Area Forecast Discussion
Issued by NWS Northern Indiana

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877
FXUS63 KIWX 211159
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
659 AM EST Wed Feb 21 2018

.SYNOPSIS...
Issued at 335 AM EST Wed Feb 21 2018

Rain will slowly end from west to east today and there may be a
brief period of wintry mixed precipitation this morning across
northwest Indiana and southwest lower Michigan. Widespread
significant flooding will continue over northwest Indiana and
southwest lower Michigan as well. Moderate to major flooding is
expected along main rivers and some record crests are possible. It
will be much cooler today with falling temperatures early this
morning and high temperatures ranging from the middle 30s
northwest to middle 40s southeast. There is a chance for more
wintry mixed precipitation late tonight and again Thursday night,
especially over east central to northeast Indiana and northwest
Ohio.

&&

.SHORT TERM...(Today and Tonight)
Issued at 325 AM EST Wed Feb 21 2018

What an incredible last 48 hours it has been with what may end up
being all time 2-day record rainfall for February in our area. As
expected many locations have received 2 to 4 inches of rain and
some unconfirmed reports over 6 inches. Despite no frost in the
ground per frost depth measurements here at KIWX, the water has
been slow to percolate through the saturated and still cold and
dense soil. Numerous roads reported closed and streams, creeks
and rivers in moderate to major flood with records levels likely
in some locations. Thus areal flood warnings continue in the
northwest where the most rainfall has occurred but did cancel the
watch there given widespread flooding and warning. With pcpn
finally starting to shift east have left the flood watch in place
remainder of area as some creeks, streams and rivers expected to
go into flood there and some low end areal flooding could still
develop.

Regional radar mosaic does show back edge of pcpn shield slowly
moving east and hires models show pcpn slowly ending today. Sfc
temps have dropped to near 32F in the northwest and consensus
blends drop temps to between 30 and 32 for a few hours before pcpn
ends in far northwest. Latent heat release from rain and abundant
water on the ground seems to be keeping surfaces from freezing so
far as KMCY has been reporting just rain with 32F for a couple
hours. Model soundings indicate brief period of sleet and freezing
rain possible as cold wedge deepens near ground level while warm
wedge is slow to erode aloft. Given warm ground and moderate pcpn
rates currently not expecting too many impacts with brief period
of mixed pcpn but will certainly be monitoring for possible
headlines if conditions deteriorate.

More pcpn type issues late tonight as next wave rides northeast
along slowed boundary to our south and moisture spreads back north
into our southeast areas late tonight. Critical thermal
differences exist among the models and for now have stayed close
to the consensus blends which gives chances for mix of rain,
snow, sleet and freezing rain. Confidence low in dominant type at
this time and thus will not be issuing any headlines.

&&

.LONG TERM...(Thursday through Tuesday)
Issued at 325 AM EST Wed Feb 21 2018

Pcpn type issues to linger into Thursday morning with best
chances for mixed pcpn in the far south and southeast. Some ice
accumulations possible but questions continue on thermal profiles
as well as how much moisture and pcpn will reach our area. This
period certainly needs to be watched as does late Thu night and
Friday morning as yet another short wave rides northeast. Even
more model spread is seen for this period with EC and GFS showing
a strong warm surge while NAM hinting at more evap cooling
processes and holding warmer air back. Again best course of action
to follow consensus blends and pcpn type from the builder
process. This does yield some decent freezing rain and ice accums
up to a tenth of an inch in our northeast. This all depends on
critical thermal fields and just a few degrees change will make a
big difference on actual pcpn types. Winter weather advisory may
certainly be needed. Stay tuned.

No changes made to blends beyond Friday with focus in the higher
impact shorter term concerns but above normal temps expected.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 650 AM EST Wed Feb 21 2018

Rain will continue to shift eastward this morning, and bulk of
rainfall has ended at KSBN. Precipitation has transitioned to a
light wintry mix on the backside of the precip shield, although
impacts appear to be minimal. With warmer profiles at KFWA, have
not included this mention, although cannot discount a very brief
period of sleet/freezing rain at KFWA. Otherwise, drier air to
continue to overspread northern Indiana this morning with lower
end MVFR/higher end IFR cigs transitioning to cigs above 2k feet
toward midday. Stalled low level frontal boundary across far
northeast Indiana may allow some light rain and snow to redevelop
tonight, with possibility of wintry mix south of KFWA. With
greater confidence of precip south of terminals, will limit
mention to VCSH late tonight for KFWA.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch until 4 PM EST this afternoon for INZ007>009-017-018-
     023>027-032>034.

MI...Flood Watch until 4 PM EST this afternoon for MIZ080-081.

OH...Flood Watch until 4 PM EST this afternoon for OHZ001-002-004-005-
     015-016-024-025.

LM...Small Craft Advisory until 10 PM EST this evening for LMZ043-046.

&&

$$

SYNOPSIS...Lashley
SHORT TERM...Lashley
LONG TERM...Lashley
AVIATION...Marsili


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