IWX issues Area Forecast Discussion (AFD) at Nov 24, 3:57 PM EST141
FXUS63 KIWX 242057
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
357 PM EST Sun Nov 24 2024
.KEY MESSAGES...
- Chances of rain showers and drizzle increase late evening into the
overnight. Rain chances continue into Monday. Rainfall amounts
through this period will be light.
- Mild conditions for Monday with highs in the lower to mid 50s but
turning much colder for Tuesday behind a cold front.
- Rain/snow chances return for Wednesday but low confidence in
impacts due to potential southward suppression of this system
and marginal thermal profiles rain versus snow if northward
track verifies.
- Even colder air overspreads the area for the weekend into
early next week. Highs are expected to in the 20s and 30s for
next weekend with lows in the teens to lower 20s. Single digit
wind chills at times for next weekend.
- Lake effect snow shower potential will increase by Friday, but
greatest chances of lake effect snow for the weekend into
early next week.
&&
.DISCUSSION...
Issued at 354 PM EST Sun Nov 24 2024
Low level warm front will continue to lift northward this
afternoon with low clouds eroding across southern Lower
Michigan. This low level drying will be short-lived as low level
southerly flow will ramp up late this evening into the
overnight. A small scale lead short wave is expected to race
east from the Mid MS Valley into the western Great Lakes this
evening, but stronger mid/upper level forcing will lag well back
to the west across the Central/Northern Plains. Moisture depths
with the advective forcing will remain relatively shallow as an
elevated mixed layer overspreads southern Great Lakes
tonight. This should yield more of a patchy light rain
shower/drizzle set up as elevated mixed layer feature limits
moisture depth and depth of upward vertical motion. A mid level
dry slot will advect into NW Ohio after daybreak Monday, with a
narrow temporal window for some slightly deeper mid level RH
profiles from west to east Monday afternoon as a large scale mid
level trough shifts across southern Great Lakes/Ohio Valley. The
primary low level moisture axis by Monday mid afternoon should
be shunted east of Interstate 69 corridor in weak pre-frontal
troughing zone, so some question as to coverage of afternoon
rain showers given this disconnect in moisture/forcing. Will
continue to carry scattered PoPs into the afternoon. Storm total
rainfall amounts tonight into early Monday evening should be on
the light side.
For Monday night, strong post-frontal cold advection will
provide well mixed low levels and breezy/windy conditions.
Stratocu and well mixed low levels should keep lows around 30.
Tuesday should be a quiet transition day between systems as a
low level baroclinic zone stalls from the Corn Belt into the
eastern Great Lakes. Upper flow will deamplify on Tuesday in
wake of Monday's system with little discernible forcing
mechanisms. Very dry low and mid level air will also be
entrenched across the region by this time.
For Tuesday night, a couple of upstream Pacific disturbances
will allow low level winds to back and possibly interact with
low-mid level theta-e gradient across the area for some
frontogenesis or warm advection induced light snow. Highly
sheared nature of any short waves during this period and
uncertainty as to where low level baroclinic zone will be
positioned leads to low confidence in spatial extent of these
chances. Thus, will continue broadbrush slight chance/low chance
PoPs late Tue night into Wed AM.
The Wednesday/Thursday period remains one of a relatively low
confidence with next stronger eastern Pacific wave. Part of this
uncertainty is derived how guidance is handling strength/timing
of northern/southern streams which influences how far north sfc
reflection associated with southern stream will reach, and how
much cold air there will be to work with across the southern
Great Lakes. Still feel a rain/snow mix is possible especially
across southeast half of area, but have maintained just chance
PoPs this period until greater confidence can be attained. It
does appear as though a long duration of better deep moisture
profiles may be hard to achieve when considering broad synoptic
pattern, so confidence in impacts remains quite low.
Cold conditions and lake effect snow potential will be the main
weather stories post-Thanksgiving. Depth of moisture Friday into
Saturday may be in issue in realizing significant lake effect
snow Friday and Saturday, with some consistent signal in medium
range guidance of a clipper-type system Saturday that could
delay the reinforcing shot of unseasonably cold air until the
Sunday/Monday period. Given combination of cold/light snow
potential Saturday, this could be a day to monitor for travel
impacts. Confidence also remains high in impacts from lake
effect snow showers, particularly second half of weekend into
early next week. Highs late weekend into early next week could
be limited to the 20s with lows in the teens.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1217 PM EST Sun Nov 24 2024
Stratus is finally breaking up as of this writing and thus
confidence is high in a period of VFR conditions. Low pressure
currently over far western Iowa moves east through time
bringing a chance of rain and eventually low clouds back to the
terminals. Rain amounts (and rates) will be small (and light)
due to poor moisture profiles, thus, continued here with 6SM
due to light showers. Start and end times offer medium
confidence. Probabilities are very high (>=50%) for ceilings
less than 1k FT Monday, according to the in-house blend. Via
pattern recognition and recent gloomy conditions, confidence is
high in IFR or worse toward the end of this TAF period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 3 PM Monday to 7 PM EST Tuesday for
LMZ043-046.
&&
$$
DISCUSSION...Marsili
AVIATION...Brown
Source:
IWX issues Area Forecast Discussion (AFD) at Nov 24, 3:57 PM EST---------------
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