textproduct: Seattle/Tacoma

SYNOPSIS

Warm and dry conditions will continue today. Wet and cooler conditions expected this weekend. A weak ridge will build over the region on Monday. A stronger frontal system midweek will bring lowland rain, mountain snow, and breezy winds. Even cooler temperatures follow behind the system before slowly warming back up to the end of the week.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

High clouds prevail over western Washington today as waves move up northward from a large upper level low over northern California. While temperatures will continue to be warm, the clouds will help to limit insolation and keep the high temperature down from what it otherwise could be. Similar conditions to yesterday are expected, with highs in the mid 60s to near 70, except closer to 60 along the immediate coastlines. Showers will begin to move in from the south tonight into early Saturday. There may be some showers as early as this evening across portions of southwest Washington, but the bulk of the precipitation is not expected to arrive until early Saturday morning. Rain will move across the area throughout Saturday morning and early afternoon, devolving into more scattered showers by Saturday evening. Scattered shower chances will continue into Sunday as well but many may be mostly dry for much of the day. Temperatures this weekend will also be much cooler compared to today, with highs returning into the mid to upper 50s and lows in the 40s.

LONG TERM /MONDAY THROUGH FRIDAY/

A weak upper level ridge looks to develop on Monday over British Columbia, creating split flow over the area before a large upper level low digs into the area Tuesday into Wednesday. There is starting to be more model consensus in the arrival of precipitation Tuesday night and continuing into Wednesday. This system looks to bring some decent moisture, with the potential for an inch or two of rain across the mountains, with slightly lesser amounts across the lowlands. With snow levels lowering to around 3000 ft, this will allow for several inches of accumulating snow across the mountains, including the passes. Finally, this system also looks to bring windy conditions across the area, particularly on Tuesday. Drier conditions look to prevail Thursday and beyond. Temperatures will be quite cool, with highs in the upper 40s to low 50s and lows in the 30s. Widespread freezing conditions may be possible in the morning outside of urban areas by Thursday morning. Temperatures then slowly start to warm up through the end of the week but remain below normal.

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AVIATION

Southerly flow aloft throughout the TAF period. An upper low off the US West Coast is pushing mid-high level cloud coverage across western Washington this afternoon. With it, conditions have been VFR so far today and will remain into the evening for most. However, showers are forecast to increase overnight into early Saturday morning and with them - MVFR to IFR (30-50% chance for KPWT & KHQM) cigs are slated to develop. These cigs will lift and scatter towards 21-00z tomorrow afternoon-early evening. Light surface winds under 5 kt before increasing from the south early Saturday and becoming lighter again during the evening.

KSEA...VFR conditions this evening and overnight. Cigs are expected to lower into MVFR early Saturday morning (13-15z). Showers will also begin to arrive 12-14z Saturday morning along with the lower ceilings. Light surface winds becoming more S/SW late tonight into Saturday between 5-10 kt.

DM

MARINE

An area of low pressure will swing south of area waters tonight into Saturday morning. No impacts are expected with this disturbance as it tracks into northern California and weaken. Westerly winds through the strait will pick up during this time allowing a brief spell in the potential for SCA gusts but the window is small enough to not warrant the need for an advisory at this time. The pattern will remain active into next week with a better chance for headlines. A strong frontal system looks to arrive on Tuesday with the potential for widespread wind related headlines as SCAs look to be a sure bet currently. Seas will remain below 10 ft through the weekend and into early next week, hovering between 4-7 ft. Seas will build on Wednesday towards 9-10 ft.

DM

HYDROLOGY

No river flooding is expected in the next seven days.

SEW WATCHES/WARNINGS/ADVISORIES

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