Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 200434

Area Forecast Discussion
National Weather Service Northern Indiana
1234 AM EDT Sun May 20 2018

Issued at 1221 AM EDT Sun May 20 2018

Several rounds of showers and thunderstorms will be possible into
Monday as a frontal boundary remains in the region. Locally heavy
rain is possible along with a small risk of severe weather Sunday
afternoon and evening along and south of Route 24.


.SHORT TERM...(This Evening through Sunday Night)
Issued at 246 PM EDT Sat May 19 2018

Trough axis/cold front associated with upper low was shifting
slowly east through the forecast area. A solid line of showers and
a few storms was making slow but steady progress east of I-69 and
should exit the area well before 00Z. Main threat with the line
will be locally heavy rain given high PWATs and slow movement
along with gusts to 30 mph. Behind the line, a meso low was noted
on visible satellite working across NE Illinois. A few of the CAMs
attempt to develop some showers with this feature as it interacts
with pockets of slight increased lapse rates where clearing is
occurring. Activity shouldn`t amount to much and will be done most
likely by 00Z with loss of heating.

Focus then shift to the west for our next chance of precip.
Convection ongoing across Missouri and Iowa looks to weaken as it
moves east into limited subsidence behind the wave. However,
additional activity is expected around/after 00Z across E Kansas
into Missouri which will eventually start to propagate towards
the Ohio Valley/lower Great Lakes area after 9Z. Think most if not
all of tonight will be dry with chances in the far west in the
9-12Z window. After collab have kept pops in the mid-high chc
range late tonight into Sunday AM. Timing, coverage and track of
MCS Sunday morning will play a key role in threat for convection
and severe threat Sunday afternoon into Sunday night. Frontal
boundary should be somewhere across central Indiana by morning,
with any MCS likely to raise havoc with the boundary position. NAM
has joined the more suppressed solution with instability, keep
the bulk of it along/south of US-24 Sun afternoon/night, likely
influenced by the morning MCS. While instability will be further
south, better shear will exist up here with 0-6 km shear around 50
kts. Marginal risk for Day 2 still warranted. Model trends
suggest that precip could hold off till after 6Z Mon. Made some
adjustments to maintain likely but nudge a but later.


.LONG TERM...(Monday through Saturday)
Issued at 246 PM EDT Sat May 19 2018

One more unsettled day as frontal boundary lingers in the area
and 1 or more complexes move near/over the region. Some sort of
complex will likely exist but exact location/impacts remains
questionable given volatile pattern of late. Could be period of
little/no activity behind this feature until next wave approaches
Mon afternoon/eve (or possibly later). Instability may be slightly
better with some northward return of the front possible but no
more than slgt chc to chc pops warranted for now.

High pressure settles in Tuesday night into Friday with heights
increasing to allow highs to head for the 80s. Rain chances may
arrive for the weekend as wave ejects from the SW and moves into the


.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1220 AM EDT Sun May 20 2018

Light northerly flow continued over northern Indiana on the north
side of a stationary front. Widespread postfrontal MVFR and some
IFR was over lower Michigan. Believe the post/frontal clouds will
spread into SBN by 08Z, and later in FWA. Still much uncertainty
about timing and south extent of the clouds, so amendments/updates
are likely early this morning. Much uncertainty also with the
timing development of convection this afternoon and evening. For
now, have mention of thunder after 00Z, but this timing may need
to be adjusted.




LONG TERM...Fisher

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