Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 062354

Area Forecast Discussion
National Weather Service Northern Indiana
654 PM EST Tue Dec 6 2016

Issued at 650 PM EST Tue Dec 6 2016

A trough of low pressure will clear the area this evening
resulting in decreasing cloud cover overnight. Lows will dip into
the lower to middle 20s. Colder air will filter into the region
through Thursday resulting in an increased potential of lake
effect snow showers from Thursday through Friday afternoon. High
temperatures by Thursday are only expected to reach into the mid
20s. In addition to the lake effect snow showers and colder
weather, breezy conditions are also expected Thursday and Thursday


.SHORT TERM...(This Evening through Wednesday)
Issued at 408 PM EST Tue Dec 6 2016

Primary short term forecast challenges will be cloud trends tonight
and colder temps with eventual transition to lake effect snow

Challenging sky cover forecast for this evening as patch of clearing
has developed in the vicinity of low level trough axis. Clearing
should be short lived over the next few hours as post-trough cold
advection works from west to east during the early to mid evening
hours. Back edge of stratus deck is currently working across north
central/central Illinois which should allow most areas to scatter
out this evening. Low clouds should tend to move back in across
south central lower Michigan later this evening and into the
overnight however. Colder mins in store for tonight under the
influence of cold/dry advection, generally in the mid 20s.

The extended period of cold advection will continue
Wednesday/Wednesday although deeper mixing should (at least for
Wednesday) negate temps for bottoming out significantly with highs
from lower 30s northwest to mid to upper 30s far southeast. Could
make a run at temps a little warmer than this across southeast half
if better insolation is realized, although do expect increasing
afternoon mid-cloud downstream of a sheared mid/upper level wave
across the central US.


.LONG TERM...(Wednesday Night through Tuesday)
Issued at 408 PM EST Tue Dec 6 2016

The long term period is shaping up to be quite active with possible
significant lake effect snow Thursday-Friday, followed by another
potential system for the later Saturday-Sunday timeframe. The
transition to much colder conditions will be the other big story
this period.

Inversion heights will gradually be on the rise Thursday, and
especially by late Thursday afternoon/night.  Lake effect snow
showers are expected to increase late Wednesday night into Thursday
morning, although lake-induced convective depths should be on the
shallow side at this time. Potential of more significant lake effect
snow showers still appears inline for the later Thursday afternoon-
mid afternoon Friday timeframe. An approaching secondary mid level
trough will allow for more veered flow by Thursday evening with an
upswing in lake effect snow shower intensity by this time. Increased
cyclonic flow/synoptic confluence-convergence with this wave and
increasing instability should sharpen lake response Thursday night
with deeper moisture profiles also in place. Forecast soundings
suggest strongest lift may just graze lower portions of DGZ,
although some respectable depth to DGZ noted in the Thursday
night/Friday morning timeframe. Significant lake effect snow
accumulations are possible for favored west-northwest fetch counties,
but details in exact accumulations will depend on strength of
aforementioned mid level trough and any transitory nature to
banding that may arise from the passage of this trough.

Fetch may become more stable in the late Thursday night/early Friday
timeframe in the wake of this trough when the greatest instability
profiles will be in place. Besides strongest lift possibly residing
below DGZ, a relatively short duration of deeper saturation may tend
to discourage higher end warning amounts from being realized.
Thoughts of previous shift are still intact in terms of expectation
of higher end advisory/lower end warning type event. Given best set
up appears to be 5th and 6th periods and low confidence on advisory
vs warning threshold, will defer any headlines to later shifts. Lake
effect to wind down Friday night as low level winds back and
inversion heights lower. The cold will be the other big story, as
wind chills drop into the 5 to 15 above zero range Thursday

Lull in weather should be short-lived late Friday night into
Saturday as strong eastern Pacific jet allows for amplification of
next upstream trough across the Rockies. A period of overrunning
snow is possible Saturday night, with synoptic forced precip looking
like a good possibility late Saturday night/Sunday. Depending on
strength of this wave and downstream LLJ, some ptype issues are
possible Sunday.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 664 PM EST Tue Dec 6 2016

Gradual scouring of low level clouds should persist across
northern Indiana this evening with VFR conditions likely by
midnight and beyond.


LM...Small Craft Advisory until 1 PM EST Wednesday for LMZ043-046.



SHORT TERM...Marsili
LONG TERM...Marsili

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