Atmospheric river events begin on Sunday

There were isolated showers in Western Washington during the day, but the night ended rather quietly.

A late-season atmospheric river event will begin to affect the region early Sunday. With the heaviest rain falling Sunday night into Monday morning, a Pinpoint Alert Day is in effect for both days.

Here is an estimate of total precipitation from Sunday to Tuesday:

Lowland: 1-2″

Mountains: 2-4″+

Coast: 2-4″

A flood warning is in effect for Snohomish, King, Pierce, Mason and Lewis counties from Saturday evening through Wednesday morning. River and town flooding is possible. The latest river forecast calls for the Snoqualmie River at Carnation to reach “low flood stage” by Monday afternoon.

These weather events bring with them a few important reminders:

• While impacts are insignificant in most areas, some agricultural operations may be impacted by minor river flooding this time of year, particularly in extensive flood plains such as the Snoqualmie Valley.

• Unlike atmospheric river systems that put us on high alert in the fall and winter, the net result of an atmospheric river event in the Pacific Northwest in early June would be consistently positive! This type of penetrating rain in the lowlands and mountains is very unusual after May and would result in the onset of our serious wildfire fears being “delayed” by several weeks.

As far as wind and gusts are concerned, it will be windier across the board ahead of the front. These south/southwesterly winds should have only minimal impact.

Now a weaker system is forecast for rain until Tuesday, with persistent showers possible until Wednesday morning. However, a high pressure system is beginning to strengthen, setting us up for a significant warming next weekend. Highs will be above 25 degrees, but highs of over 27 degrees are likely next Friday and Saturday!