Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 131731
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1231 PM EST Sat Jan 13 2018

.SYNOPSIS...
Issued at 432 AM EST Sat Jan 13 2018

Lake effect snow showers are expected today over portions of
northern Indiana and southwest Lower Michigan. Accumulations of 1
to 3 inches are possible through tonight in the snow belt region
before the snow showers end. Highs today will be in the upper
teens and lows tonight will dip to around zero with some locations
in the single digits below zero. More accumulating snow is
expected across the entire area Sunday night into Monday with
1 to 3 inches possible. This will be followed by more lake effect
snow Monday night into Wednesday. A warming trend looks likely late
in the week and into next weekend.

&&

.SHORT TERM...(Today and Tonight)
Issued at 431 AM EST Sat Jan 13 2018

Ongoing lake effect and temperatures main concern in the short
term period. Upper level trough to swing through the area today
with some weak DPVA. Polar airmass remains dry and not expecting
much with this wave outside of lake effect region. Slight increase
in inversion heights today as trough passes but not much more
than 5-6kft. However, long NNW fetch with some pre-conditioning
from Superior along with sfc-850mb delta Ts in the lower to mid
20s should be enough to support lake effect snow showers through
the day and into tonight. Bufkit soundings show strong lift packed
within saturated shallow lower levels so some moderate snow
showers possible at times. Low level flow will back today and
transitory band should gradually shift east today and northward
tonight as flow becomes southwest. Accumulations always difficult
in these shallow unstable events but expect generally 1 to 3
inches with some 4 inch amounts not out of question through this
evening.

Low temperatures next concern for tonight as arctic high builds into
the region. Skies will clear in the west as lake band shifts
northeast. Winds should also become light or calm as ridge axis
expands east. Have lowered temps across the west and south by
several degrees into the single digits below zero. Central and
northern areas will drop into single digits above zero but may end
up colder as well depending on how fast lake plumes shifts north.


&&

.LONG TERM...(Sunday through Friday)
Issued at 431 AM EST Sat Jan 13 2018

Clipper system remains on track to impact the region Sunday night
into Monday. Surface low track remains just to our north as left
front region of cyclonically curved 100+kt jet streak moves over the
area. Modest system relative isentropic lift develops Sunday
night ahead of this feature and light snow should spread east
through the late evening and overnight. As typical with these
clippers there is not a lot of moisture available but good lift
with diffluence aloft from jet streak and 1.5 PVU surface dropping
to around 600 mb should help system maximize pcpn/snowfall. Model
QPF has been rather consistent around two tenths of an inch and
this matches well with WPC values. Snow ratios should be near or
slightly above climo and close to 15:1 - 18:1 for this event.
Rather deep DGZ being depicted but not supersaturated and
strongest lift still near top or above this zone which will keep
ratios lower than models despite the very cold temps. Forecast
remains on track with general 1 to 3 inches across the area. Could
see some enhancement toward end of event in the far NW near the
lake as winds become westerly and some lake enhancement kicks in.

Attention then turns to lake effect potential behind this synoptic
wave. Low level winds initially will be westerly Monday night into
Tuesday as an east-west surface trough will be left across
central Lake Michigan and interior Michigan. This feature will
move south Monday night and should lead to development of another
Type VI snow event with meso low/vortex development west of Big
Sable Point MI late Monday night. This feature will drop south
Tuesday and likely will come onshore between Berrien and Laporte
counties followed by a strong single band in its wake. Models have
been rather consistent showing this band type but have some
differences in orientation of trough axis as well as when and where
meso vortex will come onshore. Short duration intense rates would
be expected with the vortex while a more prolonged period of
moderate to heavy snow would be likely in the single band.
Increased pops in the NW to likely and high chance Tue and Tue
night with refinement coming over the next few days.

A short but nice break in the weather appears likely after this lake
effect event with a gradual warming trend late week into the
weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1230 PM EST Sat Jan 13 2018

Multi-band lake effect snow showers will continue across the area
through the afternoon. Inversion heights are moderate and there is
very dry air upstream but small flake size is causing visibilities
near 1/2 mile at times in heavier showers. Expect visibility will
continue to be highly variable at KSBN until this evening when
winds back and shut off lake response. Lake effect snow showers
may also impact KFWA this afternoon based on upstream obs and
decent shortwave rotating through. VFR expected at both TAF sites
overnight into early tomorrow.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 7 PM EST this evening for LMZ043-046.

&&

$$

SYNOPSIS...Lashley
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...AGD


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