Area Forecast Discussion
Issued by NWS Northern Indiana

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864
FXUS63 KIWX 211544
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1144 AM EDT Thu Jun 21 2018

.SYNOPSIS...
Issued at 443 AM EDT Thu Jun 21 2018

Showers and thunderstorms will overspread the area today. Chances
continue through Sunday, with locally heavy rainfall possible
through Friday night. Highs today into Saturday will be in the 70s,
then climb to around 80 for areas south of US 30 on Sunday.
Overnight lows will be in the upper 50s and 60s. Expect a dry start
to next week, with high pressure building in. Highs will be in the
80s.

&&

.UPDATE...
Issued at 1144 AM EDT Thu Jun 21 2018

Previous forecast is in good shape this morning and main tweak was
to slightly slow down northeast increase in PoPs late this morning
into this afternoon. Primary upper low across northern Missouri
will continue to dig E-SE through this evening. Sfc trough is
positioned just south of the forecast area late this morning.
Elevated theta-e advection in advance of this upper low has
resulted in expanding area of showers/embedded thunderstorms
across northeast Illinois/northwest Indiana. The sfc trough is
expected to make little if any northward progress through the
remainder of the day due to the digging nature of the trough and
extensive precip.

The main feature to watch will be elevated low level boundary,
which is expected to make slight additional northward progress
through this evening. Guidance over the past 24 hours has focused
on axis of stronger low level moisture flux convergence with this
low level trough in focusing heavier rainfall. Most persistent
signal of this forcing appears to be across northwest portions of
the area generally north of Route 30 and west of I-69 from this
afternoon into this evening. Will have to watch for some
localized flooding and localized rainfall amounts in excess of 2
inches through this evening across these locations, particularly
across northwest Indiana. Still expecting any isolated severe risk
to remain south/southwest of the local area where slightly
greater instability is expected this afternoon into early this
evening.

&&

.SHORT TERM...(Today and Tonight)
Issued at 443 AM EDT Thu Jun 21 2018

The saga of the stationary front continues today, with showers and
thunderstorms observed along and just north of the boundary
triggered by weak lift ahead of a shortwave, ejecting from the
vertically stacked low pressure system currently over IA (as of 8Z).
Expect rain and thunderstorm potential to increase through the
afternoon as the incoming occluded surface low shifts the front
slightly northward again. Given the deeper warm cloud depths and
high PWATs still expecting the potential for heavy rain today into
Friday night. Flooding is possible in areas that receive more
intense/copious amounts of rainfall. Severe weather is not
expected with any thunderstorms given the limited
shear/instability. Highs today will be in the 70s. Lows will be in
the 60s, warmest south of US 30.

&&

.LONG TERM...(Friday through Wednesday)
Issued at 443 AM EDT Thu Jun 21 2018

As the occluding system moves in Friday into Sunday with the
associated upper level low, we`ll see continued showers and
thunderstorms. While any strong-severe storms are expected to remain
south of our area, heavy rain still poses a main threat given the
anomalous moisture and deeper warm cloud depths. Flooding is a
possibility in areas that receive the greatest amounts/intensities.
Gusty winds are possible in storms Friday afternoon. High
temperatures will remain in the 70s and low 80s, with lows in the
upper 50s and 60s.

Surface high pressure will build in underneath an amplified upper
level ridge for the start of next week (Mon/Tue), leading to dry
conditions. Highs will rise again into the mid and upper 80s by
Tuesday afternoon, with increasing warm air/moisture advection
moving into the west and bringing in chances of showers/storms by
Tuesday night (or Wednesday morning depending on which model
solution you prefer).

Went conservatively as far as timing is concerned for pops Tue
night, slowly introducing them by Wednesday morning and continuing
into Thu morning from west to east as a low level trough progresses
eastward across the Great Lakes region. Strong warm air/moisture
advection will develop in tightening pressure gradient between high
pressure centered over the eastern seaboard and approaching the
approaching trough from the northern plains. Highs will be in the
mid-upper 80s once again, and humidity will be on the rise.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
Issued at 636 AM EDT Thu Jun 21 2018

Mixed bag of flight categories for the start of the 12Z TAF cycle.
Low stratus has persisted at KSBN while KFWA has improved to VFR.
The improvement at KFWA will likely be short lived as upstream
observations show MVFR/IFR ceilings. Diminishing showers shouldn`t
impact either terminal for the first couple of hours, but the next
round of convection will likely impact the terminals around 18Z.
Have introduced a tempo group for these chances. Lowered ceilings
and visibility, as well as, erratic winds should be expected for
any thunderstorm which impacts the terminals directly.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

UPDATE...Marsili
SYNOPSIS...MCD
SHORT TERM...MCD
LONG TERM...MCD
AVIATION...CM


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