Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 202332

Area Forecast Discussion
National Weather Service Northern Indiana
730 PM EDT Sun May 20 2018

Issued at 320 PM EDT Sun May 20 2018

Showers and thunderstorms will move in from Illinois towards
Monday morning and work east across the area. Additional showers
and thunderstorms will be possible Monday 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 00Z TAFS through 00Z Monday Evening)
Issued at 730 PM EDT Sun May 20 2018

VFR/MVFR cigs expected to persist most of this TAF cycle on
prevailing easterly flow. Mainly dry conditions expected for much of
the overnight hours before arrival of remnants of nocturnal
convective complex by the early morning hours. Will have -SHRA
prevailing with VCTS mention. Once this system moves through expect
lull in precip chances until arrival of surface low pressure toward
the end of the TAF cycle. Uncertainty with timing and being the end
of the period will just go with a VCSH for now.




LONG TERM...Fisher

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