IWX issues Area Forecast Discussion (AFD) at Sep 13, 7:16 PM EDT686
FXUS63 KIWX 132316
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
716 PM EDT Sat Sep 13 2025
.KEY MESSAGES...
- Scattered showers and storms are possible this evening and
early overnight along and south of US 30. Storms will be
capable of producing small hail and gusty winds.
- A persistent dry and warm pattern sets up starting on Sunday
and lasting through next week. Expect highs in the upper 80s
to low 90s each day.
- Minimum relative humidities as low as 30% to 40% next week may
be conducive for elevated fire danger.
&&
.UPDATE...
Issued at 649 PM EDT Sat Sep 13 2025
Showers are diminishing and are nearly out of the area at this
time. On visible satellite imagery, clear skies can be seen over
Lake Michigan and central Lower Michigan. Expect clouds to
gradually decrease from northwest to southeast tonight. Given
that there is leftover moisture near the surface from today's
rain, with clearing skies and light winds overnight, still
thinking that patchy dense fog will be possible. The best
timing for fog will likely be between 5 to 9 AM EDT, with fog
dissipating pretty quickly 1-2 hours after sunrise. Lows tonight
drop down into the upper 50s to mid 60s.
&&
.DISCUSSION...
Issued at 242 PM EDT Sat Sep 13 2025
In the wake of the widespread, steady rain that moved through
earlier today, scattered showers and storms are possible this
evening and early overnight. Development is already occurring
southeast of Chicago in northwest Indiana. Showers and storms will
move southeast this evening along a remnant boundary, with gusty
winds, small hail, and heavy rain. SPC has maintained the Marginal
severe risk for today although the threat appears isolated. Mid
level lapse rates are decent but the better instability gradient is
to our west. The best chances for any additional rain or storms
today will be along and south of the US 30 corridor. Overnight,
expect skies to gradually clear and showers to diminish. With
lingering ground moisture, light winds, and clearing skies, areas of
patchy fog may develop early Sunday morning.
For Sunday and into early next week, an Omega Block pattern sets up.
An upper level ridge axis will build over the Midwest and Great
Lakes regions, allowing for warmer temperatures and persistent dry
conditions. Highs will be in the upper 80s to near 90 degrees each
day from Sunday through the middle of next week. The humidity will
be noticeable with dewpoints in the mid 60s. While not uncommon
this late in the summer, the heat will also allow for large
diurnal temperature swings as dry conditions persist through the
week. In fact, given that we have been lacking significant
rainfall since mid August, drought is likely to persist and/or
develop in the coming weeks.
By Friday and into next week, a return to seasonable
temperatures appears possible. Long range guidance hints at a
pattern change coming around this time next week. The upper level
ridge pattern breaking down and allowing for a cold front to sweep
through sometime between Friday and next Sunday, which would usher
in a cooler Canadian airmass and opportunities for rain.
One additional concern for next week given the above normal
temperatures and dry conditions is fire danger. Sunny skies and
persistent warmth should allow for minimum afternoon relative
humidity values to drop between 30 to 40 percent. However,
should any grass or brush fires develop, winds should be light
enough that it likely won't spread quickly. Avoid outdoor
burning!
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 712 PM EDT Sat Sep 13 2025
A quiet stretch of weather is ahead over the next week with dry
conditions prevailing. Skies are currently BKN to OVC across the
area with VFR ceilings, but clearing is observed upstream on
satellite imagery. Expect clouds to decrease over the next
several hours, especially near Lake Michigan. KSBN should be
mostly clear by 04-06Z, while clouds may linger longer overnight
around KFWA and areas southeast. The biggest concern during the
TAF period is patchy dense fog Sunday morning, especially in
locations that got in on rain earlier today. Leftover ground
moisture, light winds, and raditional cooling due to clearing
skies should result in fog developing (particularly along and
west of US 31). Have added a TEMPO in at KSBN as confidence
increases in fog between 09-13Z Sunday. MVFR visibilities are
possible, although have stuck with 6 SM for now. Future TAF
updates will need to evaulate fog potential and make any needed
changes. Sunday will be a dry, sunny day with lights winds out
of the south.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Johnson
DISCUSSION...Johnson
AVIATION...Johnson
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 13, 7:16 PM EDT---------------
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