Late May-Early June Outlook

So far our spring weather has been less than desirable. Many have said that this spring has been the worst spring in a long time with many believing that rainfall must be close to a record for spring.

Rainfall since April 15th has been well above normal (normal is 3.7"). Interestingly rainfall has been almost identical to the last 2 spring seasons.

So why does it seem that the weather recently has been much worse?

I used 3 different measures in determining how the spring has gone. 

* Number of days with rainfall

* Cloudy Days (at least 50%)

* Temps vs normal

I used the last 30 days (April 15 - May 15) as the time period.

Sure enough, we've had more rainy days and cloudy days for sure with very little breaks.  But contrary to popular belief, the temperatures have not been all that cooler than normal. 

Will the pattern start to dry out or will a rainy pattern redevelop in the long term?

The PNA is starting a dive below normal in the next 10 days. By itself, this indicates troughiness west and ridging (warmth) eastern half of the US.

The Euro has been picking up on this configuration for a few days. A brief warmup this weekend (May 18-19), a break followed by the ridge blowing up and expanding north to start Memorial day weekend!

Earlier in the week (May 13th), I tweeted the SOI (southern oscillation index) changes and the matching 500 mB composites for the end of the month.  Based on these, the pattern looks to do two things:  First the SE ridge flattens out and shifts south.  Secondly, the storm track re-positions itself back through the middle of the US.   The EURO is starting to pick up on this flattening by the 27th of May.

If all of this evolves like I think it will, rainfall will be above normal by month's end across the central US and portions of the Ohio Valley.  Temperatures for the Ohio Valley will be normal to slightly above normal with frequent rain systems with little breaks to start June. Will this above normal rainfall effect temperatures in early summer?   Very good chance

Lake Erie is quickly reaching near record levels

Interesting Iowa Corn Yield Data

Per Iowa Extension Agents: 

"At the state level historical USDA-NASS data indicates that if 50 percent of the corn is planted before May 15 the chances for high yield potential still exists (Figure 1). In only five of 40 years the 50 percent corn planting point has not occurred before May 15. In each of those five years, the statewide corn yield was below trend line."

14 day rainfall vs normal. Heaviest rain across Oklahoma, Missouri, Kansas, northern Illinois. Below normal rainfall in Iowa.

Long range projections show significant rainfall across the cornbelt over the next 10 days

EURO 10 day rainfall totals

GFS 10 day rainfall totals