Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 081744
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1244 PM EST Thu Dec 8 2016

.SYNOPSIS...
Issued at 1223 AM EST Thu Dec 8 2016

A strong low pressure system moving slowly east across
southeast Canada will cause cold west to northwest winds across
the Great Lakes resulting in significant lake effect snow over
southwest Michigan and far northern Indiana over the next couple
of days, with scattered snow showers over northwest Ohio and most
of the rest of northern Indiana. A low pressure system is
expected to move east across the Midwest this weekend causing snow
in our area, mainly Saturday night and Sunday. This system should
be followed by colder air overspreading the area into the middle
of next week with probably additional lake effect snows.

&&

.UPDATE...
Issued at 1046 AM EST Thu Dec 8 2016

Broad cyclonic flow, cold advection, and steep lapse rates have
allowed for lake effect snow showers to develop along with lighter
snow showers/flurries across much of the forecast area this
morning. Snow accumulation likely all not that efficient through
early PM as deepening mixed layer slowly begins to saturate better
snow growth layer. Snow shower intensity should pick by this
evening as next mid level trough sags across southern Great Lakes
and lake induced equilibrium levels increase to 8-10k feet. Fetch
considerations still suggest zone of greatest potential
accumulation from northern Berrien through Cass and St Joseph
counties, and possibly into Branch county. Some concern that
Branch county may need to be transitioned to a warning depending
on how things set up this evening, but confidence is not high
enough at this time to change headlines. Did go ahead and issue a
winter weather advisory for Hillsdale with expectation that
favorable fetch could result in 2 to 5 inch type accumulations in
western portions of the county. Did make some adjustments to
diurnal temps this afternoon showing little if any temperature
recovery in some spots due to the cold advection. Updated WSW has
been sent with Hillsdale addition to the advisory.

&&

.SHORT TERM...(Today and Tonight)
Issued at 534 AM EST Thu Dec 8 2016

Lake effect snow was already beginning north of Berrien county as
colder air was spreading over the relatively warms waters of Lake
Michigan. Few changes were made to the ongoing grids and forecast,
although have added Laporte County to the advisory given wintry
weather of blowing and drifting expected over far northern areas of
the county late today and tonight. The Lake Michigan water
temperatures over these southern portion of the lake around 45
degrees were exceptionally very warm for this time of year. Delta T
values will reach or exceed 20C with the cloud area very favorable
for snow growth. However, limited lake fetch, especially early along
with significant shear in the cloud layer will limit accumulations.
Have kept 5 to 8 inches over the advisory area, with lesser amounts
farther inland. Snow will diminish Friday as inversion heights
fall.

&&

.LONG TERM...(Friday through Wednesday)
Issued at 534 AM EST Thu Dec 8 2016

More cold and snowy weather is on the horizon for the extended.
Favor a general model blend for the approaching upper level system
this weekend. There was still considerable spread among GFS ensemble
members, so confidence in timing, track and snow amounts still
uncertain. Some members and the EC were warmer Sunday suggesting a
possible rain/snow mix. For now, kept all snow. Accumulations of
several inches are possible from Saturday through early Monday.
Otherwise, much colder air should spread over the area by Wednesday
along with snow and lake effect snow showers.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1237 PM EST Thu Dec 8 2016

Low pressure centered over quebec this afternoon will drift
eastward. Cold air advection is in full swing behind the trailing
cold front on west-northwest winds. Steep mid-level lapse rates
and daytime heating are allowing stronger winds aloft to mix down
to the surface, with gusts to 25-30 knots expected through the
afternoon. Otherwise, the main focus is on where heavier lake
effect snow bands set up this afternoon/evening into Friday
morning. Was pessimistic with the forecast at KSBN, with medium
confidence in the moderate-heavy bands reaching the site and
stronger wind gusts. If stronger bands do reach the site, expect a
trend from IFR to LIFR-especially if accumulations and wind
combine to cause blowing snow. Lesser impacts are expected at
KFWA...and confidence in any significant snow bands reaching the
site is low. Expect the bands to remain north of the
site...keeping conditions primarily MVFR. If moderate/strong bands
do manage to migrate south into the site...IFR conditions are
possible. For now, kept things conservative given the uncertainty.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 4 PM EST /3 PM CST/ Friday for
     INZ003>007.

MI...Winter Weather Advisory until 4 PM EST Friday for MIZ080-081.

     Winter Storm Warning until 4 PM EST Friday for MIZ077>079.

OH...NONE.
LM...Small Craft Advisory until 7 PM EST Friday for LMZ043-046.

&&

$$

UPDATE...Marsili
SYNOPSIS...JT
SHORT TERM...Skipper
LONG TERM...Skipper
AVIATION...MCD


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