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Winter Weather Potential - January 20-27


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Ok... going out on a limb by creating this post, but I believe there is enough model justification to warrant it.  No guarantees! 😜 The models are all beginning to show threats for this time peri

Ok, I've been playing today. So for your viewing pleasure, we're going old school. Here's your "Local on the 8's" the way the Weather Channel USE to do it in the early 90's, and this is real live data

Ok folks... here are my thoughts about what is going on right now.  With such an active pattern, the models are totally worthless and of no help at all past 5 days, not even the ensembles. We're

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Well I just got back in, I’d had enough of the cold and wind lol. Anyway GEFS got over it’s hiccup for the most part. Not quite back to what it was at 12z but, much improved over the dismal 18z run. Most of the OPs were really close to being good, but we’re just late bloomers again. Massive hit on the FV3 from Augusta area up through the Carolinas. However the GEFS favors N GA over the Carolinas still, so at this range I will lean on them.

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Some good thoughts this morning from the Atlanta NWS office

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Afterwards, models begin to diverge, but stay in agreement that the
longwave trough which will settle in over the central U.S. will be
there to stay for a bit. Given how active the long range pattern
looks to be, as more and more shortwaves move through the longwave

trough the less and less reliable model forecasts get. Regardless
both the GFS and Euro have the next shortwave kicking through on
Friday morning, but there are difference on if the system will be
dry or could hold snow flurries for far Northern Georgia.

The final storm system in the extended forecast is progged to move
through the forecast area starting on Sunday. There are differences
on storm evolution and moisture between the Euro an GFS, but they

are slowly beginning to come in line with one another. Both have
digging shortwaves moving through the larger scale trough with
surface low pressures developing along the baroclinic Gulf coast

boundary (classic for winter storms in this area). The GFS has a
stream of moisture ahead of the storm that could bring some light
snow primarily to NW GA. The Euro develops a much deeper storm
system with a more complex evolution with a lot more
moisture and 'wrap-around' precip on the backside of the low-
pressure system on Sunday night which could bring light snow to a

larger portion of the forecast area. It's far too early to nail down
further details with this system as confidence is still low in the
exact scenario that will develop, however, confidence is growing that
we could see at least minor impacts to the area with this system.

ecmwf_mslp_noram_28-21.thumb.png.f90fae4f2b8ce0c8ac835d915c46575c.png

ecmwf_slp_qpf6_noram_29-21.thumb.png.301608f0b287bb6748ddc7638e85b66f.png

ecmwf_z500_vort_noram_28-21.thumb.png.87cd095b6d54822ccea01865ca2b0dbf.png

ecmwf_th_500_noram_29-21.thumb.png.f76cc85d9d2d3b4bb9ff02edf934fc56.png

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Discussion from the Huntsville NWS office

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A chilly airmass remaining from the Arctic high and the arrival of a
stronger disturbance from the NW will bring a potential winter
weather event to the Tennessee Valley this weekend. The deterministic
GFS/ECMWF/Canadian all indicate a surface low forming along the Gulf
coast late Sat/early Sun. Although the precip will probably start out
as a cold rain, the amount of cold air in place and arrival of the
next clipper will reinforce the cold air already in place. It will
be cold enough for a rain/snow mix, with the three above models plus
the GFS ensemble all noting measurable QPF. Given a brief appearance
of measurable precip, stayed with light accumulations Sat night into
Sun morning. There is too much model disagreement with details on
where the heaviest precip could fall. The precip at this time could
become all snow Sat night, but turn to a mix before ending Sun
afternoon.

 

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The basic setup for this weekend is a classic winter setup for us, and what I've been expecting to see. If you read the clip from the AFD, they talk about the "baroclinic boundary". Storms love to track along an area with a tight temperature gradient, and the Gulf coast is a natural boundary, especially during the winter months. Very cold air over land bumps into the warm moist air over the Gulf and forms a gradient or boundary. When storms form along that boundary, moisture is thrown up and over the cold air by low pressure, and they track along that line.

This natural boundary is also the reason the storms turn left once they cross FL/GA and then head up the coast, and that's why you see a lot of east coast storms that just ride the coastline. 

So... watch the evolution of this system. We would like to see some decent cold air in place as the system is to our SW so the leading edge is snow. That in turn helps to reinforce the cold before heavier moisture arrives. Of course... that's ideal but not always thew way it happens. 

The feature for this weekend won't be onshore until  Thursday (this image), but we will need to watch and see how the models handle this wave. On the morning Euro run, it developed the low AFTER it got to the Georgia coast instead of along the Gulf coast, so we need to see some earlier development in order to get more substantial precipitation. So we'll watch the strength of this feature as it makes landfall on the west coast and track it as it begins its dive south. Right now this run looks to initialize it at 1010 mb at 06z Wednesday, so we'll check back on Wednesday to see how this compares to the real world, as well as compare the placement, strength, and orientation of the surface features. 

Snap346062315.thumb.jpg.57063ed00139dec72eb51289c9d738bc.jpg

 

Edited by NorthGeorgiaWX
Edit replace the image... I'm looking at too many. :-)
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20 minutes ago, NorthGeorgiaWX said:

The basic setup for this weekend is a classic winter setup for us, and what I've been expecting to see. If you read the clip from the AFD, they talk about the "baroclinic boundary". Storms love to track along an area with a tight temperature gradient, and the Gulf coast is a natural boundary, especially during the winter months. Very cold air over land bumps into the warm moist air over the Gulf and forms a boundary. When storms form along that boundary, moisture is thrown up and over the cold air by low pressure.

This natural boundary is also the reason the storms turn left once they cross FL/GA and then head up the coast, and that's why you see a lot of east coast storms that just ride the coastline. 

So... watch the evolution of this system. We would like to see some decent cold air in place as the system is to our SW so the leading edge is snow. That in turn helps to reinforce the cold before heavier moisture arrives. Of course... that's ideal but not always thew way it happens. 

The feature for this weekend won't be onshore until the early morning hours on Wednesday (this image), but we will need to watch and see how the models handle this wave. On the morning Euro run, it developed the low AFTER it got to the Georgia coast instead of along the Gulf coast, so we need to see some earlier development in order to get more substantial precipitation. So we'll watch the strength of this feature as it makes landfall on the west coast and track it as it begins its dive south. Right now this run looks to initialize it at 1004 mb at 06z Wednesday, so we'll check back on Wednesday to see how this compares to the real world. 

Snap346062312.thumb.jpg.30f4de142641d31fd6343bfe25b29c21.jpg

We really need to get this thing cranking as quick as possible once it gets to the coast. There are some big dog EURO Ensemble members still keeping dreams alive!

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2 minutes ago, Shannon said:

We really need to get this thing cranking as quick as possible once it gets to the coast. There are some big dog EURO Ensemble members still keeping dreams alive!

Yes, those details are still up in the air... so to speak. 🙂 It will probably take 3-4 days before details start to become clear. 

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36 minutes ago, NorthGeorgiaWX said:

The basic setup for this weekend is a classic winter setup for us, and what I've been expecting to see. If you read the clip from the AFD, they talk about the "baroclinic boundary". Storms love to track along an area with a tight temperature gradient, and the Gulf coast is a natural boundary, especially during the winter months. Very cold air over land bumps into the warm moist air over the Gulf and forms a gradient or boundary. When storms form along that boundary, moisture is thrown up and over the cold air by low pressure, and they track along that line.

This natural boundary is also the reason the storms turn left once they cross FL/GA and then head up the coast, and that's why you see a lot of east coast storms that just ride the coastline. 

So... watch the evolution of this system. We would like to see some decent cold air in place as the system is to our SW so the leading edge is snow. That in turn helps to reinforce the cold before heavier moisture arrives. Of course... that's ideal but not always thew way it happens. 

The feature for this weekend won't be onshore until  Thursday (this image), but we will need to watch and see how the models handle this wave. On the morning Euro run, it developed the low AFTER it got to the Georgia coast instead of along the Gulf coast, so we need to see some earlier development in order to get more substantial precipitation. So we'll watch the strength of this feature as it makes landfall on the west coast and track it as it begins its dive south. Right now this run looks to initialize it at 1010 mb at 06z Wednesday, so we'll check back on Wednesday to see how this compares to the real world, as well as compare the placement, strength, and orientation of the surface features. 

Snap346062315.thumb.jpg.57063ed00139dec72eb51289c9d738bc.jpg

 

The shark just came through...now it's time for the whale....

FB_IMG_1548077581227.jpg

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And again, the speed these waves are traveling as they dive south prevents a lot of development before it shifts off the coast, and the partial reason for that is the lack of a -NAO. A -NAO helps to create more of a buckle in the trough, and send those waves south instead of southeast which slows them down. But... the models are still showing a positive bump in the NAO around the weekend before going negative again.

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3 minutes ago, gatormom said:

And now I got that blasted song in my head! 🙂

 

I thought about that and you it was going to get stuck in my head and everybody else's but hey it was worth it.... I couldn't pass it up after seeing it.... the whole whale thing was my idea though

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