AFTERNOON – OVERNIGHT: An area of high pressure remains in place across the forecast area through the daytime hours today.
Through the daytime hours there looks to a mix of clouds and sun.
While today does look mostly dry across zones 6 and 7, there is an upper level disturbance that will be moving just to the south of the forecast zones this afternoon. As it moves closer to the area it will prove enough spark some isolated afternoon rain showers across zone 6. Best timing for rain showers will be after 3-4 pm, those will be moving from south to north.
Through the evening into the night-time hours any showers that are left across the area will start to fade out. It does appear we will remain dry through most of the overnight hours.
By late in the overnight into early Saturday morning a warm front will be advancing northward towards the region. As it does rain and perhaps a couple of thunderstorms will develop north of the front and move into the region around 4-5 AM.
Lows overnight will be in the mid 40’s north to mid 50’s south.
WEEKEND: By 7-8 am Saturday morning rain and possibly a couple of thunderstorms will continue moving northward across zone 6 and 7.
Through mid-day the warm front will continue its northward advancement, as it does rain and t’storms chances will move northward with it. I still think scattered areas of rain and a few storms will be possible across zones 6 and 7 by the noon hour Saturday.
Scattered areas of rain will continue across zones 6 and 7 through the afternoon hours on Saturday. As we get into the late afternoon and early evening chances for thunderstorms will be on the increase.
Highs on Saturday will be in the low 60’s north to low 70s south.
Saturday night into Sunday the warm front will lift northward through the forecast zones. As it does the area of isentropic lift will allow for rain and thunderstorms to continue across the forecast zones through the overnight.
Lows Saturday night into Sunday will be in the mid 50’s north to around 60 south.
Sunday morning the warm front looks to remain in place across Illinois, this as an area of low pressure starts to move into the state from the west. Scattered areas of rain and some thunderstorms chances will remain into the early morning hours on Sunday.
While we may see a brief lull in action late Sunday morning into early afternoon, some instability will start to build in during that time.
The instability will lead to the rejuvenation and/or redevelopment of afternoon rain and storms on Sunday. While no severe weather is forecast this weekend, a few storms Sunday could produce some gusty winds.
Highs on Sunday will be in the mid 60’s north to low 70’s south.
Sunday night the surface low will move off to the northeast of the region. As it does I think aid in drier conditions.
If this were normal circumstances I would take rain out of the forecast all together Sunday evening into the overnight. However, there is an upper level trough that will be moving through the southern portions of the forecast region. With the upward motion this will create, I will leave scattered rain chances in the forecast through the overnight.
While some areas of heavy rainfall will be possible through Sunday night, I think the average will be about .40-.60”. However, places that should get under a thunderstorm or two could see locally heavier amounts of 1 – 1.50”.
Lows Sunday night will be in the 50’s.
MONDAY: The upper level trough will be moving to the east of the region though the day on Monday. While rain chances can’t be totally eliminated from the forecast, I do think we will see the best chances for rain in the morning.
Through the afternoon hours on Monday rain chances will decline, perhaps giving zone 6 and 7 a mostly dry afternoon and evening.
Highs on Monday will be in the mid 60’s to low 70’s.
TUESDAY: A strong area of low pressure will start to develop to the regions west on Monday. This area of low pressure will move to the east into or close to the forecast area through the day on Tuesday.
As the low pressure moves through the region it will drag a cold front with it. This will be a very sharp cold front, so as it moves to the east and northeast it will provide plenty of lift for rain and thunderstorms to develop Tuesday afternoon and evening.
Yesterday I mentioned that models were having a tough time developing rain and storms along the front because of the lack of moisture. However, the latest guidance has a negatively tilted surface low. The negative tilt will allow for a stronger more southerly surface flow, therefore resulting in better moisture returns.
With strong upper level winds in place with this system the biggest question is will there be instability and if so how much. The latest GFS model places 1000 J/kg of CAPE across the region. This would prove enough to support thunderstorms, some possibly strong.
This is a forecast we will have to really fine-tune as we get closer to the event and the mesoscale details become better known.
7 DAY FORECAST
SATURDAY: MOSTLY CLOUDY WITH A 40% CHANCE OF RAIN & A T’STORM. HIGHS IN THE LOW 60’S NORTH TO LOW 70’S SOUTH. WINDS FROM THE SOUTHEAST AT 6-12 MPH, GUSTS TO 20 MPH.
SATURDAY NIGHT: CLOUDY WITH A 40% CHANCE OF RAIN. LOWS IN THE MID 50’S NORTH TO AROUND 60 SOUTH.
SUNDAY: MOSTLY CLOUDY WITH A 60% CHANCE OF RAIN AND T’STORMS POSSIBLE. HIGHS IN THE MID 60’S NORTH TO LOW 70’S SOUTH. SOUTHERLY WINDS AT 5-15 MPH, GUSTING TO 20 MPH.
SUNDAY NIGHT: MOSTLY CLOUDY WITH A 50% CHANCE OF RAIN. LOWS IN THE LOW 50’S NORTH TO UPPER 50’S SOUTH.
MONDAY: MOSTLY CLOUDY WITH A 40-50% CHANCE OF RAIN AND A FEW T’STORMS. HIGHS IN THE MID 60’S NORTH TO LOW 70’S SOUTH. SOUTHWEST TO WEST WINDS AT 6-12 MPH, GUSTING TO 25 MPH.
MONDAY NIGHT: PARTLY TO MOSTLY CLOUDY WITH A 20% CHANCE OF SHOWERS. LOWS IN THE UPPER 40’S NORTH TO MID 50’S SOUTH.
TUESDAY: PARTLY SUNNY TO MOSTLY CLOUDY, 50% CHANCE OF PM RAIN AND T’STORMS, SOME POSSIBLY STRONG? HIGHS IN THE UPPER 60’S NORTH TO UPPER 70’S SOUTH. SOUTHWEST TO WEST WINDS AT 12-25 MPH, GUSTS TO 35-45 MPH.
TUESDAY NIGHT: DECREASING CLOUDS, 30% CHANCE OR RAIN & T’STORMS EARLY. LOWS IN THE LOW 40’S NORTH TO AROUND 50 SOUTH.
WEDNESDAY: MIX OF CLOUDS AND SUN. 20% CHANCE OF RAIN. HIGHS IN THE LOW 50’S NORTH TO LOW 60’S SOUTH
WEDNESDAY NIGHT: MOSTLY CLEAR WITH LOWS IN THE MID 30’S NORTH TO MID 40’S SOUTH.
THURSDAY: MOSTLY SUNNY TO PARTLY CLOUDY, COOLER. HIGHS IN THE LOW 50’S TO LOW 60’S.
THURSDAY NIGHT: INCREASING CLOUDS FROM WEST TO EAST. LOWS IN THE LOW 30’S NORTH TO MID 40’S SOUTH.
FRIDAY: MOSTLY CLOUDY WITH INCREASING RAIN CHANCES. HIGHS IN THE LOW 50’S TO NEAR 60.
FRIDAY NIGHT: CLOUDY WITH A CHANCE FOR RAIN AND/OR SNOW. LOWS IN THE LOW 30’S TO MID 40’S.