IWX issues Area Forecast Discussion (AFD) at Aug 22, 2:19 AM EDT015
FXUS63 KIWX 220619
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
219 AM EDT Sat Aug 22 2026
.KEY MESSAGES...
- 30-60% chances for scattered rain and storms arrive tonight
through Saturday. An isolated strong storm capable of gusty
winds and brief heavy rain is possible west of US-31 late this
evening and east of I-69 Saturday afternoon.
- Dangerous swimming conditions expected for southeast Lake
Michigan beaches on Saturday and Sunday with High Swim risks
both days. Northwest winds will gust to 30 mph with waves of 3
to 5 feet.
- Dry weather returns Sunday and Monday with below normal
temperatures and low humidity.
&&
.DISCUSSION...
Issued at 132 PM EDT Fri Aug 21 2026
An upper level low over the Hudson Bay will be the focus of the
forecast for the next 36-48 hours, as the attendant cold front with
this system sweeps through our area and brings periodic chances for
rain and storms tonight through early Sunday. Mainly dry conditions
are expected to continue this afternoon, however, isolated
showers and storms remain possible through sunset east of I-69
with a leading 500 mb shortwave associated with the upper level
low. Scattered cumulus development is already noted on visible
satellite imagery this afternoon. Isolated showers are also
likely in the vicinity of Lake Michigan this afternoon where a
dying convection complex from upstream is moving in. Into this
evening, with the cold front still back in Wisconsin and the
upper level trough expected to begin to dig into the Great
Lakes, we will have to watch what additional development there
is upstream over southern Wisconsin and northern Illinois. CAMs
are in fairly good agreement in a cluster of storms developing
this evening to our northwest and diving southeast after sunset.
Given that shear and instability will wane after sunset, these
storms should be diminishing by the time they reach northwest
and north central Indiana tonight. Can't rule out an isolated
gusty storm or two but not expecting much if any severe threat.
Locations along and east of I-69 will remain dry until daybreak
Saturday.
Showers gradually become more numerous as the front pushes eastward
and as the upper level trough amplifies during the morning and early
afternoon hours on Saturday. Have maintained PoPs between 30-60% on
Saturday, with the highest chances in northwest Ohio. With the front
expected to come through between the morning and early afternoon
hours, this is not the most favorable diurnal timeframe for storms.
Again, can't rule out an isolated strong storm or two (especially in
northwest Ohio) as a corridor of up to 1500 MLCAPE could develop
east of I-69, but the likelihood of organized severe weather
tomorrow is low given marginal shear of 20-30 kts and poor low/mid
level lapse rates. With a tightening pressure gradient and strong
cyclonic flow on the backside of the departing front on Saturday
evening, I wouldn't be surprised if widely scattered lake effect
showers develop downwind of Lake Michigan for several hours late
Saturday into early Sunday. Winds will be breezy out of the
northwest through the remainder of the weekend with northwest winds
gusting as high as 25 to 30 mph.
The aforementioned frontal passage is expected to stir up southern
Lake Michigan, generating large waves and dangerous currents
throughout the weekend. Northwest, onshore flow with northwest winds
gusting to 30 mph will allow for waves to build to 3 to 5 feet with
strong currents expected. High Swim Risks will be in place both days
this weekend. Beach Hazards Statements will need to be issued this
afternoon for Berrien and La Porte counties at least for Saturday.
There will be a lull in winds and possibly waves overnight before
dangerous conditions ramp up again into Sunday, with additional
headlines likely needed. Heed beach flags/lifeguards and stay
out of the water!
High pressure builds into the Great Lakes and Midwest regions again
by Sunday, giving us the first taste of fall as temperatures and
dewpoints fall to comfortable levels. Temperatures will be slightly
below normal on Sunday and Monday with highs in the low to mid 70s
with northwest flow behind the cold frontal passage. A few crisp
nights are ahead Sunday night and Monday night with lows in the low
to mid 50s. With much drier air building in, dewpoints only in the
50s will make for several nice days! Another cold front moves in
Wednesday with low chances (20-30%) for rain/storms maintained.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 156 AM EDT Sat Aug 22 2026
Expect predominantly VFR to MVFR conditions at the terminals,
with quick periods of IFR possible. A cold front will pass from
west to east through the period, with potential for showers,
storms, and BR/Fog development. So far this evening has been
fairly quiet with respect to t-storm activity along the cold
front just west of Lake MI. Have tempos in for any
showers/storms and 3-5SM BR, first at KSBN then at KFWA. MVFR
ceilings move in behind the front and then eventually break to
VFR by mid-late afternoon.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement from 10 AM CDT this morning through
Sunday evening for INZ103.
OH...None.
MI...Beach Hazards Statement from 11 AM EDT this morning through
Sunday evening for MIZ177-277.
MARINE...Small Craft Advisory from 11 AM this morning to 11 PM EDT this
evening for LMZ043-046.
&&
$$
DISCUSSION...Johnson
AVIATION...MCD
Source:
IWX issues Area Forecast Discussion (AFD) at Aug 22, 2:19 AM EDT---------------
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