Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 040001
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
701 PM EST Sat Dec 3 2016

.SYNOPSIS...
Issued at 645 PM EST Sat Dec 3 2016

Cloudy, cool, and mainly dry conditions will persist through
Sunday morning. Lows tonight will be around 30 degrees. An area of
light snow, mixed with rain, will move through the region midday
Sunday through Sunday evening. Precipitation should mainly fall as
snow north of U.S. 24, and mainly as a mixture of rain and snow to
the south. Some light accumulation of snow may occur on grassy
surfaces. The early portion of next week will trend a little
warmer with rain possible late Monday night into Tuesday. Some
snow may once again mix in. A strong cold front then brings much
colder air and chances for lake effect snow for the second half of
the upcoming work week.

&&

.SHORT TERM...(This Evening through Sunday)
Issued at 315 PM EST Sat Dec 3 2016

Quiet and dry night in store for the area with mostly cloudy
skies as high pressure slides to the east. Once again expect cloud
cover to keep temps warmer than guidance and have used consraw
which has been performing quite well.

Fast moving short wave to move across region Sunday with quick
shot of precipitation from late morning into early evening. Models
have slowed onset by a few hours but still think leading edge of
pcpn will arrive in western areas by mid morning and move into
eastern areas by mid afternoon. Good moisture flux spreads north
ahead of short wave with period of good system relative isentropic
lift coincident with best omega ahead of wave.

Precipitation type remains tricky with cold air aloft sufficient
for ice nucleation and snow but boundary layer temps warming to
mid 30s central and north and upper 30s southeast. Expect to see
primarily light snow over far north and northwest areas with a
chance for rain to mix in during afternoon. Southeast may begin as
snow but transition to primarily rain. Any accums still look to be
around an inch or less in the north and mainly on grassy and
elevated surfaces. Surface wet bulb temps remain just above
freezing and with roads above freezing not expecting many impacts.
Could see a little better window for the accums by late afternoon
and early evening before pcpn ends as sun angle declines and
boundary layer cools a few degrees.

&&

.LONG TERM...(Sunday Night through Saturday)
Issued at 315 PM EST Sat Dec 3 2016

...Much colder weather and lake effect snow still on track for
later this week...

Prior to arrival of first shot of arctic air for the season...we
have to deal with a rather potent short wave lifting out of
southwest CONUS late Monday night and Tuesday. Models continue to
handle this energy differently with 12z NAM trending stronger and
further northwest...placing more moisture across our area with
colder air and potential for significant snow accums.
However...most other model guidance remains weaker and further
east with energy as short wave gets absorbed in southwest flow
aloft. This solution worth watching as we do see these ejecting
systems often lift out stronger and further west but without any
support at this time will continue with ensemble approach and
weight toward GFS and ECMWF. This should spread mainly rain into
the southeast Tuesday with possible mixed precipitation at onset
along the northwest periphery of pcpn shield with evap cooling
processes. Little accums expected at this time but that could
change with any additional trends northwest.

Colder air will start to bleed in Tuesday night and Wednesday
with bulk of arctic air set to arrive Wednesday night and
Thursday. This will get the lake effect machine going in earnest
and likely continue into Friday. Instability will be on the
extreme side with sfc to 700mb delta Ts pushing 30 and 0-2km delta
theta-e values dropping to nearly -6 C/km. Usual concerns this far
out center around moisture depth and trajectories along with DGZ
height. Latest guidance continues to indicate at least favorable
conditions for measurable pcpn and accumulating snow but much too
early to nail down amounts or locations other than broad brush the
usual favored snow belt region. Continue to monitor forecasts as
the week progresses and details become more clear.

Entire area to experience the coldest air of the young winter season
with lows into the teens and highs only in the 20s outside of lake
effect belt. Some single digit lows would not be out of question
with timing of clearing...snowpack and light winds late week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 644 PM EST Sat Dec 3 2016

Primary focus on deteriorating flight conditions from midday
Sunday through the end of the TAF period as warm front associated
with clipper system pushes into the western Upper Great Lakes
region. Some probability for even lower/IFR ceilings especially
into Sunday evening and beyond as rich low level moisture becomes
orphaned in light flow and sequestered beneath lowering inversion
heights.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

SYNOPSIS...Murphy
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...Murphy


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