It’s Thursday, Thursday.

Thursday, April 5, 2012

9:43 A.M.
Yes, it may not be Friday, and the weekend may actually be two days away, but I’m still pretty darn excited. Besides it being Easter Sunday, which is always in style, the weather is expected to be nicer than it has been in a while. It certainly won’t be hot and sunny, but it will be warmer than we’ve seen in a while. It will definitely be good picnic weather and a great day to go relax in the UW quad. I just can’t get enough of how beautiful the cherry blossoms are right now. Of course, I wish there were actual cherries involved, but I’ll take cherry blossoms any day.
Before then, we’ve got some weather to go through. Today could be an interesting day for weather for certain places, because we’ve got cold air overhead and strong solar insolation. When the sun heats the lower atmosphere, air expands and decreases in density, and these air parcels continue to rise through more dense and colder air in the mid-upper trophosphere. This phenomenon creates towering cumulus clouds, and, if the conditions are right, thunderstorms. The air mass isn’t too unstable today, so if there are any thunderstorms, they will be isolated. We could see some beautiful cumulus clouds though.
Cumulus congestus clouds
 Weak cumulonimbus over Seattle
And here’s a picture of a supercell thunderstorm. We will not be seeing these today.
Of course, our thunderstorms are a far cry from the thunderstorms seen east of the Rockies at this time of year, but they are interesting nonetheless. There actually was one time where we got some very well developed thunderstorms on the Cascade foothills, but they were still much weaker than storms like the one pictured above. The UW atmospheric sciences department loves this picture.
Ok, now let’s get onto our forecast. Chilly with a slight chance of thunderstorms today, especially along the coast. We could see a few showers tomorrow as well, but they will be more isolated and weaker than today.
Then comes the weekend. 
Right now we’ve got a pretty big trough off our coast, which is directing cool air into our region. 
Valid 05:00 am PDT Thu, 05 Apr 2012 – UW 36km WRF-GFS 1000-500mb thickness, SLP
But look what happens on Saturday. We get a little ridge over our area, which will direct warmer air into our region.
Valid 05:00 pm PDT Sat, 07 Apr 2012 – 60hr Fcst –  – UW 36km WRF-GFS 1000-500mb thickness, SLP
The ridge will strengthen on Sunday before a weak trough moves in on Monday, giving us a chance of showers and thunderstorms.
Enjoy your Thursday!
Charlie
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