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NC/VA Sunday Snow Threat

MillzPirate

By MillzPirate,
in Southeastern States

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RaleighWx

RaleighWx

Posted
Posted

Allan,

12z NAM looks to shift precip slightly south. Reading it directly it looks like the heaver amounts would actually be a little south of my location. What's your take?

Yeah this run it beefed up QPF but took the best band from say the northern mountains through the northern foothills, NW piedmont, central piedmont, but it could edge north again next run. Hard to say. Should be about a 50-100 mile wide corridor where best precip will fall east of the mountains.

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phil882

phil882

Posted
Posted

I hope you mean LEFT exit region. The right exit region is not favorable for upward motions.

I agree with your point about the Jet Streak (I think you meant left exit) that would certainly work in our favor as would the overnight timing but I just don't feel comfortable being close to the line with the partials.

Whoops! Thanks for the correction guys... too early to be forgetting my directions.

For what its worth, it does appear that the NAM is indicating accumulating snowfall across portions of eastern NC. If the NAM is anywhere close to reality with the precipitation totals, I wouldn't be all that surprised if it was right with the snowfall forecast either since 850mb temperatures are solidly below freezing across the northern half of NC. If this does end up being a nighttime event, the we won't have to contend with major boundary layer issues that plague us during the day. All in all it wouldn't be all the unreasonable to get 1-2" out of this event..

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WeatherNC

WeatherNC

Posted
Posted

Purely for entertainment, as after this we will be in for a stretch of dry, cold, and non-entertaining weather...

accumulated snowfall maps from the 12z NAM at 48hrs

Modified to use fixed 10:1 ratio

Using fixed 10:1 ratio, total precip, and snow flag

Using Mr. Evan Kuchera algorithm for snow to liquid ratio

Legend

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packfan98

packfan98

Posted
Posted

Those snowfall maps can really get someone excited! I don't think there is any way that the central piedmont will get over 2 inches. How much will we lose to evaporation? I hate VIRGA storms where it snowing right above me for hours and I'm straining my eyes trying to see a flake! And I guess it's time to ask the dreaded snowfall ratio question. It seems that the upper levels will be turning very cold as the event is unfolding. Will that result in higher snow ratios so that we may see more on the handy-dandy snow measuring stick? Can someone give the link to the soundings at GSO which show the snow ratios? Thanks! I keep telling myself not to get excited over this event. I will not bite! I will not bite! Save me GFS!

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Cold Rain

Cold Rain

Posted
Posted

This is certainly fun to look at and very interesting for so early in the season, and I do like the look of the snow maps above. But I have to respectfully disagree with any accumulation forecast outside of the mountains, really, for the following reasons:

1) If temps get into the mid 40s or higher tomorrow, as forecast, the boundary layer will not cool down enough to support snowfall that will be meaningful enoungh to accumulate. A few flakes mixing in, or a snow burst, if it falls hard enough, maybe. But there will be no radiational cooling. By the time evaporative cooling brings the boundary temps down low enough to support all snow, the bulk of the precip will probably be gone.

2) The NAM is most likely overdoing the amount of precip. We have seen this several times over the last couple of years. Less precip intensity, less effective evaporitive cooling, less snow making it to the ground.

3) Ground temps are way too warm.

We'll see how this evolves, but I would be very, very surprised if we see anything end up on the ground. I have a feeling that this will be one of those times where you're watching light rain come down, waiting for the changeover and thinking that you keep seeing a snowflake every now and then.

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Jon

Jon

Posted
Posted

WeatherNC thanks for posting the weenie food, Brick is chowin down! :popcorn:

This storm looks to be nice for my area, however if 2" does fall we all know it will not stick. I'm really interested in seeing the rates we get out of this system, and when the cooling takes place.

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burgertime

burgertime

Posted
Posted

This is certainly fun to look at and very interesting for so early in the season, and I do like the look of the snow maps above. But I have to respectfully disagree with any accumulation forecast outside of the mountains, really, for the following reasons:

1) If temps get into the mid 40s or higher tomorrow, as forecast, the boundary layer will not cool down enough to support snowfall that will be meaningful enoungh to accumulate. A few flakes mixing in, or a snow burst, if it falls hard enough, maybe. But there will be no radiational cooling. By the time evaporative cooling brings the boundary temps down low enough to support all snow, the bulk of the precip will probably be gone.

2) The NAM is most likely overdoing the amount of precip. We have seen this several times over the last couple of years. Less precip intensity, less effective evaporitive cooling, less snow making it to the ground.

3) Ground temps are way too warm.

We'll see how this evolves, but I would be very, very surprised if we see anything end up on the ground. I have a feeling that this will be one of those times where you're watching light rain come down, waiting for the changeover and thinking that you keep seeing a snowflake every now and then.

This...when you have good moisture coming from the gulf the NAM over does it. So you know when a system that doesn't have a good feed for moisture the NAM probably isn't going to do it.

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SBUWX23

SBUWX23

Posted
Posted

Im gong to throw a wrench in everyones It will not stick assumptions... If you can dodge a wrench you can dodge a ball....:thumbsup:

If the snow falls at decent rates, there will be accumulations. If the snow is occuring at night, grassy surfaces and elevated areas will see aummulations no question since the sun is down. Roads stay wet but it could make for a pretty scene if snow actually falls. November 2000 event rings a bell with this as snow fell late afternoon and evening unexpectedly accumulated to everything but roads. Different type of storm but similar idea.

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WeatherNC

WeatherNC

Posted
Posted
EXPECT THERE TO BE A CORE OF MDT SNOWFALL ACRS THE FAVORED W AND

NW FACING SLOPES OF THE HIGHER TERRAIN DOWN ACRS ERN KY...SRN

WV..AND SWRN VA AS THE ENERGY CROSSES THE REGION. THE PCPN

COVERAGE E OF THE APPALACHIANS SHOULD BE LIGHT WITH DEEPER LYR

DOWNSLOPE FLOW SETTING UP. HPC QPF FAVORED A MORE PROGRESSIVE

NON-NAM CONSENSUS...LED BY THE ECMWF.

d13_fill.gif

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Jon

Jon

Posted
Posted

I am debating on working up a call map this afternoon.

Honestly, I'd like to see it...As I stated in previous threads, I love seeing the call maps mets put out, even if it is a clipper! Snow potential = call map time, imo.

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griteater

griteater

Posted
Posted

Matthew East just posted this in the Dec thread.

FWIW, the latest run of our in-house RPM (WRF based) is showing considerably less snow east of the mountains than its previous few runs had shown.

I agree though, this one bears watching for at least a little trickiness at least....

I lost a little faith in the 'in-house' model with the early March storm when he said it went bonkers and was showing over an inch of precip...but we ended up with 0.28. Granted, it's only model guidance - but it's hard to forget the storm fails.

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SBUWX23

SBUWX23

Posted
Posted

The GFS timing actually isn't bad for those of us in the western part of the state. It's cold enough for snow when the precip gets here which could mean precip rates would be the deciding ptype factor.

Sorry Jeremy, I totally forgot about you guys and I agree. Its hard for me to remember west NC let alone central NC sometimes while posting with you guys when I live on Long Island.

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WeatherNC

WeatherNC

Posted
Posted

I lost a little faith in the 'in-house' model with the early March storm when he said it went bonkers and was showing over an inch of precip...but we ended up with 0.28. Granted, it's only model guidance - but it's hard to forget the storm fails.

I am interested to see what the highres ncep models show this afternoon, as the event is finally coming into there range. Looking over the graphics on twisterdata, the NAM develops what I interpret as a lee side trough, and the GFS does not. That is at-least one of the reasons why it is not as progressive and has greater QPF totals east of the mountains, as the trough enhances lift ahead of it. The 33 hr 700 mb vv panel clearly shows this. Is this a case where the higher resolution models are able to pick up on small things like this the global models miss? Don't know, as sometimes higher resolution hurts performance in that it overdoes features in the grid.

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