Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 211709

Area Forecast Discussion
National Weather Service Northern Indiana
109 PM EDT Mon Sep 21 2020

Issued at 247 AM EDT Mon Sep 21 2020

Dry conditions will persist through the end of the week with
gradual warming. Highs today will be in the low to mid 70s. The
next chance for showers and thunderstorms is next weekend.


.SHORT TERM...(Today and Tonight)
Issued at 247 AM EDT Mon Sep 21 2020

The upper level ridge building from the south and the surface high
to the northeast will both strengthen some today, and temperatures
will therefore continue to warm due to subsidence and warm air
advection. Highs will be a few degrees warmer than yesterday,
rising slightly above normal, into the low to mid 70s. It will
remain dry, but upper level smoke will start advecting in from
western wildfires, creating a hazy sky, and possibly keeping
temperatures from reaching their full potential. Overnight lows
will still be cool, but also warmer, in the mid 40s.


.LONG TERM...(Tuesday through Sunday)
Issued at 247 AM EDT Mon Sep 21 2020

The upper ridge holds on for Tuesday, though a very weak northern
stream cold front attempts to break through. This may result in
some increased upper cloudiness, but otherwise it will stay dry
and continue to warm. On Wednesday, tropical moisture will start
advecting into the region from the Gulf of Mexico, but as a more
progressive upper flow develops, this will get pushed east and the
area should stay dry through Friday.

A low pressure system will be developing over the southern Plains
during this period, and could bring rain and possibly thunderstorms
by Saturday evening. A strong cold front will then swing through
on Sunday with perhaps an even better chance of showers and
thunderstorms. The thunderstorm chances will be dependent on whether
any lingering rain from the night before limits destabilization,
but rain does seem likely.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
Issued at 1234 PM EDT Mon Sep 21 2020

VFR conditions expected for the next 24 hours. The main aviation
concern will be increasing smoke from western US wildfires
advecting over the terminals starting this evening.

Per HRRR guidance, smoke is currently just to the NW of the KSBN
terminal and generally between 5 and 15 kft with the highest
concentrations generally between 8 and 190kft. As early as 22z,
higher concentrations of smoke are expected to slide ESE as the
upper winds become more zonal. While these higher concentrations
may affect KSBN as early as 22z, the timing for KFWA looks to be
delayed until 08z. A stagnant upper air pattern on Tuesday will
allow the higher concentrations to linger through the end of this
TAF cycle. Over this period expect smoke generally between 5 and
17kft with the highest concentrations generally between 8 and
12kft. There was also a brief hint at a brief secondary layer
generally around 20 kft overnight, but did not account for as it
may stay north of the terminals. Have inserted a SCT deck at 10kft
to address timing of the onset of the thicker smoke. Given that
the smoke will not impact surface visby, will keep the terminals
unrestricted at this time.





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