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Jan 25/26 Storm Part IV


burgertime

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Phil, the 6z nam soundings came in much warmer for Franklin than before. It now shows a big warm nose from 850 to 700. Before it was below freezing above 850 and only about 33 to 34 at 850. Huge jump.

Well yea... the nam was out in la la land with regards to the 850mb low and the surface low at 00z. There was no way in the world that was going to verify. The 06z nam is much more realistic with the 500mb features and thus, a better representation of the 850mb low and stronger WAA.

Unless we see a significant trend southward with the 500mb low, the mountains below 3,500 feet are not going to stay all snow for the entire event. That trend southward could still occur, but I wouldn't hang my hat on it. Instead, most of our snowfall will likely come from the deformation band that will rapid intensify overhead as the 500mb low goes negative tilt. For this we want to see a stronger 500mb low thats placed just south of our location so we end up with deep layer backing flow into the mountains. This will set up the deformation band right overhead and allow us to have a good 3-6 hour period of heavy snow Wednesday Afternoon.

148ek41.gif

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I encourage everyone in the Lee of the Appalachians to closely follow where the 850mb low streamlines are oriented. If you are just slightly north or east of this feature... you likely will experience crashing 850mb temperatures and quickly switch over to heavy snow. The 06z NAM is actually further south with this feature, meaning a lot of those subzero 850mb temps the gfs is showing would likely be shifted about 25-50 miles southeastward.

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phil (or any other of our more knowledgeable folks), as i look at the center of the circulation on this map, which appears to be located just on the lee side of the Apps in NC, i have to ask: should that placement and circulation direction verify, will that create upslope on the lee side, and therefore enhance any precip rates for the escarpment, for instance?

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New discussion and video up....

I get the frustration and disappointment from some, although I don't know that anybody ever said "it is going to snow in X or Y location" with this system. Myself, as well as the others mets and forecasters I saw on the board, kept giving potential and possibilities.

At any rate, the upper air low on the back side of this system just screams that it will put down a period of heavy wet snow in spots somewhere across the region.....again, see the discussion on the blog.

Another great blog Matt,I look forward to reading your blog every morning...

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phil (or any other of our more knowledgeable folks), as i look at the center of the circulation on this map, which appears to be located just on the lee side of the Apps in NC, i have to ask: should that placement and circulation direction verify, will that create upslope on the lee side, and therefore enhance any precip rates for the escarpment, for instance?

I wouldn't look at the 850mb level for moisture in this example, because we will have a strong 700-500mb low going overhead just to the west of the 850mb low. The southerly flow out ahead of the features aloft will be what allows the lift and precipitation to occur. If the 500mb low becomes defined enough, we might also see a feature known as a trowal (trough of warm air aloft). This works in much the same way as isentropic lift, as the flow at a certain isentrope (300K for example) will lift as parcels travel from the high pressure to the east, and lower pressure to the west.

GSP has a great discussion of this feature in the March 1-2 2009 case study... here is a nice Satellite image describing the features.

http://www.erh.noaa....2MarchSnow.html

Conv_Belts_2025Z.jpg

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Another great blog Matt,I look forward to reading your blog every morning...

Thanks!

I always enjoy watching these ULLs and the dynamic cooling snow they can produce. Always fun. N MS is the winner on the 12z NAM.

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Indeed, great blog as usual and yes NMiss gets .75-1.0" on this run. Can it hold together long enough :popcorn:

Had a dynamic cooling event like this when I was in college at MSU. 8" in a few hours, then as you lose the precip rates, drizzle and 33-34 the next morning.

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Didn't see anything about it earlier in the thread, so...

Charleston has mentioned a small chance of "isolated thunderstorms" in the HWO:

SEVERE THUNDERSTORMS...ISOLATED THUNDERSTORMS WILL BE POSSIBLE

TUESDAY NIGHT AS LOW PRESSURE MOVES ALONG THE BEACHES OF SOUTHEAST

SOUTH CAROLINA AND SOUTHEAST GEORGIA. AT THIS TIME...THE RISK FOR

SEVERE THUNDERSTORMS WILL BE GREATEST OVER THE ADJACENT ATLANTIC

WATERS...HOWEVER THE RISK FOR SEVERE THUNDERSTORMS COULD INCREASE

ACROSS THE COASTAL COUNTIES IF THE LOW TRACKS EVEN SLIGHTLY

FARTHER INLAND. THE MAIN HAZARDS WOULD BE DAMAGING WINDS IN EXCESS

OF 60 MPH AND ISOLATED TORNADOES.

First severe of the season, perhaps?

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