IWX issues Area Forecast Discussion (AFD) at Jul 10, 2:01 AM EDT593
FXUS63 KIWX 100601
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
201 AM EDT Thu Jul 10 2025
.KEY MESSAGES...
- Dry for the rest of the overnight with potential of patchy fog
development. The fog may be locally dense.
- There is a Moderate Swim Risk for southeast Lake Michigan
beaches this morning.
- Hot and humid by the weekend with chances for rain/storms.
&&
.DISCUSSION...
Issued at 223 PM EDT Wed Jul 9 2025
A cold front is located from Grand Rapids southwest towards Des
Moines, and it will slowly sink south and east this afternoon and
evening. Ahead of the front, destabilization is already occurring
across our forecast area. A growing cumulus field is evident on
visible satellite imagery and showers have been percolating
throughout the area already today. Because of cloud cover across
much of the area, temperatures have struggled to get out of the 70s
today. Scattered multicell clusters of showers and a few storms are
ongoing east of IN 49, while a lake shadow is keeping conditions dry
along the lakeshore. Additional diurnally driven showers and storms
will be possible until sunset. Much like setups over the past few
weeks, it will be feast or famine for storms. Some locations may get
nothing while others get several inches of rain in a short amount of
time. The Storm Prediction Center has maintained a Marginal Risk
(level 1 of 5) for the far northeast portion of the forecast area,
meaning a few storms could be strong to severe today. The setup for
severe weather appears fairly unimpressive as there is ample
instability for storms to work with (2000-2500 J/kg SBCAPE), but no
source of lift (until the front arrives) and little to no shear in
place as vertical wind profiles are unidirectional out of the
southwest. Confidence in severe weather is very low. Given ample low
level moisture (dewpoints in the 70s) and high PWATs of 1.5-1.75",
flooding is a much more likely scenario today than severe weather.
Backbuilding will be possible with low level low from the
west/southwest parallel to the boundary and slow Corfidi upshear
winds. Precipitation rates should be very efficient today given
long, skinny CAPE profiles, a deep warm cloud layer, and PWATs
above the 75th percentile of normal. WPC has much of the area in
a Marginal Risk (level 1 of 4) for localized flash flooding,
which definitely is plausible given the favorable environment.
Additionally, there is a High Swim Risk for southeastern Lake
Michigan beaches today through early Thursday. As winds switch from
the southwest to northwest/north along the lakeshore behind the cold
front, waves will build to 3 to 4 feet. Strong rip, structural, and
longshore currents will all be possible, especially on the north
side of piers. Stay out of the water!
winds will shift to be coming from the northwest after the front
passes through and skies will start to clear out. Forecast soundings
show an inversion developing tonight as well as a stable airmass
moves in. With mostly clear skies, light winds, and residual ground
moisture, patchy ground fog may develop Thursday morning. Confidence
is medium in fog developing, but low as to the extent of visibility
impacts. Thursday will be dry as high pressure briefly builds into
the Upper Great Lakes region for 24-36 hours.
An upper level ridge expands across the southwest and central US
this week and progresses eastward. Heat and humidity will build
across the Midwest as the upper level ridges expands and WAA
increases later in the week. Depending on where the periphery of
the ridge sets up and how much destabilization occurs, we could
see some showers/storms on Friday. Better chances for
rain/storms arrive by the weekend as another cold front moves
through, although long term models disagree on exact timing and
positioning.
&&
.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 149 AM EDT Thu Jul 10 2025
A weak sfc cool front has become more diffuse across extreme NE
Indiana/NW Ohio early this morning. Residual low level moisture
and near sfc moisture source from yesterday's rainfall will
likely yield a zone of most preferred fog formation immediately
in the wake of this low level front from west central Indiana
through KFWA vicinity extending into NW Ohio. Have maintained
previous TEMPO IFR mention at KFWA in the 10Z-13Z timeframe,
with a potential of some shorter-lived vsby restrictions at
KSBN. A weak intrusion of low level dry air behind the front
should limit the overall potential at KSBN. Mainly dry
weather is expected through the remainder of the period, with
VFR conditions prevailing.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement until 1 AM CDT early this morning for
INZ103.
OH...None.
MI...Beach Hazards Statement until 2 AM EDT early this morning for
MIZ177-277.
MARINE...None.
&&
$$
DISCUSSION...Skipper
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Jul 10, 2:01 AM EDT---------------
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