898
FXUS63 KIWX 200501
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
101 AM EDT Sun Apr 20 2025

.KEY MESSAGES...

- For tonight, expect partly to mostly cloudy skies with lows
  in the 40s.

- There are chances for rain with isolated thunderstorms Sunday
  afternoon into Monday afternoon. The highest chances will be
  Sunday night into Monday morning. Additional low to mid range
  rain chances are possible through the work week, with the best
  potential on Friday afternoon.

- High temperatures in the 50s and 60s Sunday will rise into the
  mid to upper 60s and 70s for Monday and Tuesday. Highs from
  the middle to latter portion of the work week will climb as
  high as the mid to upper 70s before falling back to around 70
  for the weekend.

&&

.DISCUSSION...
Issued at 743 PM EDT Sat Apr 19 2025

A sprawling trough across the western US becomes cutoff across
the southwestern US as the northern stream continues eastward.
This allows a baroclinic zone to set up from TX to arcing
towards the Lower Great Lakes region. What`s left of that energy
in the southwestern US moves up towards the Lower Great Lakes
Sunday evening. So, as the cold front that caused this morning
showers and storms slowly shifts southeastward, rain shuts off
for all areas by after midnight tonight. This brief reprieve in
the rain is caused by surface high pressure nudging into the
area. It attempts to shut rain off as mid 30s to mid 40s dew
point air nudges in from the north. Better moisture exists south
of US-30, so am not as sold on rain as far north as the GFS and
ECMWF have. For what it`s worth, the NAM doesn`t have rain in
the area at all Sunday. This thinking would keep the forecast in
line with the previous shift of having mostly slight chance
PoPs and a pocket of chance PoPs west of IN-15 at times and
other times south of US-30. A warm front attempts to lift
northward Sunday evening and may provide a time period with some
thunderstorms as the NAM indicates some variation of 250 to
1250 J/kg of CAPE coupled with 30 to 40 kts of effective shear
may be around. All of that appears marginally severe, though.
The timeframe with the best moisture appears to be late Sunday
night into early Monday morning as an occluded front swings west
to east through the area, but dry air is quick to fill back in
in the mid levels shutting off heavier rain to either drizzle or
off altogether. Rain should be done Monday afternoon as sfc
high pressure noses in from the south and heights become looser
across the area. Expect gusty winds (25 to 35 mph) Monday
afternoon as a cold front pushes through and CAA takes over.

The aforementioned sfc high pressure area is west of the area later
day Tuesday and this allows WAA to take over Tuesday night into
Wednesday morning. Warmer high temps with 70 degree highs may be
more prevalent Wednesday through the end of the week as a result.
One dampener on that warm of high temps would be that there`s some
model consensus around bringing some convection eastward through
Lower MI on a stationary front similar to an MCS type evolution on
the eastern edge of LLJ. Although the resultant location (and if it
even happens) could change in the days to come.

Medium range guidance diverges Wednesday night through the end of
the work week as the GFS is already bringing in the next trough and
allowing for rain Wednesday night with some thunder possible. The
ECMWF does have some connection to the Gulf during this time and it
would only require some forcing to get showers and maybe some storms
started. With the northern stream jet north of the area and the
subtropical jet weakening, more defined areas of forcing will be
harder for models to find and track between Thursday and Friday
allowing quite a bit more uncertainty. Will keep slight to chance
PoPs during the end of next week to indicate the possibility of rain
and thunder, but nailing down a day and time comes with uncertainty
at this time.

Look for drying some time next weekend as high pressure comes in and
cooler/drier air arrives from the north.

&&


.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1254 AM EDT Sun Apr 20 2025

High pressure centered over Lake Superior is keeping dry
conditions around the upper Great Lakes for the first half of
the TAF forecast period. Ceilings have gradually lifted from
MVFR to VFR over the past few hours. Winds will remain light
overnight, ramping up by mid morning with easterly wind gusts
20 to 25 kts possible through much of the day today. As a warm
front lifts north today, a few scattered showers will be
possible in the afternoon. Have kept PROB30 groups at both KFWA
and KSBN for showers and MVFR ceilings/visibilities; the NBM has
20-30% chances of MVFR for a few hours in the afternoon today.
Winds remain elevated through the evening and overnight hours as
our next weather system approaches. Just beyond this TAF
forecast period, a line of showers and storms is expected to
move through the area, likely between 04Z-12Z Monday.

&&

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

&&

$$

DISCUSSION...Roller
AVIATION...Johnson