• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Wintry January 21-23 2025

CAE:
THE LATEST 00Z MODEL GUIDANCE HAS TRENDED FURTHER INLAND WITH
THE WINTRY PRECIPITATION, MAINLY SNOW LATE TUESDAY INTO
WEDNESDAY. THE CANADIAN MODEL CONTINUES TO BE THE MOST
AGGRESSIVE WITH THIS STORM BUT THE LATEST GFS AND ECMWF ARE
SUGGESTING A STRONGER AND MORE PHASED SYSTEM (EARLIER IN TIME)
BETWEEN THE NORTHERN STREAM TROUGH MOVING OUT OF THE NORTHERN
PLAINS AND THE TROUGH MOVING OUT OF THE DESERT SOUTHWEST. THE
BASE OF THE UPPER TROUGH MOVES INTO THE GULF OF MEXICO. THIS
LEADS TO SURFACE LOW DEVELOPMENT IN THE GULF OF MEXICO WHICH
TRACKS EAST ACROSS FLORIDA TO OFF THE GA/SC COAST TUESDAY NIGHT.
THE ECMWF LOW CENTER IS CLOSER TO THE COAST THAN THE GFS. THE
ECMWF ENSEMBLES HAVE TRENDED MORE TOWARD THE CANADIAN ENSEMBLES
WITH A GREATER THREAT OF WINTRY PRECIPITATION. THE MODELS
CONTINUE TO POINT TO HIGHER PROBABILITIES OF ACCUMULATING SNOW
SOUTH AND EAST OF I-20, BUT NOTE PROBABILITIES APPEAR TO BE
INCREASING TO THE NORTHWEST.
Click to expand...
 
Shawn said:
Big time Westward jump vs just it's previous run not long ago. Very interesting.

I'd like to note, that if it still holds true, the GFS has had a history of being too fast with the Northern Stream. If that is still the case, it may take a little while for it to correct with it. In other words 06z might not be amazing changes, but don't fret.
Click to expand...
Looks like your gonna be right here
 
Brent said:
Winter Storm Watch in Louisiana already. 5-7 inches possible
Click to expand...

11c7f5367764afacd4eb6f06bfaa2495.png

Winter storm watch posted for the southern half of LA, extreme eastern TX, and extreme southern MS


Sent from my iPhone using Tapatalk
 
Upstate, SC Model Update:

Major hits:
00z CMC - significant accumulations (holding steady)
00z CMCE - 5 inch mean (holding steady)
00z CFS - significant accumulations (holding steady)
00z EPS - 2.5-3 inch mean (trending much better)
06z NAM - past it's range but was gonna be a banger
00z JMA - only goes out to 72hrs, but was gonna be a banger
00z NAVGEM - moderate accumulations

Light hits:
00z Euro - light accumulations - (1 inch) (trending better)
06z GFS - light accumulations - (1/2 inch) (holding steady)
06z GEFS - .3 inch mean (trended worse)

Complete Whiffs:
06z Icon - snow along coast (trending better)
00z Euro AI - snow along coast (trending better)
18z GFS graphcast - snow along coast
00z ukmet - snow along coast (trended better)
00z Spire - a few flurries (trended better)
 
I know I sounded like I was beating a dead horse these past couple of days but this is why you can’t just look at the pretty colorful maps to decide if you have a chance. Overrunning and WAA always trend more NW. 500mb jet screaming SW to NE over the gulf into a very cold air mass just screams more precip. It’s really the first thing you learn about weather. When you mix warm moist air and cold dense air together you get precipitation. It’s just physics at that point. Hopefully we can continue these trends but we really don’t need the perfect h5 look to score here. Just need to get enough lift to let overrunning an arctic boundary do what it does best here. But it’s really good to see the N/S continue to slow down as it trucks east which is a typical thing that happens. That gives the CMC big dog looks a much better chance of verifying
 
Peachtree City (ATL)
Hazardous cold to start the week -- portions of north Georgia
are likely to see dozens of hours below freezing Monday through
Wednesday

- Monitoring increasing chances for winter weather Tuesday into
Wednesday

We enter the extended range on Monday with north and central Georgia
freshly post-front, and the center of a strong (1035+ mb) Arctic
surface high nudging toward the Eastern Seaboard. With a reinforcing
shot of cool, dry air rounding the base of the broad mid-level
trough situated across southern CONUS, the stage is set for a
hazardous cold snap. The airmass that is progged to settle in across
the South originated from over Siberia, and it will certainly feel
like it. Highs on Monday and Tuesday will be in just the 20s to near
40 areawide (20-28 degrees below average) -- with highs in the teens
possible on Monday for portions of northeast Georgia at elevation.
Lows will be positively frigid, in the single digits to lower 20s
each morning through Wednesday. Lingering breezy to gusty winds in
the wake of the front Monday will support morning windchills as much
as 5-10 degrees below zero for portions of northeast Georgia, and in
the single digits to teens elsewhere. We`re looking at a slam dunk
for Cold Weather Advisory conditions pretty much everywhere, but
cannot rule out the necessity for Extreme Cold products for the far
northern part of the forecast area. Some areas along and north of
the I-20/I-85 interchange may not see real chances for temperatures
to rise above 32F until Wednesday. Proper precautions will need to
be taken to prepare for an extended period of frigid temperatures --
remember the 4 P`s of winter preparedness (people, pets, pipes,
plants) and be sure to leave your faucets dripping and under sink
cabinets open before heading to bed.

Beyond Monday, the elephant in the room is increasing confidence in
some type of wintry precipitation impacting portions of north and
central Georgia from Tuesday afternoon through Wednesday morning.

What We Know:

1) Unlike the previous storm system, greatest impacts are likely to
be felt further south. WPC`s Key Messages yesterday evening painted
a 40% chance of moderate winter impacts primarily along and just
slightly north of the Columbus to Macon corridor. Highest GFS and
Euro ensemble probabilities of >=1" of snow also highlight areas
south of the Metro. Some especially interesting probabilities to
note from the 01Z (most current as of the time of writing of this
AFD) NBM run:

- Probability of at least 1.5" of snow in the 24 hour period
ending 7AM Wednesday for Columbus/Macon corridor: ~40-43%

- Probability of at least 2" of snow in the 24 hour period
ending 7AM Wednesday for Columbus/Macon corridor: ~30-35%

- Probability of at least 2.5" of snow in the 24 hour period
ending 7AM for Columbus/Macon corridor: ~30%

2) 24-36 hours of unseasonably cold conditions before precipitation
onset will support very cold ground/road temperatures, allowing for
impacts to ramp up quickly. It will not take much accumulation to
create hazardous travel conditions, and what accumulation does fall
is likely to linger courtesy of the cycle of diurnal melting (highs
in the 30s Wednesday, near 40 Thursday) and re-freezing (lows in the
teens Wednesday night, 20s Thursday night).

3) Our initial airmass looks to be much drier than January 10th`s.
We are currently forecasting dewpoints in the single digits to teens
areawide mid-morning/early afternoon Tuesday. This increases the
potential for wet-bulbing (evaporation of precipitation falling into
a drier airmass removes heat and introduces moisture, tugging
temperatures down and dewpoints up), which could result in
temperatures cooler than forecast.

4) The dominant p-type at this time appears to be snow for a
combination of the above reasons, with chances for freezing
rain/sleet/a wintry mix relegated to our far southern/southeastern
tier. At this time, any ice accumulations are unlikely to be as
impactful as forecast snowfall, but things can and will change over
the next several days as features become better resolved.

5) The 00Z runs of the GFS and Euro ensembles have trended wetter
than their 18Z counterparts (with the GFS serving as the theoretical
floor for this event). The Euro ensemble has also trended toward a
broader and higher snow accumulation footprint, and progs the onset
of winter precipitation to be earlier than the GFS (late
morning/early afternoon vs. mid-to-late afternoon, respectively).
The Canadian ensemble continues to be the coldest and snowiest
solution, and remains our far upper bound/ceiling for this event.
Our chances of a non-event precipitation-wise thus appear to be
lower.

What We Don`t:

1) How much wet-bulbing will occur -- could have a large impact
on who receives snow and just how much (we saw the upper bound of
wet- bulbing with the band of heavy snow that set up across the
Metro last week, and dewpoints this time around are forecast to be
even lower.

2) Exact accumulation amounts. This will depend heavily on
temperature profiles, the number of p-types, and the placement of
any surface features. Once we introduce HiRes guidance into the
mix (the next day or so) details will be able to be expounded
upon.

Given remaining uncertainty (coupled with the knowledge that
ensemble guidance overall has trended toward at least SOME snowfall
for much of the area, with higher totals the further south you go),
feel that the NBM continues to have a decent handle on the forecast.
Interests in the Atlanta Metro and points further south -- and
especially areas along and south of a line extending from Columbus
to Macon -- should keep a close eye on the forecast. If trends hold
(BIG if), this could pan out to be one of the more impactful
southern/coastal winter storms in recent memory. Stay tuned.
 
GSP much more conservative as compared to CAE and Peachtree City in regards to precipitation area wide

As of 2:55 AM EST Saturday...the extended fcst picks up at 12z
on Tuesday with expansive upper trofing centered over the Great
Lakes taking on a more positive tilt. Over the next couple of days,
the upper trof will lift NE and move off the Atlantic Coast with
heights briefly recovering over the Southeast in its wake. Most of
the long-range guidance still suggests that another upper trof will
amplify across the central CONUS late next week as the period is
ending. At the sfc, a weak low will be spinning up over the Gulf of
Mexico as the period begins early Tuesday. This low is expected to
rapidly move NE and out over the Atlantic by early Wednesday. At
the same time, high pressure gets reinforced from the west across
our area and lingers thru at least Thursday. By the end of the
period late next week, most of the long-range guidance tries to
develop another low somewhere to our south, but the location and/
or timing remains unclear at this point. Overall, the long-range
guidance appears to be coming into better agreement wrt the low
on Tues/Wed. With the cold air in place during that time, it`s
still likely that any precip that does materialize would be snow
for our CWA, however PoPs remain capped in the chance range at
this time. The other main concern for the period will be the very
cold airmass that lingers for most of the period. This airmass
will produce very cold temperatures and wind chills, especially
across the mtns. High temperatures will struggle to get above
freezing both Tuesday and Wednesday across most of our CWA. Temps
are still expected to rebound somewhat on Thursday and Friday, but
still remain well-below climatology. Low temps early Tues, Wed, and
Thurs are expected to drop into the single digits in the mtns and
teens outside the mtns. Wind chill values will be dangerously cold,
especially across the mtns, with single digit to below zero wind
chills expected both Tues and Wed morning. Wind chills outside the
mtns are expected to range from the single digits to the teens each
morning. Thus, a Cold Weather Advisory looks likely for at least a
portion of our area during this period.
 
Looks like precip held serve or maybe was a little worse this run, but there was definitely more improvements at 500mb. Excellent run to hold on to the major flip at 00z... and plenty of time to tick north before go time. Hopefully the EPS will be similar to last run or better.
 
Seems like we're are down to two main scenarios and one less likely scenario:

1. We get a full alignment of the northern and southern pieces like the NAM/JMA/CFS/00z CMC show and we get widespread foot+ totals

2. The Southern piece gets left behind, but the northern trough digs deep enough for a light/high ratio event for most of us(and maybe precip trends a little better as we draw closer), and a major event for the coast.

Less likely 3rd option:
northern trough doesn't dig and we get a coastal scraper

I will take 1 or 2 and be happy. Just getting a coating on the ground with temps so cold will be awesome.
 
MHX tweaked the overnight AFD, they have a habit of reusing the same long term write-up for a couple shifts. Scenario 2 now appearing more likely with the EC op on board, <20% of B word, highest OBX.

SCENARIO #1 - The upper wave remains positively-tilted, and
progressive, as it traverses the Southeast U.S. This scenario
favors a weaker, faster, and more suppressed, low track from the
Gulf of Mexico east into the SW Atlantic. This scenario
supports the potential for a glancing swath of light,
accumulating snow, across parts of ENC, with the greatest risk
along the coast, and a decreasing chance further inland. In an
extreme case, the low may end up being too far suppressed to the
south and ENC would remain cold and dry with little winter
precip. Although this remains the most likely scenario, it has
ceded some ground in probability to the second scenario:

SCENARIO #2 - The upper wave slows down as it emerges out of the
Southern Rockies, and takes on a negative tilt before translating
across the Southeast U.S. This scenario favors a deeper surface low
over the Gulf, with a subsequent track closer to the Gulf and
Southeast U.S. coastline. For ENC, this would be the more impactful
scenario, as it would potentially open the door for a period of
moderate to heavy wintry precip. If a deeper low tracks too
close to the coast, however, that could introduce more warmer
air and less wintry weather, especially along the water. The
mod/heavy winter precip scenario has gotten a little more
ensemble support this morning, along with the 00Z ECMWF which
made a rather astonishing flip-flop from a suppressed low-snow
forecast at 17/12z (although a 1-run change does not
necessarily mean a trend).

In addition to potential snowfall, strong northerly winds are
forecast to develop as the pressure gradient north of the parent
low quickly tightens, and some ensemble members suggest gusts in
excess of 35 mph are plausible. If this does occur along with
any amount of snow, blizzard conditions may develop with the
highest risk along the Outer Banks. At this point the
probability of this is low (less than 20%).
Click to expand...
 
Last edited:
WeatherNC said:
MHX tweaked the overnight AFD long term , they have a habit of reusing the same long term write-up for a couple shifts. Scenario 2 now appearing more likely with the EC op on board, <20% of B word, highest OBX.
Click to expand...

Love seeing the B word even if it is probably gonna be confined to the IBX/OBX.....
 
06z EPS took a step back, but still much better than the runs from yesterday. Essentially we're trending towards leaving that southern piece behind, but digging the northern part enough for a light event for most of us, and a major event for the coastal plain/beach.

The problem is the while the northern trough has continued to tick west and deeper, so has the southern part. We need the southern part to stop trending west and give the northern part a chance to catch up to it. But ultimately we can't complain, still in the ball game with chance to go for a home run.
 
The 06z Rgem and 06z Euro are nearly indentical at 500mb. Yet look at the much more expansive precip shield developing on the rgem... that's where we need the Canadians to come through for us.

Edit to add: It looks like the rgem is digging the northern part just a tiny bit deeper over Kansas/Missouri, maybe that's the difference.

Screen Shot 2025-01-18 at 7.00.46 AM.pngScreen Shot 2025-01-18 at 7.00.11 AM.png
 
I think it also needs to be mentioned that for most this snow will most definitely fall at a 10:1 ratio or higher (I think higher) in most areas. This is more impressive than the snow itself across the South. I'd lean on higher totals than shown on model outputs.
 
Mitch West said:
I think it also needs to be mentioned that for most this snow will most definitely fall at a 10:1 ratio or higher (I think higher) in most areas. This is more impressive than the snow itself across the South. I'd lean on higher totals than shown on model outputs.
Click to expand...
Yep one of the rare times when we can legit question the ratios. The fact we have model output showing mid to low 20s and ripping fatties is what dreams are made of down here
 
Looks like 06z keeps my forecast alive after making me sweat some at 00z 😉

Shows how volatile the system is overall. One small step in either direction and you get a widespread different surface reflection.

Gotta see that 00z euro trend for a consistent few cycles before we call it a trend and it took a bit of a step back at 06z.

Long day ahead.
 
NickyBGuarantee said:
Looks like 06z keeps my forecast alive after making me sweat some at 00z 😉

Shows how volatile the system is overall. One small step in either direction and you get a widespread different surface reflection.

Gotta see that 00z euro trend for a consistent few cycles before we call it a trend and it took a bit of a step back at 06z.

Long day ahead.
Click to expand...

I wouldn’t hyper fixate on one particular run or two from a model suite. These kinds of storms usually trend in one direction inside the medium range
 
It cannot be overstated just how drastic the amping/NW trend has been in the Northeast with this weekends system. While I don’t think we are THAT drastic, please prepare yourself for continued shifts north and west all the way to Tuesday. They may come in 25 mile increments, but they are coming.
 
Last edited:
You must log in or register to reply here.
Back
Top