period. The threat for rain/snow mix will end by Tuesday afternoon. Breezy southerly winds this afternoon will decrease after 03z but will maintain out of the south through Tuesday.

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 4 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.

Small Craft Advisory until 4 PM PST Tuesday 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.