Feb. 18-20, 2012 Disco/Analysis

[Cold Rain]

I'd say that is spot on Cold R. Sfc low will have little say in the deformation band precip. You want that trailing vort max to be as far south and as strong as you can get it for both colder and more lift / precip. You also want the 850mb and 700mb lows trending south

It actually looked a little stronger and farther south on the 12Z NAM than the new one. But it may just be bad interpretation on my part though. It's a pretty stout little piece of energy...hopefully it catches up in time to phase in and set up a nice deform band across the area.

[WeatherNC]

0z NMM, getting kind of interesting... 250mb, central NC in the right entrance region of a 160kt jet, 500mb, 40 s^-1 vort going off around ILM attempts to close off, 850-700mb, sick kind of nasty once it gets offshore, closed off at both levels and rapidly deepens, 2 contours at the H7 and 5 on the 850. Quick heavy hitter, verbatim 6 hrs here for a chance of SN, even some convective 40+ dbz in the band through the northern coastal plain on sim. Have not looked at the arw yet but imagine it is similar...

[WeSuck]

WOW, Nice post WeatherNC, THat could play a big roll for NE NC and SE VA . Will be interesting to see if this occurs

[Carvers Gap]

0z GGEM holds its position for the most part, but w/ lesser qpf. Yesterday, it was thrown out by HPC if I remember correctly.

[NCMET]

I think it's time for nowcasting at this point guys. Get some rest. No need to stay up for the Euro. Tomorrow is going to be a long day.

[WeatherNC]

WOW, Nice post WeatherNC, THat could play a big roll for NE NC and SE VA . Will be interesting to see if this occurs

Thanks, yeah it will be fun to watch this unfold as it never plays out exactly as planned. Best part of the hobby, tracking a threat for 10 days, watching the solutions evolve, then actually watching what materializes... This is the 850 graphic from the 0z NMM, deepens late, but man does it! Comes off just south of Cape Lookout, great track for areas between about Mt Airy and Roanoke Rapids.

[Carvers Gap]

Looking at the radar, sure does look like a low pressure riding due east from the tip of the Louisian panhandle. The question, is can that piece of energy(barely discernable front in the plains) catch it. Makes the NAM look a bit too far south.

[Tullioz]

This may belong in the banter thread, but since we are between models and it's getting late here goes. I was not going to make any more posts in this thread because I didn’t want to offend those who fail to look at this system in an objective way. However; I have been biting my tongue all this time as I wanted to point out some of the obvious factors that so many are over looking. So many are wondering why the NWS and even some TV outlets are down playing this even though the models are putting down all types of warning and advisory type accumulations. Despite what many believe, those “Clown” maps do not factor in everything and very often miss the mark. And just because the soundings show all snow, there are several other factors to consider. The NWS looks at all of those factors and then issues what they believe to be the best product for the public. You can call it being “Conservative”, but the real term should be keeping it “Real”. This is why they are not forecasting much outside of the higher elevations . It is easy to get caught up in the “Herd Mentality” as many on here have appeared to have done by reading at their expectations, and seeing their snowfall maps. When the excitement of a few takes off, it is not hard for the rest to follow suite and start seeing what they want to see while over looking the obvious, especially when the models look the way they do and have over the past day or so. As I said two days ago, I do not care which path the models show this storm taking, I do not see how anyone South of the NC/VA border outside of the Mountains and perhaps the Extreme Northeaster part of NC sees more than an inch. Even now with the models showing a decent hit my thoughts have not changed, looking at the current situation and trends I am more confident than ever that this will be the case.

Here are the reasons why this will not be a significant snow in NC:

1. Soil Temperatures: Many say they are overrated when it comes to snow accumulation, but in this case they do matter. See number 2.

2. Storm is too progressive: With no blocking ahead of the storm it will be in and out very fast. This will leave only a small window of opportunity for snow to accumulate as no one area will have heavy enough rates long enough to overcome warm soil temperatures. While there will be several hours of snow, most of the time it will only be light to moderate. In this type of situation you need several hours of heavy snow.

3. Track is more suppressed: While this may appear to be a good thing, it is actually bad for NC. While it brings the colder air further South, it also shifts the more intense precipitation rates further South. Areas where the entire column is now cold enough for all snow loose the heavier precipitation rates and end up with only light to moderate snow. Where the precipitation is heavy, those areas are relying on the atmosphere cooling from the top down and will only see snow when the precipitation falls heavy enough.

4. Timing: While the storm has slowed down on the models, the bulk of the heavy precipitation will fall during the Afternoon and Early evening hours which will also limit accumulations. (Except Eastern Sections) By late evening in the Western and Central parts of NC there my only be light rain and drizzle especially in Southern sections. With such warm air ahead of this system wet bulb temperatures may only bottom out around 33-34 for most areas and only fall below freezing after skies begin to clear.

5. Temperature profiles: With so many pieces of the puzzle there are likely going to be boundary layer issues for many. It is impossible to tell where these will set up, so it is a wait and see type of situation, although I do expect most areas to see an hour or two of heavy wet snow at some point.

I know I have said this before, but this will be the last time I promise. The only areas that will see a significant storm will be the Mountains in NW NC and SW Virginia. Central Virginia will do well if the moisture can get up that way, and the Northeastern sections of NC may do ok since the heaviest snow will fall after sunset. Areas South of the NC/VA border should only see accumulations in grassy and on elevated surfaces. Only the very fortunate can count on seeing more than an inch. With the more Southern track a couple of areas may be lucky enough to pull out an inch or so. When all is said and done this will be the biggest storm of the season so far and the excitement is warranted. However; by Monday afternoon it will only be a memory as whatever does manage accumulate will be melted away for sure. Good luck to everyone, and I hope everyone at least gets to see some flakes out of this.

[SN_Lover]

This may belong in the banter thread, but since we are between models and it's getting late here goes. I was not going to make any more posts in this thread because I didn’t want to offend those who fail to look at this system in an objective way. However; I have been biting my tongue all this time as I wanted to point out some of the obvious factors that so many are over looking. So many are wondering why the NWS and even some TV outlets are down playing this even though the models are putting down all types of warning and advisory type accumulations. Despite what many believe, those “Clown” maps do not factor in everything and very often miss the mark. And just because the soundings show all snow, there are several other factors to consider. The NWS looks at all of those factors and then issues what they believe to be the best product for the public. You can call it being “Conservative”, but the real term should be keeping it “Real”. This is why they are not forecasting much outside of the higher elevations . It is easy to get caught up in the “Herd Mentality” as many on here have appeared to have done by reading at their expectations, and seeing their snowfall maps. When the excitement of a few takes off, it is not hard for the rest to follow suite and start seeing what they want to see while over looking the obvious, especially when the models look the way they do and have over the past day or so. As I said two days ago, I do not care which path the models show this storm taking, I do not see how anyone South of the NC/VA border outside of the Mountains and perhaps the Extreme Northeaster part of NC sees more than an inch. Even now with the models showing a decent hit my thoughts have not changed, looking at the current situation and trends I am more confident than ever that this will be the case.

...

I know I have said this before, but this will be the last time I promise. The only areas that will see a significant storm will be the Mountains in NW NC and SW Virginia. Central Virginia will do well if the moisture can get up that way, and the Northeastern sections of NC may do ok since the heaviest snow will fall after sunset. Areas South of the NC/VA border should only see accumulations in grassy and on elevated surfaces. Only the very fortunate can count on seeing more than an inch. With the more Southern track a couple of areas may be lucky enough to pull out an inch or so. When all is said and done this will be the biggest storm of the season so far and the excitement is warranted. However; by Monday afternoon it will only be a memory as whatever does manage accumulate will be melted away for sure. Good luck to everyone, and I hope everyone at least gets to see some flakes out of this.

I think the majority of us are just glad to see a snowflake out of a depressing winter. But I do think that those wishing for Winter Storm Warning criteria will not get that. I'm only hoping for 1in ... my deck table.

[jburns]

Here are the reasons why this will not be a significant snow in NC:

1. Soil Temperatures: Many say they are overrated when it comes to snow accumulation, but in this case they do matter. See number 2.

2. Storm is too progressive: With no blocking ahead of the storm it will be in and out very fast. This will leave only a small window of opportunity for snow to accumulate as no one area will have heavy enough rates long enough to overcome warm soil temperatures. While there will be several hours of snow, most of the time it will only be light to moderate. In this type of situation you need several hours of heavy snow.

3. Track is more suppressed: While this may appear to be a good thing, it is actually bad for NC. While it brings the colder air further South, it also shifts the more intense precipitation rates further South. Areas where the entire column is now cold enough for all snow loose the heavier precipitation rates and end up with only light to moderate snow. Where the precipitation is heavy, those areas are relying on the atmosphere cooling from the top down and will only see snow when the precipitation falls heavy enough.

4. Timing: While the storm has slowed down on the models, the bulk of the heavy precipitation will fall during the Afternoon and Early evening hours which will also limit accumulations. (Except Eastern Sections) By late evening in the Western and Central parts of NC there my only be light rain and drizzle especially in Southern sections. With such warm air ahead of this system wet bulb temperatures may only bottom out around 33-34 for most areas and only fall below freezing after skies begin to clear.

5. Temperature profiles: With so many pieces of the puzzle there are likely going to be boundary layer issues for many. It is impossible to tell where these will set up, so it is a wait and see type of situation, although I do expect most areas to see an hour or two of heavy wet snow at some point.

I know I have said this before, but this will be the last time I promise. The only areas that will see a significant storm will be the Mountains in NW NC and SW Virginia. Central Virginia will do well if the moisture can get up that way, and the Northeastern sections of NC may do ok since the heaviest snow will fall after sunset. Areas South of the NC/VA border should only see accumulations in grassy and on elevated surfaces. Only the very fortunate can count on seeing more than an inch. With the more Southern track a couple of areas may be lucky enough to pull out an inch or so. When all is said and done this will be the biggest storm of the season so far and the excitement is warranted. However; by Monday afternoon it will only be a memory as whatever does manage accumulate will be melted away for sure. Good luck to everyone, and I hope everyone at least gets to see some flakes out of this.

Good post. If we do not get several hours of consistant heavy snow everything you say will be correct. That is the only way to overcome the ground temps we now have. Even if we do, I also agree that by late Monday afternoon it will mostly be gone because it will be melting from the top and bottom at a rapid rate. I still want to see some fall though. A flurry is news this year.

[BullCityWx]

We are not playing the radar trends game almost 24 hours ahead of this event.

[griteater]

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

521 PM EST SAT FEB 18 2012

VALID 00Z SUN FEB 19 2012 - 00Z WED FEB 22 2012

DAY 1...

...SOUTH/CENTRAL APPALACHIANS...MID-ATLANTIC...

WELL DEFINED SHORTWAVE TROUGH SEEN ON WV IMAGERY OVER THE SRN

PLAINS THIS AFTERNOON WILL EXIT EAST-NORTHEASTWARD TO THE

MID-ATLANTIC STATES SUNDAY AFTERNOON WITH LIMITED LATITUDE GAIN

DUE TO PRESENCE OF NRN STREAM JET OVER NEW ENGLAND. HINTS OF

INTERACTION OF THE SRN PLAINS SHORTWAVE WITH WEAK VORT ENERGY

CURRENTLY OVER THE UPPER MIDWEST CAUSES SOME RELATIVELY MINOR

DIFFERENCES IN THE GUIDANCE WITH THE NORTHWARD EXTENT OF QPF MOST

NOTED IN THE 12Z NAM/UKMET. SURFACE LOW WILL FOLLOW A SIMILAR PATH

FROM THE CENTRAL GULF COAST TO SOUTH CAROLINA BY EARLY SUNDAY

EVENING WHILE COASTAL DEVELOPMENT TAKES PLACE JUST OFF OF THE

NORTH CAROLINA COAST.

SNOW ACCUMULATION IS A CONCERN GIVEN THE ANOMALOUS WARMTH IN PLACE

WITH TEMPS WELL INTO THE 50S AND 60S ACROSS THE AFFECTED REGION

THIS AFTERNOON. HOWEVER...NRN STREAM COLD FRONT ALLOWS COLDER AIR

TO SINK SOUTH ACROSS THE MID-ATLANTIC CAUSING SNOW TO FALL ALONG

THE NORTHERN EDGES OF THE PCPN SHIELD BY 12Z SUNDAY. GOING INTO

SUNDAY EVENING...THE SURFACE LOW STRENGTHENS AND A WEAK TROWAL

SIGNATURE DEVELOPS...MAINLY AROUND 700MB WHICH WILL COUPLE WITH A

REGION OF FRONTOGENESIS MOSTLY BETWEEN 850 AND 700 MB. A WELL

DEFINED DEFORMATION ZONE IS EXPECTED TO DEVELOP AS A DRY SLOT

SLIDES UP THE CAROLINA COASTLINE MID-DAY SUNDAY...AND BANDED SNOW

IS POSSIBLE WITHIN THE FAVORABLE REGION OF ASCENT TO ITS WEST.

LOCALLY HEAVY SNOW WILL BE POSSIBLE WITHIN THE COMMA-HEAD AS THE

SYSTEM EXITS TOWARD THE EAST. MODERATE LOW LEVEL EASTERLY WIND

COMPONENT OFF OF THE SRN VA COAST WITH OCEAN TEMPS NEAR 50 WILL

LIKELY KEEP LOW LEVEL PROFILES WARM AND PRIMARILY RAIN INTO

SOUTHEAST VA AND NORTHEAST NC.

MODEL PREFERENCES REFLECTED A BLEND OF THE GFS & 00Z UKMET/ECMWF

WITH PTYPE WEIGHTING TOWARD THE GFS/NAM/SREF. PROBABILITIES WERE

TWEAKED TOWARD HI-RES AFWA MODEL GUIDANCE DUE TO ITS BETTER

HANDLING OF TERRAIN.

[WeatherNC]

Going to let the above post stay, if you are going to make an argument folks this is a textbook example of how you should back it up, great job!

0z euro coming in weaker no surprise, a little colder at 850 from about ORF to CLT, not much though. Big difference in strength, overall weaker system, less qpf, and maybe south of 12z. Surface low exits around CHS after 1pm today.

[superjames1992]

Good post. If we do not get several hours of consistant heavy snow everything you say will be correct. That is the only way to overcome the ground temps we now have. Even if we do, I also agree that by late Monday afternoon it will mostly be gone because it will be melting from the top and bottom at a rapid rate. I still want to see some fall though. A flurry is news this year.

If I recall, we had some serious problems with this in the March 2nd-3rd, 2010 storm. The Triad saw about 2" before it was all over, but it snowed all day long. Unfortunately, the rates weren't spectacular and a lot fell during the day. In Randolph County and near Sanford, where rates were heavier and most of the snow fell all night, some places got 6-8". If the snow is heavy enough, it can and will overcome warn soil temperatures, but the question is whether the rates will be high enough and whether they will be consistent.

[rduwx]

Euro looks pretty good to my eyes. At 24 all of NC is the .25 precip range...850 line runs from RDU to CLT then right along the NC/SC/Ga border. Since the euro is in 6 hr increments I would say it matches up w/ the nam and gfs and 850's supports snow in the RDU area around 21z. At hr 30 there is still .25 precip range running from the middle of NC east.

[nchighcountrywx]

I know I have said this before, but this will be the last time I promise. The only areas that will see a significant storm will be the Mountains in NW NC and SW Virginia. Central Virginia will do well if the moisture can get up that way, and the Northeastern sections of NC may do ok since the heaviest snow will fall after sunset. Areas South of the NC/VA border should only see accumulations in grassy and on elevated surfaces. Only the very fortunate can count on seeing more than an inch. With the more Southern track a couple of areas may be lucky enough to pull out an inch or so. When all is said and done this will be the biggest storm of the season so far and the excitement is warranted. However; by Monday afternoon it will only be a memory as whatever does manage accumulate will be melted away for sure. Good luck to everyone, and I hope everyone at least gets to see some flakes out of this.

Good rational post.

When all is said and done, you may very well be spot on.

I have cross country skis waxed and ready to go for tomorrow, but there is a remarkable amount of doubt in this storm even in the High Country.

Hoping for the best as anything is a blessing. This is our first 'real' winter storm threat this winter.

[WeSuck]

Ouch for those folks who were hoping that much of their snow falling after dark would make a difference.

Water temps if anything will enhance the storm faster due to warmer than normal. I disagree with HPC here and doubt it effects much once the upper level system begins to deepen

[WeatherNC]

Does not appear to be a good run for RIC, steep cutoff just north of there, pretty big shift south, likely better for RDU compared to 12z, concerned about that inverted V likely warm nose here at 850 on the 30hr panel.

[BullCityWx]

Euro looks pretty good to my eyes. At 24 all of NC is the .25 precip range...850 line runs from RDU to CLT then right along the NC/SC/Ga border. Since the euro is in 6 hr increments I would say it matches up w/ the nam and gfs and 850's supports snow in the RDU area around 21z. At hr 30 there is still .25 precip range running from the middle of NC east.

RDU looks really good this run.

[rduwx]

The 0z euro doesn't have any of the heavier precip making it north of the NC/Va border. I would be bummed if I were in Va.

[jburns]

Water temps if anything will enhance the storm faster due to warmer than normal. I disagree with HPC here and doubt it effects much once the upper level system begins to deepen

Wouldn't a stronger storm just offshore throw more low level warm air onto the coast? I think that is the thinking of HPC.

[BullCityWx]

The 0z euro doesn't have any of the heavier precip making it north of the NC/Va border. I would be bummed if I were in Va.

and I'd be looking for a hole to dive in if I was DT.

[WeSuck]

Wouldn't a stronger storm just offshore throw more low level warm air onto the coast? I think that is the thinking of HPC.

At first maybe. Will have to wait and see. I think we will fair ok here in SE VA although NE NC may have a harder time

[packbacker]

Euro appears to switch to frozen at 0z and after that 0.4" QPF falls. Maybe 2-3"....sounds good to me.

[superjames1992]

Does anyone have any QPF numbers from the Euro? I like what I'm hearing, though. Sounds like it's further south, which is great for us NC folks. It sucks for our S. VA friends, though. :-(

[rduwx]

RDU looks really good this run.

Yeah I agree...It looks around .50 falling as snow. Could possibly squeeze out 2" if the euro is right.

[rduwx]

and I'd be looking for a hole to dive in if I was DT.

Lol, the last time I checked he was holding on to the 0z RGEM and 21z sref. Who knows they could be correct but I wouldn't like the trends if I was him.

[packbacker]

How did the Euro look for NE TN?

For Tricites...Roughly 0.58" QPF with 850's below zero. Surface 32-33.5.

[Dunkman]

and I'd be looking for a hole to dive in if I was DT.

He's hardly alone in busting horribly with this storm and there were certainly people with worse forecasts. I think that writeup he made with this "final call" is what's going to bite him in the ass.

[rduwx]

Over how long a time period?

Good question...I really don't know how the euro tallies up the total. At hr 24 it shows .25 over all of NC and then at hr 30 it shows .25 from the middle of NC east. There is still some real light stuff at hr 36 from RDU east.