372
FXUS63 KIWX 200642
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
242 AM EDT Fri Sep 20 2024

.KEY MESSAGES...

- Showers and thunderstorms are expected this afternoon
  primarily west of Indiana State Route 15 (20-40% chance).

- Remaining hot today and Saturday with highs approaching 90
  degrees.

- There are frequent chances for rain beginning Sunday.

&&

.DISCUSSION...
Issued at 239 AM EDT Fri Sep 20 2024

Showers and thunderstorms are expected this afternoon primarily west
of Indiana State Route 15. Widespread severe storms are not
expected, but damaging wind gusts from a storm or two cannot be ruled
out.

Showers and thunderstorms across Wisconsin and eastern Iowa early
this morning are forming ahead of a 40-knot 500mb jet and in the
vicinity of a cold front, whose parent low resides over central
Manitoba. This activity is showing a gradual weakening trend on
satellite, but embedded stronger cells continue to come and go over
far northern Illinois. I`ll be keeping a close eye on these this
morning while maintaining the thinking that this round will decay prior
to reaching Michiana.

Overall, high resolution guidance is in strong agreement and
initializes well across a variety of parameters this morning, thus
increasing forecast confidence in rain occurring. This includes
ensemble forecast soundings which verify reasonably well against
observed soundings from 00z. While the Manitoba low is forecast to
track northeast this morning, the trough aloft and aformentioned jet
is already modifying our local air mass as dry air on upper- and mid-
level water vapor is becoming pinched (retreating) in response to
this jet approaching our eastern Great Lakes ridge. The 500-mb jet
lingers over the Midwest today, providing at least some upper-level
support. Dew points initialize well over the region and a corridor
of low-60 degree dew points are expected to spread east ahead of the
cold front. With highs once again well into the 80s, instability
will be ample with no cap noted beyond the early-morning hours (in
part why Wisconsin activity fails to reach Michiana this morning).
Steep-low level lapse rates, a byproduct of low-level moisture that
is gradually improving , indeed pose a marginal risk of damaging
wind gusts from the tallest thunderstorms. Again, not expecting
widespread severe storms today, but I have high confidence in
scattered thunderstorms this afternoon primarily west of IN-15.
Lastly, it should be noted that upstream soundings (e.g., GRB)
saturated very well over the past 12 to 24 hours ahead of
approaching rain, thus there is hope that the dry air mass that has
plagued our area can be overcome.

Beyond today, I am happy to report there are several chances for
rain in the forecast as high pressure finally gets shunted over the
far Northeast. Sunday through Tuesday, our upper-air pattern is
characterized by a decaying ridge across the far Southern Plains
extending into the Gulf. Meanwhile, a trough is ejecting from the
Rockies, splitting the gap between the aformentioned ridge and a
deep low swirling over Manitoba and Ontario. As a result, we`re
mercifully in line for periodic showers and thunderstorms Sunday
through Tuesday paired with  temperatures closer to normal. How this
upper-air pattern evolves late in the week is unclear, with some
guidance suggesting a cut-off low to finish the week. WPC forecast
rainfall today through Friday morning (next week) favors rainfall in
excess of 1" for the forecast area.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 121 AM EDT Fri Sep 20 2024

Dew points are expected to level off overnight in the mid 50s as
temperatures slowly fall into the upper 50s and low to mid 60s. This
miss for cross-over temperatures likely yields only patchy ground
fog in the FWA area. This, as a moisture axis makes its way into the
area for Friday. Winds become more southwesterly during the day
Friday and increase chances for showers during the midday and
afternoon hours. At this point, it`s hard to have confidence in
chances for rain given antecedent dry conditions, but the chance is
at least there. Will have a VCTS at SBN in the evening and a -SHRA
for FWA into early overnight. With all of this in mind, will lean
towards prevailing VFR through the period at both sites. Some
thought towards potential lowered VIS within heavier showers may
need to be considered.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ005-012>015-022-023-104-116-204-216.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Brown
AVIATION...Roller