333
FXUS63 KIWX 162345
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
745 PM EDT Thu May 16 2024

.KEY MESSAGES...

- Scattered showers and storms with local downpours this
  afternoon into Saturday.

- Very warm Sunday into Tuesday with highs in the low to mid
  80s.

- Strong storms possible Tuesday.

&&

.UPDATE...
Issued at 744 PM EDT Thu May 16 2024

An area of mainly light showers continues, with a few of the
showers managing to tap the limited instability, but poorly
sheared environment long enough to intensify with pockets of
locally heavy rain and in a few instances 30 to 35 mph gusts.
Loss of heating should allow for a slow reduction in coverage.

Small area of showers in east central IL will work ENE and may
impact far S/SE areas in a few hours. CAMs still try to expand
coverage with this area and increasing LLJ of 30 kts later
tonight. Have toned down pops in the SE overnight to no more
than likely. If these can come together the weak flow and
abundant moisture could lead to some areas of heavier rainfall
and ponding.

&&

.DISCUSSION...
Issued at 257 PM EDT Thu May 16 2024

An area of surface convergence was setting off showers and sub-
severe thunderstorms in Missouri this morning. That area of surface
convergence located behind a warm front today sets the stage for a
resurgence of moisture and, therefore, showers and thunderstorms
later this afternoon into tonight. As the parent low pressure system
moves northeast into southern Canada, a cold front slowly approaches
the area around midday Friday and pushes through during the
afternoon. This likely takes Lake MI-adjacent counties out of any
pop-shower or storm that forms during the afternoon with the 500 to
1500 J/kg of MUCAPE at their disposal. These storms will be lacking
in the shear department and that limits their severity, but locally
heavy down pours will be possible. This is most likely true tonight
as a moist environment with 60F surface dew points, 850 mb dew
points approaching 10C, and 1.3 in PWATs in addition to weak winds,
favorable MBE vectors, and hints at available large scale ascent.

By Saturday, the better moisture has shifted south and east some so
that the area conducive to pop showers and thunderstorms will likely
be lesser during the afternoon, but not zero. Storms will, once
again, have 500 to 1500 J/kg of MUCAPE to work with, but shear will,
once again, be negligible limiting the severity of these storms.
DCAPE does appear to approach 900 J/kg so perhaps a microburst could
occur in addition to locally heavy rain.

Surface high pressure and mid level ridging overhead work in tandem
to keep Sunday dry. It`ll be a nice day with highs securely in the
80s. With forcing still off to our northwest, daytime Monday also
looks dry, but with a few more clouds around. Highs will also be
securely in the 80s.

From Monday night through Wednesday morning, an active period with
some extent of forcing nearby is in store. An upper low over
southwest Canada will serve as the main channel through which areas
of vorticity will be flung towards the area. The first such one
scrapes our northwest Monday night and there will likely be
thunderstorms with this, but shear appears limited also limiting
severe weather potential. Another shortwave appears to encroach on
our western areas Tuesday morning before a cold front approaches the
area Tuesday evening and night. This begs the question how much
instability and shear will be present during this time debris clouds
around and the timing of the front may limit instability as well.
One positive for storms may be that mid level lapse rates around or
potentially surpassing 7 C/km could be around for storms to tap
into. These are generally favorable for severe hail. However, with
the rain chances around during this time, it`ll be interesting to
see how those lapse rates maintain themselves or mix out before they
make it here. Flooding could be a problem with the continued rain
chances, especially in urban areas, which are normally more flood
prone. Finally, the arrival of these pieces still has time to change
between now and then so it`s certainly not yet set in stone.

Tuesday`s active weather has been slowing down some in recent
model runs so while I have some confidence in Thursday being
dry, I have less confidence in keeping Wednesday dry, especially
the morning. Have lowered NBM PoPs Wed PM, but only to low
chance at this juncture.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 744 PM EDT Thu May 16 2024

Area of showers and isolated storms has shifted east of KSBN
with a period of partial clearing coming for at least a few
hours before stratus begins to develop and settle in with MVFR
cigs overnight into the first part of Friday. Light rain/rain
showers will persist at KFWA for a few hours with the initial
area weakening. A small area of showers/storms extended from
KDNV to south of KCMI, moving ENE over the next several hours.
Models try to expand this area somewhat, possibly clipping the
airport later this evening, but think bulk of this will remain
to the S and E. Have left a unrestricted shower mention in the
next several hours. Cigs should also begin to lower overnight,
although maybe not quite as low as KSBN since the site will be
well east of the weak sfc trough edging eastward.

&&

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

&&

$$

UPDATE...Fisher
DISCUSSION...Roller
AVIATION...Fisher