Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 122332

Area Forecast Discussion
National Weather Service Northern Indiana
632 PM EST Sun Nov 12 2017

Issued at 412 PM EST Sun Nov 12 2017

Precipitation will transition back to a light mix of rain and
snow early tonight. A brief period of very light freezing rain or
freezing drizzle is also possible before precipitation ends by
daybreak. Lows tonight will be in the upper 20s and lower 30s. It
will be dry with a warming trend Monday and Tuesday as high
pressure settles over the area. Highs will reach into the upper
40s and lower 50s by Wednesday. Additional rain showers, with
even a possible thunderstorm, will move through on Wednesday as a
cold front sweeps through the area. Yet another system will bring
more rain on Friday.


.SHORT TERM...(This Evening through Monday)
Issued at 405 PM EST Sun Nov 12 2017

Ramping height falls centroid to 80-90 m/12 hours through the
Ohio Valley through 06 UTC to hasten cyclogenesis with northern
wave moisture orphaned along with further whittling away of warm
Tw layer aloft. This will allow transition back to rain/snow mix
through the evening hours. Later tonight as primary mid level
shortwave moves eastward into the Lower Great Lakes, lagged
moisture depth to remove ice nucleation with precipitation
potentially ending as brief period of light freezing rain/drizzle.
Notable downtrend on prior enhanced shortwave cusp over northern
IL/Quad Cities region indicative of these trends as well. Overall
light qpf/high evening/early night pops wending west to east with
only low/dwindling pops beyond 06 UTC east of I-69. Dry conditions
Monday along with lack of strong cold air advection and at least
partial midday/afternoon insolation to allow surface temps to
embark on moderation trend.


.LONG TERM...(Monday Night through Sunday)
Issued at 405 PM EST Sun Nov 12 2017

Good agreement with respect to continued moderation with high
belted partial ejection of northeast Pacific system into
Ontario/western Upper Great Lakes by midweek. Strong height falls
centroid in excess of 100 m/12 hrs along with low level jetlet
moving from northern MO eastward through central IL/central IN along
with higher pool of mid level lapse rates sufficient for a slight
chance mention of thunderstorms. With respect to early weekend
system, model blends and signals continue to point at
warm/convective system, though varying degree of timing and
strength. At some point thunder may need mentioned with this system
as well, but for now with many variables/lower confidence with defer
for now and continue to assess with time.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 615 PM EST Sun Nov 12 2017

The discussion for the 18Z TAFs suggested deteriorating
conditions are likely for the overnight hours. The latest data
supports this thinking and thus our 00Z TAFs introduce a period of
IFR conditions.

Satellite and radar imagery depicts the back edge of precipitation
moving over SBN at this hour. Behind this, observations show
ceilings falling to IFR conditions; something guidance is a bit
slow on. This area of IFR ceilings ends near Madison, WI, at this
time. Therefore, we are led to believe MVFR conditions can return
early Monday morning at SBN.

FWA will face precipitation for the next several hours before the
back edge of precipitation lifts out. A few snowflakes can mix in
with rain, but we expect rain to be the dominant precipitation
type. At the time of this writing, FWA is reporting a temperature
of 35F. By the time this activity exits, we have a forecast
temperature of 34F. Then, we expect IFR conditions to unfold for
a time.

At FWA, we played the 12Z forecast ceilings a bit conservative,
but there are some solutions that suggest ceilings could be VFR.
At this time, we will pass this off to the next team to monitor.




LONG TERM...Murphy

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