Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201741

Area Forecast Discussion
National Weather Service Northern Indiana
141 PM EDT Tue Jun 20 2017

Issued at 328 AM EDT Tue Jun 20 2017

There is a chance for more showers and storms this evening as an
upper level disturbance moves through the region. High pressure
will then move across our area Wednesday providing fair weather.
The high will move east Thursday evening allowing very warm and
humid weather to return on Thursday along with the chance for more
storms through Friday. Highs Thursday should be well into the 80s
to around 90 with muggy conditions. Cooler temperatures will
return for the weekend and early next week but shower and
thunderstorm chances will continue as well.


.SHORT TERM...(Today and Tonight)
Issued at 328 AM EDT Tue Jun 20 2017

Yet another short wave expected to drop into base of long wave
trough later today and bring a chance for showers and thunderstorms
once again to the area. While there is a similar look and feel to
Monday, there are several differences in details which will lead to
a bit more uncertainty on coverage and intensity today.

Morning will begin seasonably cool and clear. Water vapor shows next
short wave across the upper MS River Valley diving southeast this
morning. Timing of this wave will be a little later today compared
to Monday which should keep convection from developing until
afternoon. Instability does not look as great today with MLCAPE only
300-600 J/KG. However...deep layer shear is much more impressive
with 0-6km values of 50-60 kts as mid level speed max dives into the
region. 500mb temps will not be as cold today...-13C to -15C...
leading to less impressive mid level lapse rates. However...lower
level lapse rates do approach 8.5 C/km late afternoon in the
southwest. The combination of these factors will likely yield
scattered showers and some thunderstorms this afternoon. Weak
instability and mid level lapse rates should keep most storms from
obtaining stronger updrafts and thus not tapping into deeper shear.
However...would not be surprised if an isolated stronger storm does
develop...especially in the southwest early evening where
ingredients briefly come together around 21z. Still only expecting
small hail and gusty winds once again but much less coverage and
more uncertainty compared to Monday. With later arrival of short
wave could see showers and a few storms linger into mid or late
evening across the south and southeast.


.LONG TERM...(Wednesday through Monday)
Issued at 328 AM EDT Tue Jun 20 2017

Wednesday still looking like best day of the week with dry
conditions...light winds and near normal temperatures. Models are
hinting at weak surface trough still lingering early in the day
across the CWA but washing out as high pressure takes over. Return
flow develops quickly Thu night with warm front returning north
and rain chances increasing once again. Best focus of low level
jet should be to our northwest but some development possible
across our area with theta e ridge lifting through. Thursday will
briefly return to warm and muggy conditions with low chances for
diurnally driven convection but atmosphere may end up capped with
no strong trigger to break it.

Upstream convective development expected Thursday night which will
likely dive southeast as cold front approaches in tandem. Timing
still in question but model consensus has pcpn moving through the
area into Friday morning. Remnants of tropical system three now
looks to intersect frontal boundary closer to the Ohio River Valley
Friday with only some residual moisture this far north and that
doubtful as subsidence likely to strengthen north of front. Held
with blend pops given uncertainty and time for changes in model

Next northern stream short wave to approach by Sunday bringing more
chances for thunderstorms back to the area along with return of long
wave trough and cooler temps to the western Great Lakes for early
next week.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 140 PM EDT Tue Jun 20 2017

Shortwave currently approaching the area and expect to see a few
SCT showers/storms along associated convergent boundary later this
afternoon as diurnal destabilization maximizes. Instability is
very limited though and confidence in coverage/impact at the
terminals is not high enough for anything more than a VCTS mention
at this point. Main change was to adjust timing a bit later based
on latest hi-res models. Otherwise, dry VFR conditions with light
winds for the rest of the period as surface high pressure builds
over the area. Slight concern for some BR Wednesday morning given
light winds but confidence in boundary layer moisture is much too
low for inclusion in the TAF at this point.




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

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