


Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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674 FXUS63 KLOT 080842 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 342 AM CDT Sun Jun 8 2025 .KEY MESSAGES... - Isolated to scattered showers and thunderstorms will move through the area this afternoon and Monday afternoon. - A few instances of pea to nickel size hail as well as 40 to 50 mph winds may occur with the strongest storms today and Monday. - A period of dry and warmer weather is expected Midweek. - Shower and thunderstorm chances return late in the week. && .DISCUSSION... Issued at 342 AM CDT Sun Jun 8 2025 Through Monday: Lingering showers continue to be observed across portions of northeast IL and northwest IN associated with a shortwave trough pivoting overhead. These showers will continued to taper over the next 2-3 hours as the shortwave exits to the east with skies clearing shortly thereafter. As skies clear, there remains the potential for some patchy fog to develop, particularly along I-39 and west of the Fox Valley, where surface dew point depressions are within a degree or two. Any fog that does materialize will quickly erode after 8 AM. While our morning will start off on a quiet note, our attention will quickly turn to the deepening trough over the ND-Canadian border and the surface cold front stretching from northeast MN to eastern NE. Scattered showers and a few thunderstorms are already ongoing just ahead of the cold front in MN and western WI this morning and with temperatures and dew points expected to increase after sunrise (into the mid to upper 70s and lower 60s respectively) conditions will be in place for additional showers and thunderstorms to develop into our area towards midday and persist through the afternoon. Additionally, an 80 kt jet streak is also being analyzed rounding the base of the trough which will lead to an increase in deep layer shear over our area this afternoon. Given that instability will be somewhat modest (around 700-800 J/kg of MLCAPE) the severe threat remains low. However, stronger storms will be capable of generating gusty to locally damaging winds (up to 50-60 mph) and small hail (up to nickle size). The cold front is expected to swing through the area by this evening which should allow the thunder (and any severe) threat to diminish after 7 PM. That said, scattered showers are expected to fester behind the front through the evening as the trough pivots overhead but will gradually taper after midnight. Otherwise, temperatures to dip into the low to mid-50s overnight with decreasing cloud cover. Heading into Monday, the upper trough will be centering over the Great Lakes which will allow another shortwave to dive across northern IL and northwest IN Monday afternoon. While moisture will be notably lower on Monday (dew points in the lower 50s), the cold 500 mb temps overhead will steepen mid- level lapse rates and allow scattered showers and storms to redevelop Monday afternoon. Though the greatest coverage does look to be along and east of a Rockford to Rensselaer line. Given that modest flow aloft will be present, cannot completely rule out another low end severe threat in the form of gusty winds and small hail Monday as well. Outside of the showers and storms, winds on Monday will also become breezy with non-thunderstorm wind gusts in the 25-30 mph range expected during the afternoon. Temperatures will otherwise be once again in the low to mid-70s. Yack Monday Night through Saturday: The upper-level flow pattern will begin to deamplify on Tuesday as the Great Lakes trough/low ejects into southeastern Canada. Rising heights in its wake will result in the development of a quasi- zonal type flow pattern across the northern CONUS for the second half of the week. The main result of this changing weather pattern for our weather will be the turn from seasonably cool conditions on Tuesday (highs in the 70s) to much warmer temperatures (highs back in the 80s) by Wednesday. Primarily dry weather is anticipated for Tuesday and Wednesday, and it is certainly plausible that most of our area will remain free of precipitation and very warm through the end of the work week. In spite of this, the official forecast will begin to carry some chances (~30-50%) for showers and thunderstorms during the Wednesday night through Friday timeframe. However, storm chances during this period will ultimately be dependent upon how far south a west-to-east oriented surface cold frontal boundary reaches before stalling ahead of the next impulse shifting into the Dakotas late in the week. If this front ends up stalling to our north across WI, the primary focus for waves of showers and storms Wednesday night through much of Friday would also likely largely remain to our north in WI. However, due to the inherent uncertainties at this time range, we made no changes to the NBM POPs. Another feature that will need to be monitored for driving storm chances later next week is the southern stream impulse that is expected to slowly migrate its way eastward from the Desert Southwest on Tuesday into the Ozarks region into early next weekend. This feature will also be a daily driver of showers and thunderstorms, but with it`s slow eastward movement, much (if not all) of the thunderstorm activity will remain south and southwest of our area through the end of the week. Ultimately, our best shot at a period of higher coverage storms may end up coming sometime next weekend (possibly on Saturday?) as the late week system moving across the Dakotas finally looks to drive the surface cold front southward across our area. Unfortunately, the specifics with timing this far out are of low confidence. Stay tuned. KJB && .AVIATION /06Z TAFS THROUGH 12Z MONDAY/... Issued at 1219 AM CDT Sun Jun 8 2025 Key Messages: - Period of -SHRA through 08Z at the Chicago area terminals - Possibility of some reduced VSBYs in fog overnight, mainly at KRFD. - Period of TSRA possible ahead of next cold front this afternoon. A period of -SHRA continues across northern IL as of this writing. This activity is expected to gradually tapper off across the Chicago area terminals by 08Z, with dry conditions expected the remainder of the night. While generally VFR conditions are expected, there is a threat of a period of low end MVFR to IFR VSBYs in fog around daybreak, primarily at KRFD. However, this threat will hing on the amount of scattered mid-level cloud cover that can occur there over the next few hours. For the 06Z TAFs, I did not make any changes to the going tempo mention of 3SM BR at RFD. Otherwise, expect the winds across the area to remain light and variable through the predawn hours. Winds will settle into a west-southwesterly direction later this morning, and will likely become a bit breezy in advance of an approaching cold front this afternoon (some gustiness up around 20 kt). This cold front is expected to become the focus for some scattered showers and thunderstorms as it shifts eastward across northern IL through the afternoon. The inherited TAFs have the timing of these showers and potential thunderstorms handled well, so no changes were made. A general timing of 19 to 21Z is anticipated at RFD, and 21 to 00Z for the Chicago area terminals. KJB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago