Rockford Scanner™: Update On The Possible Winter Storm, Winter Storm WATCH


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Winter Storm WARNING
Until Nov. 26th at 12 am.

A strong low pressure system will bring heavy snowfall to portions of the area Sunday into Sunday night. Rain is expected to quickly transition to snow from northwest to southeast, with rapidly deteriorating conditions accompanying this change.

Snowfall rates of 1 to as much as 2 inches per hour will be possible after this transition. Any minor shift in the track of the low pressure system may affect snowfall totals, however, significant impacts are expected for much of the area Sunday afternoon and evening.

Sunday…
Elevated Non Thunderstorm Wind Risk.
Significant Snow Risk.

DISCUSSION:

An early season winter storm will impact portions of northern
Illinois and northwest Indiana bringing heavy snowfall to the
region. Snow covered roads and drastically reduced visibility
will result in dangerous travel conditions. Snow accumulation in
excess of six inches is likely for areas near and northwest of
I-55 with amounts quickly tapering to the southeast. Strong north
winds developing later in the day Sunday may result in blowing and
drifting snow. Large waves battering the shores of Lake Michigan
may also produced localized lake shore flooding.


WINTER STORM WATCH IN EFFECT FROM SUNDAY MORNING THROUGH
SUNDAY EVENING…

* WHAT…Heavy snow possible. Total snow accumulations in excess
of 6 inches possible. Winds could gust as high as 35 mph.

* WHERE…Portions of north central and northeast Illinois.

* WHEN…From Sunday morning through Sunday evening.

* ADDITIONAL DETAILS…Travel could be very difficult. Snow
covered roads and significantly reduced visibility are possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

A Winter Storm Watch means there is potential for significant
snow, sleet or ice accumulations that may impact travel. Continue
to monitor the latest forecasts.

 

9am 11/24 update: Cook, DuPage, Grundy, Kendall and Will counties added to the Winter Storm Watch.

Breezy and mild conditions will continue today. An early season winter storm will bring several inches of accumulating snow and strong winds across portions of northern Illinois Sunday morning into Sunday evening. Adverse winter weather is also possible outside of the Winter Storm Watch counties Sunday evening. In the wake of the storm system, unseasonably cold conditions are in store to start the last work week of November.

DISCUSSION:

A strong winter storm will move through the region Sunday and
Sunday night. A mix of rain and snow is expected to change to
heavy wet snow during the day across north central Illinois, with
the rain snow line moving southeast across the remainder of the
outlook area during the afternoon and early evening hours.

Heavy wet snow accumulations in excess of 6 inches are possible
primarily northwest of a Peru to Chicago Illinois line, with
amounts decreasing quickly to the southeast. In addition to the
accumulating snow, northerly winds will become very gusty Sunday
afternoon and night, with gusts of 35 to 40 mph possible. This may
produce blowing and drifting snow, further impacting travel.

 

While we are still waiting on the GFS and ECMWF 12z runs, several
of the near term models are attempting to hone in on the axis of
heaviest snow and strong winds on Sunday. The general consensus to
this point has been through an axis northwest of Chicago. While
this is still generally the case, especially given the thermal
profiles, the latest NAM, the ECMWF (numerous runs to this point),
and some of the WRF NMM/ARW models suggest an axis between I-90/88
and I-80 could certainly be the favored corridor.

Once rain changes over to snow, it will likely be coming down
very hard, so in spite of the marginal surface temperatures to
start, snow once it starts to fall will rapidly accumulate with
heavy, wet slushy snow. While exact transition times are up in
the air, travelers should be prepared from mid morning northwest
to early to mid afternoon across portions of the Chicago metro,
for a quick transition/deterioration, given the challenges on
exact transition/Snow onset time.

In addition, strong winds will eventually accompany the heavy
snow, so even with snow amounts in question, heavy snow rates and
strong winds will make for very hazardous travel on a busy travel
day. Given the signal for a possibly farther south corridor, we
have expanded the Winter Storm Watch to include a tier of counties
farther south and east with this morning update. These counties
start and end a bit later than the counties farther west.