Latest Meso-scale discussion pinpoints the onset of blizzard conditions in western Illinois that will impact the Chicago area later tonight
Blizzard conditions are currently developing in west of Chicago as the early winter storm continues to strengthen. The severe conditions of heavy snow and strong winds will create blizzard conditions across much of northern Illinois and the Chicago Metro areas later this evening and overnight.
Mesoscale Discussion 1662 NWS Storm Prediction Center Norman OK 0357 PM CST Sun Nov 25 2018 Areas affected...Northeast Missouri...far southeast Iowa...portions of western Illinois Concerning...Blizzard Valid 252157Z - 260200Z SUMMARY...Rain/wintry mixed precipitation across the area is expected to transition to snow with eastward progression of the surface low. 1-2 inch/hour snowfall rates appear likely, with blizzard conditions moving into parts of the area over the next few hours. DISCUSSION...A 996 mb surface low continues to track northeast across Missouri into Illinois. Heavy snow has been abundant well to the north of the low, along a stationary front aloft, and within the northwest quadrant of the surface low, where blizzard conditions have been reported in numerous locales. The eastward progressing, deepening upper-level trough will encourage maintenance (and perhaps some strengthening) of the low's intensity, suggesting that blizzard conditions will continue within the northwest quadrant, particularly in northeast Missouri into far west Illinois. A jet of deep moisture within the 925-850 mb layer will continue to saturate the low-level airmass within proximity/north of the low, with rapid ascent expected across the discussion area, where 700 mb frontogenesis is quite strong, and saturation has already been noted within the dendritic growth/-12 to -17C layer. The surface freezing line is rapidly moving into the area from the west, and deep-layer cooling is expected. As such, a transition to snow is expected, with 1-2 inch/hr rates likely.