Deep South Winter Storm 1/20 - 1/22

Where are we in relation to the LRC theory and this event?

It shows deeper dives as the West Coast ridge becomes established the last few days of January into early Feb. LOL

The LRC will then recycle around February 5th and that’s when the heat is on.

From the NWS Mobile afternoon discussion:


Thursday night strong cold advection will be ongoing at the
surface through about the 900mb level, with temperatures crashing
into the lower 30`s by Friday morning and surface dewpoints
tanking into the middle to upper 20`s. The atmospheric profile
remains moist at and above the 900mb layer as continued
moisture/theta-e advection continues in the mid to upper levels of
the atmosphere with the main shortwave approaching from the west.
This is going to set the stage for precipitation to develop as
warm gulf moisture lifts above the surface cold dome in place.
This process, known as overrunning, will help to produce a
prolonged period of precipitation following the frontal passage.
Initially it may be too dry within the cold dome to get
precipitation to reach the ground Thursday night, however with
continued precipitation falling through the column into the cold
dome I anticipate wet bulb processes to do some work and help
moisten the low levels to the point of precipitation reaching the
ground. Now here is the real kicker, most global models have
continued their tune of it being too dry to allow for this to
occur. This has changed with the 12z ensembles of the GFS/CMC
where greater precipitation amounts are being depicted Thursday
night into Friday. The NAM has been the most aggressive and is an
extreme outlier with overrunning precipitation so far, depicting
overall qpf amounts exceeding 0.5" in spots. It is possible that
most of whatever precipitation falls northwest of the I-65
corridor late Thursday night into Friday morning will be in the
form of freezing rain. Surface wetbulb temperatures in the upper
20`s to lower 30`s and snow aloft falling into a 5 to 10C warm
nose between 900 and 700mb should favor all liquid precipitation,
and where surface temperatures are below 32F some freezing rain
accrual can be expected. For now, anticipating around one or two
hundredths of an inch of freezing rain accrual for areas along and
northwest of the I-65 corridor. It is entirely possible that
enough cold air is in place and enough precipitation continues
into the day Friday that some locations may continue to deal with
potential for freezing rain and subsequently higher freezing rain
totals. This is of rather great uncertainty, and for now I have
opted to keep light rain in the forecast for Friday into Friday
evening with surface temperatures above freezing. I will re-
emphasize that the forecast Thursday night into Friday evening is
of very low confidence and subject to change. At the same time,
subtle differences in surface temperatures will make a worlds
difference between a non-event and a high-impact event. It`s
important to remain weather aware and monitor our latest forecasts
for any changes. For now, expecting temperatures Friday to rise
into the middle to upper 30`s, with lower 40`s southeast of the
I-65 corridor. Low temperatures tank Friday night into the lower
to middle 20`s over interior portions of southeastern MS and
southwestern AL, with upper 20`s to lower 30`s elsewhere. MM/25



&&

.EXTENDED TERM /Saturday Through Tuesday/...The extended forecast
really isn`t much simpler. Rather low confidence persists into
Saturday stemming from the Friday event. A surface low develops
over the northeastern Gulf of Mexico Saturday as broad upper level
troughing shifts across the eastern CONUS Saturday into Sunday.
This low will be responsible for continuing to throw overrunning
precipitation our way Saturday, and it isn`t out of the realm of
possibility that there continues to be a threat for wintry
precipitation given the cold surface temperatures. This is of even
greater uncertainty given the propensity for low level warm
advection to attempt to establish itself, and the general track of
the developing surface low will dictate this. Beyond Saturday, a
rather active upper level pattern continues with another shortwave
tracking across the area sometime Monday or Tuesday. There is
considerable run to run consistency issues between forecast
guidance. It seems most reasonable that a slight chance to chance
of showers overspreads the area Monday night into Tuesday. Expect
cold temperatures across the forecast area for much of the
period. Saturday and Sunday will likely feature highs in the
middle to upper 40`s, with lower to middle 50`s for Monday and
Tuesday. Lows will be very cold Saturday night, dipping into the
lower to middle 20`s northwest of the I-65 corridor, and middle
to upper 20`s southeast. A gradual warming trend is evident with
low temperatures into Tuesday morning, gradually rising to the
middle to upper 30`s. MM/25

21z RAP model also appears primed to move frozen precip into South LA.

The hi-res models have been trending more toward sleet/ice for most areas except for south of the Lake.

Not a surprise. It takes a very very rare setup for the SS to get any frozen precip.