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FXUS63 KILX 121422 AFDILX

Area Forecast Discussion...Updated National Weather Service Lincoln IL 922 AM CDT Sun May 12 2024

KEY MESSAGES

- A pleasant end to the weekend for Mother's Day, with 80s across the board this afternoon.

- Widespread rains will return on Monday and continue through late Tuesday. There remains a 40-60% chance for more than an inch of rainfall south of I-74. This rain will contribute to area rivers and streams already running high, increasing the risk for localized inundation near riverbanks. This could perhaps also further delay planting and inhibit germination of agricultural seedlings.

- Below normal temps are likely (70%) Tuesday, with chilly conditions Tuesday night as low temps dip into the 40s north of I-72.

UPDATE
Issued at 917 AM CDT Sun May 12 2024

At 915am, surface observations showed temperatures in the upper 60s to low 70s across central and southeast IL - already up 15-20 degrees from our morning lows 3-4 hours ago. Given nearly full sunshine, filtered only by very thin cirrus, temperatures should continue to sharply rise through the remainder of the morning, topping out in the low to (locally) mid 80s by mid afternoon when surface moisture gets mixed out. Fair weather cumulus, some towering northwest of the IL River where HRRR mean brings SBCAPE to more than 500 J/kg, will develop late morning and build into mid afternoon to offset heating slightly, but the shift (towards the northwest) in where CAMs put precip would suggest none of these clouds produce precip in our area.

Bumgardner

DISCUSSION
Issued at 253 AM CDT Sun May 12 2024

Water vapor satellite loops depict our next weather disturbance slowly advancing across Colorado, with northwest flow aloft into Illinois bringing Canadian wildfire smoke into the region. At the surface, high pressure is providing light and variable winds early this morning, which will give way to southwest flow as the surface ridge axis shifts east of Illinois by this afternoon. Mixing of mid-level dry air today will lower dewpoints a few degrees, allowing for high temps to overachieve into the lower 80s across all of central and southeast Illinois. Weak warm advection lift this afternoon could produce spurious radar returns west of the Illinois river, however, chances of measurable rainfall will be low due to dry sub-cloud air. Therefore, most areas should remain dry today.

Rain chances will ramp up after midnight tonight from southwest to northeast, as the cutoff upper low drifts into the region.
Coverage of showers will be scattered late Sunday night and Monday morning, with widespread rains and isolated thunderstorms finally reaching our far eastern counties Monday afternoon.
Forecast soundings are indicating narrow CAPE profiles, limiting updraft strength amid a weak shear environment with 25kts of 0-6km bulk shear. Precipitable water values will climb toward 1.5" Monday afternoon through Tuesday afternoon. The NBM is still indicating 50-60% chance of at least 1" of rainfall for areas south of I-74 in the Mon-Tue time frame. The Grand Ensemble has lowered those chances a bit into the 30-50% range. Despite that, feel that pockets of 1.5"+ inches will be in play due to high PW values, especially south of Springfield to Mattoon.

A shortwave ridge will provide a break in the rain chances mid- week, amid colder than normal temps in the cloudy, cold air advection regime. Tuesday's high temps will be limited to the mid to upper 60s for areas north of I-70. Lows Tues night will dip into the upper 40s north of the I-72 corridor, with steady north winds making it feel even cooler.

Shimon

AVIATION
(For the 12z TAFs through 12z Monday Morning)
Issued at 521 AM CDT Sun May 12 2024

VFR conditions to prevail the next 24 hours, with a general increase in mid to high level clouds late this afternoon through this evening. Prevailing winds will increase from the southwest this morning, reaching around 10-12 knots by mid morning. Diurnal winds will subside below 10 kts after sunset, as shower chances increase for PIA and SPI toward the end of this TAF period.
However, any precip before 13/06z should be trace amounts of rain.

Shimon

ILX WATCHES/WARNINGS/ADVISORIES
None.

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