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Feb 25-26 Discussion/pbp


Wow

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Regarding temperatures...

 

I've looked at GFS/NAM/Euro sounding data (Euro at sfc/925/850 only).  For Charlotte on today's runs, I'm seeing this starting as a rain/snow mix with sfc wet-bulbs in the mid-30's.  As more precip works in and the column cools, the sfc temps drop to 32/33.  I would estimate we lose something around 0.15 liquid to mixing, then it goes to all snow.  That leaves 0.35 liq equiv as snow on the Euro, 0.47 as snow on the 18z NAM, and pretty much nothing on the suppressed GFS, lol

 

A couple other points...

1. The near sfc warm layer is quite shallow on the soundings...so, it's not as difficult to overcome

2. The cold air that we do have comes in tonight essentially, then hangs on until our storm arrives.  It's not like a situation where we are waiting on the cold air to come across the mountains and get here in time.

 

Having said all of that, no doubt there is very little wiggle room with temperatures in this area

 

Grit, am I getting bad numbers? this is what pops up for CLT:

 

post-62-0-82425700-1424732783_thumb.jpg

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North Georgia is the jackpot zone, jmo.

 

I agree. Right now, NGA looks like the bullseye for this storm. Best thing for Metro ATL at the moment would be for the storm track to trend south, so that the freezing line(s) can come down south more. But even if we get only 1 inch, I would be happy.

 

EDIT: Just saw Chris' maps for both storms. Seems like the local Mets disagree with TWC for the Wednesday storm. When is TWC ever right with these kinds of storms though? ;)

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Regarding temperatures...

I've looked at GFS/NAM/Euro sounding data (Euro at sfc/925/850 only). For Charlotte on today's runs, I'm seeing this starting as a rain/snow mix with sfc wet-bulbs in the mid-30's. As more precip works in and the column cools, the sfc temps drop to 32/33. I would estimate we lose something around 0.15 liquid to mixing, then it goes to all snow. That leaves 0.35 liq equiv as snow on the Euro, 0.47 as snow on the 18z NAM, and pretty much nothing on the suppressed GFS, lol

A couple other points...

1. The near sfc warm layer is quite shallow on the soundings...so, it's not as difficult to overcome

2. The cold air that we do have comes in tonight essentially, then hangs on until our storm arrives. It's not like a situation where we are waiting on the cold air to come across the mountains and get here in time.

Having said all of that, no doubt there is very little wiggle room with temperatures in this area

Thanks for posting this, Grit. It's unwise to blithely dismiss temp issues. NWS and experienced TV mets don't just throw that out there for the fun of it to torment people who like snow. They're not stupid. That said, the fact that this is not a situation where we're waiting on cold to come across the mountains and the fact that the above freezing layer is shallow is significant. So thanks for pointing that out. It helps me feel a bit better. I'll feel even better if we don't get much higher than 40.

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Grit, am I getting bad numbers? this is what pops up for CLT:

 

I was going off the wxbell maps, so our numbers may not match exactly....but, I have the precip starting on the Euro around 00z.  At that time, the sfc temp is 39 and the dewpoint is 29...so, mid-30's sfc wet-bulb.  It looks like you have a little more total qpf than what I have.

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I was going off the wxbell maps, so our numbers may not match exactly....but, I have the precip starting on the Euro around 00z.  At that time, the sfc temp is 39 and the dewpoint is 29...so, mid-30's sfc wet-bulb.  It looks like you have a little more total qpf than what I have.

 

Gotcha. I'm using extracted data from the Euro off AccuWx pro. 

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Fishel just showed a map and said right now models show around 5 inches of snow if it all accumulated but he thinks the warm ground will hinder that.

If it shifts 50 miles SE, 2 inches. If it shifts 50 miles NW, you would think a lot more snow, but the system will pull in warm air and cut down snow.

Seems to be going against what everyone here is saying, but okay. And like other mets have said here, the ground won't be that warm after the cold weather we have had the past week.
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IMHO that looks pretty good with the track, and ptypes

As usual the signals are conflicting because it's never easy. The RGEM is not way north at 54 like normal but the NavGem is uncharacteristically north, many times this winter when the NavGem had shown that it's been into something but usually it has support from another model, the ukmet is the next furthest north but it appeared to me it wasn't as far north...I still could see changes, they won't be big mileage wise but impact wise yes

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Fishel just showed a map and said right now models show around 5 inches of snow if it all accumulated but he thinks the warm ground will hinder that.

 

If it shifts 50 miles SE, 2 inches.  If it shifts 50 miles NW, you would think a lot more snow, but the system will pull in warm air and cut down snow.  

i despise the warm ground crap. i saw it snow and STICK 4" in west columbia sc on nov 1st where it was 70 DEGREES 48 HOURS PRIOR.  

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i despise the warm ground crap. i saw it snow and STICK 4" in west columbia sc on nov 1st where it was 70 DEGREES 48 HOURS PRIOR.  

 

I always tell people about a storm Albany NY had in April of 2000, they were either 80 or 86 degrees the day before and then got 16 inches of snow the next morning and it had no problem sticking.

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Soil temps aren't even a minor factor for accums here. I still got a little pile in the shade melting beside the house. Don't even sweat soil temps, put it to bed.

The only negative Nancy to even discuss is the shallow and I mean shallow above frzng surface temps at begining. Rates will trump easily if you are faced with this dilema. FEB 28 2004 I saw 17 inches with surface temp flipping between 33 and 32. You want to max your qpf at night and mby should be hammering during the wee hours Thursday a.m.

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As usual the signals are conflicting because it's never easy. The RGEM is not way north at 54 like normal but the NavGem is uncharacteristically north, many times this winter when the NavGem had shown that it's been into something but usually it has support from another model, the ukmet is the next furthest north but it appeared to me it wasn't as far north...I still could see changes, they won't be big mileage wise but impact wise yes

ya, I just think the UKIE is a bit too "strong" and likely a bit further north.  I understand the EPS has many members further south than the OP?  Either way, UKIE too far north, GFS too far south, I will take a blend and I-20 gets hit, maybe hard.  

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From Van Denton Fox 8 Met in High Point, NC...

 

2 Potentials for some snow. (Share the graphic with CAUTION).

#1. Tuesday we could see a few flurries, possibly snow showers as a disturbance moves to our south. Best chance late morning. Better chances near SC/NC line, Mtns and at the coast. Partial clearing by tomorrow afternoon.

#2. The European model is aggressive with snow for us on Wednesday night late and Thursday morning. Other models are not so favorable for a good snow. The graphic I am posting was provided by the WPC (Weather Prediction Center). The WPC is part of NOAA just like the SPC (Storm Prediction Center for Severe Weather) and TPC (Tropical Prediction Center). I am actually surprised they are this aggressive with the uncertainty in the models. This is basically putting all of ones faith in one model. Which can be dangerous.

We will have a much better idea on amounts by Tuesday evening. The track will play a very important role.

post-4599-0-50727200-1424735720_thumb.jp

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Local point forecast now calling for 1-2" Wed. night - but just a 60% chance of precipitation. Zone forecast isn't mentioning amounts yet.

 

As far as soil temps, current hourly soil temp is 39.5 here around Clayton, NC. That data can be pulled up on the Chronos page when you click on a site and enter your criteria. For those unfamiliar with the page, it covers the entire SE from VA to FL, and W to TN & KY.

 

http://www.nc-climate.ncsu.edu/map/

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I think the south movement of the precip is real if the temperature profiles are correct which are indicating a further southward push of the rain/snow line, That indicates to me that the model (GFS, RGEM) are picking up that stronger push of cold and reflecting it in the track of the surface low more to the south. This is why people are being so cautious about amounts of accumulation with the snow but it will be more refined by 12Z tomorrow either way.

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I think the south movement of the precip is real if the temperature profiles are correct which are indicating a further southward push of the rain/snow line, That indicates to me that the model (GFS, RGEM) are picking up that stronger push of cold and reflecting it in the track of the surface low more to the south. This is why people are being so cautious about amounts of accumulation with the snow but it will be more refined by 12Z tomorrow either way.

 

Read on that "other" board there is no south shift in the precip, just trending colder and precip expanding southward.  Who knows though.

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