<pre>ACUS11 KWNS 251754 SWOMCD
Mesoscale Discussion 1660 NWS Storm Prediction Center Norman OK 1154 AM CST Sun Nov 25 2018
Areas affected…Portions of eastern Iowa…northern Illinois
Concerning…Heavy snow
Valid 251754Z – 260000Z
SUMMARY…A mix of sleet and snow falling across parts of eastern Iowa into northern Illinois, is expected to transition to mainly snow over the next several hours. Very heavy snow, with accumulation rates of at least 1-2 inches/hour, is likely.
DISCUSSION…A narrow, west-to-east oriented band of mixed wintry precipitation is ongoing from an area along a Keokuk County IA to Cook County IL axis. Current KDVN and KLOT dual-polarimetric radar data suggest that mainly sleet is falling within this band of heavier precipitation.
The aforementioned band of precipitation has been sustained predominantly by 700 mb WAA/frontogenetic forcing, which should continue for several more hours. As a deepening surface low approaches the area later this afternoon/evening, large scale lift should only increase with time. Meanwhile, mesoanalysis indicates relatively strong 925 mb CAA impinging on the horizontal precipitation band to the north. Latest RAP point forecast soundings also suggest that cooling of the low-level troposphere will transpire during the early afternoon hours. As such, a change over of sleet/mixed wintry precipitation to snow is expected. With very strong lift expected within a saturating/deepening dendritic growth zone, very heavy snowfall, with rates of at least 1-2 inches/hour should prevail through the afternoon hours.
..Squitieri.. 11/25/2018
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…LOT…DVN…DMX…
LAT…LON 41189086 41039166 41509232 41919194 42309031 42408784
41768757 41598764 41209089 41189086 </pre>
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