The main focus during the end of the week and into the upcoming
weekend remains on the potential for another round of
accumulating lake effect snow (potentially a long-duration
event) as another sprawling ~1050 mb arctic high descends out of
Saskatchewan and Manitoba late Thursday night into Friday. As
this occurs, 850 mb temperatures are forecast to drop to around
minus 20 C, which in turn will result in building inversion
heights over the lake. LES parameters certainly look sufficient
to support periods of more intense lake effect snow, with lake-
induced ELs nearing 9-10 kft at times, especially through Friday
with 850 mb temps forecast to warm through Saturday.
Initial LES looks to develop late Thursday night into early
Friday morning. It`s possible that this initial activity has a
somewhat difficult time organizing given some degree of wind
shear in the boundary layer as a synoptic scale trough pivots
southwest out of the Upper Great Lakes. By later Friday night
and Saturday, however, guidance depicts generally lessening
shear as the bulk of the atmospheric flow shifts northeasterly.
Guidance then depicts LES organizing into a single dominant band
during this time as low-level convergence maximizes down the
long axis of the lake. During this time, ELs are forecast to
fall a bit as 850 mb temps warm, which may have a bit of a
modulating effect on LES intensity. That said, given the progged
increasing convergence, even 6-7 kft ELs will be more than
sufficient to support periods of heavier snowfall.
At this point, it remains too early to hone in on specifics, but
guidance trends continue towards an impactful period of lake
effect snow in our area, including Chicago, parts of NE and
east-central Illinois, and NW Indiana from late Thursday night
through Saturday night, and possibly even through Sunday.
Guidance at this time does indicate the potential for quite a
bit of band wobbling, which in turn could limit residence times
and overall totals, but a more quasistationary north-south
oriented band is also advertised (CMC, UKMET for example).
Temperatures in the teens and single digits will have the
potential to exacerbate impacts due to a very light/fluffy snow
and lessened effectiveness of road treatments.