AFTERNOON-OVERNIGHT: A stationary front is in place to the north of the region this morning. Through the daytime hours this will start to sag to the south. As we get some afternoon heating to go with the front, some scattered areas of rain and storms will start to form after 12-1 PM.
By 2-3 PM we will be watching a large cluster of rain and storms move into the forecast zones from the northwest. While some hail and gusty/strong winds could accompany this, the main concern will be heavy rainfall.
By 6-7 PM this large cluster of rain and storms will be working its way off to the south. By this time mainly impacting zone 6.
Once the rain exits the region later this evening it looks like we will see some calmer conditions overnight.
With CAPE amounts of 2000-2500 J/Kg in place this afternoon the cluster of storms moving in will be capable of damaging winds, some hail, and perhaps an embedded brief tornado. The main question I have regarding severe weather potential will be upper-level energy which is weak at best. Regardless, I will keep in that severe risk across the area today for the afternoon storm cluster.
Lows will be in the upper 50’s north to mid 60’s south.
WEDNESDAY: Early Wednesday morning the stationary front in place across southern Illinois will start to get lifted back northward as a warm front. As it does more rain and some storms will develop by 5-6 AM Wednesday morning and spread north across the forecast area.
Through the morning into mid-day some isolated to widely scattered rain and storms will be possible across zones 6 and 7 as the front remains in place.
Tomorrow afternoon and evening the warm front will continue to lift north ahead of an approaching low pressure system. By 3-4 PM more thunderstorms will develop along the northward lifting warm front.
By 7-8 PM rain and storms will be moving across Illinois, likely getting closer to the IN/Il state line by this time.
At least scattered rain and storm chances will continue through the late evening across Illinois. However, by 2-3 AM Thursday morning most of the activity will be either outside of the forecast zones or weakening.
While strong to severe storms will be possible across the zones tomorrow these will be very reliant on how much instability can be realized. The upper-level winds will be generally weak on Wednesday. However, with low-level jet winds of 30-40 mph and CAPE values of 2000-3000 J/Kg, at least a small threat of severe weather would exist across zone 6 and perhaps zone 7.
Highs on Wednesday will be in the upper 60’s north to upper 70’s south. Winds will be strong at times on Wednesday with gusts of 30-35 mph possible.
Heavy amounts of rainfall will be possible across the forecast zones through mid-day Thursday. The average rainfall totals look to be around 1-2”.
However, hi-resolution models remain very aggressive with rain through Thursday. The NAM 12km has places of 2-3” of new rainfall, while the RPM shows 4-5” in localized places! For this reason, I am very concerned about flooding potential across southern Illinois. Overall, it’s something we will watch closely and keep you updated on.
THURSDAY: The area of low pressure will move through the forecast area Thursday morning into the early afternoon.
While not much precipitation is forecast with this low, perhaps a few rain showers or storms could develop in the early afternoon.
Highs on Thursday will be in the upper 60’s north to upper 70’s south.
FRIDAY: We will be between two weather systems during the daytime hours on Friday. The first low will be exiting to the east of the region, while the second low continues to develop across the southern Plains.
At the upper-levels a ridge will build in briefly helping keep the weather calm Friday.
Friday will be a cooler day with highs topping out in the mid 60’s north to mid 70’s south.
WEEKEND: The area of low pressure across the Great Plains will move closer to the forecast area on Saturday. As it does, rain and t’storm chances will be on the increase throughout the day.
While I don’t think Saturday will be a totals washout, those precipitation chances will exist.
Highs on Saturday look to remain cooler than they have been. Temperatures on Saturday will warm into the mid 60’s to around 70.
Sunday the area of low pressure will move across the Illinois area. Along with the low pressure system and attendant warm front and cold front will be moving across the forecast area. Along the fronts rain and thunderstorms will develop.
While it is still in the longer-range, at least the potential exists for severe weather in portions of the region Sunday afternoon through Sunday night. We are still several days out so timing/location/impacts still need ironed out.