Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
360 FXUS63 KLOT 091939 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 239 PM CDT Thu May 9 2024 .KEY MESSAGES... - Period of quiet and warmer weather on Friday, followed by another chance of showers Friday night. - Periods of showers and possibly some thunderstorms early next week. && .DISCUSSION... Issued at 239 PM CDT Thu May 9 2024 Through Friday night: After our break in rainfall, our next batch of showers continues to quickly shift/develop eastward into the area early this afternoon in association with the next mid-level impulse now shifting into northwestern IL. These showers will persist across much of the area through the remainder of the afternoon before gradually tapering off from northwest to southeast across the area this evening. While the thunder threat with this activity will remain low, we cannot rule out a few storms across our far southern counties in central IL and IN late this afternoon. Either way, no severe weather is expected. Drier weather is expected during the day Friday as we await our next weather maker shifting southward across the Upper Midwest. Partly cloudy/sunny afternoon skies will allow inland temperatures to rebound back into the mid to upper 60s. However, conditions look to become favorable to allow an afternoon lake breeze to develop along the northeastern IL shores. While the lake breeze may not move more than 10 to 15 miles inland prior to sunset, onshore easterly winds will keep conditions a few degrees cooler along the lakeshore Friday afternoon. Our next chance of rain will come Friday night as the next fast moving and compact impulse digs southeastward across the western Great Lakes. This looks to be a quick hit (2 to 4 hours) of mainly some showery activity with an approaching surface cold front, though steepening lapse rates could also support a couple of embedded thunderstorms. The quick movement of the precipitation should keep total amounts rather low, so we really do not look to have any major hydro threats with this activity. KJB Saturday through Thursday: The rain chances forecast for Friday night will clear the area by daybreak Saturday. Surface high pressure building in from the south and steady height rises aloft will then bring pleasant Spring conditions to the area for the weekend. Temperatures will be rather seasonable on Saturday with highs forecast in the middle and upper 60s, lower 60s closer to the lakeshore. A tight pressure gradient behind the departing storm system will bring breezy NW winds to the area on Saturday. As the surface high moves across the Tennessee Valley Saturday night into Sunday, the mild return flow will pull highs into the middle and upper 70s to close out the weekend, again with a hefty breeze expected during the day. An upper trough looks to move across the central Plains and lower Midwest Monday into Tuesday. The surface response will be a low pressure center that medium-range guidance can agree will pass to our south. Nonetheless, broad upper forcing in a moisture-rich profile will lead to rain chances across our domain early next week along the storm`s northern flank. An ample amount of MUCAPE north of the low could bring us some elevated thunderstorms as well, although heavy rain may be the most appreciable concern. This wave will hang out in the region through Tuesday with another wave moving in right behind for midweek ushering in what could be a somewhat active week ahead with lots of room for rain chances. Luckily, nothing overly impactful appears on the scope through the middle of next week. Doom && .AVIATION /18Z TAFS THROUGH 00Z SATURDAY/... Issued at 1248 PM CDT Thu May 9 2024 Key Messages: - Another period of showers expected this afternoon. - Predominately MVFR CIGs into this evening, with a 30-50% chance for a period of IFR CIGs at the Chicago area terminals late tonight. - Lake breeze expected Friday afternoon, though confidence is low with it making it to ORD late in the day. While the rain early morning rain has moved out of the area, another batch of rain is already developing eastward into northwestern IL in association with the next mid-level disturbance. Expect this area of showers to overspread the Chicago area terminals after 19-20z, with periods of showers expected through the remainder of the day before the activity ends into early this evening (00-01z). MVFR CIGS will also persist the remainder of the day, but may improve a bit as the rain onsets this afternoon. CIG trends into tonight then remains a bit unclear. While a period of improving conditions is possible for a period mid to late this evening, the potential then exists for CIGs to trend back down again overnight into very early Friday morning, especially near the lake. As such, some terminals near Lake Michigan could experience a period of IFR CIGs after 09-10z tonight through early to mid morning on Friday. Confidence is not high with this period of low CIGs, but we have opted to hint at the opportunity with a few hour tempo mention for IFR CIGs in the latest TAF iteration. Any low CIGs will quickly improve through the mid morning hours of Friday. Wind trends also look to become tricky Friday afternoon as a lake breeze develops across far northeastern IL. It remains unclear as to how far this lake breeze will be able to make it through the afternoon, which makes a deterministic wind forecast, particularly at ORD, quiet difficult. If the lake breeze remains just east of the terminal, winds at ORD would likely trend to a west-northwesterly direction Friday afternoon, while areas just east of the boundary turn easterly. At this time, I have opted to only mention an eastward wind shift at MDW, where confidence is slightly higher. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory until 3 AM CDT Friday for the IL and IN nearshore waters. && $$ Visit us at weather.gov/chicago