824
FXUS63 KIWX 240004
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
704 PM EST Sat Nov 23 2024

.KEY MESSAGES...

- Some patchy light drizzle possible tonight into early Sunday.

- Next chance of more widespread rain/drizzle arrives late
  Sunday night into Monday .

- Still a good deal of uncertainty with midweek holiday system
  Wed-Thu. Some potential of impacts to holiday travel for
  later Wednesday into Thursday, but confidence is low.

- Trend to much below normal temperatures for Tuesday through
  next weekend.

&&

.DISCUSSION...
Issued at 338 PM EST Sat Nov 23 2024

Extensive low clouds have persisted across the area this afternoon.
Satellite trends over past few hours have shown more rapidly
clearing in eastern Iowa/western Illinois, but not expecting this
trend to make it into local area this evening. An upper speed max
across the northern Great Lakes will dive southeast across the
eastern Great Lakes this evening. Continued backing of low level
winds downstream of this feature may induce enough weak low level
lift for some patchy drizzle across the north this evening.
Otherwise, a fairly uneventful night in store with limited diurnal
temperature ranges due to low level warm advection and extensive low
cloud coverage.

Sunday should feature continued ramp up of low level warm advection,
but main item of uncertainty for Sunday centers on sky cover trends.
Low level flow should be a bit stronger and more backed southwest on
Friday which may allow for better chances in temporarily eroding low
clouds. Have maintained forecast consistency in this respect with
trend to partly cloudy conditions across the south half/mostly
cloudy across the north. While mixed layer heights will remain
shallow Sunday, the stronger low level flow and southwest flow
component should allow for better mixing in comparison to today
with highs from upper 40s far northeast to low-mid 50s far
south/southwest. The low level inversion will be hard to erode,
and thus always some concern low clouds could persist longer
than forecast.

For Sunday night, a southwesterly low level jet will nose into the
Mid MS Valley eventually veering westerly with stronger low level
moisture advection into the local area late Sunday night into early
Monday. This moisture return will be shallow in nature and with
better mid and upper level moisture support lagging back to the
west, this may end up being more of an areas of drizzle/light
rain type event into early Monday morning. Mid level trough will
build across the region Monday afternoon allowing better
low/mid level frontal forcing and deeper better RH profiles to
move into the region for continued rain chances. Good shot of
cold advection builds in Monday night behind associated cold
front, but any lake response should be weak due to shallow
lake induced instability.

Tuesday should feature dry and much colder conditions as low level
baroclinic zone stalls across the area. By Tuesday night into
early Wednesday backing low level winds downstream of next
upstream disturbance may induce fronto/weak WAA induced light
snow given expected pre-existing baroclinic zone. Greater
potential may exist just west of local area, but did include
some slight chance/low chance PoPs for this period.

The main periods of interest this forecast period are still in the
Wednesday through Saturday timeframe. 12Z suite of guidance has
exhibited some fairly dramatic changes from earlier guidance. The
GEM and EC deterministic solutions have both trended to more
amplitude with this system, and both ensemble mean representatives
of GEM/EC have exhibited a similar trend. Given these trends,
have upped blended PoPs for the Wednesday into Thursday period.
GFS/GEFS remain more northern stream dominant with a sharper
north-south cutoff in precip shield. Have maintained high chance
PoPs for this period given this is a recent trend in guidance,
bu this certainly will be a system worth watching heading into
a busy holiday travel time Wednesday-Thursday.

Amplified western CONUS ridge will provide ideal low level
trajectories for a potential significant shot of cold air late week
into next weekend, with continued good agreement in medium range
deterministic/ensemble solutions. This large scale pattern would
eventually lead to at least increased lake effect snow potential
heading into next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 655 PM EST Sat Nov 23 2024

Predominantly MVFR to IFR conditions at the terminals, with
improvement expected tomorrow afternoon. We`ll see increased
warm air/moisture advection through the overnight and tomorrow,
with the inversion tonight-early Sun AM possibly trapping in
those lower ceilings. At the moment, KFWA is at 800 ft and KSBN
has 1500 feet. Confidence is lower in regards to if/how long IFR
conditions develop. Guidance is conflicted on even the overall
trend, with some suggesting gradual improvement overnight, and
others suggesting IFR will dominate the period with possible
LIFR conditions. It seems the more pessimistic model is on the
right track, particularly at KFWA, but stayed middle of the
road as far as ceiling heights go, with KSBN staying low-end
MVFR and KFWA IFR until around 4z before potential improvement
begins.

&&

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

&&

$$

DISCUSSION...Marsili
AVIATION...MCD