Lightning and Thunderstorms Over and East of the Cascade Crest

 The National Weather Service now has a flash flood warning due to potential thunderstorms over north-central Washington, from the North Cascades northeastward.

As I will describe below, thunderstorms are a good bet, but I suspect the flooding threat is relatively low.

Convective storms, some with thunder and lightning, did occur yesterday (Sunday) over the Cascades and were even visible from Seattle:

Terminology alert:  meteorologists often use the term convection for unstable situations that result in cumulus clouds and sometimes thunderstorms.  Convection is generally associated with a large decrease in temperature with height, causing the air to convect, with up and down motions.

The convection/thunderstorms yesterday produced precipitation over northeast Washington (see totals below), with only modest lightning.

Today there is potential for more unstable air, convective showers, and some lightning and thunder over and east of the Cascades.

The visible satellite at 9 AM this morning shows considerable cloudiness over the region, with some convective cells evident over south-central WA (whiter areas).

The current (10:42 AM) weather radar is picking up some showers with this convection/instability:

Today's model runs are emphatic that convective showers will develop this afternoon over the Cascades, the Okanogan, and northeast WA.

Here is the simulated radar impact at 3 PM from the UW WRF model, with the orange colors showing the heaviest rain from the convection.

The forecast of the NOAA HRRR model at the same time is similar.

The total precipitation through 5 AM Tuesday (shown below) is moderate, with highest amounts reaching 1.5 inches.  Not enough for flooding.

The occurrence of this precipitation is associated with an upper-level low over eastern WA (see map today at 2 PM for around 18,000 ft).

My only worry about this event is that the associated lightning could start some wildfires.    One reason we have had such few fires this summer is the lack of lightning-induced fires.

This is not an accident:  the same large-scale conditions that gave us a dry summer have also reduced lightning.

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My Atmospheric 101 course this autumn.

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