CAE's latest thoughts:
Area Forecast Discussion
National Weather Service Columbia SC
335 PM EST Tue Jan 18 2022
.SYNOPSIS...
High pressure and a dry airmass will remain over the region
through Wednesday, producing more typical January weather. A
cold front moves into the area Thursday bringing a good chance
of rain. Friday into the weekend look very unsettled with a mix
of wintry weather expected through Saturday. Conditions improve
Sunday into the first part of next week. .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Wednesday looks to be the primary transition day as the surface
high pressure center will slowly shift offshore. Southwest
surface and 850mb flow will ramp up throughout the day as the
high exits and central CONUS shortwave approaches allowing
modest moisture into the area with dew points climbing into the
upper 30`s and low 40`s. Cloud cover is expected to persist
throughout the day given the overrunning and moisture return at
low-mid levels. High temperatures will finally jump above
average for the first time in several days, generally in the low
60`s across the area. Southwest flow will continue ahead of the
front associated with the shortwave off to the west into
Wednesday night. There is good consensus across guidance on the
overall timing of the front, entering the forecast area from the
northwest around 12z Thursday and progressively sliding
southeast through the area by 18z. Overall precip totals will be
fairly low given the mountain interaction and general lack of
synoptic lift. The arctic airmass begins filling in behind this
front and this is where things start to get more uncertain. The
front is expected to slow and stall as a weak area of low
pressure develops along the Gulf coast and northern Florida.
Guidance is somewhat consistent is showing PoPs continuing into
late Thursday as the front stalls but the interaction with the
diving cold air is the primary uncertainty. Regardless of model
solution, the surface layer air should remain too warm for any
frozen precip until early Friday morning. Some wintry PoPs begin
across our extreme northern counties between 06z and 12z
Friday. .LONG TERM /FRIDAY THROUGH TUESDAY/...
While a somewhat clearer picture has developed in the last few
model suites, there is still relatively high uncertainty in the
Friday-weekend system will play out. The mid-upper level flow is
inherently chaotic and unstable for run to run consistency with
numerous shortwaves embedded across the general southwest flow
across the CONUS. So this type of uncertainty is annoyingly
expected given the pattern. Each global operational model and
its corresponding ensemble are depicting somewhat unique
solutions on how both the upper level pattern will develop over
the northeast and southwest CONUS, and how the low pressure
center will develop along the stalling cold front. Friday
appears to be coming into clearer focus, albeit slowly, with
NAM, ECMWF, and GFS all developing a broad shield of overrunning
over top the southward rushing arctic airmass as strong south-
southwest flow ramps up. Associated ensembles are still quite
scattered in timing and intensity of this precip, but at least
there is a decent signal compared to 24 hours ago. Obviously
this interaction between a thin cold layer, sharp mid level
trough, strong upper level jet, and weakly developing low
pressure is tricky and guidance likely not get a good handle on
it for another day or so. So current thinking on Friday wintry
precip is increasing slightly in confidence but intensity
remains a big question mark as does spatial extent. All wintry
precip types are possible at this time across the fa,
particularly sleet and freezing rain. We should start to see
better agreement in the next suite or two over the specifics of
the Friday event.
More uncertainty develops for how the shortwave over the
southwest CONUS and western Gulf will track east and then
interact with stalled front. The GFS and associated ensembles
are more aggressive with pushing the shortwave east and spinning
up the stalled front in the Gulf. This then swings another
batch of wintry precip into the fa Saturday and would
dramatically increase impacts. The EC and Canadian ensembles and
operational are much more suppressed with this second
shortwave, so impacts would be minimal or none. Again with the
complexity of the 500 mb pattern, this will be inherently
unstable run to run so not expecting consistency for another run
or two.
In general, there is a large spread of possible outcomes with
this event ranging from mild inconvenience to highly impactful
winter storm across the Midlands and CSRA.
Cold temps fill in behind this regardless of what plays out and
the long term is expected to remain well below average.