Christmas Storm IV

[Lookout]

Classic

lol..you remember what it is? For those who don't know, it's when an eddie forms down wind of the mountains over northeast ga/upper savannah river valley when the flow is out of the north or NNE. It delays, sometimes a lot, any cold air advection. The worst case of this was a few years ago when around 20 miles of my location was rain while everywhere else was snow. It normally is a factor in cooling the low levels but It actually prevented cooling all the way to 850mb. There was a small bubble of above freezing 850mb temps here surrounding by subfreezing temps. You talk about maddening. If this is a weaker system, there is a chance this becomes somewhat of an issue but with 850mb temps as cold as predicted, I doubt it.

[nrhardin]

A quick note as everyone starts posting and dissecting afternoon AFDs...

I would like to point out that while it is easy to be overcritical of the NWS discussions and forecasts, everyone needs to keep in mind that we have some of the best discussions, forecasts, and play-by-plays going on right here. I think the tendency is for people to take the NWS forecast as what actually is going to happen. In reality, we have access to the same information many of the forecasters use (albeit not in such a one-stop shop sort of way).

Also, people get upset when a particular office doesn't "honk the horn" as much as one model or solution would depict. A lot of this comes into the forecasting process and SOP the NWS uses, which essentially "protects" against the forecaster from going all-in for one solution. With time, and as things become more clear, you will see the forecast resemble what you may expect. At the same time, be fully sure that the appropriate EM officials are kept in close contact with what to expect, and can plan accordingly.

Just keep it in mind as we move forward. Remember....we have excellent discussion and dissection of the situation as it unfolds here, so you (everyone) should be well aware of the possibilities regardless of what the NWS official forecast depicts. (end rant)

side note..... Wow (john) can I have my red tag back? thanks!

[Lookout]

lol..you remember what it is? For those who don't know, it's when an eddie forms down wind of the mountains over northeast ga/upper savannah river valley when the flow is out of the north or NNE. It delays, sometimes a lot, any cold air advection. The worst case of this was a few years ago when around 20 miles of my location was rain while everywhere else was snow. It normally is a factor in cooling the low levels but It actually prevented cooling all the way to 850mb. There was a small bubble of above freezing 850mb temps here surrounding by subfreezing temps. You talk about maddening. If this is a weaker system, there is a chance this becomes somewhat of an issue but with 850mb temps as cold as predicted, I doubt it.

btw, you can see this on plymouth if you check out the boundary layer winds on the gfs.

[DLI4SCwx]

There are three major pieces of energy from the Northern Stream depicted by the Euro that go into a super strong short wave coming out of the west at the exact right time.

This is NOT a typical Nina year. See that monster system out west? See the gigantic ridging almost to the North pole? That's not normal.

They are now starting to mention the "S" word as a possibility on WLTX and WIS.

[shaggy]

Agreed, a track as far west as 93 is unlikely. However, I think the models are undergoing the SLP initially in the northern GOM. If you look at the phase on the EURO, the SLP IMO, should be stronger in that area. I think we're going to see more adjustments before this is all said and done. Maybe I harp on climo too much, but I still have a hard time believing all snow soundings so far east in the coastal plain with that SLP track and this still being december as opposed to January or early February. Euro profiles 500-1000 thickness do support snow very far east, and i just find that hard to believe there will be no mixing in the mid-levels(800-700mb). Something is still slightly off at the sfc.

Despite some encouraging info from foothills and eyewall that we may only mix for a little while I have 25 years of getting screwed by the warm nose to fall back on. I am extremely nervous that we get screwed here east of 95. We need the models to hold serve or slide a bit further east for 3 more days and we know this isn't going to happen. In the end i'll channel widremans negativity and go sulk on our rainy day while everyone else gets pounded again.

Hard for me to break that 25 years of bad experiences and bite on this setup for those of us in the coastal plains.

[eyewall]

RAH update:

SATURDAY INTO SUNDAY...

THE 00Z ECMWF IS EXTREME IN ITS PRECIPITATION GENERATION AND WITHOUT

SUPPORT OF OTHER MODELS. IT DOES HOWEVER MAKE METEOROLOGICAL SENSE

AND HAS AT LEAST A CHANCE TO VERIFY. THE NEW 12Z ECMWF SUPPORTS THE

00Z RUN WITH A STENGTHENING SURFACE LOW CLOSE TO THE COAST AND IS

DISTURBING. THIS WOULD BE A SIGNIFICANT SNOW EVENT FOR ALL OF

CENTRAL NORTH CAROLINA. HOWEVER THE 12Z MODEL RUNS OF THE CANADIAN

AND GFS ARE COMING INTO MUCH BETTER AGREEMENT IN GENERATING A

SURFACE LOW OFF THE GULF COAST STATES FRIDAY NIGHT AND SATURDAY AND

PLACING IT SOMEWHERE OFF THE COAST OF CHARLESTON SUNDAY SUNRISE. THE

GFS LOOKS LIKE A GOOD COMPROMISE BETWEEN SOLUTIONS IN ITS PLACEMENT

AND STRENGTH OF THE SURFACE LOW. A LOW EITHER STRONGER OR CLOSER TO

SHORE (ECMWF MODELS) WILL GREATLY INCREASE THE IMPACT OF THE EVENT.

THE ECMWF MODEL IS SLOWER WITH A MIDWEST SHORT WAVE... ALLOWING IT

TO PHASE WITH THE GULF COAST ENERGY... PRODUCING AN UPPER TROUGH

FURTHER WEST THAN THE GFS AND CANADIAN MODEL SATURDAY MORNING. THE

GFS AND CANADIAN ARE FASTER WITH THIS SHORT WAVE AND ALLOW THE

MEAN UPPER TROUGH TO CENTER FURTHER EAST... MAKING FOR A MORE

OFFSHORE SURFACE LOW AT OUR LATITUDE. THIS LATTER SCENARIO IS

FAVORED AT THIS TIME WITH MEDIUM CONFIDENCE.

SNOW AMOUNTS ARE WAY TOO UNCERTAIN TO DISCUSS MORE THAN GENERALLY.

BEST CHANCES FOR ACCUMULATION PERHAPS IN THE TWELVE HOURS PRIOR TO

NOON SUNDAY... WITH HEAVIEST AMOUNTS FAYETTEVILLE CLINTON AREA.

WHEREVER PRECIPITATION FALLS DURING THIS EVENT... IT WILL BE SNOW.

SNOW TAPERING BACK AS ONE APPROACHES HIGHWAY ONE... AND AREAS TO THE

WEST PERHAPS EVEN MISSING SIGNIFICANT SNOW ENTIRELY. WITH THE EVENT

MORE THAN 72 HOURS OUT... THIS IS BUT ONE OF SEVERAL POSSIBLE

SCENARIOS. SOME VERY LIGHT ADDITIONAL SNOW SUNDAY AFTERNOON WELL

INTO SUNDAY NIGHT IN THE EAST AS THE UPPER LOW LINGERS OVER NORTH

CAROLINA.

AFTERNOON HIGH TEMPERATURES IN THE 30S SATURDAY AND SUNDAY. SATURDAY

NIGHT LOWS 25 TO 30.

SUNDAY NIGHT AND MONDAY...

EASTERN SKIES WILL CLEAR AND A STEADY NORTH BREEZE WILL ADVECT COLD

AIR INTO THE STATE FROM VIRGINIA. LOW TEMPERATURES 18 TO 23. A

PERSISTENT NORTH BREEZE MONDAY WITH HIGH TEMPERATURES MID TO UPPER

30S.-- End Changed Discussion --

[Wow]

That's a good explanation, Nate. I think people really jump to conclusions before thinking this through regarding the process that the NWS offices partake.

[oconeexman]

A quick note as everyone starts posting and dissecting afternoon AFDs...

I would like to point out that while it is easy to be overcritical of the NWS discussions and forecasts, everyone needs to keep in mind that we have some of the best discussions, forecasts, and play-by-plays going on right here. I think the tendency is for people to take the NWS forecast as what actually is going to happen. In reality, we have access to the same information many of the forecasters use (albeit not in such a one-stop shop sort of way).

Also, people get upset when a particular office doesn't "honk the horn" as much as one model or solution would depict. A lot of this comes into the forecasting process and SOP the NWS uses, which essentially "protects" against the forecaster from going all-in for one solution. With time, and as things become more clear, you will see the forecast resemble what you may expect. At the same time, be fully sure that the appropriate EM officials are kept in close contact with what to expect, and can plan accordingly.

Just keep it in mind as we move forward. Remember....we have excellent discussion and dissection of the situation as it unfolds here, so you (everyone) should be well aware of the possibilities regardless of what the NWS official forecast depicts. (end rant)

side note..... Wow (john) can I have my red tag back? thanks!

Don't have a problem with ours...think they are tops in the area GSP!

[jburns]

RAH update:

SATURDAY INTO SUNDAY...

THE 00Z ECMWF IS EXTREME IN ITS PRECIPITATION GENERATION AND WITHOUT

SUPPORT OF OTHER MODELS. IT DOES HOWEVER MAKE METEOROLOGICAL SENSE

AND HAS AT LEAST A CHANCE TO VERIFY. THE NEW 12Z ECMWF SUPPORTS THE

00Z RUN WITH A STENGTHENING SURFACE LOW CLOSE TO THE COAST AND IS

DISTURBING. THIS WOULD BE A SIGNIFICANT SNOW EVENT FOR ALL OF

CENTRAL NORTH CAROLINA. HOWEVER THE 12Z MODEL RUNS OF THE CANADIAN

AND GFS ARE COMING INTO MUCH BETTER AGREEMENT IN GENERATING A

SURFACE LOW OFF THE GULF COAST STATES FRIDAY NIGHT AND SATURDAY AND

PLACING IT SOMEWHERE OFF THE COAST OF CHARLESTON SUNDAY SUNRISE. THE

GFS LOOKS LIKE A GOOD COMPROMISE BETWEEN SOLUTIONS IN ITS PLACEMENT

AND STRENGTH OF THE SURFACE LOW. A LOW EITHER STRONGER OR CLOSER TO

SHORE (ECMWF MODELS) WILL GREATLY INCREASE THE IMPACT OF THE EVENT.

THE ECMWF MODEL IS SLOWER WITH A MIDWEST SHORT WAVE... ALLOWING IT

TO PHASE WITH THE GULF COAST ENERGY... PRODUCING AN UPPER TROUGH

FURTHER WEST THAN THE GFS AND CANADIAN MODEL SATURDAY MORNING. THE

GFS AND CANADIAN ARE FASTER WITH THIS SHORT WAVE AND ALLOW THE

MEAN UPPER TROUGH TO CENTER FURTHER EAST... MAKING FOR A MORE

OFFSHORE SURFACE LOW AT OUR LATITUDE. THIS LATTER SCENARIO IS

FAVORED AT THIS TIME WITH MEDIUM CONFIDENCE.

SNOW AMOUNTS ARE WAY TOO UNCERTAIN TO DISCUSS MORE THAN GENERALLY.

BEST CHANCES FOR ACCUMULATION PERHAPS IN THE TWELVE HOURS PRIOR TO

NOON SUNDAY... WITH HEAVIEST AMOUNTS FAYETTEVILLE CLINTON AREA.

WHEREVER PRECIPITATION FALLS DURING THIS EVENT... IT WILL BE SNOW.

SNOW TAPERING BACK AS ONE APPROACHES HIGHWAY ONE... AND AREAS TO THE

WEST PERHAPS EVEN MISSING SIGNIFICANT SNOW ENTIRELY. WITH THE EVENT

MORE THAN 72 HOURS OUT... THIS IS BUT ONE OF SEVERAL POSSIBLE

SCENARIOS. SOME VERY LIGHT ADDITIONAL SNOW SUNDAY AFTERNOON WELL

INTO SUNDAY NIGHT IN THE EAST AS THE UPPER LOW LINGERS OVER NORTH

CAROLINA.

AFTERNOON HIGH TEMPERATURES IN THE 30S SATURDAY AND SUNDAY. SATURDAY

NIGHT LOWS 25 TO 30.

SUNDAY NIGHT AND MONDAY...

EASTERN SKIES WILL CLEAR AND A STEADY NORTH BREEZE WILL ADVECT COLD

AIR INTO THE STATE FROM VIRGINIA. LOW TEMPERATURES 18 TO 23. A

PERSISTENT NORTH BREEZE MONDAY WITH HIGH TEMPERATURES MID TO UPPER

30S.-- End Changed Discussion --

I posted this earlier and we have been discussing the statement I bolded. What's your take on that?

[Hugo]

I don't get all the criticism of the NWS offices. Every office, with the exception of ILM, has put snow in the forecast. People in the South need no more warning than that. We understand that when the first flake falls, traveling will become a nightmare. It is rare to see snow in the forecast 3 days out, so they're being less conservative than usual.

People just want to see big numbers in the forecast so that it justifies their excitement.

[Wow]

BTW, Euro ensembles look better than 0z. Stronger over all and a bit further west, though still a little east of the OP.. looking at 102 hrs, so there is some divergence.

[jburns]

I don't get all the criticism of the NWS offices. Every office, with the exception of ILM, has put snow in the forecast. People in the South need no more warning than that. We understand that when the first flake falls, traveling will become a nightmare. It is rare to see snow in the forecast 3 days out, so they're being less conservative than usual.

People just want to see big numbers in the forecast so that it justifies their excitement.

Actually no. I want to know the reason pro mets in Raleigh decided to disregard the Euro, that has been consistent for six runs, in favor of the GFS which has been all over the place and is slowly heading toward the Euro solution.

[tnweathernut]

Agreed, a track as far west as 93 is unlikely. However, I think the models are undergoing the SLP initially in the northern GOM. If you look at the phase on the EURO b/n 72-96, the SLP IMO, should be stronger in that area. I think we're going to see more adjustments before this is all said and done.

Maybe I harp on climo too much, but I still have a hard time believing the all snow soundings so far east in the coastal plain with that SLP track and this still being december as opposed to January or early February. Euro profiles (500-1000 thickness) do support snow very far east, and i just find it hard to believe there will be no mixing in the mid-levels(800-700mb). Something is still slightly off at the sfc.

strongly agree. It's this reason that leads me to believe that while the track may not adjust a whole lot from here and may even be a tad east of the current Euro, the western and northern flank of the precip could be underdone (and maybe by quite a bit.)

[Hugo]

Actually no. I want to know the reason pro mets in Raleigh decided to disregard the Euro, that has been consistent for six runs, in favor of the GFS which has been all over the place and is slowly heading toward the Euro solution.

Ok, if you're a forecaster employed by the NWS, which one are you going to go with in the South, 3-4 days out?

Option 1: Snow, accumulation possible.

Option 2. Heavy snow. 2-4 feet of accumulation possible.

Honestly, only one of those makes sense right now.

[earlwx]

Ok, if you're a forecaster employed by the NWS, which one are you going to go with in the South, 3-4 days out?

Option 1: Snow, accumulation possible.

Option 2. Heavy snow. 2-4 feet of accumulation possible.

Honestly, only one of those makes sense right now.

LOL, very nice. Most of the time when the storm starts to take shape, that is when people will really know the ifs and ands of snowfall accumlation...

[UNCCmetgrad]

Well there is a lot of room between an historic storm and no significant snow. Three days out yes, but the third and part of the second are holidays with everything closed. If there job is to alert to allow time for people to prepare they are dangerously close to blowing it.

Good point, and I'm sure forecasters are pulling their hair out because some data points to a small event while other data points to a paralyzing snowstorm that could last days. You don't want to cry wolf, but public safety is first and foremost. There is still three days until this event unfolds so if the EURO holds for a couple of more runs you will begin to see stronger wording.

BTW... wasn't one of DT's rules of forecasting something like the more extreme and historic solution a model showed, the less likely it would be correct.

[lilj4425]

NAM a little slower at hr36.

[jburns]

Ok, if you're a forecaster employed by the NWS, which one are you going to go with in the South, 3-4 days out?

Option 1: Snow, accumulation possible.

Option 2. Heavy snow. 2-4 feet of accumulation possible.

Honestly, only one of those makes sense right now.

Option 1: No significant accumulation.

Option 2: The possibility exists for a major winter storm across the entire CFA. Stay tuned to future forecasts.

[Wow]

Nam about the same position... A little stronger vort over the 556 ht line that seems more poised to fall into the back side of the wave quicker

[GreensboroWx]

Yes, I understand the NWS has to be cautious...I would be too, but that's in their forecast to the public. How many people in the "public" read or care about their forecast discussions? What I don't understand and probably never will is why don't they use their forecast discussions to say what they are really thinking. I guess they do sometimes but often you read it and say "what the heck are they talking about!"

Good point, and I'm sure forecasters are pulling their hair out because some data points to a small event while other data points to a paralyzing snowstorm that could last days. You don't want to cry wolf, but public safety is first and foremost. There is still three days until this event unfolds so if the EURO holds for a couple of more runs you will begin to see stronger wording.

BTW... wasn't one of DT's rules of forecasting something like the more extreme and historic solution a model showed, the less likely it would be correct.

[Lookout]

I don't get all the criticism of the NWS offices. Every office, with the exception of ILM, has put snow in the forecast. People in the South need no more warning than that. We understand that when the first flake falls, traveling will become a nightmare. It is rare to see snow in the forecast 3 days out, so they're being less conservative than usual.

People just want to see big numbers in the forecast so that it justifies their excitement.

With the exception of ffc, I think the local nws's have been remarkably bullish...more so than usual. At the very least most have discussed the possibility of more than what is being advertised in the official forecast. At this stage of the game, you really can't ask for much more than that.

I do make an exception for ffc though (shocking i know). Other than today, they have barely discussed the system and put little thought into it.

[jburns]

Good point, and I'm sure forecasters are pulling their hair out because some data points to a small event while other data points to a paralyzing snowstorm that could last days. You don't want to cry wolf, but public safety is first and foremost. There is still three days until this event unfolds so if the EURO holds for a couple of more runs you will begin to see stronger wording.

BTW... wasn't one of DT's rules of forecasting something like the more extreme and historic solution a model showed, the less likely it would be correct.

Yeah but here is DTs take on the very thing we are talking about. GFS/Euro

Lets think about that

the Model that ahs held course for 6 runs in a row

should be compromised with the model that 6 hours ago had the Low over Bermuda

and has shifted dramatically towards the Euro?

Really?

[Wow]

yeah s/w further SW and/or slower at 42

[RaleighWx]

My afternoon update and some comments on the 12z ECMWF Ensembles

http://www.examiner.com/weather-in-raleigh/major-snowstorm-possible-for-parts-of-the-southeast-and-mid-atlantic

[HKY_WX]

wow nam is significantly slower than the 12 and 6z runs w/ the southwest s/w.

[lilj4425]

Yes, I understand the NWS has to be cautious...I would be too, but that's in their forecast to the public. How many people in the "public" read or care about their forecast discussions? What I don't understand and probably never will is why don't they use their forecast discussions to say what they are really thinking. I guess they do sometimes but often you read it and say "what the heck are they talking about!"

This is why i'm glad to be living in the GSP forecast area over FFC or RAH. I personally think GSP did a GREAT job on their AFD today and last night.

[nrhardin]

Good point, and I'm sure forecasters are pulling their hair out because some data points to a small event while other data points to a paralyzing snowstorm that could last days. You don't want to cry wolf, but public safety is first and foremost. There is still three days until this event unfolds so if the EURO holds for a couple of more runs you will begin to see stronger wording.

BTW... wasn't one of DT's rules of forecasting something like the more extreme and historic solution a model showed, the less likely it would be correct.

This is what I'm referring to. Statistically, the greater the solution is from the "mean", the less likely (in terms of probability) that the event happens. I believe I've seen Isopycnic quote the ever-famous "when in doubt, go with climo". This is a similar idea...if the event is extreme, it should be blended with a less extreme solution the farther out in time it is.

There is still plenty of time for models to come into agreement, WFOs to put out the appropriate watches/warnings, etc. Yes, it is the holiday weekend and I'm sure they're pulling their hair out. I don't envy them in this instance. They have out the appropriate HWO, and are following protocol for keeping the proper officials informed, while accurately conveying uncertainty. At the same time, as a forecaster, a high-impact event is when you can add the most value. Unfortunately, when on shift, you don't exactly have time to pour over every minute detail that you are afforded when browsing this forum from friendly confines.

All of that being said, I sure as crap hope the Euro verifies....back on topic.

[GreensboroWx]

Exactly my point with RAH discussion. Have they seen the EURO's consistency the past 6 runs? I know, the EURO is showing an epic storm, but common, the GFS/Canadian had OTS runs just 1 run ago and is now trending back towards the model with the greatest run to run consistency. I guess I just don't get it......

Yeah but here is DTs take on the very thing we are talking about. GFS/Euro

[Amos83]

wow nam is significantly slower than the 12 and 6z runs w/ the southwest s/w.

LOL, yes it is.... at this rate the storm will be winding down about the time I get back on Tuesday. LOL

[Wow]

NAM definitely further SW with the wave at 48. much slower. 558 height line begining to bend back into trough a bit... looks like a good phase setting up