Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 231733
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1233 PM EST Tue Jan 23 2018

.SYNOPSIS...
Issued at 1230 PM EST Tue Jan 23 2018

Rain and snow showers have largely exited the area at this hour.
The exception is the greater South Bend area where flow off the
lake is promoting some continued snow showers. This activity is
expected to decrease over the next few hours. Temperatures will
continue to fall into the low-30s through this afternoon. Wind
gusts from the northwest at 25-30 mph will diminish early tonight.
Dry conditions will be with us tonight through Friday afternoon,
with a late week warm up expected.

&&

.SHORT TERM...(Today and Tonight)
Issued at 257 AM EST Tue Jan 23 2018

Unsettled pattern to continue today with several disturbances
rotating through parent upper low across the Mid MS Valley this
morning.

One vort lobe is current working across east central Illinois this
morning which will provide some light rain showers for areas
especially along and south of Route 24 through daybreak. Cold air
advection across east central Illinois into central/northeast
Indiana will be a bit more pronounced early this morning as colder
air wraps into this system, which could allow rain/snow shower mix
through daybreak across these locations. No snow accumulation is
expected at this time in association with this area of precip
through daybreak. Passage of this vort will then allow a small
scale mid/upper wave across northeast Illinois to drop across
northern Indiana in the 12Z-16Z timeframe with better chance of
rain/snow showers transitioning to mainly snow showers with brief
period of lake enhancement expected.

Some light snow accumulations still appear possible this morning
with stronger forcing and deeper mid level moisture in place. Wet
nature of snow and initial rain/snow mix potential should cut down
on ratios however, and still only expecting limited snow
accumulations of less than an inch across the northwest. For this
afternoon, DGZ does indicate some drying, although deepening mixing
with cold air advection should begin to saturate lower portions of
the DGZ again. A smaller scale wave rotating through western
periphery of this upper low across southeast MN/eastern IA should
track across southern Great Lakes region later this afternoon into
this evening with continued isolated/scattered snow showers. Bulk of
any snow accumulations should occur through 18Z however.

Otherwise for today, high temps expected to be reached early in the
day with steady to slowly falling temperatures. Deepening mixing
will allow west-northwest gusts in the 25 to 30 mph range late
morning/afternoon. Quiet weather tonight as upper low finally
lifts out of the area with short wave ridging building into the area.

&&

.LONG TERM...(Wednesday through Monday)
Issued at 257 AM EST Tue Jan 23 2018

Weak Pacific upper trough will dig across the area on Wednesday,
with maybe a few flurries in the morning, but meager moisture will
limit any accumulating precip potential. Low level thermal trough
will be slightly reinforced by this wave providing near
seasonable temperatures. For late Wednesday/Thursday Great
Lakes/Ohio Valley become positioned in upper level inflection zone
which will mark onset of moderating temperatures for Thu-Fri as
long wave upper ridging across central CONUS approaches. Air mass
will remain dry across the area through Friday as southeast US
anticyclone allows low level southwesterlies to feed drier low
level air northeast across the Ohio Valley. A series of Pacific
waves will allow for weak cyclogenesis across Northern Plains
late this work week with fairly robust southwest gradient in place
by Friday. Breezy/windy conditions are possible Friday, but this
should also provide highs back close to the 50 degree mark.

Rain chances should increase again for late Friday-Saturday as low
level flow trajectories become more favorable for better low level
moisture transports in advance of approaching Pacific wave. Medium
range models still exhibiting quite a bit of spread in terms of
phasing southern/northern stream and resultant amplification with
this pattern, and thus will keep previous forecast idea of limiting
to chance PoPs, with possible transition to snow before precip ends.
Temps should transition back closer to normal by late
weekend/early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1212 PM EST Tue Jan 23 2018

(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 1230 PM EST Tue Jan 23 2018

SBN has been experiencing some lake enhanced snow showers during
these late morning hours. The observed IFR, and even LIFR,
conditions were unique in duration when compared to surrounding
observations. Due to this persistence, I have allowed for TEMPO
IFR conditions until the upper level vorticity maximum exits the
region.

For both SBN and FWA, we expect gusty northwest winds to diminish
near midnight with MVFR conditions for the overnight period. By
the very end of the TAF period, there are some indications that
there could be VFR conditions. For now, I will pass this along to
the 00Z TAF team.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory until 9 AM EST Wednesday for LMZ043-046.

&&

$$

SYNOPSIS...Brown
SHORT TERM...Marsili
LONG TERM...Marsili
AVIATION...Brown


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