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356
FXUS63 KIWX 260858
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
458 AM EDT Sun May 26 2024

.KEY MESSAGES...

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- 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 tornados.

- 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.
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&&

.DISCUSSION...
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Issued at 349 AM EDT Sun May 26 2024

Warm front boundary associated with a low pressure system over
central IA this morning is now pushing into eastern MO and will
move east/northeastward this morning. Latest HRRR model has a
well defined line of rain/thunderstorms moving into the western
parts of the CWA around Noon EDT today, which would be the
first batch of strong to severe storms. The line should continue
to move east/northeast and get through the rest of the CWA by 6
PM EDT. MU CAPE values around 1000-1200 j/kg late this morning
with the warm frontal boundary passage. Bulk shear values of
around 25 to 35 knots. Mid level lapse rates of 6.5 to 7.5
deg/km. Downdraft CAPE with boundary passage will sit right
around 1000 j/kg. SR Helicity values around 150 m2/s2. So all
threats with the first batch will be possible. However, wind
threat seems to be the highest threat with hail right behind and
one or two qlcs type tornados possible with the line. With
PWATS of nearly 200 percent of normal, 1.65 inches, localized
flooding will be possible with the first batch of storms but
with storm motion perpendicular to the front will limit the
widespread flooding issues.

With more moist air pumping northward we will see dew points
begin to modify higher with mid to upper 60s dew points behind
the warm front and ahead of the cold front by early evening.
The uncertainty increases with the second batch of storms
accompanying the cold front which at this time looks to be more
scattered and potentially weaker than the first batch of storms
as the airmass was pretty worked over with the convection with
the warm front and only a couple hours of recovery will be
possible. Even so, there seems to be another increase in CAPE
post frontal (500-1000 J/kg) which should be enough instability
to allow for convection. Bulk shear will be slightly less with
20 to 30 knots available. These scattered storms look to move
through the CWA from about 8 PM EDT until Midnight EDT. There
may be a higher threat for localized flooding issues with the
second batch of storms as already wet soils will be further
saturated with any additional downpours, but PWATS will drop to
around 1 inch post warm front storms. Highs today in the high
70s and low 80s.

With the cold front through the area by the morning of Memorial
Day a cooler airmass will be in place. With troughing sitting
over the Great Lakes region several shortwaves will translate
through the trough bringing periods of rain showers with even a
few embedded thunderstorms each day from Monday through
Wednesday. High temperatures will range each of those days from
the mid 60s to the low 70s. The coolest day looks to be on
Wednesday with most locations struggling to get out of the 60s.
By Thursday morning, with the help of clearing skies from the
incoming broad ridging pushing into the area late Wednesday, low
temperatures on Thursday will drop into the mid 40s.

We do start to see a warming trend by the end of the week with
the ridge pushing eastward into the area. Thursday highs will be
in the 70s for most locations with temps a few degrees cooler
near Lake Michigan. Friday and Saturday will see highs in the
upper 70s with a few spots seeing the low 80s. Chances of rain
showers return on Saturday as a trough pushes through the upper
midwest.
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&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 153 AM EDT Sun May 26 2024

VFR conditions are expected through the first portion of the
forecast period at both terminals with high pressure at the
surface and a mid level ridge aloft. Winds are light and
variable, but will eventually strengthen out of the ESE through
the afternoon. We deteriorate to MVFR/IFR later in the
afternoon-mainly for visibility, then after 00z for MVFR
ceilings. We could see brief dips to IFR or less in strongest
storms. A warm front will lift northward across the Ohio
Valley/Great Lakes region this afternoon, stemming from low
pressure centered over MO/IA/IL. This will shift winds more
southerly and bring a line of showers and thunderstorms through
both terminals between 19-21z. Forecast confidence decreases
after that as model solutions vary quite a bit in terms of
additional storm development in the wake of the front. Some of
the guidance has most of northern IN dry until 1-2z, then bring
in additional storm development ahead of the system cold front
(low moves generally ENE through Mon AM, depending on model,
into either central Lower MI or eastern Upper MI). Other models
have a more widespread nature to the convection after the warm
front. Opted to keep just a generic VCTS from 22-01/02z at both
sites given the conflicted guidance, as I suspect there will be
showers/storms around eventually as we inch towards 00z.
However, confined the better chances to after 01/02z for now,
with MVFR ceilings possible as well (most of guidance has
between 1500-3000 ft). It is quite possible some of the storms
could be severe, especially towards the late afternoon and
evening hours.

&&

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

&&

$$

DISCUSSION...Andersen
AVIATION...MCD