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Pattern Jammin' January

For the midsouth it has been around the 20th we should see colder temps. Now this is mby. Every one has a different mby. So I stand corrected. It is the timeframe for mby for the pattern to change.
 
The 20th has always been the day for the cold to come in. That has been locked in for a few days. We just need a system locked in now. Eventually that should come to fruition


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All you analog folks, these dates ring any bells? 13 and 14 IIRC were very -EPOy and had a SE event around those dates, not sure if they're referencing storms or not though. Also have no idea on the January 13 SSW. I don't recall a SSW ever working in our favor, so....

Very interested to see if this look is in week 2 of the weeklies and what week 3 looks like.

1547502809276.png
 
ForsythSnow said:
I just checked the free maps and I see 9 is the low here and across N GA. I wonder if it's a blip or if the FV3 actually was onto something, but just about 10 degrees too cold.
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That is fun to look at but the odds are the Euro is too cold. I mean this has @pcbjr at only 31-32, Orlando at only 37, and me at ~28 at 1 PM on 1/21 under clear skies! I realize the airmass is cold but think this is a bit overdone lol. Other models are cold but not that cold.
 
GaWx said:
That is fun to look at but the odds are the Euro is too cold. I mean this has @pcbjr at only 31-32, Orlando at only 37, and me at ~28 at 1 PM under clear skies! I realize the airmass is cold but think this is a bit overdone lol. Other models are cold but not that cold.
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I agree, likely too cold...BUT its funny that the euro also has a 2m warm bias as well....lol
 
deltadog03 said:
I agree, likely too cold...BUT its funny that the euro also has a 2m warm bias as well....lol
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Chris,
Except over snowcover. Radiant has discovered the Euro is too cold when over snowcover. Although there's no snowcover nearby, maybe it is too cold to the north where there is snowcover projected and thus has it too cold even down here since the air is coming fast directly from up there. That is all I can think of for a possible reason.

Edit: I do recall the Euro having unrealistic 2M temperature falls over projected snowcover in the SE at times when ther's good radiational cooling conidtions. So, I believe Radiant. I mean they assume too much cooling due to it.
 
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GaWx said:
Chris,
Except over snowcover. Radiant has discovered the Euro is too cold when over snowcover. Although there's no snowcover nearby, maybe it is too cold to the north where there is snowcover projected and thus has it too cold even down here since the air is coming fast directly from up there. That is all I can think of for a possible reason.

Edit: I do recall the Euro having unrealistic 2M temperature falls over projected snowcover in the SE at times when ther's good radiational cooling conidtions. So, I believe Radiant. I mean they assume too much cooling due to it.
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Very true. Snow pack of the building to our north quickly.
 
GaWx said:
Chris,
Except over snowcover. Radiant has discovered the Euro is too cold when over snowcover. Although there's no snowcover nearby, maybe it is too cold to the north where there is snowcover projected and thus has it too cold even down here since the air is coming fast directly from up there. That is all I can think of for a possible reason.
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The GFS has an even larger decoupling bias that leads to spuriously cold temperatures particularly over snow pack, the Euro's bias is much smaller than it used to be because the model was tweaked several years ago.

What's actually happening in the model is that the GFS uses the Monin-Obukhov (MO) (1954) similarity hypothesis (described in the linked paper below) as a surface layer parameterization to describe turbulence in the surface layer. Using this similarity hypothesis leads to a bias may result in unrealistic decoupling between the surface and underlying atmosphere which yields unrealistically cold temperatures in the lowest levels of the atmosphere, especially over snow cover. Cold air drainage, gravity waves, and land surface heterogeneity at the sub-grid scale provide sources of turbulent mixing even in stable regimes that aren’t adequately represented by spectral NWP models like the GFS. These neglected sources of turbulence often manifest in a regime with a shallow layer of cold air underneath considerably warmer air (cases where there’s snow cover) or during cases characterized by strong radiative cooling of the surface at night.

See: https://journals.ametsoc.org/doi/pdf/10.1175/MWR-D-16-0438.1
 
18z goof is holding serve thru hr 138 with the LP system for this weekend...maybe a little backside action for TN/KY, but nothing more than a novelty if I had to guess.
 
NWS in Jackson Mississippi sniffing out the pattern change to winter weather:

Saturday night through next Monday: The primary concern later this weekend into early next week will be the first significant arctic air intrusion this winter, and the potential for a hard freeze event. Guidance consensus indicates temperatures falling below freezing Saturday night, then struggling to rise above freezing during the day Sunday...and potentially falling into the teens Sunday night. This will be in combination with strong gradient winds resulting in wind chill values in the teens to perhaps single digits Sunday night. Given higher than normal agreement among global model guidance and quick arrival of fresh arctic air moving south across snowpack over the Midwest, have lowered forecast temperatures for this period. Given the event looks marginal for meeting hard freeze criteria, will hold off on any mention in the HWO at this point. In terms of any winter weather potential, it looks like the cold air will mostly be "chasing" the rain as it moves east of the area. With that say, strong cold advection/mixing will help yield steep lapse low level lapse rates and positive surface CAPE as H850 temperatures fall to near -10 deg C, and expect there will be enough moisture for a few flurries/light snow showers if this forecast verifies. With very little if any accumulation there is no need to mention impacts. Looking down the road beyond this forecast and through the end of January, a wintry weather pattern, with future threats of significant cold and perhaps wintry precipitation, should remain in place over our region given strong global model ensemble agreement for high latitude blocking. /EC/

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The GFS has a 1055 high pressure in the upper plains at hour 192. That’s impressive!! Other day the FV3 had one that strong also. Going to be another cold hit in mid range..C12951D8-5C1E-45CA-BF87-35FBC29AED7F.png
 
DarkKnight said:
The GFS has a 1055 high pressure in the upper plains at hour 192. That’s impressive!! Other day the FV3 had one that strong also. Going to be another cold hit in mid range..View attachment 11113
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This should also push the cold air in the south giving a better chance of wintry weather down the road in this run..
 
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