Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 201043

Area Forecast Discussion
National Weather Service Northern Indiana
643 AM EDT Wed Jun 20 2018

Issued at 419 AM EDT Wed Jun 20 2018

Intermittent showers and storms are expected today as a weak low
pressure system moves through the area. Heavy rain is possible. High
temperatures will range from the low to mid 70s into the low 80s,
warmest south of US 30. Expect mostly dry conditions overnight, with
lows bottoming out in the upper 50s and 60s. Additional showers and
storms will move into the area Thursday morning from southwest to
northeast, and linger through the weekend. Highs will be in the 70s
and low 80s.


.SHORT TERM...(Today and Tonight)
Issued at 419 AM EDT Wed Jun 20 2018

The primary weather concerns today are showers and thunderstorms
associated with a stationary front elongated from west to east
across central portions of our CWA. As of 820 we sit at the
periphery of an upper level ridge, with forcing associated with an
incoming shortwave kicking off showers and storms over the
Michigan counties. Expect this activity to wane with time as the
weak surface low drifts eastward from north central Indiana into
Ohio by the late morning. This will serve to pull the front
southward, along with our POPS. By early afternoon, have
precipitation chances confined to areas south of US 24, given
the abundant moisture, the front or other spurious leftover
boundaries, and daytime heating. Otherwise, temperatures today
will be on the cooler side, with locations north of US 30 in the
low-mid 70s and areas south in the upper 70s-low 80s. Tonight
will be fairly quiet weather-wise, with lows dropping into the
upper 50s and low 60s for areas north of US 30. South of there,
expect lows in the mid 60s.


.LONG TERM...(Thursday through Tuesday)
Issued at 419 AM EDT Wed Jun 20 2018

Attention then turns to the big ol` bowling ball (500 mb low) over
the central plains with a deepening surface low out ahead of it. As
of this morning, an MCS is trekking across IA/KS. Models are
consistent in bringing this upper low into the Ohio Valley by this
weekend, which makes it yet another soggy period for our forecast
area. As the saying goes, upper level low look out below.
Thankfully, temps will remain on the cooler side, relatively
speaking-so those wanting a break from the oppressive heat will be
happy. Kept high temperatures in the 70s and low 80s through the

By the time the low reaches the MO/IL border Friday morning, it is
vertically stacked and working towards occlusion at the surface.
While models consistently bring both the upper/sfc low across our
CWA this weekend, they differ in terms of whether the sfc low will
continue to weaken and fill or deepen slightly before filling as it
exits the area. The problem comes in with attempts to phase the
system with a wave rotating around the much larger and deeper trough
over Hudson Bay. For now, went with a blend of the ECMWF/GFS and
have the pops slowly increasing from southwest to northeast
Thursday. Think we`ll have the best chances further south, assuming
the warm front is lodged just south of our CWA border with the
occlusion to our southwest. The main threat again will be heavy
rain, with PWATS along the front around 2 inches and decent synoptic
from the occluding low. At this point, threat for severe weather is
low (focused further south).

Have likely showers/storms in the forecast for Friday and Saturday
as the surface low lifts northeastward, eventually reaching
southeast Lower Michigan Friday evening. At this time we`ll be in
the left exit region of a cyclonically curved 90 knot jet in the
upper levels, giving us a qvector convergence maximum around the 850-
500mb layers. Best effective bulk shear remains south of our area
(with only around 20-30 knots available for a short time period),
but with abundant moisture (PWATS about 2 inches still), we get
around 500-1500 J/kg of MUCAPE (depending on your model of choice).
Though we have paltry mid-level lapse rates of 5-6 C/KM, can`t rule
out some wet microburst potential (especially given what we saw this
week with storms).

Otherwise, other than some low chances for showers/storms Sunday
afternoon associated with the trough extending from Ontario and
Quebec, expect a dry start to the work week. The amplifying mid-
level ridge will build over the area through Monday and Tuesday
before yet another upper level low over the northern plains drifts
into the Great Lakes on Wednesday and Thursday. This will bring us
additional chances for showers and storms, with highs climbing
towards the mid-upper 80s again.


.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 637 AM EDT Wed Jun 20 2018

LIFR conditions have rapidly settled in at both sites as inversion
strengthens. KSBN is being impacted by the frontal boundary, lots
of moisture and even some help from Lake Michigan. The front will
shift south of KSBN around 15Z with winds becoming NE. This should
push the lower vsbys out and start to slowly work on ceilings.
Will be some mixing of cloud bases at KFWA but impacts from any
showers that develop still possible. Will keep KSBN dry but add
VCSH later this morning into mid afternoon for KFWA. Thunder is
possible but confidence as to where and when convection will fire
on the front remains low as models struggle to work out the

Attempt to bring back in VFR conditions towards evening but may
be too optimistic given stratus and some fog across Michigan
behind the front.





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