Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 210447

Area Forecast Discussion
National Weather Service Northern Indiana
1247 AM EDT Mon May 21 2018

Issued at 1224 PM EDT Sun May 20 2018

Showers and thunderstorms will move in from Illinois early this
morning and work east across the area. Additional showers and
thunderstorms will be possible this afternoon and evening with a
threat for severe storms existing mainly south of Route 24. Drier
weather will arrive Tuesday and continue into Thursday with highs
climbing to near or above 80.


.SHORT TERM...(This Evening through Monday Night)
Issued at 320 PM EDT Sun May 20 2018

Rather drastic changes made to forecast for Monday into Monday
evening as models finally keying in on MCS to move across the area
Monday morning.

Before that, we are watching the departure of an area of showers
across the far N/NE in association with a weak wave. Additional
light showers were moving along the US-24 corridor in association
with a weak mcv riding axis of limited instability. Some of the CAMs
still try to develop isolated storms but looking less likely so slgt
chc pop held onto in far south into evening.

Focus then shifts to expected convective develop upstream across
Missouri and Iowa this evening, eventually propagating northeast
towards the region and growing upscale in coverage and to some
extent intensity as it moves into Illinois late tonight. Models
generally agreeing on MCS working across most if not all areas
Monday morning, arriving somewhere around 12Z Mon in the west or sw
and then translating rapidly NE. Threat should be confined to heavy
rain and maybe locally gusty winds but a few CAMs (namely 12Z NMM)
develop a rather pronounced line of storms that races into the area
with over 1000 J/KG MUCAPE feeding in ahead of it. After extensive
coordination with surrounding offices pops were ramped up to
categorical by Monday morning and transitioning across the area in
the AM. Will need to watch trends for any severe potential, but
think greater concern will end up in afternoon. Low pressure moves
northeast across NW areas, influx of higher instability will edge
into S/SE areas mainly south of US-24 but could see some potential
further north. SWODY2 has introduced a slgt risk in this area which
is on track given plenty of instability, 30 to 40 kts of shear and
proximity of sfc low. Chances for precip will linger into Monday
evening, mainly SE areas as cold front sweeps across. Minor
adjustments to pops.


.LONG TERM...(Tuesday through Sunday)
Issued at 320 PM EDT Sun May 20 2018

Increasing 500 mb heights (582-585 dm) will bring a fair amount of
sunshine and period of dry weather through Thursday with above
normal temps.

Closed upper low over Nevada on Tuesday will eject northeast into
the northern Plains and then work east, amplifying as it heads for
the northern Great Lakes. Shower chances will likely increase into
the weekend, but exact timing remains uncertain with model
differences in strength and timing of the wave. Forecast will remain
muddled with slgt chc to chc pops into Sunday.


.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1222 AM EDT Mon May 21 2018

Some lingering MVFR clouds with isolated IFR sections were on the
north side of the stationary from northern Indiana to far
southern Indiana. Conditions should deteriorate early this morning
ahead of a storm complex moving across northeast Missouri. The
pattern should remain active later today with additional chances
for storms.




LONG TERM...Fisher

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