National Weather Service Jackson KY
500 PM EST Thu Jan 13 2022
.LONG TERM...(Saturday through Thursday)
Issued at 500 PM EST THU JAN 13 2022
Lots of uncertainty remains with the well-advertised weekend
system. The systems upper level and surface low track would
typically favor heavy snow across our area this time of the year.
However, this is not a slam dunk scenario this time due to the
complex low structure, which in many solutions could lead to an
above-freezing warm nose intrusion and possible downsloping off of
the Great Smoky Mountains. These poorly resolved issues continued
to plague the 12z NWP output. Model agreement should improve over
the next 24 hours as the system, which just came ashore the
Pacific Northwest, is better sampled by RAOBs and surface-based
obs.
The latest model suite analysis shows our system of concern over
the South Central US by 12z Saturday. The 545 dam low, embedded
with in a positively tilted trough extending SW from the Great
Lakes, will be spinning over KS/OK while supporting a surface low
situated near/over the Ark-La-Tex. Meanwhile, cold Canadian high
pressure will be over the Eastern Great Lakes/Ottawa Valley. Cold
northeasterly low-level flow on the periphery of this high will
seep into the Ohio Valley through the day on Saturday.
Simultaneously, mid-level WAA should develop ahead of the system
leading to increased mid to high cloud cover. Cannot rule out a
bit of light snowfall from this mid-level forcing but whether that
actually reaches the ground will strongly depend upon how dry
lower levels become under the shallow CAA -- some guidance
suggests teens or single digit dew points filtering into the
Commonwealth by Saturday evening.
Heading through Saturday night and early Sunday morning, WAA will
intensify ahead of the surface low as it moves into the TN valley
and occludes. A new triple point low takes shape along the Gulf
Coast. A warm nose attempts to push northward into Eastern
Kentucky early Sunday as the original occluded low drifts into
eastern TN and fills. The warm noses depth and degree of warmth
is still very uncertain and just a few degrees difference would
support anything from rain to freezing rain, sleet, and/or snow.
The warm nose might be enhanced by the southeasterly downslope
flow off of the Southern Appalachians as well. The remnant surface
low and warm nose fades later in the day as low-level winds turn
more easterly in response to the passage of the 850 mb low.
Meanwhile, the triple point low becomes the primary surface
circulation and rapidly consolidates/deepens over the Carolinas
under the favorable right entrance region of a 300mb jet. As this
occurs, several of the models hint at the potential for
frontogenetic banding along the back size of the system,
associated with a deformation zone. This deformation band,
depending upon where it occurs, could be best opportunity for
locations to pick up a heavy accumulating snow later Sunday
afternoon and evening. Snowfall with this system should be fairly
heavy and dense (low SLR) given the likelihood for a deep riming
and aggregation layer below 700 mb. Needless to say, the weekend
forecast remains low confidence at this time.
Once the system departs early Monday, another quick-moving
shortwave will bring the potential for some light precipitation
later Monday -- likely in the the form of upslope snow showers
and flurries on modest west to northwest CAA. Surface high
pressure returns with quiet and seasonably cool weather by
Tuesday. The next chance for rain and snow returns Wednesday or
Thursday with a cold front and postfrontal upslope. High
temperatures will be very typical of mid January with highs mainly
in the 30s, except in the 40s on both Tuesday and Wednesday
afternoon. Lows will mostly be in the 20s. The colder sheltered
valleys could drop into the teens Monday night and early Tuesday
morning.