Corunna, Indiana Weather Forecast Discussion

708
FXUS63 KIWX 051615
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1215 PM EDT Fri Sep 5 2025
.KEY MESSAGES...
- Breezy and briefly warmer today with gusts of 25 to 35 mph.
- Mainly dry over the next 7 days. Only real rain chance is for
  a few sprinkles mainly N of US-6 Saturday night.
- Cool temperatures this weekend begin to trend warmer as we
  head to mid week next week. Some 80 degree temps are possible
  on Wednesday.
- Dangerous swimming conditions expected for Lake Michigan beaches
  through Saturday.
&&
.DISCUSSION...
Issued at 324 AM EDT Fri Sep 5 2025
Atmospheric waves breaking over the eastern and northern
Pacific allow for the continued enhancement of a ridge over
western North America. As a result of this Eastern Pacific
Oscillation (which has gone negative over the last 30 days), a
downstream trough has formed over the eastern US and thus our
cooler temperatures and rain chances.
An upper low exists within the aforementioned trough across the
Eastern US and this slings a vigorous vort max and colocated
surface low toward the lower Great Lakes and Lower MI. The
strong pressure gradient allows a 45 kt low level jet to move
across the area this morning and depart before midday. A cycling
frontal boundary also moves through this morning and this is
probably too early to allow isentropic downglide. So, by the
time we get to early afternoon, it does appear that mixing gets
up to around 850 mb where 25 to 30 kts exists and that would
allow for 35 mph gusts at times. Perhaps, FWA and other areas
south of US-24 get into the strongest gusts as that`s where the
better jet dynamics reside when the better mixing gets going.
North of US-24, the jet is already weakening back to 25 kts
during the afternoon. Because the front is already pushing
through during the morning, there`s not enough instability to
produce thunderstorms and there`s low level dry air indicated in
the time section plots to eat into rain intensity. Models, in
concert, are dry with their precip output, but perhaps a
sprinkle or virga could be had here or there due to forcing
intensity midday into the afternoon north of US-6.
Saturday also appears to largely be dry. The only wrinkle in that
would be when a shortwave comes laterally across Lake MI Saturday
night. Now, there also appears to be some lake-induced instability
and some low level moisture. There is some precipitation output in
response to that in models that appears possible, but at the same
time, surface level moisture or the lack thereof may limit overall
precip output. That departs with the shortwave being overtaken by
surface high pressure through the day Sunday or perhaps by Sunday
night. Have also upped cloud cover from the NBM, which is
notoriously less cloudy than it needs to be in the long term.
The surface high pressure taking over Sunday night into midweek next
week acts to keep the area largely dry again. At the same time, a
warming trend occurs from Sunday through Wednesday so that highs in
the 60s trend to reach 80 degrees in some spots on Wednesday.
Pattern-wise, a trough comes into the western US and this pushes the
ridge that was across the western US towards the middle of the US
and this helps to usher in the dry and warming trends and also hints
at the negative EPO breaking down. There`s some discrepancy on the
timing of pushing the trough through the area Wednesday with the
ECMWF hanging around and the GFS taking it through. Perhaps, at
least Wednesday gets some light precip, especially if there`s a Gulf
connection as the ECMWF advertises.
&&
.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1215 PM EDT Fri Sep 5 2025
West winds will gust 25-30 knots at times this afternoon behind
a cold front. Loss of diurnal mixing and a diminished pressure
gradient allows winds to quickly subside to 5-10 knots by early
this evening. VFR otherwise through the period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement through late tonight for INZ103.
OH...None.
MI...Beach Hazards Statement through late tonight for MIZ177-277.
MARINE...Small Craft Advisory until 5 AM EDT Saturday for LMZ043-046.
&&
$$
DISCUSSION...Roller
AVIATION...Steinwedel

NWS IWX Office Area Forecast Discussion