Showers and isolated thunderstorms possible Wednesday afternoon and evening


It was another sun-filled afternoon Tuesday as temperatures once again reached the low 70s, officially warming to 73 degrees in Rockford, twelve degrees above average. Skies remain clear for most of Tuesday evening, but we should begin to see a few more clouds filter in through the night. This will help keep temperatures on either side of 50 degrees by Wednesday morning.

A strengthening low pressure system developing over eastern Colorado Tuesday evening will begin moving east, pulling into northwest Iowa by Wednesday morning. Southerly winds ahead of the low will bring temperatures into the low 70s for the afternoon. A slight increase in moisture ahead of the low, and ahead of the cold front, will allow a few showers and isolated thunderstorms to develop during the afternoon and evening. However, with southwest winds for much of the day it’s likely we develop a cap, or lid, on our atmosphere by the afternoon and early evening. This could help prevent thunderstorm development as the cold front nears. A rather strong upper level jet streak is forecast to round the southern edge of the low/trough, moving over northwest Illinois and southern Wisconsin. This will help increase the shear throughout the atmosphere (increasing winds with height), but instability remains somewhat limited.

If, however, there is enough energy to break through the cap during the late afternoon and evening it’s possible that a strong thunderstorm or two could form, with the greatest risk being wind and hail. By Wednesday evening the cold front will have passed and this should help us remain mostly dry through Wednesday night. Moisture wrapping back in around the low Thursday morning could bring us an isolated shower or two, with skies remaining mostly cloudy through Thursday afternoon and evening.

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