Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 161942

Area Forecast Discussion
National Weather Service Northern Indiana
342 PM EDT Fri Jun 16 2017

Issued at 336 PM EDT Fri Jun 16 2017

Showers and thunderstorms will remain possible prior to the
passage of a cold front on Sunday. The best chance for organized
thunderstorms, including the risk for severe weather, looks to
exist Saturday night into early Sunday. Lows tonight will drop
into the 60s tonight and should warm back into the middle 80s


.SHORT TERM...(This Evening through Saturday)
Issued at 336 PM EDT Fri Jun 16 2017

Second of 2 MCV`s working across the area, sparking little more
than a few showers at this time. As it works into eastern areas
can`t rule out a rumble of thunder as it encounters a narrow axis
of better instability. Behind the area, satellite would tend to
suggest a good deal of subsidence. However, SPC meso data shows at
least some instability still lingering back in portions of
Illinois where temps have recovered into the middle 80s and
dewpoints were slightly higher. Vis sat showing a few cu starting
to pop which could indicate some isol shower/storm development
could edge in towards evening as advertised by a handful of CAMS
as a weak disturbance noted on water vapor edges in. Not
comfortable dropping pops entirely so leaning towards 20 to 30
pops through 03Z then a lull until later tonight when remnants of
upstream convection may be arriving, which brings a set of
challenges all it`s own for Saturday.

CAMS showing several scenarios with upstream convection, any of
which are plausible ranging from a dying area of showers and storms
approaching overnight into early Saturday to showers and storms
diving southwest of us along what may be best instability and
moisture gradient. As a result have kept highest pops NW late
tonight into Sat AM with more changes likely to come as complex
evolves to the west. Going into Sat afternoon, should be at least
some clearing in the wake of morning activity that will allow
destabilization across the area. Forcing mechanisms may exist in the
form of leftover outflow boundaries or even a MCV that could impact
the area during the afternoon, which could bring isol to sct storms.
Confidence low in how this will unfold so have opted to broadbrush
pops in mid chance range for the afternoon. Focus on greatest severe
threat will be into long term period.


.LONG TERM...(Saturday Night through Friday)
Issued at 336 PM EDT Fri Jun 16 2017

Threat for severe weather still looms with only subtle changes to
SWODY2 with Enhanced risk now bumping up against our western
counties. For the time being, think this was a good move as
several factors still remain in question for severe threat,
including those mentioned in short term discussion.

Have generally held with likely pops much of Saturday night given
gambit of solutions in terms of timing, possibly as early as 3Z to
as late as 7Z for arrival in the west. Main mode of severe should be
damaging winds, which could be on the stronger side if well
established cold pool and forward propagation of the line hold
together which is normally a challenge into the less favorable
convective window of the overnight hours. However, as eluded to in
past discussion dynamics and potential organization may very well
negate these issues. For more details on the mesoscale setup, refer
to DY2 outlook which matches close with thinking here.

Otherwise, cold front will sweep through by Sunday with cooler and
less humid air arriving through mid week. Warm front will begin to
edge back north for the second half of the week, slowly increasing
both temps and humidity. No major system, but arrival of warm front
could bring some precip chances as well as hit or miss convection
south of it into the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 115 PM EDT Fri Jun 16 2017

Latest Visible imagery depicting cloud shield from remnant MCS
moving across the CWA this afternoon. KIWX radar indicating some
light showers associated with this feature over southern lake
Michigan and NW Indiana and approaching the KSBN area...will begin
TAF cycle with VCSH as no lightning detected and no indications on
radar of any intensification. Will continue to monitor and adjust
accordingly as needed. Hi-res guidance continues pattern of showing
additional nocturnal MCS development out in mid-MS valley and
approaching the area after midnight. Coverage and intensity in
question as it reaches our area so will stay with just VCTS
overnight at both sites. Outside of convection expect VFR conditions
with S/SW winds less than 10kts.




LONG TERM...Fisher

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