AFTERNOON – TONIGHT: The area of high pressure that was in place yesterday has moved off to the east of the forecast zones. This has allowed for southerly winds and low pressure to take control of the weather for the next couple of days.
While Wednesday has started off dry, clouds and rain chances will increase through the day. While isolated chances of some showers will be possible through the morning, more widespread rain will develop around 12 – 1 PM this afternoon.
Through the afternoon and into the evening rain/storm coverage will increase across zones 6 and 7. By 4-5 PM some pretty decent areas of rain will be ongoing across Illinois.
By 7-8 PM this evening a widespread area of rain and a few storms will still be occurring across the forecast zones. While the HRRR may be a bit overdone with coverage, I do believe there will be rain across portions of the forecast zones.
Through the overnight rain and storms will continue across Illinois. Scattered areas of rain will remain possible through Thursday morning.
Lows overnight will be in the low 50’s to near 60.
THURSDAY: Some isolated to scattered areas of rain will be ongoing across Illinois very early in the morning on Thursday. By 7-8 AM you can see the models depicting those areas of rain.
However, as we progress through the morning hours most, if not all, of the rain looks to move off to the east giving zones 6 and 7 some dry time.
Highs on Thursday will be in the low 60’s north to low 70’s south. Winds will be very strong with gusts of 40-50 mph possible, with perhaps a few stronger gusts.
Through late morning into early afternoon the NAM model remains persistent with some clearing clouds as a dry slot works into the forecast areas. This will be crucial in the forecast tomorrow because if sunshine can get through it will allow the atmosphere to destabilize and for the severe weather threat to increase.
Tomorrow afternoon the NAM 12 km places of 1000-1500 J/Kg of CAPE across the forecast zones. I do think the Hi-Res NAM 4 km may be a little bit more reasonable with CAPE values of 900-1200 J/Kg. Regardless, both would be supportive for thunderstorms and severe thunderstorms to develop.
Aloft winds will be impressive, especially at the mid-levels of the atmosphere. At 500 mb southwesterly winds will be streaking in at 95-110 mph! At low-levels (850 mb) winds will be coming in from the southwest at 45-55 mph. With the winds increasing with height it will help the atmosphere to spin, this will also help aid in creating severe storms as we add shear to an unstable environment.
The latest SPC outlook has southeastern Illinois in a slight risk. However, I wouldn’t be shocked to see this extended a little west. Main risks will be damaging winds, hail, and an isolated tornado.
Rain and t’storms could form as early as 12-1 PM just ahead of the cold front Thursday afternoon to the northwest of the forecast area.
Rain and storms will continue to move into the forecast area through the evening. By 4-5 pm the main line of storms will be across portions of zone 7 and northwestern zone 6.
Through the evening the front and associated storms will quickly race across zones 6 and 7. By 7-8 PM the line of storms looks to be in the vicinity of the IL/IN state line. The cold front looks to be in place across central zone 6 into eastern zone 7.
Through the evening rain and storms will move off to the east and southeast of the forecast area. While drier conditions will be in place, some isolated showers will remain possible.
It does appear a large portion of the zones will see soaking rains through late Thursday night. The NAM 12 km model shows widespread .40-.80” of new rainfall. However, models are honing in on heavier precipitation across zones 6. The NAM 12 km shows localized areas of 2-3” possible. This is actually conservative compared to the higher resolution NAM 4 km that has areas of 3-3.75” of new rain.
Regardless, with this much rain forecast there is a definite concern for flooding where the higher totals do occur.
Overnight temperatures will fall behind the cold front. Lows will fall into the mid 30’s north to mid 40s south.
FRIDAY: An upper-level trough of low pressure will be in place across the region on Friday. This will keep the temperatures cool, but also as an area of vorticity moves through it will keep some rain shower chances around through the day. These showers look isolated to widely scattered at best.
Highs on Friday will be cool with temperatures topping out in the low 50’s north to low 60’s south. Winds will remain strong at times with gusts of 35 mph possible.
Friday night will be dry out as the upper level energy exits the region. It will be a bit cool though with lows dropping into the low 30’s to low 40’s.
WEEKEND: Another piece of energy will move across the region on Saturday. This will allow for an increase in clouds along with a few isolated rain showers to form across the region. Right now better chances of rain look to be in place across northern Illinois and northern Indiana. However, even those rain showers look to be really light in nature.
Highs on Saturday will be in the low 50’s to low 60’s. Winds will be very strong once again on Saturday, gusts of 45-55 mph will be possible across the region!
Saturday night winds will be on the decrease and skies will be mostly clear. This will allow for temperatures to cool overnight.
Lows will be cold as temperatures fall into the mid 20s north to mid 30’s south.
Sunday an area of high pressure will ridge in from the south. This will allow for winds to calm and more sunshine to get through during the day on Sunday. This looks to be the nicest day of the weekend.
Highs on Sunday will be in the upper 40’s north to near 60 south.
7 DAY FORECAST
THURSDAY: PARTLY CLOUDY WITH A 60% CHANCE OF RAIN/STORMS. SOME STRONG TO SEVERE POSSIBLE, WINDY. HIGHS IN THE LOW 60’S TO LOW 70’S. 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 MID 60’S SOUTH. WINDS FROM THE WEST/NORTHWEST AT 5-15 MPH, GUSTING TO 35 MPH.
FRIDAY NIGHT: MOSTLY CLEAR TO PARTLY CLOUDY, COLDER. LOWS IN THE LOWS 30’S NORTH TO LOW 40’S SOUTH.
SATURDAY: MIX OF SUN AND CLOUDS 10-20% CHANCE OF AN ISOLATED RAIN SHOWER, WINDY. HIGHS IN THE LOW 50’S NORTH TO LOW 60’S SOUTH. WINDS FROM THE WEST TO NORTHWEST AT 15-25 MPH, WIND GUSTS OF 45-55 MPH POSSIBLE.
SATURDAY NIGHT: MOSTLY CLEAR AND COLD. LOWS IN THE MID 20’S NORTH TO MID 30’S SOUTH.
SUNDAY: SUNNY TO MOSTLY SUNNY WITH HIGHS IN THE UPPER 40’S NORTH TO AROUND 60 SOUTH. WINDS FROM THE SOUTH AT 5-15 MPH.
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 AND T’STORMS. HIGHS IN THE MID 50’S NORTH TO THE UPPER 60’S SOUTH.
MONDAY NIGHT: DECREASING CLOUDS, RAIN COMING TO AN END. 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: MOSTLY CLEAR TO PARTLY CLOUDY. LOWS IN THE AROUND 30 NORTH TO AROUND 40 SOUTH.
WEDNESDAY: PARTLY CLOUDY WITH SCATTERED AFTERNOON RAIN/STORMS. HIGHS IN THE UPPER 50’S TO UPPER 60’S.
THURSDAY: MOSTLY CLOUDY WITH SCATTERED RAIN AND STORMS. LOWS FALLING INTO THE UPPER 30’S AND 40’S.
THURSDAY NIGHT: MOSTLY CLOUDY WITH ISOLATED TO SCATTERED RAIN AND STORMS, ISOLATED SNOW SHOWER LATE? LOWS AROUND 30 NORTH TO AROUND 40