Feb 15-16 Possible Mixed Event.

[Iceagewhereartthou]

"But as you noted, the gfs is pretty light for the most part (save north carolina where they get a good bit by morning). If not for that fact, i would be almost 100% certain this is an all subfreezing event for the usual damming areas in northeast ga. I'm already there really for the carolina"

 

 

 

Lookout this is one of the issues we usaually have with the upstate and NEGA. For some reason (perhaps the climo for tracks?) the leading finger of precipitation ahead of these systems almost always (like 98% of the time) pushes through Tennessee and NC, but is too far north for GA or SC. That always has them under the returns, thus holding their temps down and getting snow or ice on the ground while GA and SC have no precip to keep the cold locked in. By the time the precip does get to us, we have warmed just enough for it not to matter. The leading precip always seems to stop at the TN/GA, NC/SC state lines. I have watched this happen countless times over the years and it is always hard to watch that leading snow and ice go North, and hit NC for hours while we wait and warm. 

[wxduncan]

Parties over for those who still stuck around. CMC moved north and joined its friends. 

For me here just west of Hickory(I40). I get a nasty ICE storm along with snow:

[beanskip]

CMC trended north, but still keeps favored CAD regions below freezing for most of the event with an inch or more of precip. 

By the way, your post adds nothing and should be deleted by mods.

Parties over for those who still stuck around. CMC moved north and joined its friends. 

[weatherheels]

I am fully prepared to see token flakes for a few hours to begin before the washout. Storm looks like a joke. You get some light precip out in front of the main storm thanks to the northern stream, and then bam,the actual storm gets cranking way too late, cold air gets destroyed and raindrops dump downlikecrazy as the low plows through the Piedmont. Next.

[Jon]

Was there ever many on here thinking this was gonna be an all snow event? If so they crazy 95% of this board that has common sense knows this is a thump of snow to Ice storm to backside rain. I'm speaking of the CAD areas

All snow was not the best wording on my part. I didn't realize the entire forum was sold on a mostly icing event in the CAD region (just poke my head in from time to time). It seemed like people wanted large trends in the cold from what I was reading. With that said change "all snow" to "all frozen" in my post. I agree with your last sentence. It's hard for me to trust the colder solutions and people are hugging a model which has a cold bias.

[BIG FROSTY]

JB's thoughts!  Here is the snow idea we had from Thursday and Friday for the period 00z Tue through Wed. I think timing has to be monkeyed with but overall I still like this... also

 

The period started 00z Tuesday so it did not included totals to the southwest as we divide this into time increments. I think this may be a better 12z Monday to 00z We picture. In any case in terms of models, Last nights Euro Operational with an adjustment east for the idea you see in the big cities above was close but again I would adjust it east 50-100 miles

 

[Blue_Ridge_Escarpment]

All snow was not the best wording on my part. I didn't realize the entire forum was sold on a mostly icing event in the CAD region (just poke my head in from time to time). It seemed like people wanted large trends in the cold from what I was reading. With that said change "all snow" to "all frozen" in my post. I agree with your last sentence. It's hard for me to trust the colder solutions and people are hugging a model which has a cold bias.

I think people are just holding onto the model that has been consistent for the past 4 days and not like other models who have flip flopped more than John Kerry.

[Blue_Ridge_Escarpment]

JB's thoughts!

Lol. Please find me one model that has DC getting a half a foot of snow. Or 1/4 of that. Geez Louise.

[SN_Lover]

 

For me here just west of Hickory(I40). I get a nasty ICE storm along with snow:

 

Not happening. You need constant CAA and thats non-existent. Hickory will switch over to all rain. 

[superjames1992]

Not happening. You need constant CAA and thats non-existent. Hickory will switch over to all rain.

In-situ CAD, man. Yeah, latent heat release and such will eventually turn them over to rain, but it won't happen instantly as long as precip is falling. I've seen it a number of times here.

[Blue_Ridge_Escarpment]

Not happening. You need constant CAA and thats non-existent. Hickory will switch over to all rain.

No. You don't need constant CAA. In-situ wedge.

[wxduncan]

Not happening. You need constant CAA and thats non-existent. Hickory will switch over to all rain. 

I agree with you on the totals but there will be warning criteria ICE before the change over. Maybe not that much snow/ice(as shown on that map) but ICE of at least .25+ and maybe 1-3 inches is a good bet.

[beanskip]

Completely wrong and ignorant. In-situ cad events have given the region some of it's most crippling ice storms. 

Please take a break from posting.

Not happening. You need constant CAA and thats non-existent. Hickory will switch over to all rain. 

[Jon]

I think people are just holding onto the model that has been consistent for the past 4 days and not like other models who have flip flopped more than John Kerry.

I understand that, but maybe the most consistent model is going to end up consistently wrong and correct as we get closer? Will be interesting to see verification for this event, no doubt. CMC 5day verification score in last 7 days is .88 with the op/para euro both at .94, hard to argue with that.

[snowlover91]

A summary of the models while we wait for the 12z Euro shows the following results:

CMC- LP south and goes through central AL

GFS- similar to CMC but much warmer in cad regions. LP cuts late.

NAM- similar to GFS and CMC but faster with the LP and much colder/stronger CAD.

UK- further north over TN and cuts.

ARPEGE- 06z run takes low on a similar track to CMC.

RGEM- low track through Northern Louisiana at end of run, hour 48, with nice overrunning into NC. Close to the CMC. Much colder in CAD areas with low 20s and upper teens.

Hope this is helpful, just goes to show that as of now the GFS is a middle road solution with UK north while CMC, NAM and RGEM are further south. It's tough to bet against UK and Euro combo but then again the ARPEGE/RGEM/NAM have been doing better for my area the past two weeks.

[msuwx]

There is no such thing as  a "In-situ CAD".  As the high moves off the coast, it will cut the CAA off. WAA will overwhelm the shallow cold layer transitioning to all rain. 

 

 

In-situ CAD is absolutely a type of CAD... there's hybrid, classic, and in-situ.

 

See here, especially figure 5:

 

http://www.theweatherprediction.com/weatherpapers/050/index.html

 

"An In-Situ CAD setup (see Fig. 5) is one in which little or no cold air advection is occurring because the high pressure center which we relied on in the classic setup is too far to the south. Cold air is established through evaporational cooling caused by a pool of dry air east of the Appalachians. Surface winds still tend to be from the northeast along with some mountain-parallel ridging but no cold air advection is occurring from a high to the north. 850mb and 500mb patterns will be very similar to those of a classic setup."

[Brick Tamland]

It's also just one run of one model with the CMC. Can't just forget what the RGEM showed because of one run of the CMC.

[msuwx]

Nope. Never said it's right  -- I said that claiming that there is no such thing as "in situ CAD" is wrong and ignorant and that saying "party's over" based on a CMC run that still shows a major winter storm for I-85 CAD regions is the same. 

 

Here is an entire NWS paper on CAD, which includes references to in-situ.

 

http://www.erh.noaa.gov/er/hq/ssd/erps/tem/tem4.pdf

 

Yep..... I wrote an entire graduate student research project on CAD in the Carolinas...... in-situ actually extremely common. 

 

For whatever reason, I find CAD to be one of the absolute most fascinating occurrences in weather.

[BIG FROSTY]

Yep..... I wrote an entire graduate student research project on CAD in the Carolinas...... in-situ actually one of the most common. 

 

For whatever reason, I find CAD to be one of the absolute most fascinating occurrences in weather.

Yes Sir, I've seen it below freezing here and Icing and 50 degrees in Greensboro!!! 

[beanskip]

Oh absolutely. And this storm is a great illustration -- GFS: Rain and 50; CMC: Freezing rain and 30! 

It has to be one of the great micro-climate setups in the world.

 

Yep..... I wrote an entire graduate student research project on CAD in the Carolinas...... in-situ actually extremely common. 

 

For whatever reason, I find CAD to be one of the absolute most fascinating occurrences in weather.

[jburns]

Let's stay on topic.

[msuwx]

Yes Sir, I've seen it below freezing here and Icing and 50 degrees in Greensboro!!! 

 

 

Oh absolutely. And this storm is a great illustration -- GFS: Rain and 50; CMC: Freezing rain and 30! 

It has to be one of the great micro-climate setups in the world.

 

I've told many people that want to learn to forecast in this area.... learn the wedge. It will humble you in a heart beat.

[Blue_Ridge_Escarpment]

I've told many people that want to learn to forecast in this area.... learn the wedge. It will humble you in a heart beat.

Matt since you know this type of setup and this area so well, what do you see for the CAD areas?

[beanskip]

Back to this event and the Canadian's rogue-ness -- something's been ringing in my head that I went and checked on just now.

StrongWX, HKY, QueenCity and others will remember the famous 2003 lee trough surprise snowstorm. If not, you can read about it here -- it was amazing. http://www.weather.gov/media/gsp/localdat/cases/2003/23Jan_Snow/23January2003.pdf

 

Well, that setup was much different than Monday's event.

 

BUT ...

 

One sentence from the post-event NWS discussion sticks out for me -- it was on Page 6:

 

 

"Interestingly, the model that seemed to handle the event best was the Canadian model.

We have noticed several times in recent years the Canadian regional model has been one

of the most consistent and accurate models when it comes to wintry weather in the

western Carolinas and northeast Georgia."

 

 

[burrel2]

Another interesting tidbit from the link msuwx posted; I think it applies here.

 

"When attempting to forecast conditions during a CAD event, often times the grid spacing from models will be too coarse to show certain features. Don’t rely on the grid population. Models will typically handle the start of CAD better than its erosion.They handle erosion via a cold frontal passage and a coastal low better than they handle erosion via a surface low passing to the northwest and a surface low moving southwest to northeast through the area. If the model has a surface low passing to the northwest, often times it will bring the warm front too far northwest. If the model is moving the surface low southwest to northeast, it will often try to drive the low straight through the wedge which is a very rare occurrence. "

[msuwx]

Matt since you know this type of setup and this area so well, what do you see for the CAD areas?

 

Hey, I learn something every single CAD event and have been wrong plenty of times....haha.

 

How long the ice sticks around is so very dependent in this type of setup on precip rates into the initial dry air. That is really the aspect of the forecast I am most concerned with nailing down....how much precip Sunday night-Monday, and hard will it be. 

 

If the precip is significant through the day, heart of the CAD areas will likely either remain below freezing or rise just above only very late in the event. 

[superjames1992]

Another interesting tidbit from the link msuwx posted; I think it applies here.

 

"When attempting to forecast conditions during a CAD event, often times the grid spacing from models will be too coarse to show certain features. Don’t rely on the grid population. Models will typically handle the start of CAD better than its erosion.They handle erosion via a cold frontal passage and a coastal low better than they handle erosion via a surface low passing to the northwest and a surface low moving southwest to northeast through the area. If the model has a surface low passing to the northwest, often times it will bring the warm front too far northwest. If the model is moving the surface low southwest to northeast, it will often try to drive the low straight through the wedge which is a very rare occurrence. "

Yeah, we see that again and again. In the storm in January, every model showed RDU changing over to rain, which didn't happen. A lot of models showed this area changing over to rain and we never got out of the low 20s. Similar story in February '14, March '14, etc. I can't imagine that people who start out in the 20-25 degree range won't see a pretty decent storm, although I'm not a met, obviously, so take it with a grain of salt.

[weatherheels]

Lol. Please find me one model that has DC getting a half a foot of snow. Or 1/4 of that. Geez Louise.

And that's why he's a meteorologist. Not saying he's right or wrong but if all there was to meteorology was looking at models and nothing else, we all might be employed as meteorologists.

[Blue_Ridge_Escarpment]

Hey, I learn something every single CAD event and have been wrong plenty of times....haha.

How long the ice sticks around is so very dependent in this type of setup on precip rates into the initial dry air. That is really the aspect of the forecast I am most concerned with nailing down....how much precip Sunday night-Monday, and hard will it be.

If the precip is significant through the day, heart of the CAD areas will likely either remain below freezing or rise just above only very late in the event.

Very nice info. Much appreciated

[Cheeznado]

If the Euro comes in with a similar stronger cutter like the UKMET it's game over. That would make 4 runs in a row with that general solution. The best that can be hoped for IMO is some light-moderate ice from NE GA to western NC, with a change over to rain except maybe in the NW foothills of NC. We are way too close for any big shift back south, sorry.