May 29, 2024

Heavy Precipitation Event with Record River Levels

An extraordinarily heavy precipitation event for early June will occur next week, with daily rainfall records falling and many regional rivers hitting record levels for June.

Rain so heavy that the wildfire threat will be greatly diminished for an extended period and regional reservoirs will get a mighty "top off" before our normally dry summer season.

Let me show you the latest forecasts, and be prepared to be amazed by the soggy bounty ahead.

Consider the latest European Center accumulated precipitation forecast for their model run starting 5 AM this morning (below).

The total through 5 PM today (Wednesday) is wet enough, particularly on the western side of Cascades where as much as an inch should fall.


With more showers on Saturday, the totals become more substantial over Northwest Washington.


But you haven't seen anything yet.   A very moist atmospheric river comes in on Sunday/early Monday and precipitation totals go crazy, with 2-4 inches on the western slopes of the regional mountains.

The totals by Wednesday morning are staggering, with some favored locations getting to 4-6 inches of rain.  This is unusual for June, to put in mildly.


Even in rain-shadowed Seattle, the ensemble forecast of many simulations suggests we will receive about 2.5 inches (blue and black lines are the ones to look at). 
Much more than the average TOTAL rainfall for the ENTIRE MONTH OF JUNE here in Seattle (1.42 inches)

Such heavy precipitation will saturate the regional soils and cause rivers to rise rapidly, with the NOAA/NWS River Forecasting Center (RFC) predicting a rapid rise to action levels and the exceedance of the previous daily records (red up arrows).


Most impressive of all is that this heavy precipitation period is associated with multiple strong atmospheric rivers.  To illustrate, below are plots of water vapor transport, the best measure of atmospheric river activity.  Blue colors are very high.

Sunday night at 8 PM an amazingly strong river heads across the Pacific and then slams into our region.


On Tuesday morning, ANOTHER river plows into the Northwest.  Really unusual for June.


Expect many precipitation records to be broken.





22 comments:

  1. Cliff,

    Could you expand this to include a closer look at Eastern WA/Northern ID during this rain event?

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  2. Unfortunately, it doesn't look like it's coming from Hawaii. I prefer warm rain to cold rain. Can it actually be true, the warm rain (such as we get) doesn't come in summer?

    NOAA says it will turn warm and dry in about a week. I hope they're right.

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    1. Friends here, job here, family here... Might retire somewhere sunnier though.

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  3. I fear for the ripening cherries.

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  4. The Seattle Times will cry wolf and tell us how we're all doomed come summer. Drought and massive wild fires. They are part of the Climate Crisis Industrial Complex.

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  5. It's at this time of year that I really hate the wet weather here.

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  6. Followed by a potential heatwave afterwards according to the cpc.

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    1. Tim... that is not correct. No following heatwave...just checked the latest forecasts..cliff

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    2. All I know is, the 8-15 day forecast (NOAA) is for above normal temperatures and below normal precipitation. And after 3 cold weekends, I hope they are right.

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    3. Dunno about you westsiders, but over here in Tri-Cities they're forecasting upper 90s and even triple digits. But anything over four days is speculation.

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    4. Even if we get a good rain out of this I think it would be too early to write off the fire season, especially east of the Cascades. June can be a critical month in determining the severity of the up-coming fire season but one good rain early in the month will likely not lead to an easier fire season, if the month as a whole ends up warm and dry, and July and August are warm and dry as predicted in most extended outlooks. Some models are forecasting a quick change to hot and dry later next week and if this predominates for the rest of June, the fire season could be on us pretty quick. Consider what happened in June 2021 when a period of rain in mid June was supposed to delay the season, but a very hot, dry pattern followed which quickly brought high fire danger to Eastern Washington.

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    5. You must be part of the "industry".

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    6. Tim is this blog's own personal Eeyore. Never fails to come through with a gloomy take on everything weather - related.

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    7. This just in: Tim was right (https://cliffmass.blogspot.com/2024/06/new-podcast-heavy-rain-event-heat-wave.html).

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  7. I see the next weekend June 6-7 is in the mid 80s for Olympia

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  8. Professor Mass, I’m not disagreeing with you, I’m not qualified to, but UW’s Atmospheric Science Discussion this morning mentions deterministic models forecasting a potential hotter spell. https://a.atmos.washington.edu/data/disc_report.html#ksew

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  9. Loving the cool start to "summer". This is the latest I have seen potential for frost/freeze. We have those advisories in North Central to northeast Washington. How often has that occurred end of May?

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  10. Accuweather thinks Ellensburg will be 90° on Sat the 8th. Then 81 and 77. Not much of a heat wave.

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  11. According to CPC and NWS the 8-14 day period is looking like 80-90% chance of above normal temperatures with a high pressure parked overhead us. Starts on/around June 6.

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  12. I have been surprised at the lag in reporting on this anticipated event, only yesterday, Thursday, did NOAA finally publish a hydrological outlook. And both the Weather Channel and Weather Underground still only report "showers" for Sunday and Monday.

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