220
FXUS63 KIWX 040522
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
122 AM EDT Tue Jun 4 2024

.KEY MESSAGES...

- Warm and humid conditions will bring increasing chances for
  showers and thunderstorms Tuesday afternoon into Wednesday. Severe
  weather is not expected, but locally heavy rain is possible.

- Becoming cooler (closer to normal) for the second half of the
  week with drier conditions (low chances for showers/storms
  around 20%).

&&

.DISCUSSION...
Issued at 225 PM EDT Mon Jun 3 2024

A southerly flow, courtesy of slowly departing high pressure to the
east, will bring a summer-like feel to the area with highs well into
the 80s (warmest Tuesday) and dewpoints in the low to mid 60s (heat
indices mid to upper 80s). Scattered showers and storms are
expected to develop further west across eastern Iowa/NW IL and S
WI ahead of a MCV that will track NE. While a stray model run
still attempts to bring this activity into far NW areas this
evening, impacts of the ridge, loss of daytime heating and
departure from the best moisture and dynamics should result in a
weakening trend that warrants no more than slgt chcs for a few
hours this evening.

While instability will increase Tuesday afternoon as highs in the
mid 80s and dewpoints in the low to mid 60s bring roughly 1000 J/KG
of SBCAPE which would normally lead to "pop-up" showers and storms,
several factors lean against development until the glancing blow of
the trough from the cut off upper low in Canada. Low and mid level
lapse rates will be below 6 C/KM and shear will be almost non-
existent and no real boundaries/triggers are anticipated in the
area. The only potential for a trigger could be with any MCV from
today`s convection that maybe drifts into the area. Have went silent
14% or less pops Tuesday morning and trimmed back/lowered pops
Tuesday afternoon.

Main trough arrives Tuesday night into Wednesday with some
concerning signals that could indicate less in the way of
coverage and impacts for the area. The trough is moving through
a bit quicker, resulting in a less than favorable timing for
fropa Tuesday night into early Wed. Models are picking up on
this with any development in the west Tuesday night likely
weakening or dissipating overnight with re- development moreso
Wednesday afternoon when the trough will be exiting the area as
will the cold front. Overall model blends are still bringing
likely to cat pops, but may very well need some serious
adjustments over the next 24 hours or so.

GFS/EC/GEM are in somewhat better agreement on deep upper low diving
SE from northern Michigan Thursday morning to somewhere in the PA/NY
area by 12Z Sat. This will lead to cooler temperatures (near or
somewhat below normal) and scattered showers (isolated storm?) with
each disturbance rotating through the flow. Forecast will remain
muddled with slgt chc or chc pops mainly in the afternoon and
evening hours through the rest of the period as overall NW flow
remains in place. We will remain on the edge of it, which may result
in some larger temp gradients SW to NE. Highs may be too warm as
noted by the last shift, but given the strong June sun, doesn`t take
much to warm up.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 122 AM EDT Tue Jun 4 2024

Relatively dry low levels and shortwave ridging aloft will
support VFR conditions for much of the period. Low level
moisture and instability increase by this evening and an
approaching trough could generate some isolated storms after
00Z. Confidence in coverage and impact is still low. Best
forcing doesn`t arrive until late Tuesday night after the
instability has waned. MVFR conditions and isolated storms are
possible around/just after 06Z but will hold off on including
with this TAF package.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Fisher/Johnson
AVIATION...AGD