IWX issues Area Forecast Discussion (AFD) at Jan 8, 8:05 PM EST
734
FXUS63 KIWX 090105
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
805 PM EST Wed Jan 8 2025
.KEY MESSAGES...
- Scattered to numerous snow showers persist into this evening,
mainly north of US 30 where light accumulations and minor
travel disruptions will be possible.
- Widespread light snow (1-3") Friday into Friday night, mainly
during the PM hours. Slippery travel conditions possible.
- Continued near to below normal temperatures through this
weekend.
- Arctic air and chances for lake effect snow and sub-zero wind
chills arrive for the first half of next week.
&&
.UPDATE...
Issued at 804 PM EST Wed Jan 8 2025
A well defined upper level short wave is currently making its
way across the southern Great Lakes this evening. This forcing
extends east across the eastern Great Lakes and is anchored
across the western Great Lakes by an upper speed max dropping
across Lake Michigan vicinity. Earlier regional radar mosaic
indicated stronger lake effect snow showers across west central
Lower Michigan, but over the past hour, some signs that dry air
entrainment is beginning to transition this band to more
cellular in nature. This should continue to be the case over the
next few hours as drier air continues to build in from the
west, and also as synoptic forcing wanes between 02Z-04Z.
Brief, heavier lake effect snow showers across Cass County MI
into western St. Joseph County MI could put down a half inch to
inch of accumulation through 03Z, but otherwise additional
accumulations across the area should be minimal. Some minor
travel impacts still possible, primarily across southern Lower
Michigan through 04Z. No significant changes anticipated to the
forecast at this time.
&&
.DISCUSSION...
Issued at 141 PM EST Wed Jan 8 2025
Scattered to numerous snow showers will persist this afternoon and
evening for locations mainly north of US 30. A potent mid level
shortwave dropping south through the area and an associated lake
enhanced plume/trough the culprit, with embedded lake effect
mesoscale vorticity centers and cloud tops into at least the
lower portion of the DGZ likely supporting brief heavier snow
showers within the trough axis. Additional light accums and
minor travel disruptions remain possible.
Ridging does build in through the column overnight into Thursday.
This will bring an abrupt end to the snow shower activity with some
sunshine anticipated. Enjoy it because clouds and light synoptic
snow move in for Friday and Friday evening in advance of an
amplifying positively tilted upper trough and associated cold front.
Decent isentropic ascent and moisture advection (2-2.5 g/kg in the
85-7H layer) under a potent 150 kt plus upper jet crossing the OH
Valley should support increasing coverage of light snow during this
time. GFS ensemble probs are near 90%, and ECMWF ensemble 60-70% for
a tenth of an inch or more of QPF with the bulk of guidance
generally suggesting a 1-3" type snowfall.
Deep trough will exit east in time for the weekend with dry and
seasonably cold wx Saturday into most of Sunday. A hybrid clipper
system and arctic front arrives late Sunday into Monday with the
next opportunity for a nuisance light snow (WAA driven followed by
frontal forcing). Models then in general agreement with a shot of
blustery/cold wnw winds Monday through Wednesday with chances
for sub-zero wind chills and periodic bouts of lake effect snow
for wnw flow snow belts.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 624 PM EST Wed Jan 8 2025
The bulk of lake effect snow showers have diminished at KSBN,
with chances persisting at KFWA until 02 or 03Z. The next strong
upper level vort max is dropping south across the southern Great
Lakes tonight, more tied to the nose of a 90 knot upper jet
streak. This synoptic forcing has enhanced the lake effect snow
showers, particularly across west central Lower Michigan.
Slight backing of low level winds and entrainment of drier low
level air from the west should keep the potential of the heavier
lake effect snow showers to the north and east of the terminals
this evening. Passage of this vort max should see an
accompanying decrease in lake effect snow shower coverage
overnight along with scattering low clouds. Conditions should
remain VFR this period outside of the potential of brief cigs
below 3000 feet through 01Z or 02Z this evening at KFWA. Winds
to become south around 10 knots on Thursday as low level ridge
drops across Ohio Valley.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Marsili
DISCUSSION...Steinwedel
AVIATION...Marsili
Source: IWX issues Area Forecast Discussion (AFD) at Jan 8, 8:05 PM EST (https://mesonet.agron.iastate.edu/p.php?pid=202501090105-KIWX-FXUS63-AFDIWX)
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