Fwd: severe threat Tuesday + season to date + Memorial Day outlook + summer outlook

---------- Forwarded message ----------
From: Philip C. Ordway <pcordway@gmail.com>
Date: Mon, May 23, 2016 at 9:13 PM
Subject: severe threat Tuesday + season to date + Memorial Day outlook + summer outlook
To: "go@blogger.com" <go@blogger.com>

• After another picture perfect day (and the 10th straight without any rain), tomorrow (Tuesday) features a good chance of thunderstorms, mostly in the afternoon and evening. Some of the storms may be severe and watches/warnings may be required. Dewpoints will also climb into the 60s on Tuesday night -- the first real dose of humidity of the season. 
• The thunderstorm threat will continue through Wednesday night, although the likelihood of severe weather is lower. The likelihood of storms is high but they will not be continuous -- there will be plenty of breaks in between. The entire area will not see uniform rainfall, but average rainfall in the next few days is likely to exceed 1" and any locations favored by thunderstorms could see 2" or more.
• High temperatures all week should stay in the 70s to low 80s (with slightly cooler temps along the lakeshore).

• It's not your imagination: spring to-date in the area has been running cool and cloudy. Sunshine is running well below average, and we've only posted 14 Cooling Degree Days* -- that's the fewest since 2008 and compares to an average of 44. (The 50-year average at Midway for the full year is 1,045.)

• It is still very early, but the overall pattern for the upcoming Memorial Day weekend looks pretty good. It won't be as good as the past couple of days, but nothing to complain about either. A few passing storms look likely, but the majority of hours will be dry with high temps in the 70s to low 80s. 

• With the usual caveats (seasonal outlooks are marginally informative at best, subject to significant ongoing revision, etc. etc.) here is an update on the summer (June - August) seasonal projection. As with year, when an exceptionally strong El Niño provided helpful information about the likelihood of a mild winter ahead, we are now dealing with the transition to a La Niña and the attendant likelihood of a hot summer. Again, the causality is not well understood, but the correlation is strong enough to deserve a mention. 

* A Cooling Degree Day is a crude approximation of demand for air conditioning. Take the simple average of the day's high and low temperatures and then subtract 65 to calculate CDDs. For example, yesterday at O'Hare the high was 77 and the low was 53 for an average of 65 -- no CDDs were recorded for the date. Today we bottomed out at 48 but if we hit the forecast of 83 we'd record 5.5 CDDs. The same principle works for temps below 65F with regard to Heating Degree Days.