AFTERNOON – TONIGHT: An area of high pressure remains in control of the weather today. This will allow for sunny to mostly sunny skies to remain in place through at least mid-afternoon.
By 4-5 pm clouds will start to increase from west to east across zones 6 and 7. However, no precipitation is forecast to occur with these.
Through the overnight clouds will continue to thicken up from west to east. While most of the overnight will be dry, by 5-7 am a few isolated light showers will be possible across western Illinois.
Lows overnight will fall into the low to upper 40’s.
WEDNESDAY: Through the morning hours on Wednesday only isolated rain showers will be possible across zones 6 and 7. However, as we get to the 11 AM – 12 PM hours more scattered areas of rain and even a few t’storms will develop, especially across northern zone 6 and zone 7.
Through the afternoon scattered afternoon rain and some t’storms will continue across Illinois. By 4-5 PM the better chances of rain/storms look to be located across northern zone 6 and zone 7.
Highs on Wednesday will be in the low 60’s north to around 70 south. Winds will be strong at times with gusts of 30-35 mph possible.
Overnight Wednesday into Thursday morning scattered areas of rain and some t’storms will continue across both zones 6 and 7. While I’m not anticipating any severe weather Wednesday night, a couple gusty storms with some periods of heavy rain will be possible.
Lows Wednesday night will be in the low 50’s north to around 60 south.
THURSDAY: Isolated to widely scattered rain and a few storms will remain possible through 7-9 Am Thursday morning, but rain chances will come to an end at least briefly by the mid-day hours.
Late morning into the evening a low pressure system will move to the north of the forecast zones. As it does, an associated cold front will move to the east and southeast across Illinois through the afternoon and evening.
Highs on Thursday will be in the low 60’s west to upper 60’s east/south. Winds will be very strong through the day on Thursday. Sustained winds between 15-25 mph and non-thunderstorm winds gusts up to 50 mph will be possible.
By noon the cold will be in place across northwestern Illinois. Out ahead of the front models depict precipitation ending. The NAM even shows some clearing ahead of the cold front late morning into the afternoon.
This clearing will be crucial to determining the overall weather forecast. If clearing is realized late morning into the afternoon and some sunshine does get through it would allow instability to build. This is what is forecast via the NAM as CAPE values across the forecast area would be around 1500-2000 J/Kg.
Aloft strong southwesterly winds would be present. A strong 500 mb flow of 95-105 mph from the southwest would be in place across the region. This coupled with 45-55 mph 850 mb winds from the southwest would be supportive of organized strong to severe storms Thursday.
With winds from the surface and upwards into the atmosphere from generally the same direction storms would likely develop into lines quickly after initiating. With that in mind, damaging winds, hail, and possibly a few tornadoes would be the main threats.
The cold front will continue to swing south and southeast across Illinois through Thursday afternoon. Rain and storms look to develop along said cold front around 2-4 PM.
As they do, these storms will race very quickly off to the east and southeast. By 6-7 PM the line of storms will be racing into west-central Indiana and southern zone 6.
By 10 PM Thursday night the cold front and storms will be to the south and east of the forecast zones. However, a few leftover shower will remain possible before midnight.
New rainfall totals through Friday morning do look pretty impressive across both zones 6 and 7, especially from I-70 south. The NAM shows a majority of the area getting .60-1” of new rainfall, with some places getting up to 1.80” right across I-70.
The GFS keeps the heaviest rain south of I-70, mainly across the southern half or so of zone 6. That’s where wider spread totals of .50-1” would occur. However, much heavier totals would occur closer to the Ohio River. The thing to keep in mind is, the GFS is quicker than the NAM with a cold front passage Thursday. If that occurred, it would keep the heavier rains farther south.
Regardless, with heavy rain expected over portions of the area flooding will remain a concern for the areas that do see higher totals.
Overall the weather forecast for Thursday will need some fine-tuning over the next 24 hour or so as models are still off synch with each other. We will keep bring you the latest as needed.
FRIDAY: Overnight Thursday into Friday rain will end across the forecast area. Behind the cold front an upper level trough will build into the forecast area.
With the upper level trough in place Friday will be a cooler day with highs in the low 50’s north to low 60’s south. Winds will remain strong with gusts up to 35 mph possible.
By 12-2 PM Friday afternoon an upper level vorticity max will move across the forecast area. As it does it will allow for some isolated to widely scattered rain to develop across zones 6 and 7.
7 DAY FORECAST
WEDNESDAY: PARTLY TO MOSTLY CLOUDY WITH A 30% CHANCE OF PM RAIN AND A STORM, ESPECIALLY WEST. HIGHS IN THE LOW 60’S NORTH TO AROUND 70 SOUTH. WINDS FROM THE SOUTH AT 8-16 MPH, GUSTING TO 30-35 MPH.
WEDNESDAY NIGHT: MOSTLY CLOUDY WITH A 50% CHANCE OF RAIN AND STORMS, SOME HEAVY. LOWS IN THE LOW 50’S TO NEAR 60.
THURSDAY: PARTLY CLOUDY WITH A 50% CHANCE OF RAIN/STORMS (SOME STRONG/SEVERE?), WINDY. HIGHS AROUND 60 WEST TO AROUND 70 EAST. WINDS FROM THE SOUTHWEST TO WEST AT 15-25 MPH, GUSTING TO 40-50 MPH.
THURSDAY NIGHT: PARTLY CLOUDY, RAIN AND STORMS COME TO AN END. LOWS IN THE MID 30’S NORTH TO MID 40’S SOUTH.
FRIDAY: MIX OF CLOUDS AND SUN, 10-20% CHANCE OF AN ISOLATED RAIN SHOWER. HIGHS IN THE LOW 50’S NORTH TO LOW 60’S SOUTH. WINDS FROM THE WEST/NORTHWEST AT 5-15 MPH, GUSTING TO 35 MPH.
FRIDAY NIGHT: MOSTLY CLEAR AND COLDER. LOWS AROUND 30 NORTH TO LOW 40’S SOUTH.
SATURDAY: MOSTLY SUNNY AND COOL. HIGHS IN THE LOW 50’S NORTH TO AROUND 60 SOUTH. WINDS FROM THE WEST SOUTH WEST AT 10-20 MPH, WIND GUSTS OF 40-50 MPH POSSIBLE.
SATURDAY NIGHT: MOSTLY CLEAR AND COLD. LOWS IN THE MID 20’S NORTH TO UPPER 30’S SOUTH.
SUNDAY: SUNNY TO MOSTLY SUNNY WITH HIGHS IN THE UPPER 40’S NORTH TO AROUND 60 SOUTH.
SUNDAY NIGHT: INCREASING CLOUDS WITH A 10-20% CHANCE OF A RAIN SHOWER NORTH. LOWS IN THE UPPER 30’S NORTH TO NEAR 50 SOUTH.
MONDAY: MOSTLY CLOUDY WITH A 30% CHANCE OF RAIN. HIGHS IN THE MID 50’S NORTH TO THE UPPER 60’S SOUTH.
MONDAY NIGHT: MOSTLY CLOUDY WITH A 20-30% CHANCE OF RAIN, CHANGING OVER TO SOME SNOW SHOWERS? LOWS IN THE MID 20’S TO MID 30’S.
TUESDAY: MOSTLY SUNNY AND COLDER. HIGHS IN THE LOW 40’S TO LOW 50’S.
TUESDAY NIGHT: INCREASING CLOUDS WITH A 10-20% CHANCE OF RAIN SHOWERS. LOWS IN THE LOW 30’S TO LOW 40’S.