A couple of other rain chances appear Wednesday/Wednesday night and again Friday, while temperatures generally remain near or just slightly below average through the week. Key long term forecast items include dry weather developing Monday night with decreasing north-northwest winds allowing hazardous swim conditions on Lake Michigan to gradually improve. While a Flood Watch has not been issued at this time, one may be needed tonight into Monday morning after further analysis of upstream trends today. Low-level moisture from PWATs of 2" feeding into the slow-moving low along with weak elevated instability and light deep-layer flow will support the potential for small pockets or a narrow corridor for heavy rain of several inches somewhere across the southern half of the forecast area. The slow-moving trough/mid-level low entering the area this evening will pivot across central Illinois overnight, focusing a general west to east axis with the northern deformation zone into the CWA. Of greater concern for the area overnight into Monday is a renewed flood risk for some of the area, especially those areas that saw substantial rain Saturday afternoon. While some isolated instances of gusty winds are possible, the late-arriving forcing this evening will struggle to generate surface-based convection. Weak mid-level capping and abundant cloud cover will limit convective potential across much of the forecast area while focusing sufficient instability south and west of a stalled surface front in central Illinois. The mid-level trough originally advertised for a potential severe storm risk through our area today has been largely altered by Saturday's rather strong MCV, ultimately deflecting/slowing the trough. With continuous (albeit gradually weakening) NE flow through the day, the current Beach Hazard Statement looks good for the Illinois shore into mid-evening, while some higher waves also sneak into the IN shore into this afternoon.Ĭonditions look to remain relatively quiet this afternoon as weak ridging edges across the Mississippi River due to weak Rex blocking from the remnant MCV. Also, as noted by the stronger winds, wave heights have neared 7ft along the Cook County shore early this morning. Little is expected to change through at least mid- morning, so have maintained notably higher PoPs through the morning for Cook County and around the adjacent lakeshore region in northwest Indiana. Saturated cloud heights barely reaching the freezing level around 14kft have supported highly-efficient warm rain processes during this time. Low-level isentropic ascent originating from a better moisture reservoir in central Indiana has continued to fuel a band of rain focused into northeast Illinois for the past several hours. This has been evident by 25kt+ (30-35kt over water) NE/E gusts wrapping around the northern periphery of the low. The PV anomaly remains quite prominent and has still maintained some mid-level warm core characteristics. Placement of the low ranges from just north of Lafayette at the surface to near the southern tip of Lake Michigan in the mid-levels. The remnants of yesterday's MCV continue to churn while becoming gradually more sheared early this morning. Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 626 AM CDT Sun Aug 6 2023 NWS Precipitation Image overlays are provided by the National Weather Service. USGS rain-gage data shown in the table are available at Water Data for the Nation : Current Illinois Precipitation “ – – ” Parameter not determined, usually due to missing data.The "no data" icon is the result of an NWISWeb status code: The colored portion of the icon will represent the precipitation amount for that time interval. Half colored icons designate gage data that appears to be logging correctly but is over 1 hour and 15 minutes older than the NWISWeb time stamp at the top of the Rainfall page.Hourly and Daily values are calculated from the last time a gage value was updated, which is not necessarily the time this web page was updated. * For precipitation values less than 0.01 inches, the USGS gage symbol is white and the NWS overlay is transparent. Legend colors apply to both USGS gage and National Weather Service precipitation overlays (at full opacity).
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