400
FXUS63 KIWX 271018
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
618 AM EDT Thu Jun 27 2024

.KEY MESSAGES...

- Hazardous swimming conditions are expected on Lake Michigan
  today. Dangerous currents are likely, in addition to waves of
  3 to 5 feet.

- Friday we`ll see increasing clouds from west to east through
  the day, with highs in the upper 70s and low to mid 80s.
  Chances for showers and thunderstorms begin Friday evening and
  persist through Saturday night.

&&

.DISCUSSION...
Issued at 422 AM EDT Thu Jun 27 2024

Patchy fog developed this morning along US 30 and southward, with a
couple locations in Cass and White Counties in IN dropping to about
1/4 to 3/4 of a mile for a couple hours. Was considering an SPS,
however in the last hour there was rapid improvement, likely due to
a very slight increase in wind speed and drop in humidity behind a
weak surface trough. Winds are expected to continue to stay up
around 5 mph or greater through morning hours in the north and west,
with the far southern CWA near Grant/Blackford/Portland, IN Counties
still showing calm winds with visibility between 1SM or less on the
observations. It is possible some fog re-develops, or becomes more
widespread in the area, especially where winds stay on the calm side
further south for longer. I will hold off on any SPS  until I see
more consistent observations of 1 mile or less. Otherwise, I think
most places will linger between 2-5SM until sunrise at worst, then
improve.

Quiet weather conditions today and during the day on Friday thanks
to the upper level ridge and surface high building over the Great
Lakes. Highs will be in the 70s today, then rise into the upper 70s
and low to mid 80s Friday. Lows will be around 60 degrees.

Otherwise, northerly winds behind the trough that is moving through
right now have picked up on Lake Michigan to around 10 to 20 mph
with gusts up to around 25 mph. Surface high pressure builds in
rapidly behind the trough through the day, and is will be favorably
positioned to allow for slightly gustier N-NE flow and longer fetch
on Lake Michigan. Waves quickly came up to around 4-5 feet per the
latest observations at Michigan City, IN Buoy and Bridgman, MI-with
wave periods around 4-5 seconds.  Wave direction will be more shore-
parallel further north and become more oblique in La Porte county,
IN. This will generate a strong southward flowing longshore current,
which will re-direct offshore as a structural current on the north
side of any piers or breakwalls. Rip currents are possible, but more
likely further south in LaPorte where the wave angles of approach
relative to shore fall more into the 30-59 degree range.

Furthermore, if winds shift more N-NW this afternoon with the lake
breeze, the more direct wave angle of approach, in combination with
wave heights of 2 to 5 feet (lesser this afternoon), will make rip
currents more likely within the sandbars. Maintained the going high
swim risk and left the beach hazards statement as is (ending at 21z
today). It`s possible if winds stay stronger than forecast and have
a more NW-component to the wind/wave direction (vs N-NE) we may need
to extend the beach hazards statement through this evening,
particularly at La Porte where the conditions are most favorable
longer into the day. Stay dry when waves are high, and steer clear
of the piers! Waves could wash you off the pier and into the water,
where you will most certainly be met with a staunch structural
current that pulls you to deeper water. Those visiting the beaches
should plan to stay out of the water.

Last but not least SPC has added our entire CWA to a Marginal Risk
for strong to severe storms on Saturday, which is reasonable given
the forecasted synoptic pattern. It`s somewhat convoluted this far
out, however it appears there are two potential rounds of storms,
the first with the surface warm front lifting northward Friday night
into Saturday morning (with a weak shortwave rippling through the
upper level flow). The second round would be from around 15z -21z
Saturday when a cold front moves west to east across our CWA. In
terms of severe weather, the best potential will be with the cold
front in the afternoon hours. The first round may not even develop
over our area (some of the guidance pops it just east of us, some
have little to no precipitation with it. Strong moisture transport
will be ongoing from the gulf thanks to return flow over our exiting
high pressure system (Sitting over the Atlantic by 6z Sat), with
pwats reaching 150 to 200 percent of normal! Second, we have decent
synoptic forcing with the cold front, 0-6 km bulk shear of 35 to 45
knots, and lastly-we will likely have some instability (models have
between 400-1200 J/kg. This is of course conditional upon the first
round-if it develops, how much convective debris is leftover, and
how quick we can recover. It will also depend on timing, some
of the models suggest the cold front coming through in the
12-15z time frame, which could limit the intensity of the storms
(versus when instability is maximized further east as they have
the best chance to recover from morning convection). Mid level
lapse rates aren`t that great-around 5-6C/km, which could limit
intensity as well, but it`s definitely worth watching.

Sunday into Monday will be cooler and dry with highs in the 70s and
low 80s. Additional rain and storm chances approach for the middle
of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 614 AM EDT Thu Jun 27 2024

Following the earlier AMD, TAFs were in pretty good shape.
Critical TAF period wind was adjusted to match the latest
observations and the overnight winds were refined as well. High
confidence of VFR conditions through the TAF period with some
fair weather cumulus this afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement until 4 PM CDT this afternoon for
     INZ103.
OH...None.
MI...Beach Hazards Statement until 5 PM EDT this afternoon for
     MIZ177-277.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for LMZ043-
     046.

&&

$$

DISCUSSION...MCD
AVIATION...Brown