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000
FXUS63 KIWX 240450
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1250 AM EDT Wed Apr 24 2024

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms through this
  evening, tapering off over night.

- Threat for frost continues Wednesday night/Thursday morning
  with some concerns for brief period of freezing temperatures
  NE.

- Trending warmer and at times stormy Friday through Monday.

&&

.DISCUSSION...
Issued at 324 PM EDT Tue Apr 23 2024

Through this evening...

Main area of rain will continue to sink SE with most locations
expected to remain dry thereafter. However, that may not be the case
in far N and NW areas as the initial front/trough dives SE early
this evening accompanied by strong upper level dynamics and some
decent shear. In addition, 500 mb temps dropping to -25 C will move
in, causing steepening low level lapse rates of 8 to 8.5 C/km
especially in pockets where a touch of clearing may occur. Bulk of
the convective response seems to be across portions of Lwr MI, but
far N/NW parts of the area could be clipped by some development.
With the timing possibly as early as 22Z but more likely in the 1Z-
4Z Wed period, loss of daytime heating may impact development
somewhat. Pops may be overdone, but will hold with persistence.
If any convection does wander into the area, small hail and
gusty winds would be possible (non-zero threat of an isolated
severe wind gust or hail report). At this point, the Marginal
risk of strong to locally severe storms in the far NW.

Although temperatures may fall into the upper 30s (maybe a few mid
30s) in NW areas, the lingering clouds and winds will limit any
frost development.

Wednesday into Thursday...

While the period will be rather quiet, frost potential will need to
be monitored as temperatures likely fall into the mid 30s by
Thursday morning, with the potential for a brief window of 29 to 32
degrees in the NE third to half of the area. The timing of clearing
wrt CAA stratus will likely be the main determining factor in how
much frost develop occurs as well as the extent of freezing temps.
Another weak disturbance looks to arrive as well Wednesday night
that could have some mid/high clouds to result in some impacts in
the sw half or so of the area, possibly arriving towards 12Z Thu in
NE areas. While a frost advisory seems pretty likely for most, if
not all the area in the 4Z-13Z Thu time frame likely be needed for
much, if not all of the remainder of the forecast area. Although
reservations exist on whether a freeze will occur in the NE vs
more widespread frost, coordination has resulted in the hoisting
of a Freeze Watch from 4Z-13Z Thu in roughly the NE half of the
area where temps are forecasted to hit 32 degrees or less.

Thursday night into Friday night...

Rapid shift in the pattern commences Thursday night as 500 mb
heights quickly increase in response to the first of 2 closed upper
lows set to move to southeastern SD by 6Z Sat. Models in general
agreement on 850 mb warm front quickly taking shape and moving
northeast across the area Friday afternoon into Friday night. Warmer
air will arrive Friday with this feature (60s) but moisture may
still be somewhat limited. Pops may be a bit on the aggressive side
Friday night, but are at least heading in the right direction
regarding the better chances NW (closer to the upper low and better
lift) vs SE.

Saturday into Tuesday...

The initial upper low will track NE into western Lake Superior by
00Z Sunday. A strong southwesterly flow will setup as yet another
closed low ejects from the Four Corners region Friday night and then
NE from thereby Sunday afternoon. Models diverge on handling of this
feature with 18Z Sun locations ranging from over Nebraska
(GFS/Canadian) vs SW Minnesota (EC). With the main upper level
features remaining west of the area, some concern as to how far east
the cold front will make it and how much convection may accompany it
before outrunning the best dynamics. Plenty of moisture will be
around and afternoon highs over the weekend will be well into the
70s and maybe a few 80s so will keep pops in place focused on Sunday
night for the time being.

Slightly cooler, but still above normal temperatures will settle in
for Monday and Tuesday as most of the energy remains across the
northern tier of states with the frontal boundary likely to meander
across the region.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1151 PM EDT Tue Apr 23 2024

A cold front was just northwest of SBN. This system will move
across northern Indiana and bring a wind shift to the northwest
and eventual post frontal clouds. High res/WPC models have not
initialized the clouds very well; have opted to delay lower post
frontal ceiling given upstream satellite clouds. Otherwise,
skies should eventually clear later today with VFR conditions
eventually prevailing.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Freeze Watch from late Wednesday night through Thursday
     morning for INZ005>009-018.
OH...Freeze Watch from late Wednesday night through Thursday
     morning for OHZ001-002-004-005-015-016-024-025.
MI...Freeze Watch from late Wednesday night through Thursday
     morning for MIZ078>081.
MARINE...Small Craft Advisory until 10 PM EDT Wednesday for LMZ043-046.

&&

$$

DISCUSSION...Fisher
AVIATION...Skipper