Unusually Strong Cold Front (with Lightning) Hits the Northwest

Summer cold fronts are generally unimpressive around here, often bringing cooler marine air accompanied by a transition to increased onshore flow.   But last night we had a stronger than normal summer cold front that brought lightning and burst of heavy rain.

The radar image around 6 PM Sunday was impressive, with the yellow colors indicating heavy precipitation.

By midnight, the heavy precipitation reached Puget Sound and as many folks can attest, there was some serious lightning with the frontal band.

In fact, the regional lightning detection network observed hundreds of lightning strikes during this frontal passage (the figure below shows the strikes for the 24-h period ending 1 AM Monday).

If you want to get a real feel for the lightning, here is a video looking north from the northern Kitsap Peninsula from Greg Johnsons Skunk Bay Weather facility.  Pretty exciting at Skunk Bay.  No missile shots or UFOs!


The infrared satellite image at 8 PM Sunday was impressive for June, with a strong frontal band making landfall on the WA coast.

The precipitation totals from this band were modest...precipitation was heavy but it moved through quickly.  Particularly, heavy precipitation fell over the north Cascades (half inch), but lots of locations observed a tenth or two of rain.

On top of the atmospheric science building at the UW, the frontal passage was very obvious around
07-08 Z (GMT)--around midnight to 1 AM Monday.  About .15 inch of rain (bottom panel), an increase of wind (top panel), and an interesting, sudden jump down of pressure (fourth panel).

So why did we have so much action last night?   The front was fairly strong but a key was elevated instability (known as elevated CAPE, Convective Available Potential Energy, in the weather business).  The upward motion with the front released the instability, resulting in numerous thunderstorms.

This week should be cool with plenty of low clouds in the morning and early afternoons.  Typical weather for this time of the year.  But don't worry....the latest model runs suggest a big improvement by early July.

from Cliff Mass Weather and Climate Blog https://ift.tt/2yFtRbw