493
FXUS63 KIWX 250719
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
319 AM EDT Wed Sep 25 2024

.KEY MESSAGES...

* Lake effect rain showers early this morning followed by
  isolated showers area-wide this afternoon.

* Rain showers associated with a tropical system enter the
  forecast late Friday afternoon through the weekend.

* Seasonable temperatures are replaced by a temporary dose of
  fall by the middle of next week.

&&

.DISCUSSION...
Issued at 317 AM EDT Wed Sep 25 2024

Lake effect rain showers this morning give way to isolated showers
this afternoon. This occurs as there is hint of destabilization and
weak impulses of mid-and-upper-level vorticity in the vicinity of
stacked upper-level low moving across the mid-Mississippi Valley.
Moisture return is modest, primarily because the cold front that
moved through yesterday (now approaching the Appalacians) is the
primary focus of such moisture advection. Additionally, early-
morning thunderstorms ongoing over Arkansas and Oklahoma will
negatively impact any poleward moisture transport in the short term.
Therefore, I`ll hold steady with the inherited isolated shower
mention.

While fog has failed to materialize early this morning, fog is
plausible again tonight per ensemble forecast soundings. But, this
is at odds with high-resolution visibility guidance which indicates
otherwise. Dew point depressions will be low, but afternoon forecast
soundings appear well-mixed leaving me to think our local moisture
source could dry out, thus limiting the fog risk. With this
dichotomy, I`ll omit fog for now but pass on to the next shift for
consideration.

Friday through the weekend, our weather will be driven by a closed
low over the southern Mississippi River Valley interacting with what
is currently Tropical Storm Helene. This low will gradually drift
north toward drought-stricken southern Ohio Friday and Friday night.
The in-house blend still strikes me as woefully too-fast with the
local arrival time of POPs. This happens among the backdrop of high
pressure over the Great Lakes that needs to be displaced. So, Friday
will be primarily dry but some showers could slip into the far
southern US 24 corridor late in the day. POPs then increase through
Friday night. Passing showers will persist through the weekend,
though there will be some dry time here and there.

Look out next week as a brief, but big temperature change is
favored.  While the aformentioned low swirls just off to our south
this weekend, a ridge centered over the southern 2/3 of the CONUS
will promote anomalous 500-mb heights and permit our local
temperatures warm into the upper-70s Monday. Tuesday, in comes a
Canadian cold front. This kicks the cut-off low well to the east and
our high temperatures Wednesday will be locked into the 60s.
Temperatures rebound soon after.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 105 AM EDT Wed Sep 25 2024

Generally stayed close to the existing TAFs for this issuance.
Stratus is blossoming quickly between KSBN and KFWA and this was
captured accordingly in the TAF. Fog is becoming less certain
amid this rapidly developing stratus field which will likely preclude
any fog development at KFWA, while a mid-level cloud deck at
KSBN has most likely squashed the FG potential there.

Forecast cross sections are rather soupy though the day but with
decreased subsidence through time which should allow any
subsidence inversion to ease late-morning. Isolated showers are
anticipated (lake effect or otherwise) but indeed, coverage
will be isolated. Therefore, carried on with the dry TAF for
now.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Brown
AVIATION...Brown