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The Big One - Forecast & Discussion


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Sref has come in wetter farther west. Has the 1" line to the Tennessee border now.

 

The SLP track hasn't gone west, it's been very consistent, the precip maybe has reached farther west, not looking at that, but the SLP is definitely deeper.  But I do agree with you, Euro will win this one.

 

This is the 9z run...

 

 

sref_namer_054_mslp.gif

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Some info on snow/sleet/freezing rain...

 

 

dwzb.gif

 

Keep in mind also you need to have around -6c at the 700mb layer for good snow growth

 

http://www.wxonline.info/topics/thickness_pcp.html

 

First Approximation to the Rain-Snow Line

A first approximation to the location of the rain-snow line can be made using temperature data at the 850 mb and 700 mb level. The table below lists this approximation:

 

HhQxb70.png

 

This method does not involve thickness, but gives a good first guess to the location the rain-snow line. Its major shortcoming is that it looks only a data from one level and does not consider the vertical temperature distribution which is important to determining precipitation type.

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I thought a warm layer of 1C was usually too warm for snow?  Interesting.  I don't think a model has gotten GSO or CLT above +1C at 850 mb in quite a few runs now (well, except maybe the RGEM).

 

It will be interesting to see if the new recon data will bring about any changes in the 00z model suite.

Also, the thickness of the warm layer comes in to play as the graphic mentions. You can't just pick a temp and say it will rain as so many here tend to do. As with anything else to do with weather, it's a lot more complicated than it seems.
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I thought a warm layer of 1C was usually too warm for snow?  Interesting.  I don't think a model has gotten GSO or CLT above +1C at 850 mb in quite a few runs now (well, except maybe the RGEM).

 

It will be interesting to see if the new recon data will bring about any changes in the 00z model suite.

yea,

 

I’m not sure I by that.  I know i’ve seen real time soundings where it seemed like we were only 1C above freezing in just like a 500ft layer and I was getting sleet when I had assumed it would be snowing.

 

IMO,  I would not count on snow in this storm if there is any layer showing up on a sounding above .5C

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Also, the thickness of the warm layer comes in to play as the graphic mentions. You can't just pick a temp and say it will rain as so many here tend to do. As with anything else to do with weather, it's a lot more complicated than it seems.

 

Exactly why programs such as bufkit or other skew-t programs are immesnsely important with the "inbetween" levels not shown on raw text sometimes.

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rap continues to extend the finger toward north ga.

 

2840m line entrenched through KCAE.  This is most likely temporary; but good to see it.  1300m is heading into augusta/macon area and nosing southward every hour.  1540 up north of rock hill and enveloping the upstate and far north GA.

 

I can not stress enough for everyone to view the soundings at every 50mb of the atmosphere.  If there is a thick layer of warm air; many can get screwed.  850's cant be the only deciding factor.

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SLP is just south of Brownsville, TX. If anything, it's further south than expected. Looking @ SPC maps.

Once it gets off the SC coast, where exactly does the gulf channel run? Sometimes youll see these bombing storms prefer to stay and follow the channel even though the models have it more westward sometime.

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KCAE proper, using soundings at every level of the atmosphere is in for a Hell of a sleet/snow mix to very very start it.. if we have precip.. and then boom ZR.  multiple layers above 0c, going into the +1.5c + based on the RAP

 

Be safe guys.

 

PS.  Sleet MAY try to form if the surface cold is thick; but idk.

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The HRRR looks very odd- especially with the snow way down to central GA? Not gonna happen. The FFC sounding has a pretty good warm layer already at 850.

 

Well keep im ind ATL is far enough west that they will be on the backside of the developing 850 hPa low. They won't have as much WAA to deal with so dynamical cooling has the chance to produce an isothermal layer if you guys get under some really heavy rates.

 

I'm hoping you and them are wrong  :guitar: . I guess the bigger question is shouldn't the low take a path of least resistance and go around the wedge out along the coast line? What's pulling it inland vs. going just off the coast? Does it even matter for people from CLT to RDU?

 

You are right in theory, but the coldest temperatures are right at the surface up to 925 hPa... and the wedge at 850 hPa is not nearly as intense. Thus, when the WAA starts, many folks along and south of I-85 will start changing over. Dynamical cooling will try to compensate for a time, but this is a very dynamic system and the WAA will win over to areas that are right under the 850 hPa and don't have neutral or CAA at 850 hPa. 

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@24 low is staying inland. Yuck. Has CLT in a raging sleet storm. 

 

Sorry man... if you have to bet on the NAM to get the solution right vs. all the other models, you will be wrong 9/10. The NAM unfortunately is not a very good model these days relative to the rest of the global suite.

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Sorry man... if you have to bet on the NAM to get the solution right vs. all the other models, you will be wrong 9/10. The NAM unfortunately is not a very good model these days relative to the rest of the global suite.

 

Can't it just be right once? lol I was just badly not wanting anything to trend to the RGEM. 

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This run sets the 850 mb 0C isotherm more NE-oriented than in prior runs.  It looks like tons of sleet for CLT-proper, but I think it's actually a snowier run for places like Greensboro, Winston-Salem, Statesville, Shelby, etc.  I'll have to wait for the text to make sure my weenie eyes aren't deceiving me.

 

Your probably front end snow then sleet/snow mix from the temp's I have for GSO, INT is all snow.  It's the NAM past 18 hours, crazy we are even talking about it.

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