A Review of the Spring 2017 Season

Spring 2017 continued the warm trends seen in each of the seasons during the last two years. Most of the country averaged warmer than normal, except for New England. The March to May period ranked as the 8^th warmest and 11^th wettest out of the last 123 years according to NOAA data. The following maps show the average temperature anomalies across the country during the spring season, along with the individual state rankings.

There were some cool periods, though, as the plot below shows. Mid-March and early May featured some cooler than normal weather, but the second half of March and all of April were quite warm.

While, warm, much of the country was also quite wet, and additional heavy snowfall was seen across the Rockies, Cascades and Sierra. The following maps show the average precipitation anomalies across the US (average of the monthly precipitation anomalies) and the state precipitation rankings. The Corn Belt and Great Lakes region were very wet along with the Northwest, and the heavy rains around the Great Lakes have helped to push the water levels on the Great Lakes to the highest levels in seen in 20 years. This only 10 years after the Great Lakes were running at near record low levels.

Severe weather has continued to run at higher than average levels as well. Tornado activity slowed some in the last month relative to earlier in the year, but year-to-date counts remain above normal. Historically, years following a La Nina winter have seen much more tornado activity than normal earlier in the year, but also a faster end to the tornado season.  That pattern has largely played out this year. The following plot shows the tornado totals to date compared to normal. Note that tornado activity normally diminishes after mid-June, with over 70% of the annual number of tornadoes normally occurring by the end of June.

While tornado activity has likely peaked for the year, we have not yet reached the normal peak in high wind events. Strong thunderstorm wind events normally peak around late June, but stay elevated right on through early August. So, the risk for damaging wind events will remain high for a couple more months even though the risk for tornadoes diminishes quite a bit after mid-June.

The summer season is so far off to a warm start as well, and the map below shows the current temperature anomaly projection for June 2017. This map includes observations-to-date plus the forecast for the balance of the month. Like the spring season, most of the country looks to once again average warmer than normal for the month of June.