The latest suite of computer model forecasts--and from more than one meteorological agency--are worrisome in terms of July 4 weather here. A number of the latest runs appear to heighten concern that sections of the Chicago area is in line for rainfall Friday night into Saturday. Thundery downpours have been predicted for the early weekend downstate--part of a swath of significant precipitation which has been expected extend from Missouri across sections of downstate central and southern Illinois and Indiana. In at least sections of that area, rains have been predicted to top 2" in the Friday night/Saturday period. But now (as of early Thursday afternoon), several models are aggressively shifting the eastbound storm onto a more northerly storm track increasing rain prospects over at least portions the Chicago area with rain accumulations trending heavier the farther south one travels. Hitting the northward shift in the wet Friday night/Saturday storm's movement are the Canadian, European and Navy global forecast models. Less impressive are the lighter, more scattered rains projected here by the Weather Service's GFS and WRF models. These models continue to highlight southern Illinois and Indiana as areas likely to be at the epicenter of the heaviest early weekend rains--south of a Quincy to Terre Haute line by in large.
If you've been following our weather programs this week, you know this is hardly a completely surprise---it's been a development we've viewed as a wildcard scenario for some time. We're in the midst of evaluating the new data and model runs and will have more here and on our 5:30pm and 9 pm programs and on our WGN radio reports this afternoon--and on the Chicago Tribune weather page Friday.
What has happened to summer? That was the question from many area residents Wednesday amid May-level 60-degree temperatures. The day's high of 65-degrees marked the chilliest open to a July here since 1930 and was one of the three coolest July 1 readings on the books in 139 years of weather records since 1871. Summer temperatures at that level are truly rare. Of 7,452 meteorological summer (June through August) highs on the books since 1928 at Midway, only 184 of them--just 2 percent---have registered temperature as cool or cooler.
Scattered lake-enhanced rain showers amid the Wednesday's chill lowered cloud bases in the downtown area, obscuring the tops of skyscrapers while producing periods of upper 50-degree temperatures.
While Chicago missed the July 1 record low maximum of 61-degrees set 1904 and 1924, record low daytime highs occurred at Rockford (65-degrees) and downstate at Lincoln where the high was just 70-degrees.
Thundery downpours could be part of the holiday weekend downstate
Thunderstorms expected to erupt in the Plains later Friday threaten to track east/southeastward into sections of downstate Illinois and Indiana where they may produce downpours totaling 2 or more inches for a portion of the upcoming July 4 holiday weekend.
Dear Tom,
Our family vacations every summer on Cape Cod, and we usually enjoy the sun,
ocean and beaches. But the weather there has been awful the last half of
June: fog, clouds, rain, chilly temperatures. Any thoughts on what has been
happening?
Ron Szafranski, Wheaton
Dear Ron,
Blame it on a large, stubbornly persistent atmospheric feature known in
weather circles as a "cutoff upper low." It consists of a huge (a few
hundred miles in diameter) nearly stationary pool of very cold air aloft
that has become isolated from prevailing upper wind patterns.
The weather beneath such systems is cloudy, rainy and chilly, and Cape Cod
was caught in that pattern while an unusually persistent cutoff upper low
sat just off the New England Coast. Now, though, it's gone and a more
typical summer weather regime has settled across New England: pleasant
temperatures, plenty of sun, but some showers too.
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