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December Forecast Discussion


REDMK6GLI

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968mb over Lake Surperior. Tons of cold air trying to wrap around the backside. The Western half of PA is either a rain/snow mix or possibly snow. BL is borderline.

It goes from Lake Erie to Lake Superior?  Seems geographically unlikely, kiddo, unless there's one hell of a phase / retrogression.

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It goes from Lake Erie to Lake Superior? Seems geographically unlikely, kiddo, unless there's one hell of a phase / retrogression.

Both the GFS and Euro retrograde the storm. I wonder if winds will be an issue for us, surface windwinds look kind of Meh on the GFS.
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The Euro has 30-40kt surface winds along the coast for a period on Christmas Eve.

Seems like a run of the mill November storm as far a sensible weather is concerned for our area. Warm rain with strong but not damaging onshore winds over to marginally cold air on the backside with a flake or two possible.

I really can't wait until we are out of this pattern. Hopefully this is the pattern changer we have been waiting for

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Ah I see. Thanks fellas

 

To get the heaviest seasonal snowfall potential you have to live downwind of  the Great Lakes 

or up in the mountains since they do well with storms that cut to their north or west. The

benchmark track with enough cold locked in place for snow is a very small subset of all our

precipitation producing winter storms. Models can be off by quite a bit on cutter forecasts

since it's still a cutter at 50 miles west of NYC or 750 miles west. So people won't really

notice since it's rain in either case. But long range forecasts of hitting the exact BM

track can vary widely since it such a specific track and be off by enough for a big

change to the snowfall potential.

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To get the heaviest seasonal snowfall potential you have to live downwind of  the Great Lakes 

or up in the mountains since they do well with storms that cut to their north or west. The

benchmark track with enough cold locked in place for snow is a very small subset of all our

precipitation producing winter storms. Models can be off by quite a bit on cutter forecasts

since it's still a cutter at 50 miles west of NYC or 750 miles west. So people won't really

notice since it's rain in either case. But long range forecasts of hitting the exact BM

track can vary widely since it such a specific track and be off by enough for a big

change to the snowfall potential.

Great explanation, i appreciate it man
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So what you guys are saying is that if this Xmas Storm cuts, it will be mild and rainy... Sigh. So much for the pattern(gotta wait longer?. What's up with this delaying.

 

IMO it is not even as much a delay as it is a transition occurring. Patterns (globally) do not just flip like a light switch, there are often times where numerous events must occur in order to set the wheels in motion. As the global teleconnectors begin to shift, energy  is displaced and eventually all that energy  that is put into motion can trigger a wave breaking event (much like what we may see with x-mas) that will finally serve to put the new pattern in place. A massive cutter as shown for x-mas may actually help us out much more heading into the New Year then a marginal event ever could.

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18z GFS blows up the trailing vort on Monday, just offshore. No real phasing or mechanism to pull it back towards the coast. Throws back almost an inverted trough feature into New England.

 

The PGFS is further NW and has a coastal hugger with rain for the area. A bit more northern stream interaction on that model.

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It'll be interesting to see once the new pattern is established, if we will either have a storm shortly thereafter, or we might  go through a  period of cold @ dry before any storm. Any mets thoughts?

 

Impossible to say, in an El Nino cold and dry is not very likely.  I now think though we may clear this month with no additional snowfall, I did not think that was likely a few days ago but unless something comes around 12/29-12/31 I'm not seeing it now.  This weekend's storm failing may make people more happy in the end anyway, this air mass is going to be quite a bit more stale than it appeared 3 days or so ago...likely even if it did happen it would have been rain.

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18z GFS blows up the trailing vort on Monday, just offshore. No real phasing or mechanism to pull it back towards the coast. Throws back almost an inverted trough feature into New England.

 

The PGFS is further NW and has a coastal hugger with rain for the area. A bit more northern stream interaction on that model.

 

That may be the best chance to get the 12/24 system to end up more East...if that can really explode and force the trof/baroclinic zone east a bit it may force the X-Mas eve system to go over or slightly to our east...we'd still be mostly snow but it would likely induce a faster pattern flip and we could hope for some sort of action on the backlash.  At the same time it comes with some risk that it would severely weaken the 12/24 event...its not common to get 2 strong systems back to back, if that trailing vort does indeed explode its likely that while the X-Mas event is more East it won't be a sub 980 bomb.

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Massive differences on the 18z OP GFS in part due to the handling of the 12/24 system. Instead of phasing early on and sending a bomb into the Ohio Valley, the 18z GFS holds back 12-18 hours. The result winds up being an explosively developing low to the west of New Jersey that deepens from roughly 984mb over Washington DC to about 961 over NY state. Besides the obvious potential for flooding rains and strong winds, there would probably be a good chance for some gusty snow squalls on Christmas day for most of this sub-forum which I assume is what everyone cares about. 

 

Not sure why I'm diagnosing the 18z GFS, but I thought it was a particularly interesting scenario. 

gfs_mslp_uv850_neus_31.png

gfs_mslp_pcpn_frzn_neus_29.png

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I'm really curious what the final result ends up being, the gfs has been forcing the evolution further east because there are other players out there that will determine how this storm evolves. Interesting combination of a major storm phasing along with the formation of a blocking pattern with several lows around, in particular the one gfs is blowing up offshore a day prior to the storm. 

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Massive differences on the 18z OP GFS in part due to the handling of the 12/24 system. Instead of phasing early on and sending a bomb into the Ohio Valley, the 18z GFS holds back 12-18 hours. The result winds up being an explosively developing low to the west of New Jersey that deepens from roughly 984mb over Washington DC to about 961 over NY state. Besides the obvious potential for flooding rains and strong winds, there would probably be a good chance for some gusty snow squalls on Christmas day for most of this sub-forum which I assume is what everyone cares about. 

 

Not sure why I'm diagnosing the 18z GFS, but I thought it was a particularly interesting scenario. 

 

 

 

That's a really strange track...even for December...up the spine of the Appalachians up to Quebec...then around the time it gets to the latitude of Hudson Bay it begins to retrograde back towards Ontario & Manitoba...maybe caught up in the flow or the polar easterlies...before ultimately filling & dissipating. 

 

Probably wouldn't yield too much precipitation on the backside for the C.P. with the hills to their left...good squall potential downwind of the Lakes, of course. 

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In that scenario it snows in Philly. And most of the sub-forum, to bad its the 18z.

 

Most definitely not a classic snow setup for Philly or any city on the immediate east coast...so forget it.

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Most definitely not a classic snow setup for Philly or any city on the immediate east coast...so forget it.

its too early Pamela. All we know is there's going to be a strong storm in the eastern half of the U.S. track is impossible to nail down. Though the intensity of this storm could be the strongest low pressure thus far this season
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its too early Pamela. All we know is there's going to be a strong storm in the eastern half of the U.S. track is impossible to nail down. Though the intensity of this storm could be the strongest low pressure thus far this season

 

It has potential to be the strongest winter system in the U.S. since 1993 if the current projections were to verify.  There is not a whole lot of cold air to work with which would make the overall snow area rather narrow however.  Ryan Maue has been hammering the idea all day he does not think much snow will fall with the system at all...he may be thinking the somewhat double barreled nature some models/ensembles are showing will take away from the thunder of the system til it reaches the lakes, by then it sort of occludes and mostly is a lake effect machine.

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