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Central PA Fall Thread II


JamieOber

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edit... ok so this thing doesnt like me pasting it... but

sat 12z .24", sat 18z .87", sun 0z .66".....

SAT 06Z 29-OCT 3.7 -5.0 1021 82 99 0.06 557 540

SAT 12Z 29-OCT 1.4 -3.0 1016 94 100 0.24 554 541

SAT 18Z 29-OCT 0.3 -1.8 1008 100 100 0.87 548 541

SUN 00Z 30-OCT 0.2 -3.6 1012 97 84 0.66 543 533

text output for MDT... unreal rates

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Quick question...how much precip would be needed for say 6 inches of snow?? I'm hearing 5 to 1 ratios...so .8 would be like 4 inches??

I'm guessing it would take almost an inch of liquid or so to spit out 6" of snow in this setup. Ratios should be in the 5-7 to 1 range given the time of year and temperatures.

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Quick question...how much precip would be needed for say 6 inches of snow?? I'm hearing 5 to 1 ratios...so .8 would be like 4 inches??

I'm using an overall 5:1 to be somewhat conservative. If more interior locations such as yourself got involved like the GFS and good lord the 0z GEFS mean has you progged, ratios might be somewhat better. I would think 4-5:1 in the farther southeast portions (lower sus and towards the philly burbs )and 5-7:1 elsewhere in PA that ends up with good snow rates.

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I'm guessing it would take almost an inch of liquid or so to spit out 6" of snow in this setup. Ratios should be in the 5-7 to 1 range given the time of year and temperatures.

Lol i wasn't copying, I swear.

Seriously, I'm not sure i've ever seen the GEFS be quite so bold with having the mean wetter/farther west vs the operational GFS. I would imagine CTP would need to consider a wide coverage of watches if the euro looks anything like the gfs. Of course the question is will the Euro cooperate? I think it'll at least hold things around where it was at 12z. Who knows though. Climo would argue for a low track that stays right near the coast and given the thermal gradient thats gonna be in place because of how warm the ocean still is, someones probably gettin dumped on.

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Oct 28-30 Early Snow Disco

After having a weak wave pass through the region, colder area has pushed into the area. A shortwave will dig towards the TRV late Friday night and spawn a rapidly developing mid latitude along the Eastern seaboard Saturday.

A unusual setup has presented itself on guidance, in that a weak split flow regime has overtaken the Eastern third of North America. Along with the split flow, a 50/50 feature can also be seen (the system that has just moved through) on all guidance.

This will cause the cold air to become anchored over the Eastern third of Canada and the Northeast.

Again, the same setup but presented on the Euro.

While this is fine and dandy for New England and places further North, this does not really help the Mid Atl as the cold air is marginal and the lower level cold is not fully anchored. The deal maker continues to be the strengthening system that will develop offshore.

As the system winds up, the pressure gradient will increase causing further cold air to be wrapped on the NE side of the system. Lower level cold will be pulled towards the center and eventually be locked in place.

The above paragraph is a crucial piece to the forecast for those throughout PA,NJ and even down into MD and DE. The stronger the system, the stronger the winds, the tighter the gradient and more lower level cold gets drawn South.

Unfourtantetly, one man's joyous jubilation is another's woeful song as a stronger system usually means a more amplified or NW track. This can spell doom for those working on the balancing act between being just close enough to the surface and 850 low and being too close...causing the lower levels to be filled with warmth.

So who's where? Who's too far? Who's too close? Who's just right?

Above is my first call from earlier today.

It appears that places along the I81 corridor over to the mountains of NW NJ will find themselves at that perfect placement. These places should have it all. Enough low level cold feed to stay primarily snow. The farthest South counties in PA and NJ will have the greatest chance at mixing with rain, but eventually temps should crash and be conductive for all snow. A prolong period of heavy deformation banding as a very pronounced CCB swings through. Further anchoring of lower level cold as the gradient tightens and winds pull out of the NE (Northeaster) causing the cold air to continuously be feed out ahead of the system. These places stand the best chance of having a crippling, historic snowfall. Right now I have decided on the wording of "moderate". Accumulation totals are still being bounced around, but having temps so marginal and a few more runs to go through, I'll avoid exact numbers right now. Generally those that find themselves in this area can expect accumulations of 3-6 inches, with 3 inches for those in the valleys and 6 inches on the ridge tops.

For those further away from the I81 corridor, the lower level cold should be locked in, but a lack of QPF will be the biggest debbie downer (if one can say that of perhaps a once in a life time early season/low elevation snowstorm). People who find themselves in this target zone will see light accumulations that will easily stick. Heaviest accumulations of upwards of 3 inches along the Southern most zones to trace amounts in the most NW areas.

Finally you have the low lands of the coastal plain. This area will be incredibly difficult to forecast...especially for those on the NW side of I95. There is no doubt that the majority of the event will take place as plain rain, but the question becomes "When do they change over?" Just a short prolong period of crashing temps and heavy wet comma head snows can be the difference between a location just from just seeing the storm end in snow with no accumulations to a location picking up an inch or two. For now I will have to side with climo, marginal model support, a overzealous lower level warmth and say these places do not accumulate much of anything.

Comments and constructive criticism would be appreciated...especially pointers to a more effective use of terminology. Thanks. Let there be snow!

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