IWX issues Area Forecast Discussion (AFD) at Sep 30, 7:33 AM EDT044
FXUS63 KIWX 301133
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
733 AM EDT Mon Sep 30 2024
.KEY MESSAGES...
- Mainly dry except for a chance for non-severe storms east of
I-69 Tuesday afternoon. Unseasonably warm temperatures through
Sunday with highs daily around 68 to near 80. Cool nights with
lows mainly in the 40s.
- Fog likely tonight into Tuesday morning, with the most
impactful areas east of Interstate 69, where patches of dense
fog are possible.
- There is a moderate swim risk early today for Lake Michigan
beaches in Southern Berrien County, MI and La Porte County,
IN. There is a high swim risk for Tuesday for the entire
lakeshore.
&&
.DISCUSSION...
Issued at 257 AM EDT Mon Sep 30 2024
The upper low that merged/absorbed Helene was still over Kentucky
early this morning and continued to gradually weaken. To the
north of this system, light showers were occurring over Ohio.
Some of these showers had spread into the Lima area overnight
where over a tenth of an inch of rain had fallen since 8 PM EDT.
Other very light rain/sprinkles were over northern Indiana,
apparently enhanced with the moisture flux from Lake Erie. Given
obs, trends, and the latest HRRR, this activity should continue
at times today and then end by early tonight as the upper level
system finally lifts out of the region to the northeast.
Challenges Tuesday include fog development early followed by
chances for thunderstorms during the afternoon. Very high dew
points for this time of year will persist over the forecast area
as the remnants of Helene/upper low move out of the region.
Some clearing is expected with light winds which should allow
fog to form before daybreak. Added areas of fog east of I-69
which appears to have the best chance for fog formation. Any fog
should mix out by mid morning ahead of an approaching upper
level system just coming out of the Rocky Mountains into Montana
and the Canadian Prairies. Expanded storm coverage slightly in
area and duration Tuesday afternoon. Storms should have
somewhat limited energy (CAPE generally up to 1000 J/Kg) and
limited low level wind shear up to the mid levels, so severe
storms are not expected. Otherwise, mainly dry weather is ahead
for the rest of the week. It appears cold air will remain north
of the area allowing highs to be generally above to much above
normal in the 70s.
&&
.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 720 AM EDT Mon Sep 30 2024
Predominantly MVFR conditions through the period-improving to
VFR for a bit this afternoon, then dropping back to MVFR/IFR at
mainly KFWA later tonight into Tue AM. IFR also possible this
morning, especially at KFWA.
KSBN cleared out but have yet to see any BR so removed that for
this morning, and the stratus edge is just to the south and
west (KGSH BKN009 BKN030 at 1130z; KC65 is showing BKN025).
Expect this to move in this morning, though confidence with
regards to whether the IFR ceilings will materialize at the
site, so kept just a tempo from 13-15Z for 900 ft ceilings
(Given GSH is already showing 900 ft).
At KFWA, they are beneath the stratus deck, with quite a variety
of ceiling heights upstream (300-500 ft at some sites, then
1000-2500 in others). This made for a challenging forecast. Most
of the guidance suggests ceilings lingering around 1000-1500 ft
at the site, with a few suggesting a period of 700 ft ceilings,
which is not out of the question. Opted to have a tempo from
13-16z for BKN007, keeping it MVFR outside of that for today.
Fog development is expected overnight, with KSBN seeing a more
patchy and more MVFR nature than KFWA, who could very well drop
to LIFR or VLIFR closer to 12z. Kept it conservative given we
are further out-with 2SM BR after 6z.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Skipper
AVIATION...MCD
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 30, 7:33 AM EDT---------------
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