Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201424

Area Forecast Discussion
National Weather Service Northern Indiana
924 AM EST Tue Feb 20 2018

Issued at 642 AM EST Tue Feb 20 2018

Very wet and mild weather will continue through Wednesday morning.
Heavy rainfall will lead to flooding on rivers, streams, and low
lying areas prone to flooding. Temperatures will rise to record
or near record highs today from 65 to 72 degrees. Cooler and drier
air should return to the area accompanied by a light wintry mix
Wednesday into Thursday.


Issued at 920 AM EST Tue Feb 20 2018

Forecast updated to expand QPF further east based on current radar
trends as well as increase somewhat (still won`t capture banded
heavy rainfall that is expected). Also added more expansive
mention of thunder as described below.

Area of rain was continuing to work NE across NW parts of the
areas. There has been a rapid expansion of development eastward in
the form of showers and even a few embedded storms. Looking
upstream, a conveyor belt of showers and embedded storms is
visible back into Illinois, Missouri and Arkansas with coverage
slowly increasing as well. All this does not bode well for the
area, especially NW half of so that has seen 1 to over 3 inches of
rain through 8 am and more in store. ILX 12Z RAOB shows even
higher record PWATS with 1.44" Areal flood warnings are in effect
for the areas with the greatest concern at this time as an
additional 1 to 2 inches of rain may fall in some areas with even
higher amounts locally possible. Road closures have been reported
with county highway crews likely still catching up as water levels
continue to rise.

While the SE half of the area has thus far been spared any major
impacts, the boundary responsible for providing the focus for
rainfall will begin to shift southeast today into tonight and
bring flooding concerns to these areas as well.


.SHORT TERM...(Today through Wednesday)
Issued at 318 AM EST Tue Feb 20 2018

River flooding and some areal flooding was already underway with
event rainfall totals so far closing in on 3 inches over
northwest Indiana. There was still plenty of convection in the
warm sector with the front northwest of Chicago and Grand Rapids.
Ample rain on the way. Have issued flood warnings for many
counties given ongoing flooding reports, observed/mesonet rainfall
amounts and radar rainfall estimates. Substantial rises on many
river will cause many to reach moderate and some to reach major
stage. The latest GFS ensemble run has several rivers reaching
major flood stage at some point this week. Indications continue of
a rather extreme precipitation event with precipitable water
values between 1.3 and 1.5 at times. A note from the Lincoln
Illinois office revealed the 00Z run from last night (evening run)
had the precipitable water value at 1.33" (which was a record).
Will continue the flood watch into Wednesday afternoon as more
rounds of rain develop in the warm sector and then along/ahead of
the front.

Much colder air will spread underneath the warm air early
Wednesday as the front moves southeast. A brief wintry mix is
possible. Given very mild temperatures at the onset and given a
brief mix, believe there should not be any significant travel
issues Wednesday morning.


.LONG TERM...(Wednesday night through Monday)
Issued at 318 AM EST Tue Feb 20 2018

Much colder air will continue to spread across the area Wednesday
night with temperatures falling below freezing by daybreak. A
wintry mix may cause travel issues by Thursday morning. More rain
from Thursday night into Saturday will aggravate ongoing flood
issues. Highs Friday through Monday will be generally in the 40s.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday Morning)
Issued at 642 AM EST Tue Feb 20 2018

Numerous showers and some storms continue to develop well into the
warm sector over much of Il and track northeast. For SBN, training
showers and a few storms through much of the day. The winds should
shift overnight. Still much uncertainty how fast temps will fall
below freezing. There is potential for freezing rain late; for
now, left just rain. Otherwise, better conditions at FWA; have
conditions becoming MVFR as bands of heavier rain move in tonight.


Issued at 920 AM EST Tue Feb 20 2018

River forecasts will be updated this morning to handle the
rainfall that has fallen across several basins over the last 24
hours. For the latest forecasts, monitor AHPS or river flood
warnings from our office.

Conditions will continue to worsen across the IWX hydro area.


IN...Flood Watch through Wednesday afternoon for INZ003>009-012>018-

MI...Flood Watch through Wednesday afternoon for MIZ077>081.

OH...Flood Watch through Wednesday afternoon for OHZ001-002-004-005-

LM...Small Craft Advisory until 7 PM EST this evening for LMZ043-046.



SHORT TERM...Skipper
LONG TERM...Skipper

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