Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 210012

Area Forecast Discussion
National Weather Service Northern Indiana
812 PM EDT Mon Mar 20 2017

Issued at 814 PM EDT Mon Mar 20 2017

Skies will partially clear overnight with patchy fog possible
late tonight. Lows will drop into the 30s. Tuesday will be mainly
dry with highs in the upper 40s and lower 50s. There is a slight
chance for rain primarily south of U.S. highway 24 in Indiana. It
still looks cold midweek with highs on Wednesday only in the
middle to upper 30s. A warmup is expected by Friday with
temperatures climbing well into the 60s but rain chances return
for late week and the weekend with this warmup.


.SHORT TERM...(This Evening through Tuesday)
Issued at 313 PM EDT Mon Mar 20 2017

12z ILX sounding tells the story today with impressive EML over
stout low level inversion. Plenty of elevated instability with good
shear of 30-40 knots. Weak short waves and approaching surface front
have led to scattered thunderstorms this afternoon. Storms over
eastern IL and west central IN have robbed rest of our area from
steeper lapse rates advecting in and thus less intense storms and
only pea size hail reports. CAMs and most hires model guidance point
to only some additional showers and maybe an isolated tsra north of
current activity leaving our southern CWA at issuance time. With
good shear and modest lapse rates still in place will carry mention
of small hail for a few hours until late afternoon then end thunder
chances from north to south. Still a few light showers near main
front to our northwest and a few of these could move across the area
early this evening. Overall diminishing pcpn trends and gradual
clearing from north to south. Models do hint as clouds hanging on in
the southeast into the overnight hours along with some fog
development. Winds do drop off behind front and with moisture from
rainfall and still a relatively mild airmass over recent cold ground
could see some patchy fog develop.

Models still having some issues with fast moving wave on Tuesday
into Tuesday night. Several models have shifted pcpn chances south
but GFS...NAM4k and a few other hires models spread pcpn across
southern areas. Have stayed with last forecast for now with slight
chance pops confined to far south.


.LONG TERM...(Tuesday Night through Monday)
Issued at 313 PM EDT Mon Mar 20 2017

Wednesday still looks cold with highs mainly in the 30s as high
pressure slides across the Great Lakes with cold north to northeast
flow over our area. Return flow develops as high slides east with
gradual warmup Thursday and much warmer Friday with highs well into
the 50s. Warm air advection pcpn expected Thu night and synoptic
pattern looks very similar to what occurred last night. Held off on
adding thunder to mesh with neighbors but low level jet looks
potentially stronger than this morning. Dry slot then works in
Friday and if we scour clouds should be well into 60s but a breezy

Medium range models trending back north with closed upper low this
weekend and we now hold in warm sector longer than previous runs.
Still a lot of model spread and uncertainty so no changes to
Superblend. Still looks relatively wet for weekend into next week
but at least temps back to normal or above.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 134 PM EDT Mon Mar 20 2017

Some concern with respect to late morning BR formation. However
with sufficient surface winds/remaining partially mixed and drier
air advecting into northern IN, will err on side of optimism as BR
should be primarily shallow/quite patchy. Strong south central
Canadian anticyclone presses southeastward towards the Upper Great
Lakes through the forecast period with gradual improvement to VFR
into KFWA by midnight anticipated, then VFR for remainder of the




SHORT TERM...Lashley
LONG TERM...Lashley

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