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December 2017 Mid-Long Range Disco

WxUSAF

By WxUSAF,
in Mid Atlantic

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CAPE

CAPE

Posted
Posted
7 hours ago, losetoa6 said:

Fri / Sat looks to have some potential for a light to med event. Wednesday's low pumps higher  hieghts into GL. per Gfs . The west ridge is hanging on still. Here's the Ukie 0z...not far from something 

120

GZ_D5_PN_120_0000.gif

144

 

GZ_D5_PN_144_0000.gif

Euro op/EPS are hinting at a couple potential light events in the Thursday to Saturday time frame.

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donsutherland1

donsutherland1

Posted
Posted

The recent snowstorm brought 4" or more snow to Philadelphia, New York City, and Boston. Such December snowstorms have often provided an early indication of what would go on to become a snowy or very snowy winter in the Middle Atlantic region, including the Washington, DC area.

Below is a list of such storms (1950-2016) with the Washington, DC winter snowfall:

December 3-4, 1957: 40.4"

December 11-13, 1960: 40.3"

December 23-24, 1963: 33.6"

December 23-25, 1966: 37.1"

December 25-28, 1969: 14.0"

December 5, 2002: 40.4"

December 18-21, 2009: 56.1"

La Niña climatology notwithstanding (and I don't think a broad brush composite will offer much insight into the pattern going forward through the remainder of December), the EPS is continuing to indicate that relaxation in the medium-term will likely be temporary. 

 

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mitchnick

mitchnick

Posted
Posted

Echoing the thoughts of a few already regarding the relaxation period, this handy tool (no, not you JI :P) from weather.us is the Euro operational and mean ensemble for temps off the current run; most have probably used the site for its snow forecast. Anyway,  max temps (highs) occur next Sunday-Tuesday and for Baltimore are 45, 45, & 47 respectively.  What a difference a year makes, ehh? Last winter we called those kinds of temps a cool down! Lol

https://weather.us/forecast/4347778-baltimore/ensemble/euro/temperature

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pasnownut

pasnownut

Posted
Posted
51 minutes ago, donsutherland1 said:

The recent snowstorm brought 4" or more snow to Philadelphia, New York City, and Boston. Such December snowstorms have often provided an early indication of what would go on to become a snowy or very snowy winter in the Middle Atlantic region, including the Washington, DC area.

Below is a list of such storms (1950-2016) with the Washington, DC winter snowfall:

December 3-4, 1957: 40.4"

December 11-13, 1960: 40.3"

December 23-24, 1963: 33.6"

December 23-25, 1966: 37.1"

December 25-28, 1969: 14.0"

December 5, 2002: 40.4"

December 18-21, 2009: 56.1"

La Niña climatology notwithstanding (and I don't think a broad brush composite will offer much insight into the pattern going forward through the remainder of December), the EPS is continuing to indicate that relaxation in the medium-term will likely be temporary. 

 

Thanks for the stats Don.  Looking forward to those kind of numbers (you can toss 69' though).  

Nut

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AfewUniversesBelowNormal

AfewUniversesBelowNormal

Posted
Posted
6 minutes ago, mitchnick said:

From the prayers of east coast snow weenies and commodity traders long nat gas.

It seems it would be MJO related, but tropics are probably this way because of EPO wave.

Stratospheric vortex is strong
La Nina conditions

-NAO tendency so far? where does that come from? 

 

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AfewUniversesBelowNormal

AfewUniversesBelowNormal

Posted
Posted

There could be a serious storm on our doorstep

Healthy -NAO right now 

t0.thumb.gif.390e8891b515dcbf94f75eb74fcb4363.gif

12z NAM 500mb (loop)

http://mag.ncep.noaa.gov/Imageanis.php

 

nam_namer_051_500_vort_ht.thumb.gif.9e1e6e3049fb8cbd71d6f76a53893d05.gif

This is happening 51hours from now

 

nam_namer_066_500_vort_ht.thumb.gif.aff11f56f0338962ef8a34020be00dac.gif

Models Greenland ridge getting ripped apart in 48 hours by marginal low pressure.... it doesn't happen this way.

 

If -NAO remains, significant snowstorm potential. 

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showmethesnow

showmethesnow

Posted
Posted

First time I have taken a somewhat hard look into the extended in the last week or so. Haven't looked into the EPS yet, just the GEFS so the following is just on that. The next week looks somewhat uneventful with the potential for some minor snows (flurries, isolated snow squall, etc...) as the NS looks to stay mostly to our north. Never know though, a little more dig with any of these pieces of energy getting underneath us and the potentially goes up a little. 

But the period shortly after (roughly centered around next Mon/Tues) has drawn my attention a touch. Very little to show on the GFS/GEFS at this time to show the possibility but looking over the last few days of runs suggest that it may exist.

Below is the 156 hr of today's 06Z GEFS run. As you can see the look isn't one that particularly pops out as a high potential look for our region as it argues that most/all the action in would be confined to our north with warmer temps inbound for our region. And this is one of the better looking setups of the last few days of runs to boot. But what I have seen the models moving towards makes me think that maybe we should keep an eye during this period. What we have showing is a PV rotating through Alaska. Ridging developing between that and a trough dropping down into the midsection with a surface low embedded within that. And higher heights to our south with a 50/50 low and corresponding trough to our NE.

Now one of the key pieces in the whole setup is what the models intend to do with the PV rotating through Alaska for the PV has downstream implications on most of the other features in their placement and evolution (domino effect). The other key feature is the 50/50 which is backing up the flow behind it. These two features will determine what occurs through the CONUS through this period of time as the flow gets squeezed between them. What I have seen is that the GEFS is becoming more progressive, stronger and aggressive in swinging that PV farther to the south which is essentially squeezing the backed up flow. What that in turn does is create better ridging in front of the PV. The trough in the North central part of the country would respond to this better ridging by sharpening on the backside and digging even farther south. This deeper dig should in turn create SE ridging between the trough and the 50/50 which will also impact the trough by creating a sharper front side to the trough and a less positive tilt. These changes to the trough would keep it from quickly withdrawing to the north, as we see currently, and would probably argue that the trough would actually swing farther to the east. The last feature I want to point out is that the models have been pretty steadfast on having strong NS energy embedded within that trough as represented by the surface low I have marked below. That energy is located on the front side of the trough which is not a favorable location for our location for that point of time. But if we see sharper ridging and troughing that feature would move farther and farther to the west (in a more favorable location on the trough to have an impact on our region) as it will have more real estate to cover.

So in a nutshell. I will be watching what the models do with that pv in coming runs. A deeper and more progressive dig from that feature and I would not be surprised to see a much more favorable setup begin showing up. This is of course dependent on the models be somewhat accurate with their current depiction. Take away just that 50/50 that is backing up the flow and the whole thing would go down the toilet.  Now for those that would argue that temps argue against possible snow, just keep in mind that the whole temp profile would probably change somewhat significantly if we were to see such changes in the Alaskan PV.

 

Dec18thpotential.thumb.gif.e697ef234d55b62843070a93978c0c1b.gif

 

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showmethesnow

showmethesnow

Posted
Posted
42 minutes ago, StormchaserChuck said:

The Alaska vortex does not pop a ridge, it amplifies Pac Jet to create zonal, warm flow

As shown now it would and does. Deeper dropping, more distinct pv lobe and you get a more favorable initial response from the ridging at higher latitudes that would impact the trough digging before it breaks that ridging down. 

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WxUSAF

WxUSAF

Posted
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Posted
1 minute ago, StormchaserChuck said:

Not sure why my posts are being moved all the time... Dec 2 I made a thread "High risk for Dec 8-10 snowstorm", trash. This(1105) is 51 hours away, not medium-long range, and it identifies a significant inconsistency worthy of separate attention

Because we don't have separate threads every time someone sees something cool on a individual model panel.  Neither does any other subforum on here that I'm aware of.  Keeping things together keeps the conversation organized and easy to follow for people who don't post as much as you or I.  

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showmethesnow

showmethesnow

Posted
Posted

These are op runs at roughly day 6 so take them for what they are worth but they do show what I was referring to on my previous post. The first is today's 06Z run now compare it to today's 12Z run. What we are seeing is a more distinct PV feature swinging into Alaska and the associated trough is digging deeper. What this is in turn doing is creating better ridging feature initially in front of it which is impacting the trough diving into the midsection of the country with a much deeper drop and better axis. Notice we also see the SE ridging building better between that trough and the low moving into the 50/50 region. Just something to watch over the coming days.

 

 

gfs_z500a_namer_27.png

gfs_z500a_namer_26.png

 

 

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pasnownut

pasnownut

Posted
Posted
21 minutes ago, losetoa6 said:

End of week with cold already in place..per Gfs energy under us ...too progressive verbatim but could trend sharper . ..low chance but we're 120 hours out.  A couple Gefs members were near misses. 12z below definitely sharper the 6z was 

500hv.na.png

after what we saw this past week, I'd not call anything a lock until 24 hours out.  Once tuesdays cold comes, subtle corrections may get us into the next game.

Nut

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