Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 302340
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
640 PM EST Wed Nov 30 2016

.SYNOPSIS...
Issued at 633 PM EST Wed Nov 30 2016

A strong low pressure system over Wisconsin will move slowly
northeast over the next couple of days causing mostly cloudy and colder
conditions in our area with scattered rain and snow showers over
southern Michigan and far northern Indiana. Lows the next couple
of nights will be in the lower to middle 30s with highs Thursday
and Friday in the upper 30s to lower 40s.

&&

.SHORT TERM...(This Evening through Thursday)
Issued at 301 PM EST Wed Nov 30 2016

Cold air advection underway and cold wedge to deepen overnight as
upper low over the upper Midwest drifts closer. 850mb temps will
drop to around -6C this evening over lake. Mid lake temps around 10C
so SFC to 850mb delta T/S will be in the mid teens representing
modest lake induced instability. Delta theta-e values still just
around -1C/km and only rather briefly around 06z tonight. This is
coincident with deepening inversion heights and increasing moisture
depth. These factors should result in at least scattered lake effect
precipitation but west southwest trajectories should confine
majority of pcpn to Michigan counties. Thermal profiles inland will
support mainly snow showers but modifying effects of Lake Michigan
on boundary layer will keep sfc wet bulb temps above freezing and
may lead to a rain and snow mix at times. Should be mainly liquid
closer to lake with brief wet snow mixed in. Only a small chance for
accumulation and this would be very light and primarily on grassy
surfaces well inland if a stronger band were to develop.

Troughiness to remain over the Lakes Thursday with a much colder
and cloudy day. Scattered rain and snow showers again off the lake
transitioning to mainly rain showers during the day with small
diurnal warming. Again primarily in our Michigan counties but
trajectories suggest a bit more southerly component into far
northern Indiana and maintained low chance pops with measurable pcpn
in question. Little recovery in temps expected with most locations
staying in the 30s or just tapping 40 for highs.

&&

.LONG TERM...(Thursday Night through Wednesday)
Issued at 301 PM EST Wed Nov 30 2016

Relatively active pattern expected this period with mainly low
amplitude short waves every few days bringing pcpn chances.
Temperatures should remain seasonable through day 7 before potential
for significantly colder air invades late next week per latest 12z
model runs.

Persistent weak lake effect pcpn will extend into early Saturday.
Lowering inversion heights and drying low levels will likely lead to
only sprinkles or flurries but maintained inherited slight chance
pops for consistency. Semi-perma cloud to remain in place over the
north but may see some sun develop away from lake plume.

Large scale upper low expected to dig deep into southwest CONUS this
weekend but eject northeast early next week. Prior to this...a weak
northern stream short wave will race across the area Sunday. Thermal
profiles suggest rain and snow mix on track for now with more detail
in later forecasts. QPF looks light with deeper moisture shunted
south and east of local area.

Models have had various solutions with respect to how strong the
southwest low will be and where it will move when it lifts out next
week. 12z runs have continued with weaker shearing wave and latest
forecast continues this trend. Warm air advection ahead of this
system likely to lead to all rain per latest thermal profiles with a
more substantial rain event given expected Gulf of Mexico tap. Will
still need to watch for any model changes as energy becomes better
sampled. Still a long way off and changes likely. Mid range pops
works for now and will keep all liquid given ECMWF and GFS relative
agreement. Both models also hinting at much colder air arriving in
the 8-10 day window more representative of winter.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 633 PM EST Wed Nov 30 2016

Low level moisture wrapping around a strong low pressure system
centered over WI will cont to overspread nrn IN early this eve.
The deep low will be slow to move ne maintaining cold/moist
cyclonic flow and associated mvfr strato cu through the period.
Snow showers associated with upr trof should move across nw IN
including SBN overnight. Veering winds aloft will cause lake
effect showers to spread as far south as SBN Thu, with diurnal
heating resulting in a change of ptype from snow to rain during
the day. The showers should all be light with little impact on
aviation.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 11 PM EST Thursday for LMZ043-046.

&&

$$

SYNOPSIS...JT
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...JT


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