347
FXUS63 KIWX 202322
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
722 PM EDT Fri Sep 20 2024

.KEY MESSAGES...

- Some areas may see rainfall this afternoon with widely
  scattered to scattered showers/storms.

- One more warm day Saturday with highs possibly reaching (or
  exceeding) 90 degrees before a trend to cooler temperatures.

- Confidence increasing on 1 or more chances for much needed
  rainfall Sunday into Monday, with timing/coverage details
  still to be sorted out.

&&

.DISCUSSION...
Issued at 312 PM EDT Fri Sep 20 2024

An area of storms developed over southern Lake Michigan and has
worked inland, holding its own, but struggling to develop further SW
despite unstable conditions. Main wind shift remains back over
Chicago, working slowly east. Big question is does the convection
expand further southwest of have we seen the southern extent of the
needed rainfall.  So far the main features have been brief but heavy
rainfall with locations picking up a quick half inch to over an inch
in the stronger storms. Have adjusted pops to lower somewhat further
SW based on satellite trends. Agitated cu field still is showing up
so suspect more widely scattered development could take place with a
newly developed cell near Rensselaer. Everything will move east at
around 25 mph and is expected to weaken after 00Z with loss of
heating. Higher dewpoints will remain in place overnight with drier
air not arriving till Saturday. After coordination, have added
patchy fog with areas that manage to see some rainfall today seeing
some potential for locally dense fog.

One more hot day is in store by mid Sept standards  for Sat with
highs at least into the mid to maybe upper 80s. MAV guidance remains
rather aggressive on highs in the low to middle 90s, possibly due to
increasing mixing/subsidence. Not ready to jump into that arena, but
something to watch in later forecasts.

Confidence does continue to increase on 1 or more chances for
showers and storms, possibly as early as Sunday afternoon, lingering
into Monday night as a series of disturbances move into the area and
northern stream trough digs and deepens. Trends seem to suggest the
first round being Sun afternoon/evening with another Monday
afternoon and evening. Keeping pops capped at likely for now, but
signs point towards at least some needed rainfall for many areas.

Models diverge on handling of the trough through the rest of the
period (and beyond) ranging from strong ridging overhead to a deep
cutoff low near/west of the area. To further complicate things, some
sort of tropical development is expected next week, but location and
track of this feature is equally uncertain. At least a brief dry
period seems likely late Tue night into Wednesday before remainder
of forecast has slgt chc to chc pops.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 715 PM EDT Fri Sep 20 2024

Behind the cold front, conditions will be very favorable for the
development of fog overnight. Winds become light and variable
this evening, and with leftover ground moisture from today`s
rain, this will result in areas of patchy dense fog Saturday
from about 10Z to 13Z. For both KFWA and KSBN, the NBM has about
a 60% chance for LIFR ceilings, a 40% chance for IFR ceilings,
and a 30% chance for visibilities less than 1 mile. With such
strong probabilities, fog appears likely to develop Saturday
morning, and as such, have added a TEMPO group into the TAFs to
reflect this.

&&

.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...Fisher
AVIATION...Johnson