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Wintry January 21-23 2025

packfan98 said:
Well, we made it through the 12z models much better than I was expecting. @rburrel2 here's the CFS for your chart. It's on board!
snod-imp.conus.png
Click to expand...
CFS has been rock solid with this

1737057784147.png
 
So the only real model not on board even a little bit right now is the GFS right? If so hopefully it starts shifting back during the next few runs.
 
packfan98 said:
Well, we made it through the 12z models much better than I was expecting. @rburrel2 here's the CFS for your chart. It's on board!
snod-imp.conus.png
Click to expand...
That is snow depth. According to this model, my hypothetical snow doesn't melt away until 2/4/2025. That's on the ground for almost 2 weeks. Insane.
 
FFC discussion written by S Nelson...

.LONG TERM...
(Saturday morning through next Wednesday)
Issued at 251 PM EST Thu Jan 16 2025

A dreary start to the long term (Saturday) is expected with periods
of widespread light to moderate rainfall across much of the forecast
area through the day. A lack of surface instability or notable upper
level support should negate any thunder chances overall. Rain
chances will gradually come to an end from west to east Saturday
night as the system exits eastward. A rain/snow mix is not out of
the question at the highest elevations in northeast GA as
temperatures begin falling late Saturday night. Another wave of
energy swings through the base of the trough on Sunday and may
support post-frontal cloud cover and a low chance of flurries in
North GA during the afternoon. By Sunday night temperatures plummet
and frigid temperatures look to stick around through at least mid-
week...

Early next week, the forecast area becomes situated near the base of
a very broad 500mb trough. At the surface, latest global ensembles
are painting a strong arctic surface high sliding south into the
north-central CONUS by early next week. Energy rotating through the
base of the broad trough will act to reinforce the colder air which
looks to stick around through at least mid week next week. At the
time of this writing, we`re looking at temperatures Monday and
Tuesday 20 to 25 degrees below normal! Early morning temperatures
Monday through Wednesday are forecast to be in the teens to low 20s
and forecast daytime temperatures ranging from the mid 20s to mid
30s. Many locations (a line north of LaGrange to Griffin to Athens)
will struggle to rise above freezing. Breezy winds will not help the
situation at all keeping wind chills (aka the `feels like`
temperature) in the teens to single digit values Monday through
Wednesday. We are in the midst of winter and now is the time to prep
for the cold! Pipes, plants, pets and people!

Finally, the thing on everyone`s mind -- will another winter storm
impact portions of North and Central Georgia? Right now a few things
we can say...

-Latest deterministic and ensemble guidance is still highly
inconsistent with the bulk of the difference in outcomes depending
on the 500mb pattern. As we know here in the south, that placement
of upper level features as well as moisture can make or break a
winter wx forecast and is really what leads to the difficulties
surrounding it.

-Regardless of winter precip -- VERY cold and frigid temperatures
are highly likely next week. Please prepare now.

The pieces of this potential winter weather puzzle will continue to
come together in the coming days. So stay tuned for details
including exactly what, where, and how much...

&&

.AVIATION...
(18Z TAFS)
Issued at 1228 PM EST Thu Jan 16 2025

VFR conditions with SKC through the forecast. West winds will gust
to 24-28kts this afternoon before decreasing to 4-8kts after 23Z.
Light NW winds Friday morning will shift to SSE 4-7kts after 19Z
Friday.
Click to expand...
 
I went back and looked in our last storm thread, and in the 132-144hr timeframe... the Euro completely lost the storm. People weren't even posting snow maps for it b/c there was no snow to show. The only Euro related anaylysis was "improved but still has a ways to go" type posts. Just food for thought.
 
CAE with a good AFD on next week's potential:

.LONG TERM /SUNDAY THROUGH THURSDAY/...
- A very strong cold front arrives late Sunday as the lingering
surface low lifts northeast.

- Temps 15-25 degrees below average expected Monday through Thursday.

- Wintry precip chances continue for mid-week, but confidence
remains low.


The aforementioned surface low will lift northeast Sunday, followed
by the long discussed cold front. So there will not likely be
much of a diurnal swing Sunday as strong advection arrives
during the day. For Monday and Tuesday, the broad trough of the
Arctic airmass will settle into the central and eastern US. EC
and NAEFS are in excellent agreement over the general nature of
the initial airmass with highly anomalous cold, but not record
setting; temps 15-25 degrees below average yield highs in the
~30`s or low 40`s, along with overnight lows in the teens or low
20`. EC EFI continues to show EFI values between 0.9 and 0.95
Monday and Tuesday, but SoT is very low; a classic high
confidence in well below average, but not extreme temps, signal.
Regardless, the LREF output suggests we will approach or exceed
Cold Weather Advisory criteria at some point next week, so stay
aware of that potential new product issuance. Frozen pipes and
related impacts are becoming more likely during the mid- week
period as high temps will only make it above freezing for a few
hours each day.

Late Tuesday and into Wednesday is when the wintry precip potential
starts to enter the picture. Based on the last handful of guidance
suites, there is only a little more clarity on the possibility of
winter weather next week. Based on extent of the cold airmass and
associated surface high pressure, a suppressed low track
solution looks more and more likely with any wintry precip
chances actually increasing the further south you go in the
Midlands and CSRA. GEFS, and ECE to a lesser extent, have
trended towards this solution over the past several runs with
probabilities of 1" of snow in the central and northern
Midlands decreasing notably as the surface high settles into the
TN Valley. The GEFS and deterministic GFS remain the most
suppressed, with little-no precip into the forecast area. The
Canadian and at its ensemble are the other end of the spectrum,
with a northern GoM oriented storm track and significantly more
moisture overrun into eastern GA and SC; the EC and its
ensemble looks to be directly in the middle of these two
solutions over the last fews suites. The key feature of the
forecast is how the low level cold air and surface high pressure
is handled and how far southeast it can reach. How this high
pressure progresses is a result of extremely strong confluence
along the western flank of the trough main trough. And how this
confluence progresses is a result of a cutoff low in the Pacific
and its interaction with the main trough. A faster phase of
this cutoff drags the surface high further west, and a slower
phase causes the opposite. Unfortunately with chaotic nature of
cutoffs sitting under ridge axes, it will take several more days
to get consistent model guidance on this event. But generally,
the GFS-EC solution of a slower decay of the cutoff-ridge
pattern in the Pacific is more likely given typical model biases
in blocking patterns.

Overall, the forecast hinges on a notorious synoptic scale
interaction. But beyond that the general pattern is favorable
with a suppressed GoM storm track solution looking likely.
Whether that yields snow- wintry precip into the Midlands and
CSRA is highly uncertain at this time.
 
Cad Wedge NC said:
GSP says we are trending drier for next week. How much drier can you get when they already forecasted cloudless skies? Are they not looking at any models?
Click to expand...
No shocker there. They obviously think they know more than any of us all looking at the models. They are going to ride cold and dry until the bitter end and only forecast winter precip until they have to. I guess they have to have every model showing something but they are always so conservative when It comes to winter weather. I hope they can get brought back down to earth one day with a good snow storm.
 
J1C1111 said:
No shocker there. They obviously think they know more than any of us all looking at the models. They are going to ride cold and dry until the bitter end and only forecast winter precip until they have to. I guess they have to have every model showing something but they are always so conservative when It comes to winter weather. I hope they can get brought back down to earth one day with a good snow storm.
Click to expand...
I think a lot of the old school forecasting has given way to model watching. I'm not saying these guys do that. I don't know. But there's a lot of that that goes on out there, even in the pro world.
 
Rain Cold said:
I think a lot of the old school forecasting has given way to model watching. I'm not saying these guys do that. I don't know. But there's a lot of that that goes on out there, even in the pro world.
Click to expand...
If you go read the latest forecast discussion on NWS RAH you will see they only reference the Euro & GFS for their look ahead at this storm. They still are top scorers at this range--especially the 0z eps ens mean.
 
Rain Cold said:
I think a lot of the old school forecasting has given way to model watching. I'm not saying these guys do that. I don't know. But there's a lot of that that goes on out there, even in the pro world.
Click to expand...
Agree 100% RC..you never hardly hear "Analogs" any more. I know they aren't gospel but a great forecasting tool imo
 
Rain Cold said:
I think a lot of the old school forecasting has given way to model watching. I'm not saying these guys do that. I don't know. But there's a lot of that that goes on out there, even in the pro world.
Click to expand...
Model watching has become a very big thing, especially for broadcast meteorologist. I know we give him a hard time but Brad P is one of the best at being able to look beyond the models and can look at the entire picture to make a prediction. My local guys on all 4 stations are entirely fixated on models and what they show. And yes that includes Chris Justice who I really like and tends to be more hopeful when models show something good and the people at fox carolina who are quick to go to the worst outcome if the models even hint at no snow. It’s one reason I tend to be more hopeful. You start dropping troughs in California and the typical response is almost always amplification out east. Especially when the biggest driver here would be overrunning in that situation which itself is notorious for NW trends.
 
"
BUT GENERALLY,
THE GFS-EC SOLUTION OF A SLOWER DECAY OF THE CUTOFF-RIDGE
PATTERN IN THE PACIFIC IS MORE LIKELY GIVEN TYPICAL MODEL BIASES
IN BLOCKING PATTERNS. "
 
lj0109 said:
CAE with a good AFD on next week's potential:

.LONG TERM /SUNDAY THROUGH THURSDAY/...
- A very strong cold front arrives late Sunday as the lingering
surface low lifts northeast.

- Temps 15-25 degrees below average expected Monday through Thursday.

- Wintry precip chances continue for mid-week, but confidence
remains low.


The aforementioned surface low will lift northeast Sunday, followed
by the long discussed cold front. So there will not likely be
much of a diurnal swing Sunday as strong advection arrives
during the day. For Monday and Tuesday, the broad trough of the
Arctic airmass will settle into the central and eastern US. EC
and NAEFS are in excellent agreement over the general nature of
the initial airmass with highly anomalous cold, but not record
setting; temps 15-25 degrees below average yield highs in the
~30`s or low 40`s, along with overnight lows in the teens or low
20`. EC EFI continues to show EFI values between 0.9 and 0.95
Monday and Tuesday, but SoT is very low; a classic high
confidence in well below average, but not extreme temps, signal.
Regardless, the LREF output suggests we will approach or exceed
Cold Weather Advisory criteria at some point next week, so stay
aware of that potential new product issuance. Frozen pipes and
related impacts are becoming more likely during the mid- week
period as high temps will only make it above freezing for a few
hours each day.

Late Tuesday and into Wednesday is when the wintry precip potential
starts to enter the picture. Based on the last handful of guidance
suites, there is only a little more clarity on the possibility of
winter weather next week. Based on extent of the cold airmass and
associated surface high pressure, a suppressed low track
solution looks more and more likely with any wintry precip
chances actually increasing the further south you go in the
Midlands and CSRA. GEFS, and ECE to a lesser extent, have
trended towards this solution over the past several runs with
probabilities of 1" of snow in the central and northern
Midlands decreasing notably as the surface high settles into the
TN Valley. The GEFS and deterministic GFS remain the most
suppressed, with little-no precip into the forecast area. The
Canadian and at its ensemble are the other end of the spectrum,
with a northern GoM oriented storm track and significantly more
moisture overrun into eastern GA and SC; the EC and its
ensemble looks to be directly in the middle of these two
solutions over the last fews suites. The key feature of the
forecast is how the low level cold air and surface high pressure
is handled and how far southeast it can reach. How this high
pressure progresses is a result of extremely strong confluence
along the western flank of the trough main trough. And how this
confluence progresses is a result of a cutoff low in the Pacific
and its interaction with the main trough. A faster phase of
this cutoff drags the surface high further west, and a slower
phase causes the opposite. Unfortunately with chaotic nature of
cutoffs sitting under ridge axes, it will take several more days
to get consistent model guidance on this event. But generally,
the GFS-EC solution of a slower decay of the cutoff-ridge
pattern in the Pacific is more likely given typical model biases
in blocking patterns.

Overall, the forecast hinges on a notorious synoptic scale
interaction. But beyond that the general pattern is favorable
with a suppressed GoM storm track solution looking likely.
Whether that yields snow- wintry precip into the Midlands and
CSRA is highly uncertain at this time.
Click to expand...

Anybody want to translate? Sounds like they’re putting the blame of suppression on the high pressure and how far east it can get. That’s an element I don’t remember discussing yet.

And why no NWS talk of overrunning precipitation threat? Like @griteater mentioned even the models that don’t show a strong low show that underlying possibility right?

Ukmet Ens, and CMC Ens have me hanging on. That’s not a bad combo, but patiently waiting for the EPS to get back in the game.
 
CaryWx said:
If you go read the latest forecast discussion on NWS RAH you will see they only reference the Euro & GFS for their look ahead at this storm. They still are top scorers at this range--especially the 0z eps ens mean.
Click to expand...

RDU hasn’t updated the AFD for next week since 3am this morning


Sent from my iPhone using Tapatalk
 
CaryWx said:
If you go read the latest forecast discussion on NWS RAH you will see they only reference the Euro & GFS for their look ahead at this storm. They still are top scorers at this range--especially the 0z eps ens mean.
Click to expand...
I wanted to re-post the latest H5 scores. For a time, the UKMET has been right up there with the Euro lately and the CMC as of late had a bad run along with the GFS. You can see how inconsistent it is, whereas the UKMET and Euro are typically the best.
evs.global_det.acc.hgt_p500.last31days.timeseries_valid00z_f120.g004_nhem.png
 
Excerpt from a nice AFD from TLH.
(Sounds like Scenario 1 is GFS, Scenario 2 is UKMet and Scenario 3 is ICON and Canadian -- Euro/AIFS don't seem to fit neatly, but would be close to 2 and 3).


TLH AFD:

All that said, the three scenarios mentioned in the previous couple
of AFDs remain on the table:

Scenario 1: We remain cold, but dry. The H5 trough and surface high
are too far south and the H5 shortwave mentioned above is too slow
to strengthen to allow for any sort of precipitation to develop near
or move over the region. This keeps all of our forecast area cold
and dry with just a few clouds floating through. The most impactful
thing from this scenario would be bitterly cold temperatures and the
issuance of additional cold weather and/or (hard) freeze products.

Scenario 2: The H5 trough is just far enough north along with the
surface high to allow the low pressure in the Gulf of Mexico to
traverse along the northern Gulf Coast. This would lead to primarily
rain over most of the region. A very cold rain, mind you, but rain
nonetheless will fall for all but our northern Georgia counties,
which stand the best chance of picking up wintry precipitation. This
scenario could lead to flooding concerns if Saturday`s system
overperforms or if the heaviest rain falls over the same areas
during both events. As such, nuisance flooding and/or riverine
flooding would be the most impactful thing from this scenario.

Scenario 3: The H5 trough and shortwave are oriented in such a
manner to allow for the low to track well offshore and towards the
Tampa area. Couple this with the sprawling 1040+mb high providing
the cold temperatures and wintry precipitation enters the forecast
picture across most of the forecast area away from the cast. Ice, in
the form of sleet and/or freezing rain, would be the primary concern
as a layer of warmer air aloft around 6,000 to 9,000 feet over our
heads, or what we call a warm nose, would preclude any snow making
it to the surface. It`s way to early to be specific about amounts,
but a high-impact event would occur with this scenario.

All that said, there is a 10% to 30% chance of wintry precipitation
with this event for most of our area away from the coast, which
means that it`s unlikely to occur at this time.

Remember, whenever you`re talking about wintry precipitation chances
in the Southeast that a lot can, and usually does, go wrong. Seeing
as this is still several days out, a lot can and will change in the
coming days. Please make sure to stay tuned to local, trusted
sources of weather information and to continually check back in with
the forecast the rest of the week and through the holiday weekend.
 
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