Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 180410

Area Forecast Discussion
National Weather Service Northern Indiana
1210 AM EDT Tue Jul 18 2017

Issued at 1207 AM EDT Tue Jul 18 2017

Warmer and more humid conditions will develop this week as
southwesterly flow deepens on backside of departing surface
ridge. Chances of storms will begin to increase by Thursday, with
periodic chances of showers and thunderstorms through this
weekend. Overnight lows around 60 will rebound into the mid 80s
later today.


Issued at 800 PM EDT Mon Jul 17 2017

Weak inverted sfc trough has allowed for a few isolated showers to
develop across central/east central Indiana this afternoon/early
evening. Over past hour isolated light returns also have
developed across Jay county. Will continue with trend of previous
forecast in taking any PoPs below mentionable ZFP levels for
remainder of the afternoon/early evening hours due to loss of
diurnal instability and tendency for mid/upper level height rises
to commence. Light winds, clear skies, and lingering low level
moisture may promote some patchy fog formation overnight. Best
chance appears to be across northwest portions of the area where
earlier lake breeze modification may be more preferential versus
earlier deeper afternoon mixing across east/southeast portions of
the area. Will hold off on ZFP fog mention at this time, with low
confidence at this point.


.SHORT TERM...(Today and Tonight)
Issued at 247 PM EDT Mon Jul 17 2017

Weak return flow within residual low level theta-e ridge through ern
IN/wrn OH aggravating cu field across far se and still expect
isolated convective development this aftn. Nonetheless whatever does
materialize will die out this evening as instability wanes.
Otherwise sfc ridge will shift off into the ern lakes Tue with weak
swrly flow developing. This will yield  warmer temps tomorrow aftn
as low level thermal trough continues to modify in place.


.LONG TERM...(Tuesday through Sunday)
Issued at 247 PM EDT Mon Jul 17 2017

Decidedly warmer this period as substantial upper ridge builds
across the plains. Enhancing baroclinic zone along nrn/nern extent
of this feature will foster increasing chances for convection mid to
late period as perturbation laden nrn stream flow persists through
srn Canada.

First system of note crosses srn ON Thu with vigorous mid level flow
aligned through the srn lakes along with what should be a
significant instability plume in place along ewd extension of quasi-
stationary frontal zone. Will favor nrn zones for highest chc pops
at this range per trending consensus solution.

Lead sw disturbance followed by upstream strong wave into James Bay
vcnty late Sun. Ewd shift/expansion of upper ridge should keep
active frontal zone in proximity to local CWA of which favors a
protracted period of pops. Primary uncertainty will be propensity
for upstream MCS generation followed by downstream evolution and
track both Fri and Sat before initiation zone shifts overhead Sun
and Mon. Will again hedge pops toward periods of better large scale
model consensus per inherent low predictability at this range.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1151 PM EDT Mon Jul 17 2017

A surface ridge of high pressure was over the area overnight. A
few clouds were present in a narrow layer of moisture around 045
AGL per AMDAR obs; however, the lower levels were overall quite
dry except for near the surface. Retained a mention for fog at
SBN; favored a TEMPO group for MVFR conditions from 09 to 13Z.
Any fog will mix out quickly early this morning followed by
prevailing VFR conditions.





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