Area Forecast Discussion
Issued by NWS Northern Indiana

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714
FXUS63 KIWX 201737
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1237 PM EST Tue Feb 20 2018

.SYNOPSIS...
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.

&&

.UPDATE...
Issued at 1227 PM EST Tue Feb 20 2018

Heaviest rainfall has temporarily shifted away from those areas
hard hit overnight into this morning with focus further SE for the
moment. However, radar trends suggest the band of rain was
beginning to migrate back to the northwest. Thus far most of the
rain has remained along/west of Interstate 69 and may do so for
the remainder of the afternoon. Main cold front still looming to
the west with additional rainfall noted on it as well as upstream
in Illinois, Missouri and Kansas.

Even though some areas could see brief breaks in the rain, no
significant change in thinking with flooding concerns to continue
and likely expand as we get into tonight. Will address more in
afternoon forecast, but status quo on watches and areal flood
warnings. May need to issue for locations to the south of the
current areas but waiting to see if NW retreat holds or not.

&&

.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 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1227 PM EST Tue Feb 20 2018

Heaviest rain and greatest impacts currently residing both TAF
sites, with KSBN likely to get back into IFR conditions over the
next several hours as band of rain that temporarily shifted SE
moves back in. In addition, cold front will sweep in tonight with
lower cigs/vsby and continued rain resulting in IFR and possible
LIFR conditions. KFWA will likely remain on the eastern edge of
the precip and may see highly variable conditions through the
afternoon and early evening, but will eventually drop into IFR
later this evening into the overnight hours. A few lightning
strikes are possible at both sites through tonight, but
low confidence on coverage/impacts on the airports so will leave
out.

While concerns are low at this point, the rain could end as a
period of light freezing rain at both sites near/after 12Z Weds as
colder air rushes in. Surface temperatures and warm raindrop
temperatures may prevent any icing, but something that will be
monitored.


&&

.HYDROLOGY...
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.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through Wednesday afternoon for INZ003>009-012>018-
     020-022>027-032>034.

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

OH...Flood Watch through Wednesday afternoon for OHZ001-002-004-005-
     015-016-024-025.

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

&&

$$

UPDATE...Fisher
SYNOPSIS...Skipper
SHORT TERM...Skipper
LONG TERM...Skipper
AVIATION...Fisher
HYDROLOGY...Fisher


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