Saturday, June 12, 2021

Rare June Atmospheric River Bringing Rain, Muggy Conditions

From late Saturday through Sunday, a rare June atmospheric river will bring subtropical moisture, heavy rain, and muggy conditions to Western Washington.

Below is the UW forecast for water vapor for 5 AM Sunday.


The current of wet & moist air from the subtropics will bring the upcoming rain. This pattern looks more like winter...when atmospheric rivers frequent our coasts.  

How much rain will this system bring? The graphic below from NWS Seattle shows the rain forecast on Sunday.

Expect 0.5 to 1 inch of rain in the Puget Sound area, most from Seattle southward. There is also the possibility of heavier showers and rain rates, which could produce ponding and standing water on area roadways. Be prepared for more water on the roads than we usually have in June.

Below is the 
Weather Underground forecast for Puyallup.


Expect the most rain from late Saturday through Sunday. Saturday night will be warm & muggy, with lows only reaching the upper 50s. Sunday will be muggy, with highs in the mid-upper 60s and lows in the mid-upper 50s. Monday will be drier (showers possible), with highs in the low-mid 70s. 

Tuesday will be showery, but the atmosphere will be unstable (large decrease in temperature with height), and there is a chance of thunderstorms. Remember, "when thunder roars, go indoors!" I will have more on the Tuesday thunderstorm potential in the next blog.

The most abnormal part of this upcoming weather is the high dewpoints on Sunday. Expect dewpoints of 60 to 65 degrees, near record highs for Seattle. It will feel muggy outside, and will likely be one of the muggiest days in 10+ years, along with the potential for rain records to be broken.


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