Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 012017

Area Forecast Discussion
National Weather Service Northern Indiana
317 PM EST Thu Dec 1 2016

Issued at 317 PM EST Thu Dec 1 2016

Scattered lake effect rain and snow showers will continue mainly
along and north of the toll road tonight into Friday. Cloudy and
cool otherwise with lows in the 30s and highs in the upper 30s to
near 40. Dry conditions and similar temperatures are expected into
Saturday before a weak upper level disturbance brings chances for
drizzle and light snow Sunday into Sunday evening. Little to no
snow accumulation is expected. Milder temperatures are expected
into early next week with the next chance for rain later Monday
night into Tuesday.


.SHORT TERM...(This Evening through Friday Night)
Issued at 317 PM EST Thu Dec 1 2016

Cool/wnw cyclonic flow will likely sustain extensive low
stratocumulus cloud deck through Friday night on the backside of low
pressure edging east through southeast Canada. Lake plume in this
flow has generated scattered lake effect rain showers/sprinkles
mainly north of US 6 so far today. Expect coverage/intensity to
lessen into tonight/Friday in these areas as convective layer
becomes increasingly shallow and drier air becomes better
established. Could see flurries or light snow showers mix in away
from the lake tonight into Friday morning given some diurnal
boundary layer cooling, though lacking moisture above the -10C
layer a limiting factor. Little diurnal range to temps otherwise
through the period.


.LONG TERM...(Saturday through Thursday)
Issued at 317 PM EST Thu Dec 1 2016

An increasingly active/progressive pattern is expected with first
true shot of cold air possible late next week...

The weekend will begin dry/uneventful with similar temps Saturday
into Saturday night as high pressure builds in under low amplitude
shortwave ridge axis. This subsidence may be enough to allow for low
cloud deck to scatter out at some point, best chances
along/southwest of US 30, though confidence is low. This partial
clearing (if it materializes) will be brief as moisture streams
north in advance of a quick-moving northern stream shortwave Sunday
into Sunday evening. Shot of theta-e advection/isentropic ascent on
Sunday appears sufficient for a period of pcpn. Thermal profiles
continue to look marginal for ptype, with current expectations for a
quick period of light snow to drizzle kind of evolution as ice is
lost in cloud and warm advection persist. Some light snow
accumulation cannot be ruled out on grassy/elevated surfaces but
marginal surface temps should prevent any problems on the roads.

The last several model cycles have come into better agreement on cut-
off upper low into northern Mexico eventually opening northeastward
early next week in response to renewed Western US height falls. This
system should bring a period of rain through the local area sometime
later Monday night into Tuesday given associated surge of deeper
moisture in deepening southwest flow aloft.

The deep Western US longwave trough is then expected to march
eastward mid-late next week. The coldest air of the season is
expected in wake of the leading arctic cold front under significant
negative height anomaly modeled to emerge over the northern
Great Lakes/southeast Canada by late next week. The main
uncertainty at this range is timing of frontal passage (Wednesday
or Thursday) and possible strong cyclogenesis into the
western/northern Great Lakes on leading edge of cold airmass.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1232 PM EST Thu Dec 1 2016

Persistent MVFR cloud deck still expected to persist this period
with cyclonic flow and winds off of Lake Michigan. Low level winds
will veer some tonight and should see light rain and snow showers
move back south toward KSBN. Inversion heights lowering along with
decreasing moisture depth so reductions to VIS do not look likely
unless within an isolated shower. Will carry VCSH for now at KSBN.
KFWA remains within trajectories/cloud plume off of lake but with
shallow moisture and inversion doubtful much pcpn can make it this
far inland so no shower mention here.


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



SHORT TERM...Steinwedel
LONG TERM...Steinwedel

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