Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 211146

Area Forecast Discussion
National Weather Service Northern Indiana
646 AM EST Thu Jan 21 2021

Issued at 148 AM EST Thu Jan 21 2021

Breezy with sunshine today and high temperatures ranging from the
mid thirties to near forty. Lake effect snow showers are expected
tonight. An active pattern looks to take shape beginning Sunday.


.SHORT TERM...(Today through Friday)
Issued at 148 AM EST Thu Jan 21 2021

Surface low passing to our north will promote breezy conditions
today. Wind will gust from the west at 25 to 30 mph. Temperatures
will be a few degrees warmer than today, though the breezy
conditions may not make that readily apparent.

Cold air aloft pushes south over the lake through the day, such that
modeled 850mb temperatures fall from about -2C at the time of
this writing, to -10C in 24 hours. Along this thermal gradient
aloft, high resolution models are picking up on what could be a
brief band of snow moving through central MI, perhaps surviving
into at least northeast Indiana. This trend will need to be
monitored through today. Confidence is higher regarding the
opportunity for lake effect snow in the favored northwest flow

As the previous AFD mentioned, inversion heights are a bit shallow;
struggling to reach 5,000 ft. Additionally, at the start of the
night, low-level saturation resides outside of the DGZ. It is not
until the pre-dawn hours that the DGZ is forecasted to saturate.
As such, this would suggest that lake effect snow could become
most organized in time for the Friday morning commute which is
troublesome, to say the least. Inversion heights fall through the
day on Friday which will eventually bring an end to the lake
effect snow. Between the poor saturation of the time, and the
transient nature of the bands according to high resolution
guidance, snow accumulation of one inch or less is plausible in
portions of Berrien and Cass (MI) counties, perhaps extending into
northern St. Joseph (IN) county. Snow showers could extend inland
through the U.S. 30 corridor in Indiana.


.LONG TERM...(Friday night through Wednesday)
Issued at 148 AM EST Thu Jan 21 2021

High pressure will be in place through the early morning hours on
Sunday, promoting dry conditions and especially crisp (but
seasonable!) low temperatures early Saturday morning; lows in the

The forecast period of Sunday through Tuesday continues to look
messy with a trough ejecting from the Desert Southwest, and an
upper- level low stretching out over south-central Canada. A
clipper may bring a quick period of snow on Sunday, but there are
still some solutions that try to phase this with a weak low
emerging from the Central Plains. This would then be followed by a
Southern Plains low lifting in later Monday. This is where model
guidance is especially divergent, owing to different amplitudes
and axis locations of the 500-mb trough off the Pacific coast.

How those upper-air features evolve is critical to how the midweek
forecast pans out. The short story is: an active pattern is favored
beginning on Sunday, and continuing into midweek. All precipitation
types are possible.


.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 646 AM EST Thu Jan 21 2021

VFR will persist through the day given abundant dry air through
the column. Decent gradient and mixing will support WSW winds
gusting up to 30 kts at times today. Next trough and associated
CAA/veering winds will lead to lake effect snow showers and
stratus tonight...particularly at KSBN. Snow showers expected to
remain SCT and likely not arriving until closer to 12Z but MVFR
stratus will return around 03Z at KSBN and 06Z at KFWA.


LM...Small Craft Advisory until 4 AM EST Saturday for LMZ043-046.




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