Tuesday, July 4, 2017

Fourth of July and Severe Weather Potential Thursday

Happy Fourth of July!  The weather has been pretty nice so far, but it has been fairly hot and humid with heat index values hitting the upper 80°s to low 90°s.  These conditions have allowed for a couple of isolated showers and an isolated thunderstorm to develop down in Ogle county, but these are expected to clear out before the fireworks start this evening. 

The humidity will stay with us through the overnight, so patchy fog is a possibility early tomorrow morning.  We have a chance for some isolated thunderstorms during tomorrow afternoon as a weak low will approach our area, continuing the inflow of heat and humidity.

We are under a Slight Risk for severe weather Thursday evening when a cold front will move down from the north.  This, combined with the continuous heat and humidity inflow, will allow for strong thunderstorms to develop along the front.

We'll dry up to and cool off a little into the low 80°s, but isolated storms will return for Sunday and hot temperatures will come back on Monday.  However, we'll cool right back down into the low 80°s next Tuesday.

Thursday evening:
Temperatures are expected to hit the upper 80°s to low 90°s on Thursday as that heat and humidity will continue moving up from the south due to a low-level trough will dig southwestward into the plains.  The upper level jet will be moving out of the northwest, allowing for colder temperatures aloft.  This will make it easy for the hot and humid air at the surface to rise and create isolate thunderstorms during the afternoon.  These thunderstorms will be capable of producing hail and gusty winds.  The front will move in a little after 7pm, which will increase our wind shear and allow for stronger thunderstorm development.  Hail and strong winds will be the main threats with the storms that form along the cold front, but higher instability and wind shear will be seen to the northwest.  That will allow for a few isolated tornadoes in those thunderstorms, but any thunderstorms that form in our area will not likely see tornadoes.  The storms will be tracking southeast, but even though the storms forming to the northwest may produce tornadoes, they more than likely won't produce tornadoes by the time they get to our area as our wind shear environment will be weaker.  The front will move out after 1am, which is when the thunderstorms are expected to die down.

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