AFTERNOON-TONIGHT: A stationary front remains in place across northern Illinois this morning, while a warm front continues to move closer to the region from the south. Between those two fronts fog and a coupe isolated areas of rain have developed.
Through the morning hours the fog will burn off across zones 6 and 7. This will allow for at least some sunshine to break through by mid-day to early afternoon.
As the sunshine does get through it will rapidly destabilize the warm, moist environment in place. CAPE values this afternoon look to quickly rise to 3000-4000+ J/Kg across zones 6 and 7.
Through the day the low to the west will move closer to the forecast area and the warm front will lift northward across Illinois with it. By 2-3 PM there will be enough lift and instability in place for rain and t’storms to develop along the warm front.
By 6-7 PM scattered storms will be ongoing along the front in Illinois.
Through the evening hours a line of storms will be developing to the west and northwest of the forecast zones along the surface cold front. As the front progresses eastward through the evening, so will the storms. By 10-11 PM the line of storms will be moving into zone 7 near Springfield, IL.
Through the overnight the storms will continue southeast across zone 7 and into zone 6. However, it does appear once we lose daytime heating that storms will weaken as they move across the state late tonight.
Lows overnight will be in the low to mid 60’s.
While I do think strong to severe storms will occur today across zones 6 and 7, the limiting factor to the mention of a greater threat will be upper-level winds. 500 mb winds of 30-40 mph and 850 mb winds of perhaps 25-35 mph (optimistically), will really hinder any significant severe weather risk.
With that being said, there are a couple of things worth mentioning. Any storm that can rapidly develop this afternoon and “latch” onto the warm front would have the potential to become severe. The other area of greater risk would be to the northwest of the forecast zones where much better 850 mb low-level winds are forecast to be. Overall, strong to severe storms will be possible this afternoon/evening with damaging winds and hail the main threats. However, in the areas aforementioned I do think the potential exists for at least a couple of tornadoes.
THURSDAY: A few areas of rain and storms look to be ongoing early Thursday morning as initial front exits. However, by 7-8 AM only a few isolated storms are being depicted by models. I’m not surprised as storms will be largely helped by instability which will decrease quickly through the overnight into early Thursday.
Through the morning into early afternoon the cold front will move off to the east and south. By 1-2 PM the front will still be slowly moving across eastern/southern Illinois. As it does, a few scattered areas of rain and storms may develop around the vicinity of the front.
Highs on Thursday will be in the low to mid 70’s.
Through the afternoon into the evening the front will exit out of the region. However, a little piece of upper-level energy will be moving through. This allow a few rain showers to stick around through the evening.
New rainfall totals late Thursday into early Friday will likely be around .25-.50”. However, places that get under the strong to severe storms could see 2.5-3.5” of new rainfall locally.
Thursday night into Friday an area of high pressure will start to ridge in from the south. As it does, dry air will work in and skies will clear from west to east overnight.
Temperatures Thursday night into Friday will be chilly with lows in the upper 40’s north to mid 50’s south.
FRIDAY: Through most of the day on Friday high pressure will remain in control of the weather across zones 6 and 7. This should allow for sunny to mostly sunny skies to persist through at least the afternoon hours.
Highs on Friday will be in the mid 60’s north to low 70’s south.
By late Friday afternoon into the evening we will be watching a front that will moving into the area. This will allow clouds to increase from northwest to southeast through the evening into the overnight. By 10-11 PM scattered rain and a few storms will be moving into the forecast zones from the northwest.
Through the overnight the front will quickly push south and out of the area. By 7-8 AM Saturday morning, most of the zone forecast area will be drying out.
WEEKEND: Once the rain moves out early on Saturday morning an area of high pressure will start to build into the forecast zones from the west. This will allow for skies to clear across zones 6 and 7 once again.
However, with the high in place it will be a cool start to the weekend with highs only in the mid 50’s north to low 60’s south!
Sunday the high pressure system will be in place. However, there will be two other systems moving closer to the region. Models do vary on the exact forecast for Sunday. The GFS would support some isolated to scattered showers across southern zones.
However, the EURO and CMC both suggest high pressure would suppress the rain to the south of the region allowing for mostly to partly sunny skies and dry conditions to continue.
Right now I do favor the CMC/EURO solution with the high pressure suppression. However, we will fine-tune the forecast over the next few days.
Highs on Sunday will be in the upper 50’s north to upper 60’s south.
LONG-RANGE (NEXT WEEK): Models do continue to show a more active pattern once we get past the weekend. Models do suggest at least isolated to scattered rain/storm chances will be possible several days next week. However, we also could see a couple of drier days as well.
Right now models would suggest we continue with 60’s most of next week. However, some hints at a warm up do come by late next week. Which is not a surprise as I would expect May to end warmer than normal.
7 DAY FORECAST( TEMPERATURES VARY GENERALLY COOLER NORTH TO WARMER SOUTH)