Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 221911

Area Forecast Discussion
National Weather Service Northern Indiana
311 PM EDT Sat Jul 22 2017

Issued at 304 PM EDT Sat Jul 22 2017

Weather tonight will be primarily dry, with the exception of the
far southern forecast area where we could see some isolated
showers or storms. Lows will be in the upper 60`s and low 70`s. A
weak front will move through the region Sunday afternoon and
evening, bringing additional chances for showers and storms. Highs
will be in the 80`s. Drier and cooler air will then prevail for
the first part of the upcoming week.


.SHORT TERM...(This Evening through Sunday)
Issued at 304 PM EDT Sat Jul 22 2017

Tonight will be dry for most areas, with the exception of areas far
south that may see precipitation associated with a system to our
south. Thinking this may stay mostly south of our area, so have just
slight chance/chance for the most part along the IND/IWX Border.
Otherwise, lows will be in the upper 60`s and low 70`s, warmest
south of US 24.

One last pesky forecast to go, as we deal with Sunday`s potential
for showers and storms. SPC still has us in a slight risk for the
day 2 severe wx outlook. In all honesty, I`m having trouble getting
on board with severe chances tomorrow. Bringing down confidence
is the widely varying model solutions, both from run to run and
between the models themselves. Even in the best solutions, the
severe wx ingredients are rather disjointed.

We have an upper level trough swinging through Upper Michigan, and
extending down towards our CWA Sunday. This will bring a couple of
waves through, which could offer support for shower/storm
development. However, the strongest forcing remains to our north,
that is until Sunday evening. Though I have slight chance pops in
for early Sunday with the initial wave, I am doubtful anything much
will come of it as we`ll be under an area of subsidence behind the
earlier front. As we move into the late afternoon/evening, we`ll see
better synoptic support-particularly in the western CWA around 00z,
and continuing eastward through about 03Z. Kept generally slight
chance pops for now, given all of the model disagreement. The GFS is
most optimistic-showing a system creeping into our west around that
00z time frame with the arriving trough/shortwave, but by the time
the best forcing gets here-the instability begins to wane. Bulk
effective shear is decent though, so I suspect if we can get storms
to develop before instability disappears we may have potential for
an isolated damaging wind gust. Again, confidence is extremely
low at this point.

After 6z, sunday night, it looks like our potential for
precipitation diminishes as a high pressure ridge builds in, thus
starting the cooler, drier forecast period.


.LONG TERM...(Sunday Night through Saturday)
Issued at 304 PM EDT Sat Jul 22 2017

Thankfully, the long term forecast is much quieter than the short
term. The cold front moving through Sunday night will usher in
cooler, drier air. As a result, kept all precipitation chances out
of the forecast through Wednesday afternoon. High temperatures
will range from the upper 70`s to the low 80`s for most of the
week, with the exception of Wednesday-where we could see highs in
the mid 80`s. It will be a welcome break from the humidity as

The only concern Monday, as mentioned in yesterdays discussion will
be the northerly flow developing over Lake Michigan. With the long
fetch over the lake, wave heights will build into the 2-3 ft range.
Additionally, with wave directions of NW to N and wave periods of
around 4-5 seconds, we could see strong rip current development
within sandbars, and strong structural currents near the
piers/breakwalls. Check out our beach hazards page Monday if you
were planning a trip to Lake Michigan-we may end up with a moderate
to high swim risk in Berrien/LaPorte Counties.

Wednesday night into Friday features our next chance for showers and
storms. An upper level low will drop into Hudson Bay, bringing a
trough through the Great Lakes region on the periphery of the ridge
that extends from the desert southwest to the midwest. Our forecast
area will be under the right entrance region of a 250mb Jet
Thursday, and with the trough arriving we`ll have support in the
mid levels. Mid level lapse rates are okay, around 6-7C/Km, and if
the front arrives during the day Thursday as the GFS indicates we
may even have some instability-on the order of around 2-3K J/kg
(granted, this is still far away). Bulk shear values look to be
around 25-30 knots as well, so we could see the threat of some
stronger storms. It`s something to keep an eye on, and have kept
consensus chance pops/storms in the forecast for now.


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 101 PM EDT Sat Jul 22 2017

Any lingering MVFR stratocu at KFWA should mix out to VFR at or
shortly after issuance leaving mainly VFR/dry conditions and light
wnw winds at the terminals this afternoon into this evening.
Moist low levels and light winds may allow low stratus/fog to
build into northern Indiana later tonight into early Sunday
morning, though confidence in coverage remains of lower confidence
at this forecast range.





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