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March 24-25 Winter Storm Threat


Mitchel Volk

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Whether it's cold or not, C NJ and the likes will have mixing issues. The 850 mb low to our west is almost invariably a killer for areas to the east.

 

Yea it is going to be(unless the Canadian is right), but on paved surfaces were talking about a mid September sun now.

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Climo argues for a New England hit. I still stand by this, though obviously, the models are proving me wrong.

You're better than this. Climo argues what it wants, but I don't listen to Climo when there's a historically negative AO and a huge block extending into Central Canada.

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only two years had measurable snow on March 25th...The last time was in 1899...this year could be the 3rd time...If it comes after dark we will get some measurable snow...Not many storms accumulated during the mid day this time of year and in April as well...March 29th 1970 and 1974 had accumulating snow during the mid day hours...April 6th 1982 during Aprils only blizzard and the 7th 2003 had accumulating snow in the mid day hours...Most accumulating storms came before noon or after dusk...

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You're better than this. Climo argues what it wants, but I don't listen to Climo when there's a historically negative AO and a huge block extending into Central Canada.

which is the the point i was trying to make when i got attacked by him.....do the new rules not apply to mets?   anyway, gfs still somewhat suppressed, but signs are encouraging tonight.

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If I had to wager...PHL doesn't see 6-12 in. out of this (take from that what you will). My concern is that this will be a "pretty snow;" the type of event where virga flies for hours, it finally reaches the ground at rush hour, sun comes up and it snows all morning, at times heavy, but with not much to show. Timing seems to be just about right, but things WILL change (how much is still a toss up).

 

You're better than this. Climo argues what it wants, but I don't listen to Climo when there's a historically negative AO and a huge block extending into Central Canada.

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The 3/22 0z run of the GFS has continued to show slow improvement in the 500 mb pattern. At the surface, the GFS has brought the area of moderate to heavy precipitation northward from the 3/21 18z run. The 18z run was south of the 3/21 12z run when it came to the extent of moderate to heavy precipitation. The 0z run is better than the 12z one in terms of northward extent of the precipitation.

 

Below is a comparison of the three runs:

 

GFS032220130z_zps8987ad96.jpg

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The 3/22 0z run of the GFS has continued to show slow improvement in the 500 mb pattern. At the surface, the GFS has brought the area of moderate to heavy precipitation northward from the 3/21 18z run. The 18z run was south of the 3/21 12z run when it came to the extent of moderate to heavy precipitation. The 0z run is better than the 12z one in terms of northward extent of the precipitation.

 

Below is a comparison of the three runs:

 

Nice graphical illustration of what's been going on. I think the changes aloft were pretty marked by 60-66 hours or so. The global models have been slowly trending (As they usually do) towards less of a compressed mid level height field over the Northeast US around that time...valid 18z Sunday. With a major disturbance over the Tennessee Valley at that time...I think it's a very good sign to see them trending that way. 

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The more you analyze the GFS height field, the more you realize that it continues to tick towards the more amplified solutions. It's generally been trending towards a better oriented upper level low north of New England for 5 or 6 model cycles now, despite some expected variations in between. The vort spoke that rotates around the upper level low and meanders southward towards New England has been trending less impressive for that same duration...and as spoken about before this allows for a bit of a window for the height field to amplify as the shortwave moves into the Tennessee Valley.

 

This is arguably the most important time frame for us as it allows the best lift to shoot northward towards our area. The small window in the height field expansion to the north actually allows the surface low to redevelop and tuck in farther north closer to the coast like the NAM shows. I still believe the GFS might be struggling with a lead vort and de amplifying the height field a little too much ahead of the main vort max. You can see this on the mid level vort charts from PSU ewall.

 

 

post-6-0-85843600-1363927864_thumb.png

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It has def limited the northern extent of the precip.. There is gonna some real pissed up ppl wherever this gradient sets up.

 

Could've seen this coming a mile away given the timing of the vort max underneath the block. These historically low AO periods, and presence of really robust high latitude blocking, are notorious for producing big cutoffs on the NW fringes of winter storms. 

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The more you analyze the GFS height field, the more you realize that it continues to tick towards the more amplified solutions. It's generally been trending towards a better oriented upper level low north of New England for 5 or 6 model cycles now, despite some expected variations in between. The vort spoke that rotates around the upper level low and meanders southward towards New England has been trending less impressive for that same duration...and as spoken about before this allows for a bit of a window for the height field to amplify as the shortwave moves into the Tennessee Valley.

 

This is arguably the most important time frame for us as it allows the best lift to shoot northward towards our area. The small window in the height field expansion to the north actually allows the surface low to redevelop and tuck in farther north closer to the coast like the NAM shows. I still believe the GFS might be struggling with a lead vort and de amplifying the height field a little too much ahead of the main vort max. You can see this on the mid level vort charts from PSU ewall.

 

 

attachicon.gifgfsleadvort.png

 

Great post. I thought the GFS spawned the secondary too far southeast based on where the H5 vort was. That run was very close to showing a much better solution

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Great post. I thought the GFS spawned the secondary too far southeast based on where the H5 vort was. That run was very close to showing a much better solution

 

I'm not sure it redeveloped it too far south...but that lead vorticity always makes me pause especially on the GFS. The Dec 26 2010 event is permanently engraved in my memory and there's nothing I can do about it...the GFS suffered from deamplifying the ridge axis ahead of the main shortwave and a lead vort from Gulf convection was the culprit. Obviously there were other things at play there but I won't ever forget it. 

 

The NAM is farther northwest not only because it is more amplified with that ridge axis ahead of the main vorticity...but because the vort to the north over New England is better oriented. It really doesn't compress the height field over New England nearly as much as the GFS. So the secondary low has some room to come northward nearer to the coast. 

 

This isn't only important for the track of the surface low...but we need the mid level height field to be favorably positioned to have favorable jet dynamics and get good precipitation into our area. This has the potential to be a bomb. 

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