Area Forecast Discussion
Issued by NWS Northern Indiana

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641
FXUS63 KIWX 150740
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
240 AM EST Fri Dec 15 2017

.SYNOPSIS...
Issued at 109 AM EST Fri Dec 15 2017

A weak system will pass across the Great Lakes today bringing
scattered to numerous snow showers north of the Toll Road. Some
light snow accumulations of an inch or two are possible from today
through tonight, especially across southern Lower Michigan where
lake effect snow showers are expected to be more numerous. High
temperatures this afternoon will range from the mid 20s to lower
30s. Lows tonight will not be as cold, ranging from the mid to
upper 20s. The moderating trend will continue into the weekend
with highs in the 30s and 40s for Saturday and Sunday. The next
chance of rain and snow will arrive by Sunday afternoon.

&&

.SHORT TERM...(Today and Tonight)
Issued at 239 AM EST Fri Dec 15 2017

A mid level shortwave will rotate southeast through central/upper
Michigan today, with the trailing trough axis swinging through the
local area from west to east this morning through early-mid
afternoon. Most of the impacts/accums will bypass north given far
northerly track of the system sfc reflection, though there will be
enough lake enhancement in strengthening westerly flow to generate
scattered to numerous snow showers mainly north of Route 6.
Steepening lapse rates/mixing into the lower portion of the DGZ
could support some stronger snow squalls and light accums in these
areas, which when combined with wind gusts of 20-30 mph and snow
already on the ground could promote patchy blowing snow and reduced
visibilities. Cool/breezy/cloudy with flurries possible elsewhere
today.

Warm advection regime tonight will likely allow light snow to
develop near a trailing baroclinic zone leftover from the Upper
Midwest southeast into the Lower Great Lakes. Models are in pretty
good agreement in best snow chances (maybe up to an inch) northeast
of US 30 mid evening into the overnight.

&&

.LONG TERM...(Saturday through Thursday)
Issued at 239 AM EST Fri Dec 15 2017

Positive PNA ridge along the West Coast will break down and allow
positive height anomalies to finally overspread the Eastern US this
weekend into early next week. The result will be a warming trend and
mainly dry conditions, though will have to watch a shearing southern
stream shortwave lifting northeast out of Texas for light rain
(possibly mixed with some snow) on Sunday. A rather benign, yet
still mild, pattern is then expected to persist into the middle of
next week as models agree on flatter/split flow downstream of an
amplifying Western US trough. This trough does eject east late in
the week with a decent mid latitude cyclone likely making a run for
the Great Lakes. The northerly track would favor more of a rainer
locally followed by colder/drier air in time for next weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 109 AM EST Fri Dec 15 2017

Primarily VFR low clouds persist across northern Indiana early
this morning. Weak warm advection should get going during the
overnight hours in advance of next fast moving clipper system.
This short wave passage should mark a brief window of higher snow
showers chances at KSBN in the 15-19Z timeframe. Have not made
significant changes from previous TAFs in trend to MVFR cigs 2-3k
feet and MVFR vsbys in scattered snow showers during this period.
Brief residence of weak mid level thermal troughing and primarily
westerly fetch should allow for some isolated-scattered snow
showers this evening at KSBN, but chances should gradually lift
northward into southern Lower Michigan toward the end of the
period as flow becomes slightly more backed. Have also maintained
previous mention of MVFR cigs at KFWA 2-3k feet through much of
this period. West winds to become gusty for a time late morning
through late afternoon with better mixing associated with this
weak trough, but decoupling should occur fairly early this evening
as thermal trough begins to retreat.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 5 AM EST Saturday for LMZ043-046.

&&

$$

SYNOPSIS...Marsili
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Marsili


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