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Central PA Thread - Met. Winter 11-12 Obs/Disco


PennMan

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Wow, central PA snow lover's nemesis Martin at the NWS has this in his Aviation part of the latest AFD:

SOME DRY AIR IN PLACE FOR WED AM. SOUTHERN STORM HAS A HISTORY

OF CONVECTION. THESE FACTORS...ALONG WITH STRONG UPWARD MOTION

MAY MIGHT IT DROP OFF WED NIGHT TO NEAR 32...THUS PCPN TYPE

COULD BE A PROBLEM.

Well this has suddenly become a pretty intriguing scenario. I suppose we could have been underestimating the possibiility of the models not really grasping the CAD in the medium ranges to now suddenly start seeing it as we approach the event. The low being progged a bit further southeast helps as well, but most model solutions have been pretty keyed in on putting a low on the coast. So we have an OK setup for interior central PA showing itself currently, with a high to the north and a northeasterly ageostrophic flow setting up between the coastal low and the northern branch system to the west to help bleed in marginally cold air in central PA. Certainly not the most spectacular setup you'll ever see by any stretch, but it may be enough for the higher elevations and the further interior locations to get more of a prolonged wet snowfall before a changeover. Once southeast of the ridge and valley region of central PA, the southeast flow from the developing coastal low is likely to overwhelm the cold air damming and keep things at rain or brief snow/mix to rain. West of the laurels in the Pit region, the southwest flow from the other system is likely to have a free run and keep things liquid.

The brings me to the other key aspect which is the dynamics of this system. Martins comments as well as the statement that north pgh put on earlier today should indicate that this is a very feisty system that is currently in Texas. Even with a lack of a great cold air mass in place, we're talking about the second week of January and not say.. October or April.. so this might get interesting to watch if we can capitalize with this dynamic system.

To add a bit of details on what the 12z Euro had, it had what appeared to be a snow to rain scenario for most of central PA. Hour 66 had 925 temps 0 or below for all C-PAers nw of HGR-MDT-ABE. At hour 72 though it modified it slightly, moving the 0 line up into the far north central while everyone else generally is in between the 0 and the +2. 2m temps remain in the 30-35 range in the Poconos, the PA northern tier, and the Central mountains on down into MD and WV. So it seems that the Euro is portraying a front end snow to rain type deal, with possibly the higher elevations seeing the threat of ice.

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You guys are getting worked up over a cold rain. Caution. Caution!

I don't know if anyone's locking it in, but it's not like just the 06 GFS is showing this. The models are showing a definite trend. Things could trend the other way, but for now, it's just as silly to say nothing but a cold rain as it is to expect snow up here. Sort of up in the air right now.

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21z SREFs offer some pretty decent support for this to be an event that features more than just rain. Pretty widespread probs immediately light up for snowfall for everyone in true central and above I-78 in the east. Solid 4+ bullseye shows up centered on Clinton and Clearfield.

post-1507-0-03001800-1326164139.gif

Also noteworthy is the freezing rain probs. In the north central the p-type probs are primarily made up with either snow or freezing rain. The southern Laurels have a couple frames of high ZR probs.

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GFS will win NAM overdoes CAD......never feel good about a storm to the west with little cold air in place.

Don't think NAM over does CAD. It is better at picking up this little features. GFS was the first to be cold. Maybe just a bit off this run. Will see what Euro has tonight as it was not bad this afternoon.

Still think 1-3" down to MD line over to Gettysburg and 2-4" up toward UNV.

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Thinking it may have been a blip with the cold run....run to run it was warm, then cooled down a couple of runs, now back rainy solution. Onto the next threat.

Please don't start with that. It is a bit warmer. Could be a a little off. Still shows some snow. Nam is cooling off. Will need to see other models to confirm. SERFS cooling off too.

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Have you seen these CAD events before. Low to west and east should provide some snow/ice.

Yeah I have. I known you need a nice surface high with a nice Northerly flow to keep feeding in lower level cold.

We have neither due to the cyclonic nature of the flow and placement LP.

I also know that even though the clown maps show accumulation, it would be hard to get said accumulation where we live with highs in the upper 30's.

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Yeah I have. I known you need a nice surface high with a nice Northerly flow to keep feeding in lower level cold.

We have neither due to the cyclonic nature of the flow and placement LP.

I also know that even though the clown maps show accumulation, it would be hard to get said accumulation where we live with highs in the upper 30's.

Models have the temp at 32-33

temp60.gif

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