AFTERNOON-OVERNIGHT: The upper-level low that has brought cool, damp conditions to the forecast zones over the past several days continues to move off to the southeast today as it weakens. Behind it, an area of high pressure is building in from the northwest. This has allowed drier air to work into zones 6 and 7 bringing the rain to an end and allowing skies to become mostly clear this morning.
Through the morning clouds will rotate to the south and southeast around the surface low. It does look like by late morning through mid-afternoon some clouds may build back in, especially across eastern Illinois.
While most areas will remain dry today, perhaps a few light showers may be possible across eastern Illinois after 3 PM or so as some remnant upper-level energy moves through.
Late afternoon into the evening skies are forecast to clear back out. This will allow from some sunshine this evening.
Overnight conditions will remain dry with mostly clear skies.
Lows will be around 40 north to the upper 40’s south.
FRIDAY: An area of high pressure will be in place to the regions southwest on Friday. However, it’s impacts will be felt across zones 6 and 7. This will come in the way of calmer winds and mostly sunny skies.
At the upper-levels a ridge of high pressure will start to move in across the Great Plains and into the Midwest. Not only will this help reinforce nice conditions, but will also aid in the northward advancement of warmer air.
Highs on Friday will be in the low to mid 70’s, with perhaps some upper 70’s in western Illinois. Winds on Friday will be in the out of the west at 5-15 mph.
Friday night into Saturday skies will remain mostly clear across zones 6 and 7.
Lows will be in the low to mid 50’s.
SATURDAY: By the morning hours on Saturday a cold front will be in place to the north of the forecast zones. Through the day this cold front will begin to sag southward into the forecast area. As it does clouds will start to mix in through the day with rising precipitation chances through the afternoon hours.
While a large part of the day will be dry, rain and some storms will become possible across northern zone 7 around 4-5 PM Saturday evening.
Through the evening rain and storms will continue southward across zone 7 and into zone 6. By 7-8 PM the rain/storms will be ongoing across central Illinois.
Highs on Saturday will be in the mid to upper 70’s north where clouds move in earlier. However, to the south highs in in the upper 70’s to possibly mid 80’s will be possibly depending on the timing of clouds/precipitation. Winds on Saturday will be out of the southwest turning to the northwest after the frontal passage, with wind gusts of 30 mph possible.
I do think Saturday afternoon there could be a strong to severe storm threat will emerge. Strong winds aloft will be present with 500 mb winds 65-80 knots and 850 mb winds moving in at 30-40 mph. This should create some speed shear throughout the environment. This allowing storms to better organize through the afternoon/evening.
Instability values do not appear like they will be overwhelmingly high with 1200-1750 J/Kg of CAPE in place. However, it would still prove enough to allow storms to become strong to severe at times. Main threats would be damaging winds, hail, and possibly some isolated tornadoes.
My biggest concern regarding severe weather potential will be wind flow. Winds from the surface will be from the west to west south west. Aloft winds will be out of the northwest at both 850 mb and 500 mb. These kinds of wind fields usually are not overly conducive for severe weather. Overall, it’s something we will watch and fine-tune over the next 24 hours or so.
Saturday night into Sunday the cold front will continue southward across the forecast area. As it does, rain and some storms will move to the south with it. While initially some strong to possibly severe storms could accompany the front, the loss of daytime heating and upper-level winds will likely cause any stronger storms to weaken by late in the evening.
Lows Saturday night will be in the upper 40’s north to around 60 south
SUNDAY: The cold front will move into southern zone 6 or perhaps south of there into Kentucky by Sunday morning before becoming stationary. The weather on Sunday will be greatly dependent on the location of the stationary front.
If the front stalls out across zone 6, clouds and sun will last through the day with isolated to scattered rain/storm chances through the afternoon.
However, if the front is in place across KY more sunshine would be in the forecast. While rain and some storms would be possible still on Sunday, most of those would be across zone 6.
Highs on Sunday will be dependent on the locations of the front. Highs along and north of the front will be in the mid 60’s to low 70’s. However, to the south of the front highs in will be in the mid 70’s to low 80’s.
MONDAY – TUESDAY: An area of low pressure will be developing across the Great Plains by late in the weekend. On Monday this will lift northward across the Plains and into the western Midwest. As it does, the stationary front that is in place across the region will begin to lift back northward as a warm front.
While some rain and storms will be possible across the warm front and even into the warm sector of the system on Monday. However, with the warm front lifting northward earlier in the day there will be no real lifting mechanism to get storms to fire in the afternoon.
While it is possible for storms to develop in the afternoon, warm sector clouds and the lack of sufficient instability may prohibit a greater threat for storms on Monday.
Highs on Monday will be in the 70’s.
Tuesday there are some differences in the model guidance regarding frontal placement and timing. Regardless, a low pressure looks to move to the north of the forecast area on Tuesday. As it does, an attendant cold front will move across the forecast area through the day.
One of two scenarios could play out Tuesday along the front. The first being rain and storms are ongoing along the front through most of the day. Or the second being, as we build instability in through the afternoon and evening storms will develop along the front.
Winds aloft also look pretty impressive with this system. Given the setup I do think that severe weather could be a threat as the front moves through Tuesday. However, timing/placement/impacts are still very fuzzy and need worked out.