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January 17th-18th Winter Storm Discussion


BullCityWx

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I haven't seen an increase in strength in the last few runs -- tilt has kind of wobbled around -- definitely north, though.

Is it further north or just stronger and taking a more neutral tilt? Either way it certainly doesn't look good for my back yard as the northern part of that low goes right over CLT. I'm still on the side of just wait and see. Models are still models.

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I haven't seen an increase in strength in the last few runs -- tilt has kind of wobbled around -- definitely north, though.

 

The contour just looked a little wider to me which is why I was wondering. Reflective puts CLT to around Shelby in a bit of a dry slot it looks like. Who knows though? I guess we'll see. 

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Yeah, I told myself last night that for this to work, everything would have to be perfect -- can't be too far away from ULL, but can't be too close. Not feeling perfect right now ....

The contour just looked a little wider to me which is why I was wondering. Reflective puts CLT to around Shelby in a bit of a dry slot it looks like. Who knows though? I guess we'll see. 

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Looking at the 00 17 rap and the current placement of the ull shows that the current placement is a touch sw of the new rap 00 850 placement.

Yeah, the short-range model trending is clear -- upper level features inching north making it more difficult for cold air to turn over the precip to the immdieate north of ULL -- that would, unfortunately, mean the I-85/US74 corridor west of Charlotte

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Now is the time to panic  :cry:

 

RAP_255_2013011718_F10_RELV_500_MB.png

Uh oh!!  Dig Baby Dig!!  Is there any chance that this is where it was before on the models?  Seems like earlier runs the system was an open wave at 04z.  I hope that nobody's forecasts busts really bad on the low side and everything shifts north 75 miles.  I know it has happened before, but I do hate to see anyone lose their fantasy predicted snowfall.

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Uh oh!!  Dig Baby Dig!!  Is there any chance that this is where it was before on the models?  Seems like earlier runs the system was an open wave at 04z.  I hope that nobody's forecasts busts really bad on the low side and everything shifts north 75 miles.  I know it has happened before, but I do hate to see anyone lose their fantasy predicted snowfall.

 

Prev run was open.. now it is closed in the same place.  

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Could a met explain a little more in-depth why the foothills are really getting the shaft on most of the hi-res models? That's not an imby question, I just want to know from a meteorlogical standpoint.

 

Its really quite simple. As the northerly flow increases as the 850 hPa low intensifies, the downsloping off the Appalachian mountains will also increase resulting in adiabatic warming and weaker precipitation rates immediately in the lee of the mountains. This is the same process that resulted in a local minima in snowfall accumulation in the immediate lee of the higher elevations in the upper foothills of NC in the March 2009 event, and it could potentially play out in a similar manor in this event. In fact, the amount of cold 850 hPa air is actually less than the March 2009 I've been mentioning so the problem could potentially be more exaggerated for those with marginal themodynamics in the lee of the Appalachians. 

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Prev run was open.. now it is closed in the same place.  

Thanks for the reply!  I thought that may be the case.  By the system remaining closed it appeared to have jumped north 50 miles, but if the 558 line is in the same spot any northward jump would be in appearance only.  There's going to be alot of ups and downs the rest of the day!

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Looking at the 00 17 rap and the current placement of the ull shows that the current placement is a touch sw of the new rap 00 850 placement.

 

There's really a lot of minor, minor shifts back and forth.  The RAP maps can be addictive.

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i wouldnt fret on the 500 low position. thats some crazy energy overhead!

Uh oh!!  Dig Baby Dig!!  Is there any chance that this is where it was before on the models?  Seems like earlier runs the system was an open wave at 04z.  I hope that nobody's forecasts busts really bad on the low side and everything shifts north 75 miles.  I know it has happened before, but I do hate to see anyone lose their fantasy predicted snowfall.

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Its really quite simple. As the northerly flow increases as the 850 hPa low intensifies, the downsloping off the Appalachian mountains will also increase resulting in adiabatic warming and weaker precipitation rates immediately in the lee of the mountains. This is the same process that resulted in a local minima in snowfall accumulation in the immediate lee of the higher elevations in the upper foothills of NC in the March 2009 event, and it could potentially play out in a similar manor in this event. In fact, the amount of cold 850 hPa air is actually less than the March 2009 I've been mentioning so the problem could potentially be more exaggerated for those with marginal themodynamics in the lee of the Appalachians. 

 

Thanks for this, me and Frosty have been asking for days. I will save this. I don't think much more can fall from the sky here after 6-12 inches of rain.

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I think everyone in Central NC anyway needs to take a breath and read the update from RAH as of 1:50pm. The person writing that tends to know what they are talking about ;)

Jeremy: When you're living on the edge of the knife, it's hard to relax. Those 20-mile wobbles are feast and famine down here!

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im sorry but is the fact it hasnt yet taken on a negative tilt by then a good or bad thing for snow

ON radar look down around Montgomery.  That's the comma's tail end.  If that's snow when it pulls through Ga. it would then depend on the angle that it's coming up.  It could slde by west of you, or through you, but you have to figure the rates and the time would be so slight you're just going to see some flakes.  If it dries up as it's coming up...then on the the next one.  T

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I think you guys are putting a little too much stock into the hour to hour runs of the RAP. THis model can be somewhat useful in short term trends, but I usually only use it to look at the the radar reflectivity trends, 700mb VV, and perhaps some surface pressure trends. It is notoriously bad with QPF forecasting.

 

To me things look on track, granted I am in a bit more safe (with respect to snow) area then areas to the south. As I have said, the southern NC area looked to be close to the sharp gradient on the model data, so small trends here are there could be important.

 

But I just caution about placing too much faith in the RAP or any of these rapid cycling models. The synoptic scenario laid out by the global models the last few days is happening, now lets see how things verify over the coming hours, by watching radar, satellite, surface trends. In my mind at least things are coming together as planned. The southern foothills, CLT area is going to be close, but that is how it has looked to me the whole time anyway, so no real surprise there.

 

I think the northern piedmont of NC, southern Va is where the money spot will be outside the mountains. What we need to watch is where this band sets up this evening.

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Its really quite simple. As the northerly flow increases as the 850 hPa low intensifies, the downsloping off the Appalachian mountains will also increase resulting in adiabatic warming and weaker precipitation rates immediately in the lee of the mountains. This is the same process that resulted in a local minima in snowfall accumulation in the immediate lee of the higher elevations in the upper foothills of NC in the March 2009 event, and it could potentially play out in a similar manor in this event. In fact, the amount of cold 850 hPa air is actually less than the March 2009 I've been mentioning so the problem could potentially be more exaggerated for those with marginal themodynamics in the lee of the Appalachians. 

Good to see/hear from you Phil!! Someone is going to get very disappointed tonight with all these big totals getting thrown around...sad to say. Still not expecting much more than some mixing in here in NW SC maybe a brief change over which would suffice. That warm nose is a spoiler on this side of the hills and without a any CAD it's a butt to get rid of or overcome. The track is very important...not too close but not too far!

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