IWX issues Area Forecast Discussion (AFD) at Sep 30, 6:56 PM EDT743
FXUS63 KIWX 302256
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
656 PM EDT Mon Sep 30 2024
.KEY MESSAGES...
- Drizzle and perhaps a few showers south of US-24 this
afternoon and evening transitions to fog by early Tuesday.
- The next chance for showers comes Tuesday and a few non-severe
thunderstorms will be possible before evening arrives.
- A break in the wet weather arrives for Wednesday and Thursday
and lows in the 40s will be common each of those mornings.
&&
.DISCUSSION...
Issued at 247 PM EDT Mon Sep 30 2024
Our pattern will be affected by the remnants of the tropical cyclone
to our south, a ridge just to our northwest, and a trough just on
the heels of the ridge to our northwest.
We've had some drizzle throughout the day today and, given the
shallow moist layer and times of continued weak forcing, cannot rule
out this continuing. There's also a chance a few light showers come
in as the weakening system to our south pinwheels a few into the
area on its northern fringes. It's also on the way to moving out of
the area between this afternoon and Tuesday so the chances for light
showers will be on the decrease. Given the incessant overcast and
stable, drizzle-causing atmosphere, have kept thunder chances out of
today.
There has been plenty of low level moisture through the weekend and
today underneath this overcast and, given the weaker winds overnight
into Tuesday, we could see some fog develop. With a cold front
arriving early Tuesday morning, there's better likelihood of
lingering fog into Tuesday morning east of IN-15 as opposed to west.
If we can break the cloudiness overnight enough to get a
strengthening low level inversion, perhaps the fog would be of
greater magnitude as well.
A cold front arrives a little bit on the early side for Tuesday in
conjunction with the trough behind the ridge to our northwest.
Instability is around 500-1000 J/kg of MUCAPE and effective shear
stays less than 30 kts so this would limit overall severity, but
could see some thunderstorms in the I-69 midday into the afternoon
before skirting out of the area before evening time. The low to mid
teens 850 mb temperatures allow for mid to upper 70s highs east of
IN-15 where the longer residence time in the warm sector exists.
Behind Tuesday's cold front, single digit 850 mb temperatures drop
in allowing for cool morning lows in the 40s and highs that only
flirt with 70 degrees before the day is done. Do expect much sunnier
skies, though, as drier air comes in in conjunction with surface
high pressure. We're still dry on Thursday, but the surface high
swings through quickly allowing warm advection to take over and for
high temperatures to achieve the mid to upper 70s once again.
There are still discrepancies for Thursday night and Friday as to
the depth of the trough arriving from the northwest. As such, the
potential for showers and maybe a thunderstorm or two is also in
question. The ECMWF's vorticity is much more progressive and more
northward into Michigan than the GFS, which brings it through the
lower Great Lakes. Given these discrepancies am inclined to go with
the NBM for PoPs, which is just going with silent 10 PoPs for now.
Models do retain some agreement/confluence on bringing in surface
high pressure with dryness for Saturday and our next trough in
for Sunday/Sunday night, which could have more rain.
&&
.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 637 PM EDT Mon Sep 30 2024
Near surface moisture will continue to remain trapped below a
mid-level high pressure inversion which has kept low clouds in
place. VFR conditions for short periods expected this evening
for both TAF sites, however KSBN will see periods of CIGS drop
into MVFR cats and KFWA will see conditions degrade to MVFR and
eventually fog development drops vsbys/cigs to IFR levels after
08z Tuesday. Drizzle will continue to be possible at times for
both sites. By Tuesday afternoon an incoming trough and
associated cold front will bring gusty northwesterly winds to
the area, especially for KSBN where winds may gust to around 25
kts before the end of the TAF period. KFWA will see winds pick
up just after this forecast period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 8 AM Tuesday to 8 AM EDT Wednesday
for LMZ043-046.
&&
$$
DISCUSSION...Roller
AVIATION...Andersen
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 30, 6:56 PM EDT---------------
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