IWX issues Area Forecast Discussion (AFD) at Nov 26, 3:33 PM EST
460
FXUS63 KIWX 262033
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
333 PM EST Tue Nov 26 2024
.KEY MESSAGES...
- Snow mixes in with rain Wednesday evening/night into Wednesday
morning. The likelihood is that snow accumulations will be
kept at less than 0.5 inch and will likely be relegated to
grassy areas.
- Colder air wraps in Thursday night and lake effect snow takes
shape across the lake effect belt. Times of snow may continue
into the weekend.
- High temperatures will be at or below freezing Friday into
next week. Lows will be in the teens with windchills in the
single digits at night.
&&
.DISCUSSION...
Issued at 307 PM EST Tue Nov 26 2024
Fairly zonal flow across the country with surface high pressure
moving through will help to keep the area dry into Wednesday. Cloud
cover continues to recede with the dry advection this afternoon,
however, the warm advection wing arriving this evening/overnight
reintroduces mid level clouds. Precipitation could get underway
south of US-30 in the morning as saturation gets down to 850 mb.
Models initially created precipitation with the warm frontal
moisture early Wednesday AM, but am not inclined to include PoPs for
that with saturation still working its way into the low levels at
that time. Temperatures will likely be able to warm into the low 40s
with the warm advection wing, although some cooling may occur as
precipitation reaches the surface. These warm temperatures allow for
a primarily rain event and likely limits accumulations especially
with road surface temperatures above 32 degrees. fgen banding begins
to work its way into the area Wednesday afternoon/evening and could
begin to see some dynamic cooling with the enhanced lift around, but
the eventual location of the banding will matter there for where
snow begins to fall. Even still, models have marginally conducive
surface temperatures in the low 30s at their lowest Wednesday
night/early Thursday as the strongest of the banding arrives in
conjunction with the surface low. Road sfc temperatures actually
become more conducive to accumulations with around freezing
temperatures, but it will likely take that fgen band working
northward to get any accumulations. With all this in mind, have
little to no snow accums Wed/Wed night. The precipitation is out of
here Thursday morning.
Even as the low continues to deepen to our east, it does wrap in
colder air. As a shortwave traverses the tear drop of Lake MI, we'll
likely see the lake effect snow become invigorated as mixing heights
rise to around 850 mb or 1.5 km. Some dry air resides at the low
levels and it does take some time for mixing to reach the DGZ.
However, NAM has good low level wind convergence just north of South
Haven with negative theta-e instability and moisture to work with.
It is interesting to see the NBM, potentially led by the ECMWF, has
an area of 50 percent chance of 4+ inches of snow with a bulls-eye
between Allegan and Kalamazoo with 20 percent probability leaking
into Cass and Berrien counties MI during a 24 hour period ending 7pm
Friday. Meanwhile, other model output keeps things much lower with
the Kuchera and 10:1 ratios. Delta T values reach 25 to 30 degrees
at their peak Friday, especially if greater mixing up to 700 mb/2.5-
3 km can be achieved. Trends moving forward will need to be watched
as this event gets closer, especially with after Thanksgiving travel
through there on major highways. Highs will be much cooler Friday
through Monday with a few areas barely reaching 32 for a high. The
moisture for this initial lake effect event lifts out Saturday as
high pressure passes by to our south and the sheared out area of
vorticity lifts northward.
Then, a clipper system rides the base of the trough from the
Northern Plains into the Southern Plains. This re-establishes the
sheared vorticity area near Lake MI and may reinvigorate the lake
effect machine Sunday into Monday. Surface high pressure returning
Monday night allows trajectories to obtain a southerly direction and
an end to the lake effect. High temps Tuesday reach and may surpass
32 degrees through the area.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1156 AM EST Tue Nov 26 2024
Mainly clear skies within the critical TAF period as the
terminals will be between weather systems. High clouds are
already spreading over the mid-Mississippi River Valley
associated with low pressure over the central Rockies, parallel
to a sagging stationary front across the Northern Plains. High
pressure in the vicinity of this boundary will promote VFR
conditions through the TAF period. As the low ejects from the
Rockies, a gradual decline in ceilings is probable just beyond
this TAF period perhaps with some rain showers at KFWA while
KSBN is likely dry.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for LMZ043-
046.
&&
$$
DISCUSSION...Roller
AVIATION...Brown
Source: IWX issues Area Forecast Discussion (AFD) at Nov 26, 3:33 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202411262033-KIWX-FXUS63-AFDIWX)
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