The past week was short on spring with featuring well below normal temperatures and record cold. Here's the temperature departures for the May so far..
The past 7 days were especially frightful with most of the Midwest 10-15 degrees below normal.
We've yet to see a stretch of warm muggy weather this spring which we all know is just a matter of time. In fact, the signs are on the wall and we're likely to get a taste of that in the near future. These are the 10 day temperature departures on the EURO ensembles. That's a dramatic change.
A significant re-alignment in the storm track will lead to the increase in temperatures. Look at the 500mb jet stream today with its northwesterly component and chilly feel.
Late this week the eastern trough breaks down and by May 20th is replaced by a strong ridge.
That type of flow aloft not only brings warmth but moisture. That is readily apparent in this graphic depicting water vapor around May 20th. The deep moisture is pumped northward all the way to the Canadian border.
At the same time the EURO shows a 70 dew point all the way to Cedar Rapids and Chicago. That would be the first of its kind this spring.
With temperatures on the EURO shown hitting the mid 80s you can bet there will also be an increase in instability and thunderstorms.
Occurring in the later half of May that also increases the chances of strong to severe thunderstorms. Surface CAPE certainly points that direction.
As the warmer air makes an initial attempt to get in here it should result in some wet weather Wednesday night and perhaps Thursday morning. Additional showers and storms are possible parts of Friday night and Saturday. The heaviest amounts appear to be poised to fall across the south where some some big rain numbers are indicated. These are totals for that period. Some 3-5" amounts are on the table near I-80.
This system never really gets the summery air into the central Midwest but it starts the process of breaking down the eastern trough. I look for highs in the 60s and low 70s during this period. It's not until early next week when the 80s and higher humidity combine to bring us a long awaited taste of summer. Time to flip the switch. Roll weather...TS