Tuesday, June 6, 2017

Ahead of schedule: When our first 90 degree day usually occurs

On average we usually experience our first 90 degree day within the first week and a half of June.  Of course, 90 degrees can occur well before that and even well after.  One year we didn't record a 90 degree temperature until September!  In any given year Rockford typically averages about fifteen 90 degree, or higher, days.

We had our first 90 degree day this past Sunday and will likely experience several more 90 degree days this upcoming weekend.  A fairly sizable pattern shift within the jet stream will occur late in the week allowing a big warm up to occur over much of the country.

A strong area of low pressure now in the Gulf of Alaska will move into the Pacific Northwest.  This will push the jet stream northward over the Plains, Midwest and East Coast by the end of the week and weekend.  With the northward shift in the jet stream, much of the storm activity will remain north as well.  With little rainfall expected in the forecast, temperatures will be free to warm into the low 90's.  Humidity will also be rising which could push heat index values into the mid 90's.

By next week, the low forming in the northwest will help carve out a trough in the jet stream over the Plains.  This will bring thunderstorms, possibly severe, over the Plains early next week.  As the low is pulled into the upper Midwest showers and thunderstorms are possible Tuesday into Wednesday, depending on when the cold front associated with the low actually moves through. 

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