Area Forecast Discussion
Issued by NWS Central Illinois
Issued by NWS Central Illinois
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691 FXUS63 KILX 191708 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1208 PM CDT Thu Sep 19 2024 .KEY MESSAGES... - Summer-like warmth continues the next few days with more seasonal temperatures returning for the start of the new week. - A more unsettled pattern arrives beginning tonight as a few upper systems bring periodic chances for showers and storms through at least early next week. && .UPDATE... Issued at 947 AM CDT Thu Sep 19 2024 An area of mid-level clouds has been clipping the extreme southeast parts of the forecast area near Lawrenceville recently, but has begun an eastward push and should move out soon. In general, skies expected to remain mostly sunny across the forecast area, with some increase in high clouds during the afternoon ahead of the front west of the Mississippi River. Temperatures have been on a quicker climb than forecast and required some updates for the remainder of the morning, but overall temperatures are still on track to top out around 90 degrees this afternoon. Geelhart && .DISCUSSION... Issued at 243 AM CDT Thu Sep 19 2024 An upper Rex block is in the process of breaking down late this week as a series of upper disturbances from the western CONUS work through the Upper Mississippi Valley and Midwest states in the coming days. Satellite imagery shows exiting cirrus over eastern parts of the state, with clear skies west of there. Temperatures as of 2 am range from the upper 50s to low 60s. Dewpoints in the 50s should allow air temperatures to drop a few more degrees through daybreak. Daytime temperatures will continue to run seasonally high the next several days with highs peaking in the middle 80s to around 90 degrees. After a rather dry start to the month, precipitation chances return late tonight into Friday as an upper shortwave lifts from the northern Plains into the southern Canadian Prairies. A cold front will approach from the west late tonight, bringing scattered showers and storms to areas mainly near/west of I-57 through Friday morning. A lull in precipitation will be seen late Friday morning as the front stalls out across the area. Showers and storms may redevelop along the front Friday afternoon as daytime heating and seasonably high dewpoints result in 1000-1500 J/kg of instability. Although the upper wave will be north of here by this time the stalled out boundary paired with increasing mid-level flow should allow some stronger storms to develop from mid afternoon through early evening. A SPC marginal risk has been introduced with the threat of damaging downburst winds and large hail being the main concerns. A stronger upper wave currently spinning off the coast of California will bring better chances for precipitation and beneficial rainfall this weekend into early next week. A couple shortwaves will work through the area Saturday night into Sunday before the main wave approaches late Sunday night. Periodic chances for showers and storms will exist through at least Monday night with the heaviest push of rainfall coming late Sunday night into Monday morning as a ~30 kt LLJ noses feeds into a warm front. QPF amounts look beneficial from this second system, though likely won`t come close to erasing our ongoing deficit. The NBM shows favorable probabilities (50-70%) of seeing at least 1 inch of rain west of I-55, with about a 30-40% of 2 inches or more. Temperatures turn cooler for the start of the new week with highs Monday through Thursday looking to stay near or below 80s degrees. NMA && .AVIATION... (For the 18z TAFs through 18z Friday Afternoon) Issued at 1208 PM CDT Thu Sep 19 2024 VFR conditions expected to prevail during the forecast period. Main aviation concerns will be in the 06-12Z time frame, when a band of showers and scattered thunderstorms moves southeast across central Illinois. Thunder chances are expected to diminish with time, so for the moment, will only include a mention at KPIA/KSPI for a few hours from 08-11Z. Once the showers exit, skies clear out again. Further into Friday, some convection is expected to develop over east central Illinois with the arrival of a cold front, but this is most likely after the current TAF forecast period. Geelhart && .CLIMATE... Issued at 947 AM CDT Thu Sep 19 2024 Rainfall over the last 30 days across much of central and southeast Illinois has been about 25% or less of normal, with the impacts of post-tropical Francine mainly limited to parts of Richland and Lawrence Counties southward. Going back 2 months, only a few pockets generally along the I-72 corridor have had above normal rain, though far enough back that its impacts have largely faded. Burn bans have been implemented in Crawford, Richland and Lawrence Counties. This morning`s Drought Monitor introduced D1 (moderate) drought conditions across the southern third of the state generally near/south of I-70, as well as in west central Illinois from about Havana to Quincy. While prospects of some decent rain have been increasing for the weekend and early next week (>50% chance of over an inch of rain north of I-72), prospects south of I-70 are more in the 20% range, with only a 40-50% chance of even a half inch. Latest CPC 8-14 day outlook for September 26 to October 2 lean near or slightly below normal for rainfall. Geelhart && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$