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Central PA & Fringes - December-January 2014-15


djr5001

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Looks like this upcoming week will be pretty quiet storm wise and even precip wise in general. Average to maybe slightly above average for the region. The main focus will turn toward the December 21st time frame where long range guidance is hinting at an amplified troughing feature for the east coast. The GFS and Euro both have a southern wave that makes things a little interesting for the time as there seems to be a storm potential for the east. The new 12z European phases the southern energy with a northern stream vort and sharpens the trough axis allowing a surface low to come up the Atlantic seaboard and wallop the southern region of the subforum. Now, this is still 7 days out and it will probably change, but the cards are on the table I believe as the overall long wave pattern is becoming more favorable for cyclogenesis providing a winter type precip over a broader area. Now, the particular setup is appealing, but a lot can go wrong. Without an established block in the North Atlantic, the progression of high pressures that slide along in Canada have to be perfectly timed and in a good position. We haven't really had that at all, and these systems keep attacking stale air masses which leads us to transition precip types from frozen to liquid. I don't think at this point we can lock in anything, even when it's close due to how marginal the pattern has been. Too much can go wrong in this sort of pattern. I'm not saying the Euro can't be correct, but it's not likely at this juncture. Hopefully the ensembles agree with the OP because that's always a good sign if they do and maybe the Euro sees something the American models might not catch up on (Wouldn't that be a shocker...).

Anyway, the LR outlook looks great and I'm confident in a period after Xmas for a greater opportunity to get a favorable setup for every here with more robust cold air masses than the weaker polar shots we've been receiving. Game on I suppose.

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small question here for folks. given the temperature profiles projected to be over this region over the next several days, I'm personally seeing a bit of an air quality risk developing, especially in deeper valleys, due to the inversion  aloft setting up between 3000-5000ft asl. I know it won't be a perfect air stagnation hazard given that the air will synopticly moving at least a little bit. but if some of the deeper valleys can have the boundary layer cut off from the main flow above the inversion like some of the model soundings say is possible, you think air quality advisories might have to be issued for Sunday and/or Monday, due to trapping?

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The 12z and now the 0z Euro bring a low up the coast for next Sunday the 21st. The 0z run brings the low from the Carolina's up to the DelMarVA coast where it strengthens and then it starts to head east once it reaches the south Jersey coast. It brings over 1 inch of liquid precip to most of the eastern half of PA. Snow map shows near 1 foot for most folks between Harrisburg and State College.

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The 12z and now the 0z Euro bring a low up the coast for next Sunday the 21st. The 0z run brings the low from the Carolina's up to the DelMarVA coast where it strengthens and then it starts to head east once it reaches the south Jersey coast. It brings over 1 inch of liquid precip to most of the eastern half of PA. Snow map shows near 1 foot for most folks between Harrisburg and State College.

 

Wow that 0z run was a thing of beauty for basically everyone in PA. But like all things at 180 hours, we must take specifics with a grain of salt. With that said, the Euro has consistently had a system in this December 20-22 timeframe pretty much since that timeframe has gotten in range. Can't really argue too much about the Euro's track record so far this season either, as it has been fairly decent at sniffing things out first. The GFS also has this system as well but weaker than the Euro.. but it's there (for now).

 

I like the look of the pattern once the weak low on Tuesday washes out across the lower Lakes and brings back generally seasonal air. There still won't be a lot of cold back in the pattern yet, but there should be enough available that if we get a well tracked system from what should be an active southern branch.. it could deliver a sizable winter weather event. 

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EURO tends to over amplify east coast lows, plus there's really no 50/50 low so I'd expect this thing to trend towards a warmer solution in a few days.  Plus the OP EURO is on it's own so far with such a dynamic presentation so it should be taken with a grain of salt.

 

EDIT:

 

Sat 12Z thru Sunday 12Z every 6 hours at BWI.....warm layer at 800/700mb.  Sleet for I-81 S&E and rain for I-95.

PRESSURE LEVELS SFC 1000 950 925 900 850 800 700 600 500

SAT 12Z 20-DEC 0 -1 -3 -4 -4 -2 -2 -5 -10 -18
SAT 18Z 20-DEC -1 -1 -5 -5 -4 -1 0 -4 -10 -17
SUN 00Z 21-DEC -1 -1 -3 -3 -2 -1 1 -2 -10 -19
SUN 06Z 21-DEC 0 0 -3 -4 -3 -1 1 -4 -12 -23
SUN 12Z 21-DEC 0 0 -3 -5 -5 -4 -5 -9 -12 -22 

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EURO tends to over amplify east coast lows, plus there's really no 50/50 low so I'd expect this thing to trend towards a warmer solution in a few days.  Plus the OP EURO is on it's own so far with such a dynamic presentation so it should be taken with a grain of salt.

 

EDIT:

 

Sat 12Z thru Sunday 12Z every 6 hours at BWI.....warm layer at 800/700mb.  Sleet for I-81 S&E and rain for I-95.

PRESSURE LEVELS SFC 1000 950 925 900 850 800 700 600 500

SAT 12Z 20-DEC 0 -1 -3 -4 -4 -2 -2 -5 -10 -18

SAT 18Z 20-DEC -1 -1 -5 -5 -4 -1 0 -4 -10 -17

SUN 00Z 21-DEC -1 -1 -3 -3 -2 -1 1 -2 -10 -19

SUN 06Z 21-DEC 0 0 -3 -4 -3 -1 1 -4 -12 -23

SUN 12Z 21-DEC 0 0 -3 -5 -5 -4 -5 -9 -12 -22 

CTP seems to have the same thinking.

 

THE GFS HAS A WEAKER AND WARMER

CYCLONE MOVING OFF JUST TO OUR SOUTH SATURDAY...WHILE THE ECMWF

/AS IT OFTEN DOES/ IS FORECASTING A MUCH STRONGER CYCLONE THAT

WOULD CREATE A SIGNIFICANT WINTER STORM THREAT FOR MOST OF THE

AREA...SHOULD IT COME TO FRUITION.

 

I was planning on heading down to Atlanta for break Saturday, but it looks like I'll be sticking around an extra day or two--if this event pans out. Hopefully we get more of a model consensus earlier than this last event!

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