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Central PA and the MD Fringes - January Part III


MAG5035

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So....anyone want to comment on the CTP discussion? I heard that stuff about snowcover and further SE tracks from the older forecasters like Elliot Abrams when I worked at AccuWx. Not sure if that will work to our advantage here. 

 

 

FROM THERE A MORE IMPORTANT CYCLONE IS MADE TO APPROACH FOR

WED...AND THERE IS BETTER AGREEMENT ON TIMING BETWEEN THE ECMWF

AND GFS/GEFS. THE ECMWF HAS ITS LOW TRACKING INTO WESTERN

PA...BEFORE REDEVELOPING QUICKLY OFF THE MID ATL COAST. THE

GFS/GEFS ARE BOTH FURTHER SOUTHEAST...WITH THE GEFS BEING THE MOST

EAST AND THUS THE COLDEST SET OF SOLUTIONS. AT THIS POINT A WINTRY

MIX IS INDICATED BETWEEN THE VARIOUS MODEL OUTCOMES AS WARM AIR

FLOODS IN ALOFT...BUT WITH SO MUCH SNOW COVER AND COLD AIR OVER

THE GR LAKES AND NE...WOULD NOT BE SURPRISED IF THE EVENTUAL STORM

TRACK WANDERS CLOSER TO THE COAST OVER THE NEXT SEVERAL MODEL

RUNS.

somewhere along the way someone here said cold generates more cold (or something like that)

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somewhere along the way someone here said cold generates more cold (or something like that)

 

Somehow it supposedly shifts the storm track south. 

I think my snowcover will be long gone by the time the midweek storm comes...unless I get snow on Monday. :)

They are referring to the pretty solid snowcover across the NE quarter of the US...well, except for the Williamsport snowhole. 

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There may be some truth to that; greater snow cover leads to a colder air mass which increases cold air damming and strengthens the baroclinic zone over the east coast. Now, the models may have properly initialized the snow cover information meaning that it is already taken into account in the solutions. Also, if the primary low is strong enough, this effect will not make much of a difference with regards to storm track.

That's what I thought. 

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Somehow it supposedly shifts the storm track south. 

They are referring to the pretty solid snowcover across the NE quarter of the US...well, except for the Williamsport snowhole. 

 

If you have good snowcover, that provides a cooling source (obviously). That can act to set up the temperature gradient further south, near the border of the snowcover. If the baroclinic zone is further south, the storm track will be as well.

 

However, I don't know how much I buy it in this case... as heavy_wx noted, the models probably have the snowcover reasonably well-modeled, which means (unless there is a model bias to ignore snowcover WRT baroclinity?) they should have a handle on its impacts.

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The 00z has a higher amplitude (though still relatively low amplitude) northern stream disturbance than the GFS which phases with the shortwave over the southern plains. That allows for a more northerly track bringing moderate QPF in to much of PA for Monday. Since both shortwaves will be moving fairly quickly it may take some luck for the phase to occur as the Euro depicts.

 

For the Wednesday event, it's the GFS that has a more substantial phase, allowing for the low to be stronger tracking through the Ohio valley into central NY. The Euro was a nice hit for areas north of about Altoona with about 5" or so at UNV. Interestingly, the southern stream vorticity maxima at 500 mb has a more southerly track into northwest Mexico on the GFS vs the Euro. The GFS however has a less amplified disturbance upstream over the four corners region. This disturbance on the Euro is more amplified and destructively interferes with the lead shortwave upstream, keeping the primary low a little weaker in the Ohio valley.

 

In both cases, the Euro seems to be more willing to amplify these northern stream disturbances originating from the North Pacific. It will be interesting to see how these shortwaves progress in both model space and reality as they are better sampled in the next several days.

this is the one thing that I often notice which ends up as the GFS' downfall vs Euro... it often struggles with northern and southern energy and timing for phasing/interaction... especially with shorter windows for interaction... I would watch here what Euro does at 12z and again at 0z tonight to see if indeed the speed has it go back and forth... if it stays consistent I would feel it to be slightly more believeable than if it waffles from run to run than what the GFS does

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Nice article reposted on the Philly side about the model volatility and how we really need to take it one day at a time: 

http://www.americanwx.com/bb/index.php/topic/38386-vendor-forecast-discussion/?p=2707193

 

As I said before what you see on the models is not set in stone in any way. This isn't an easy pattern to decipher as the models have shown us. With the atmosphere in transition it truly is down to looking at the present day or two, seeing what the results are and then going from there. Of course since the models show a plethora of solutions, one must have found just the right parameters to display what will happen, but chances are that if the model verifies it won't be because of what it had inputted today. Let's see what today's model suite says about the Monday event.

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Nice article reposted on the Philly side about the model volatility and how we really need to take it one day at a time: 

http://www.americanwx.com/bb/index.php/topic/38386-vendor-forecast-discussion/?p=2707193

 

As I said before what you see on the models is not set in stone in any way. This isn't an easy pattern to decipher as the models have shown us. With the atmosphere in transition it truly is down to looking at the present day or two, seeing what the results are and then going from there. Of course since the models show a plethora of solutions, one must have found just the right parameters to display what will happen, but chances are that if the model verifies it won't be because of what it had inputted today. Let's see what today's model suite says about the Monday event.

Steve DiMartino is a notorious snowhound.

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Fwiw the 12z GFS snow map indicates essentially no snow from UNV south.

Yeah. I see this being a potential for a nasty IP/ZR event south of I-80 in the normal tricky spots in the valleys. The CAD signature before the storm moves in is very well shown on the GFS and the event is still 120 hours away. The MO this winter has been for models to trend colder at surface closer to the event. I'm concerned for areas especially north of Harrisburg. Plenty of precip to work with for sure throughout the region. Our Upstate Subforum should be frothing at the mouth on this run

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I can't post the text output given I'm on my phone but most of the qpf is frozen. .53 falls at unv with both 850 and surface below freezing and most of the recipe is done before surface gets to freezing.

UNV

WED 06Z 05-FEB  -3.8    -2.4    1020      97     100    0.57     562     546   

WED 12Z 05-FEB   0.9     7.0    1006     100     100    0.89     558     554   

WED 18Z 05-FEB   4.0     2.3    1002     100      17    0.07     550     548   

THU 00Z 06-FEB  -1.1    -6.9    1010      89      50    0.01     543     535   

MDT

WED 06Z 05-FEB  -1.8     0.6    1022      97      98    0.60     565     548   

WED 12Z 05-FEB   1.6     6.9    1009     100      89    0.32     562     555   

WED 18Z 05-FEB   4.3     5.6    1003     100      89    0.29     556     553   

THU 00Z 06-FEB   2.0    -3.9    1009      90      24    0.01     549     542   

IPT

WED 06Z 05-FEB  -3.8    -4.0    1023      96     100    0.29     561     543   

WED 12Z 05-FEB   0.7     5.0    1007      99     100    0.94     558     553   

WED 18Z 05-FEB   2.4     3.4    1002     100      28    0.22     549     548   

THU 00Z 06-FEB  -0.2    -6.3    1008      91      62    0.02     541     535   

AVP

WED 06Z 05-FEB  -4.7    -4.8    1025      94      99    0.15     561     542   

WED 12Z 05-FEB  -0.4     3.9    1011      98     100    0.73     559     551   

WED 18Z 05-FEB   2.2     5.2    1003     100      72    0.47     552     550   

THU 00Z 06-FEB   0.9    -4.4    1006      97      49    0.02     542     538   

LNS

WED 06Z 05-FEB  -1.6     0.5    1022      98     100    0.54     566     548   

WED 12Z 05-FEB   1.3     6.7    1010     100      75    0.28     563     554   

WED 18Z 05-FEB   4.9     6.4    1003     100      98    0.41     557     554   

THU 00Z 06-FEB   2.3    -3.1    1008      91      21    0.01     550     544   

AOO

WED 06Z 05-FEB  -2.4     1.1    1018      97      98    0.77     564     550   

WED 12Z 05-FEB   1.4     9.0    1006     100      99    0.40     560     555   

WED 18Z 05-FEB   5.6     2.0    1003     100      20    0.05     552     550   

 

 

keep in mind too that the GFS will often boost QPF where it assumes is the warm sector by trying to make it more convective than stable... so these could be a little high... high rates would hinder just how much ice accretion we would see too

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