Rockford Scanner®: Snow Later Tonight and Into Tomorrow

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814 PM CST

Not planning any noteworthy changes to going forecast for this
evening. Overall, not much to add to the short term discussion
issued earlier this afternoon below.

Couple items of note to watch for:

1) The RAP continues to be quite aggressive with a deep
frontogenetic circulation persisting into tomorrow afternoon. In
addition to the more robust/persistent f-gen band in the RAP,
cross sections cut through the f-gen band show some fairly deep
pretty strongly negative layers of saturated EPV (indicative of
less stable conditions) coincident with the stronger omega. This
certainly suggests at least some potential for exists for some
bands of moderate to heavy snow embedded within the larger snow
shield. That could result in some localized 3 to maybe near 4
inch totals, but thinking is those amounts will be very much the
exception not the rule. Given the low confidence and limited areal
coverage of heavier amounts, don’t see a need to adjust going
forecast snowfall amounts as the forecast message would largely be

2) Snow, potentially at a decent clip, should continue through
midday in the Chicago area, however with temps likely to be near
or a hair above freezing and battling the time of day, suspect
that it will get increasingly difficult for accums to occur on

3) Finally, as short discussion alluded to, models are notorious
for struggling with accurate depiction of f-gen band intensity and
duration. While many models suggest a quick weakening of f-gen
circulation and resultant snowfall as it gets into northern IL, it
wouldn’t be at all surprising to see occasionally moderate
snowfall continuing through the morning and perhaps even into the

Only planned changes to the grids/forecast this evening are:
* tweaking hourly temps a bit to reflect a trend driven more by
precip than diurnal influences.
* adjust pops to 100% over northern CWA
* adjust sky cover to remain overcast through the day Saturday

Updated grids and test products will be out shortly…

Light snow is expected to spread southward across the area late tonight into Saturday afternoon. Forecast snow accumulations range from 1-2” north of I-80 to less than a half inch across southern portions of the forecast area.

If traveling late tonight and Saturday, plan for extra time to reach your destination as slippery conditions will be possible, especially on any untreated surfaces




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