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January Medium/Long Range: A snowy January ahead?


mappy
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12 minutes ago, stormtracker said:

The man, the myth, the legend! Walt Drag! The OG posters know this man well.  :wub:

As a kid growing up in southern New England, Walt's AFDs were always a great and informative read (especially before an impending winter storm).

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42 minutes ago, psuhoffman said:

Good morning

Quick summary of what I see

The first threat Sunday is actually simple, but the cause for divergence across guidance is that its delicate.  There is a vigorous SW over western AK right now.  It's going to split over western Canada with a piece going east and merging into the TPV and another part diving into the trough, rounding the base and becoming our snow threat Sunday.  This energy activates the boundary.  It's pretty simple, how much energy and what track does this wave take.  But its delicate, its a relatively weak minor player in the overall flow so models will struggle with it, but this delicate weak piece of energy holds our fate wrt snowfall sunday.  

 

The next bigger threat involves major players on the hemispheric longwave scale, but it involves lots of them in a delicate intricate balancing act so its complicated.  

 

Setup1.thumb.png.9abc0e69efd76f5c1324a9be1be6c30b.png

The main TPV (1 and 2) is going to elongate and eventually split.  How much energy resides with 1 and 2 and where 1 ends up and how quickly it clears out of the way to our north is a major factor.  How much energy trails with 2 and how it interacts with 3 is a major factor.  What 4 does and how it influences the tail of the trough is a factor.  And finally what the next major wave 5 does and whether if flattens or amplifies the downstream trough is a factor.  

There is no way guidance is going to lock all this in at this range, especially absent blocking to set firm guides in the flow for all these features.  But in general we want more energy to reside further west with 2 and 3 and less with 1 and that has been the trend across all guidance over the last 24 hours.  But don't expect this to be resolved quickly.  Even the crazy GFS idea of holding back so much energy that it becomes the next threat 48 hours later is not off the table and shows up on some individual members of the EPS.  

Lastly, what comes AFTER AFTER....

day15ens.thumb.png.e05f969c8b50fe32f7a958b205934cc8.png

EPS continues to trend towards a much more friendly look for February.  It's already backing off on the crazy SER look it was suggesting.  It continues to trend towards lower heights near Hawaii which is a key, that look of the pac jet undercutting the WPO EPO ridge typically suggests troughs won't get stuck in the southwest and press east more.  It also pushes the WPO EPO ridge poleward and often leads to AO ridging over the top, which we are seeing more and more now on long range guidance.  This also helps to deepen troughs into the CONUS.  

This look puts a lot of pressure for the cold to press southeast.  Last nights op euro is a good example of what that pattern would actually look like because it matches the h5 of the EPS very closely. 

h5whatitslike.thumb.png.e888458cd3ca2eb605942566c042f6b6.png

The SER is there at H5 but look at what it actually looks like where it matters

Whatitlookslike.thumb.png.54cee87c866284e37e776f7f5b4d57b9.png

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We are very much in the game for boundary waves in that look.  It's February and we don't need as much of a perfect pattern to get snow the first half of February as just about every other time of the year.  If that is the worst look this winter has to offer (early to mid Feb was what all the analogs suggest is likely our most hostile period in terms of the longwave pattern) we are in pretty good shape.  

 

Excellent post. 

One thing I'm watching for wrt end of Jan into Feb is how the Alaska ridge evolves or trends. The GFS ensembles want to retrograde it SW to the Aleutians, causing the crazy warm SE ridge look. But the Euro ensembles have it split down the middle, 50% retrogrades it NW and makes a poleward ridging connection, keeping the cold across the CONUS. The other half is split between the GFS look and a compromise between the two (which is still "just cold enough" for us). The run-to-run trends are favorable so far, though. Definitely gonna keep an eye on this because it could open up more opportunities for a SECS/MECS in February.

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6 minutes ago, hstorm said:

As a kid growing up in southern New England, Walt's AFDs were always a great and informative read (especially before an impending winter storm).

F’n A! You got that right! Used to get me hype reading the detailed AFD’s. 

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17 minutes ago, Buddy1987 said:

F’n A! You got that right! Used to get me hype reading the detailed AFD’s. 

now ya got me humming "Kind Of A Drag" by the Buckinghams.... LOL.  I'm originally from NJ (not as far northwest as Walt is right now) but I skiied a lot in Vermont  and New Hampshire and would always read Walt's discussions with mucho interest and enthusiasm especially during winters.

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3 minutes ago, WxUSAF said:

Differences between the GGEM and GFS for the western shortwave for the potential next week event are dramatic even at 100 hours.

 

Just now, Amped said:

Cmc and gfs trending in opposite directions with how far the troff drapes back over the rockies.

GGEM dialing up something big again here I’d wager 

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2 minutes ago, SnowenOutThere said:

does have slightly less energy out west than its legendary 0z run but still should be great.

Theres a northern shortwave that wasn't there on the 0z run as well. Im not sure what will happen but it is a different variation than 0z, which makes sense

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