Jump to content

snowlover2

Members
 View Profile  See their activity

  • Posts

    2,731

  • Joined

  • Last visited

 Content Type 

Posts posted by snowlover2

    “Let’s Talk Winter”

    in Lakes/Ohio Valley

    Posted

    Quote 
    .LONG TERM /FRIDAY THROUGH TUESDAY/...
Deep, but unphased, troughing will be positioned near the NE coast
of the CONUS for the start of the period with NW flow aloft over the
OH Vly transitioning to more quasi-zonal flow through the day on
Friday. The final day of the workweek will have the region squeezed
between the system exiting the eastern seaboard and the next one in
line, which will be progressing quickly from the Upper Midwest to
south-central plains Friday into Friday night.

By this time, attention will be squarely focused on the second of
the aforementioned systems -- the one tracking almost N-S through
the central plains on Friday. Longer-range guidance remains in
relatively good agreement showing this midlevel S/W transitioning to
a closed low by Saturday morning in the vicinity of KS/OK. This
feature will be responsible for a rather impressive band of wintry
pcpn on the NE periphery of the track, which will likely position
itself from MN to MO during this time period, with the ILN FA & OH
Vly staying pretty confidently to the east of any pcpn through the
daytime on Saturday. Cannot completely rule out a few flurries,
perhaps, near/south of the OH Rvr by later Saturday evening, but the
guidance trend in taking this feature further west has left us with
pretty high confidence in a dry Saturday here locally as highs
ranging from the mid 20s to lower 30s (N-S, respectively) locally.

This is a complex winter system that will likely evolve from the
ArkLaTex region E/NE through the TN Vly and eventually into the NE
CONUS from Saturday night through Sunday. While it seemed like
previous data runs had all but written off any notable impacts
locally, the latest trends, both deterministically and from an
ensemble perspective, suggest this perhaps may not entirely be the
case. GEFS/GEPS/EPS ensemble means have all taken considerable jumps
further to the NW with the boomerang re-curvature of the system from
the northern Gulf to near/west of the spine of the Appalachians
before eventually the primary energy transfers closer to the coast,
with the inland low becoming somewhat orphaned by later Sunday.

There are several things to break down regarding potential
accumulating wintry pcpn locally late Saturday night through Sunday.
The first, and perhaps most important, aspect will be the timing of
the transfer of energy from the initial inland low to the coastal
low sometime between Saturday night and Sunday night. The prevailing
guidance would suggest occlusion of the initial sfc low in MS/TN
Saturday night with the development of a secondary low toward SC by
Sunday morning. The occlusion of the low would signal a gradual loss
of baroclinicity associated with the inland low, which guidance
suggests may track from TN NE through the ern OH Vly during the day
on Sunday. The occlusion of the LL system, prompting the loss of
baroclinicity, due in part of the lack of arctic air building in
quickly from the NW, suggests a gradual decrease in lift/LL
convergence associated with any banded pcpn. In fact, there would
likely be frontolysis underway with this system as it tracks closer
to the ILN FA Sunday, leading to uncertainties in just how
widespread and/or intense any wintry pcpn may be. There is no sharp
temp gradient or strong frontogenetic axis to work with here,
especially as the coastal low becomes the primary one on Sunday with
explosive cyclogenesis occurring in the mid-Atlantic region.

With all of this being said, it cannot be ignored the obvious and
sudden shift to the NW with the inland low tracking to the NE
near/west of the Appalachians -- a climatologically-favorable track
for accumulating snow in the OH Vly. Although there remains some
positional variability that will ultimately play a significant role
in the evolution of the system and potential impacts locally, this
trend has shown itself almost unanimously across the GEFS/GEPS/EPS
ensemble quites. Most guidance would suggest that the column may get
/just/ warm enough to promote a mix of rain/snow during the
afternoon in N KY and south-central OH, with the predominant p-type
remaining snow elsewhere with a subzero (C) profile and ample
saturation in the DGZ coinciding/overlapping with some vertical
motion with the mid/upper level low tracking through the region.
Ensemble mean probabilities continue to suggest increasing potential
for light accumulations of snowfall (1"/3") or less near/SE of the I-
71 corridor on Sunday. These ensemble means do assume a 10:1 SLR,
which would likely just a bit higher than we would be dealing with
(we may be closer to 8:1 or 9:1, depending on location).
Nevertheless, the trends with the overall closed low tracking
further to the N/W, with implications on the track of the inland
(filling) low, have raised PoPs above the blended guidance for
Saturday night through Sunday and will introduce a broad-brushed HWO
mention for now. Certainly we are still several model runs away from
being able to hone-in on whether this system will be more of a
nuisance, or perhaps a bit more significant, so we will continue to
adjust the forecast as trends and patterns dictate.

Another "kicker" S/W will pivot SE from the Upper Midwest to the OH
Vly immediately behind the "main" system for Sunday night into
Monday morning. This system may have enough additional lift to
generate some snow showers during the day on Monday as temps remain
several degrees below seasonal norms. Have not added slight chance
PoPs yet for this time period as confidence remains low at this time
in the exact track and strength of this feature. But some lake-
effect/enhanced snow showers N of the immediate local area seem like
a good bet at this juncture for the start of the workweek.

    From ILN

×
×
  • Create New...