Storms Later Tonight and Sunday

A cool front is advancing across the plains this evening. Strong thunderstorms developed this afternoon over the northern plains in advance of the front. Our region was very warm once again on Saturday with afternoon temperatures reaching above 90 degrees. It was not as humid as expected, and the dew points dropped into the upper 50's to mid 60's this afternoon as drier air from aloft mixed down to the surface. This drier air will tend to lessen the chance of thunderstorms from developing until later tonight as the cool front to the west gets closer, and a moist tongue of moisture in advance of the front causes our dew points to rise. As of 11 pm Saturday night the moist tougue of air with 70+ dew points covers all of Iowa as far east as the Mississippi River.  This higher dew point air is expected to continue to encourage the development of strong thunderstorms as the complex moves southeast across northern Iowa into southwestern Wisconsin, and eventually northwestern Illinois later tonight. But by the time they reach north central Illinois, the storms are expected to be in a weakening phase. A lot is dependent on how moist our air becomes. There is a good chance of thunderstorms on Sunday as the cool front slides slowly through the area.  The front will move off to the southeast tomorrow afternoon allowing drier air to move into the Stateline on Sunday night.  Weak high pressure will keep the area dry on Monday.  The next disturbance to affect the area will be approaching on Monday night bringing chances of thunderstorms back to northern Illinois.  A quasi-stationary front will linger nearby for most of the rest of the week across the area.  The Stateline will be situated on the northern fringe of a massive hot air dome to our south, and we will be on the southern edge of the westerly winds.  Disturbances will move through from time to time next week causing thunderstorm complexes to develop on a daily basis from Monday night through next Saturday.  The thunderstorm clusters are called mesoscale convective complexes, and the best chances for storms in the Stateline will be at night.  Hence, the name nocturnal thunderstorms.  There is the potential for some areas to get significant rainfall in the coming week.  Many areas have received substantial rainfall in recent days.  That is not the  case around Rockford.  Rockford is running a deficit of more than a inch and a half for the month of July.  So we could use some good rains here in the Rockford area.  Next week temperatures will continue to run above normal.  Enjoy the summer weather.  Fall will be here before you know it.  Have a great Sunday.
By Meteorologist
Eric Nefstead