IWX issues Area Forecast Discussion (AFD) at Dec 18, 6:20 AM EST960
FXUS63 KIWX 181120
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
620 AM EST Wed Dec 18 2024
.KEY MESSAGES...
-There are chances for rain and snow showers today, with highs
in the 30s and cloudy skies. Little to no snow accumulation is
expected.
-Dry conditions prevail from tonight into late Thursday
afternoon, then snow is expected Thursday night into Friday.
Snow accumulations of 1 to 3 inches are possible by Friday
evening. Additional lake effect snow accumulations are possible
into Saturday evening.
-Highs will be in the 30s Thursday and Friday then fall into the
20s and low 30s for the weekend. Lows will be in the teens and
20s, coldest Saturday night and Sunday night.&&
.DISCUSSION...
Issued at 617 AM EST Wed Dec 18 2024
Our moisture starved cold front associated with low pressure just
north of Lake Huron extends down from the Mackinac Bridge through
southern Lake Michigan and IL. To the south (generally brushing our
far southeast CWA) is another surface low moving into KY as of this
writing. There is a healthy squall line along the cold front
associated with this system to the south, with an abundance of
lightning. As we anticipated in earlier forecasts, a majority of the
deeper moisture transport was hogged up in that southerly system, so
while we have some mid-level moisture to work with along the
incoming cold front, it's not probably going to produce a lot of
QPF. Have pops near Lake MI early this AM then have it gradually
diminishing as the front moves eastward, the moisture transport
dwindles, and subsidence from a ridge to the west builds in.
There was a lot of conflicting guidance regarding the POPS for
today, with some of the models developing more rain/snow along
the front as convergence increases between the phasing systems
through the afternoon. Many of the high res models were slow to
catch on to the band developing in the first place when it did,
so confidence in the evolution this morning isn't the highest.
Regardless, despite seeing reflectivity on radar there isn't
much reaching the ground- particularly in the central CWA in
between the system to the southeast and our incoming front. Any
accumulation in regards to snowfall will be limited today (less
than half an inch) as we mix with rain or drizzle at times.
Otherwise, expect cloudy skies with highs in the 30s and lows
tonight falling into the 20s. Light flurries are possible near
Lake MI in the evening, but otherwise dry conditions prevail
until at least late Thursday afternoon/evening.
Thursday night into Friday we'll see a clipper swing down into the
Great Lakes and it will likely bring us some light accumulations in
the 1 to 3 inch range (highest totals northwest near Lake MI into
Fort Wayne-with 2.3" forecast for KFWA specifically). Northwest
winds behind the system Friday afternoon will gust to around 20
to 25 mph at times with temperatures in the 30s during the day.
Overnight, we'll see a transition to lake enhanced snow as we linger
beneath cyclonic flow aloft and temperatures plummet into the teens
and 20s. There is still low confidence in the lake effect forecast
into Sunday, as models continue to refine the major synoptic
features and flow. Right now it looks like the set up favors an
initially N-S/NNW-SSE oriented band off Lake MI (La Porte, Porter
counties in IN). The ECMWF would favor additional accumulations in
our area through the weekend for N-NW/S-SE oriented bands but the
GFS forces the band over to the western side of Lake MI/hugging the
Chicago shoreline vs being on our border. Something to watch! For
now have 1" or less for just Friday night-Sat AM-with the best
totals focusing along the shoreline (over Michigan City, IN). Highs
this weekend will be in the 20s and 30s, and lows will be in the
teens and 20s, coldest Sat Night/Sun Night.
High pressure builds in eventually Sunday with a pretty decent ridge
in place (especially if ECMWF is correct). Highs early to mid next
week look to climb back into the mid to upper 30s and 40s. An upper
level low/surface low will cross Upper MI/Northern Lower MI Monday
into Tuesday, bringing a cold front into our area and chances for
rain/snow. A second system develops to our south along the cold
front (once again), and may impact our southern CWA Wednesday
depending on how the large scale pattern evolves.
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1157 PM EST Tue Dec 17 2024
Shortwave disturbance over KS early this morning will eject ewd
through the lower OH valley ahead of nrn stream disturbance digging
sewd through the nrn lakes. This puts the area in no mans land as
tongue of decent low level moisture return gets shunted south and
primary wave induced forcings pass north and south. VFR to start
will however dwindle into low MVFR/high IFR range within shallow
post cold frontal moist advection toward or just after daybreak.
Some slight improvement expected with mixing by aftn yet MVFR cig
heights will persist.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 3 PM this afternoon to 3 AM EST
Thursday for LMZ043-046.
&&
$$
DISCUSSION...MCD
AVIATION...T
Source:
IWX issues Area Forecast Discussion (AFD) at Dec 18, 6:20 AM EST---------------
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