Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 090025
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
725 PM EST Fri Dec 8 2017

.SYNOPSIS...
Issued at 240 PM EST Fri Dec 8 2017

A clipper system will bring light snow to the entire area late
tonight and Saturday morning. Most locations will likely receive
between 1 and 3 inches, though lower amounts are possible southeast
of US 24. Heavy lake effect snow is then expected to impact portions
of northwest Indiana and far southwest Lower Michigan late Saturday
morning through Saturday evening. Snow totals are expected to exceed
6 inches in favored lake effect snow belts. This accumulation, gusty
winds, and intense snowfall rates will lead to difficult travel
conditions in these areas. Cold and remaining active otherwise
through next week as several more clipper systems bring snow chances.

&&

.SHORT TERM...(This Evening through Saturday Night)
Issued at 240 PM EST Fri Dec 8 2017

Remaining cold with the first widespread accumulating snow of the
season Saturday...

A potent and compact shortwave over eastern Manitoba will dig
southeast through the Great Lakes bringing a period of light
synoptic snow later tonight into Saturday morning, followed by a
dominate LES band to nnw LE belts later Saturday morning through
Saturday evening. Strong dynamic forcing will be enough to overcome
dry CP airmass in place, with system snow beginning later tonight
into nw IN/sw Lower MI, then through the rest of the forecast area
Saturday morning. Still thinking a quick 1-2" for most locations as
brief nature to forcing and dearth of moisture limits accums.
Scattered snow showers and flurries will then be possible into the
afternoon everywhere as the trough axis and associated steeper lapse
rates pivot through.

The main focus Saturday morning into early Saturday afternoon
will turn to lake enhanced snow...then pure LES in the afternoon
and evening. The low level flow veers more nnw and then eventually
more nw, which will result in strong frictional/thermal
convergence along the long axis of eastern Lake MI. LES parameters
continue to favor good dendritic growth and the potential for
intense 1-2"/hr snowfall rates (near whiteout conditions and gusty
winds) within the dominate band. Berrien/St Joseph IN/LaPorte
still look to be within the pivot point of any banding, with lower
confidence in surrounding counties given the potential for
mesovorticies to force a more transitory/broken plume. It is worth
noting that a more organized band could reach well inland with
advisory level impacts given 35-40 knots of flow modeled at 925
mb. Steepening boundary layer depth may tap into some of this and
create strong winds and blowing snow/low visby`s, especially in
areas under a warning or advisory.

Drying/subsidence/backing winds will take its tool on inversion
heights and bring an end to any impactful LES later Saturday night.

&&

.LONG TERM...(Sunday through Friday)
Issued at 240 PM EST Fri Dec 8 2017

Highly anomalous upper troughing will remain steadfast across the
Eastern US Sunday into next week resulting in more of the same
(below normal temps and several clippers providing chances for
light synoptic snow and LES).

Weak pv filament and associated sfc trough does swing through on
Sunday. This feature may bring a few flurries to far northern zones
given some lake enhancement. Cold otherwise with another day of
highs near 30 degrees.

A more pronounced shortwave in nw flow (this one more of your
typical Alberta Clipper compared to Saturday`s Manitoba mauler) will
have good left exit upper jet support and enough of a low level
thermal gradient to force a developing sfc reflection east through
the Lower/Eastern Great Lakes Monday into Tuesday. Models continue
to oscillate a bit on where leading WAA/isentropic lift snow (1-3")
sets up Monday into Monday evening, though the trend has been more
north across WI and MI. Will continue to carry low-mid chance PoPs
during this time, highest across far ne IN/MI/far nw OH. Deep
northwest flow in CAA wing then brings LES back into play later
Monday night and Tuesday...again in favored NW flow lake belts where
significant snow accums/impacts will be possible. Rinse and repeat
then for the end of the week as another system translate through
in nw flow.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 725 PM EST Fri Dec 8 2017

VFR expected to hold until late tonight before robust upstream sw
disturbance over ern MN amplifies se into wrn IN by aftn. Tremendous
condensation pressure deficits exist downstream of this system this
evening and in light of upstream observational trends have further
delayed onset of -sn. Nonetheless run continuity among hires
guidance remains compelling for a period of at least IFR restriction
in mod-hvy snow invof KSBN by 16Z for a time before backing west in
response to synoptic low dropping down ern lake MI shoreline.

Brief/limited impacts invof KFWA Sat morning.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Storm Warning from 1 AM EST /midnight CST/ Saturday to
     midnight EST /11 PM CST/ Saturday night for INZ003-004.

     Winter Weather Advisory from 4 AM EST /3 AM CST/ Saturday to
     midnight EST /11 PM CST/ Saturday night for INZ012-014.

     Winter Weather Advisory from 5 AM Saturday to midnight EST
     Saturday night for INZ005-015-016.

MI...Winter Storm Warning from 1 AM Saturday to midnight EST Saturday
     night for MIZ077.

     Winter Weather Advisory from 5 AM Saturday to midnight EST
     Saturday night for MIZ078.

OH...NONE.
LM...Small Craft Advisory until 10 AM EST Saturday for LMZ043-046.

     Gale Warning from 10 AM to 10 PM EST Saturday for LMZ043-046.

&&

$$

SYNOPSIS...Steinwedel
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...T


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