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507
FXUS63 KIWX 261622
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1222 PM EDT Sun May 26 2024

.KEY MESSAGES...

- Showers and thunderstorms expected this afternoon and tonight.
  Damaging wind, hail and localized flooding will all be
  possible. There is the possibility of a few tornadoes.

- Lingering showers and thunderstorms may impact activities
  Memorial Day through Wednesday.

- Hazardous swimming conditions for Lake Michigan beaches in La
  Porte County in Indiana and Berrien County in Michigan
  Memorial Day through Wednesday.

&&

.DISCUSSION...
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Issued at 1220 PM EDT Sun May 26 2024

A deepening area of low pressure approaches the Western Great Lakes
today and moves into the Northern Great Lakes by Monday morning. As
it does so, a warm front pushes into Michigan by this evening.
Models expect low lapse rates to be the highest in the I-69 on
eastward where the greatest amount of sunlight and least amount of
thunderstorm overturning resides into the afternoon ahead of the
approaching storm-filled warm front. Much of the shear lags behind
this warm front so the most likely hazards out of a line like this
include strong to damaging wind gusts up to 60 mph with heavy rain
that could lead to flooding. There is some progressive nature to
this initial line so that will likely limit the residence time of
the rather moist ingredients including surface (into the 60sF) and
low level dew points (above 10C in many southern locations).

There has been some question about what happens behind this line. Do
we get clearing or does a potential cold pool keep cloud cover
around enough to restrict recovery of instability for an evening
batch of severe thunderstorms? Additionally, what time do storms
initiate? As late as the the 00z models, there were still a few
models that hang onto a possibility of pop storms after the line,
but it appears 12z guidance has since backed off that possibility.
The 6z RAP seemed keen on initiating around 5pm, but that seems less
likely than some of the other models bringing a line through our
southern zones or just to our south around 8pm. By this point, shear
would be better established with the low level jet overhead and
helicity would be present as well allowing the introduction of the
hazard of a few tornadoes. The mid level lapse rates are shown to be
replenished behind the initial warm front line that had 8C/km mid
lapse rates to work with this morning. This will also make large
hail a possibility with the potential afternoon resurgence. If
storms do initiate behind the line, storm motion will also be in
question as the continued moist environment could allow any slower
moving storms to produce quite of rain in a short time frame. The
NAM40 also seems keen on keeping some storms southeast of US-24 into
the overnight with strong to damaging wind and large hail being the
main threats along with heavy rain that could lead to flooding.
Aside from the lower res NAM, the HREF suite brings a midnight or
1am end time to this second batch of strong to severe storms with
potentially a few isolated cells thereafter as the EML and lingering
instability could keep a few cells going after dark. Again, 12z
guidance appears to back off this second batch possibility
altogether.

The cold front moves southeast vacating the area Monday morning
allowing surface dew points to drop back into the 50s indicating the
dry air mass behind the front. But it`s a quick reprieve as another
wave approaches the area for Monday night. Even the NAM only has 100
to 500 J/kg of MUCAPE around for this episode which indicates weak
thunderstorms would be the expected outcome at strongest outcome.
Highs Monday will also be cooler, in the upper 60s and low 70s with
the negative theta-e advecAndersention behind the previous
departed cold front. Still not much cooler for highs on Tuesday
with upper 60s to low 70s, but models want to generate some more
instability to the tune of 500 to 1000 J/kg, which would
indicate more thunderstorms are possible during the afternoon,
especially as another broad area of vorticity approaches Tuesday
afternoon/night.

Behind this area of vorticity, surface high pressure comes in and is
expected to provide dry weather from mid to late week as a large
ridge stations itself over the Central CONUS. Some lingering
moisture may be able to sprout a few showers Wednesday morning, but
that should be east of I-69. Expect 60s for Wednesday that trend
warmer, reaching the 80s on Sunday. Our next chance for rain likely
holds off until late Saturday.
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&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
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Issued at 1220 PM EDT Sun May 26 2024

An arcing line of elevated convection on track to lift through
both terminals in the 1830-2030z window. Brief period of
LIFR/IFR vis restrictions, frequent lightning and perhaps some
small hail the primary threats with this activity. A lull late
afternoon may then give way to additional chances for scattered
convection this evening into the early overnight as the upper
system and sfc cold front follow through. Post-frontal IFR-MVFR
cigs then settle in within a 10-15 kt westerly wind late tonight
into Monday morning.
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&&

.IWX WATCHES/WARNINGS/ADVISORIES...
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IN...None.
OH...None.
MI...Beach Hazards Statement from Monday morning through Monday
     evening for MIZ177-277.
MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Monday for LMZ043.
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&&

$$

DISCUSSION...Roller
AVIATION...Steinwedel