Central PA & Fringes - Fall 2014

[heavy_wx]

Right now I continue to think the best chance of significant snows is residing just to your east over in northeastern PA, where the rapidly deepening low will possibly have a somewhat narrow corridor of intense precipitation which will likely be snow due to dynamics and elevation. Most guidance not named the GFS seem to generally agree with this (GFS slowly getting there). What happens in the central third of the state afterwards with the storm closing off is anyones guess at this point. The Euro would suggest a couple bouts of appreciable precip backlashing into the central counties and it would be cold enough for snow at all elevations at that point. Backlash precip off a northerly flow with a low closed off to our northeast isn't necessarily our forte, but certainly the possibility exists for a few inches of snow in that scenario.

 

Despite not really being in a very reliable range yet, should note that the SREFs seem to like central PA more in the early going, as some members are going bonkers at KAOO and KPSB (the State College one) and a pretty solid representation of much heavier QPF than the operational guidance. I would wager that there's some members that are way too far west (and wet) skewing that a bit, but the QPF mean at KAOO (with 4 ridiculous members in the 2-3" QPF range eliminated) was still about 0.5". Can't really write off this storm exploding and closing more quickly.. possibly bringing the heavy band of precip deeper into central PA, but I think the Euro solution is the way to go at this point. Not even really getting into specifics of precip-type either. Definitely a tough forecast ahead, we still got a good bit of time yet

 

To be honest I'm more impressed overall with the fact that the Euro's cut off storm for several days completely denies what should have been a major warm-up charging into the northeast after midweek. Any semblance of arctic air is routed from southern Canada.  At one point around 120 hours, +10ºC temps at 850 have charged up to the shores of the Hudson Bay while the dying closed off storm anchors sub 0ºC 850 air in most of PA all the way through hour 180 (!!). Even the GFS is similar in that regard (up to around 144). While I think we're still likely to go through a warm-up before things go back to colder late this month, this would really put a dent in the amount of time that might happen. 

 

It looks like the trailing vorticity just downstream of the ridge over the mountain west is slightly more enhanced in the Euro depiction vs. the GFS around 00z Tuesday. That seems to keep the shortwaves just out of phase enough in the Euro for the trough to deepen farther south and cut-off from the main northern stream flow. This allows the surface low to redevelop near LI and retrograde into northern NJ. The lobes of vorticity associated with the cutoff low swing into central PA which, along with the deep fetch of moisture from the Atlantic, produces areas of snowfall. For these regions outside of the higher terrain in northeast PA, it seems like this is the best chance of any meaningful accumulation.

 

The GFS is more progressive with the flow, with the 500 mb low tracking from LI to northern ME between 12z Wednesday and 12z. Friday. This farther north and less consolidated system also prevents the best transport of Atlantic moisture from reaching back into central PA. In this scenerio, there may be some isolated snow showers from Lake Ontario but nothing significant.

 

If the Euro depiction pans out, it's a good example illustrating the dangers of relying too heavily on long-range model forecasts, where unresolved synoptic-scale eddies can significantly modulate the pattern.

[WmsptWx]

Non-event for anybody south of Luzerne. Before people start opening windows to jump. It's December 7. More than plenty of time.

[Santa Clause]

Non-event for anybody south of Luzerne. Before people start opening windows to jump. It's December 7. More than plenty of time.

Agreed.

[whiteout]

State College forecast discussion is interesting for about everyone. Point and click has snow/rain for me in Shippensburg Monday night and Tuesday and then all snow Tuesday night and wednesday....hmm?

[pawatch]

Looking at the models Nam doesn't look bad right now. But not really in it's range yet and it's the Nam. CMC looks like a mess and GFS is east still. But will the models take a jog to the west?

Could be interesting.

Again.....Thanks to everyone who keeps us posted on the model runs and your thoughts and predictions!

[Santa Clause]

One of those highly interesting storms to track with huge uncertainty.

[paweather]

CTP Discussion:

 

BANDS OF STRONG LOW-MID LEVEL FGEN AND LOBES OF VORT ROTATING WWD
AROUND THE 500 MB CUTOFF LOW COULD LEAD TO PERIODS OF MODERATE
TO HVY SNOW ACROSS THE EASTERN THIRD TO HALF OF OUR CWA TUESDAY
EVENING...INTO EARLY THURSDAY. WPC SNOW GRAPHICS PAINT VERY HEAVY
SNOW IN EXCESS OF 15 INCHES FROM THE POCONOS NE ACROSS THE
CATSKILLS AND INTO THE MTNS OF CENTRAL AND NRN NEW ENGLAND. THERE
IS CURRENTLY A NOTABLY LOWER PROBABILITY FOR SIMILAR AMTS ACROSS
THE SUSQ VALLEY AND CENTRAL MTNS OF PENN...BUT IT/S WITHIN THE
ENVELOP OF U.S. AND EURO ENSEMBLE SOLUTIONS...GIVEN THE
PERSISTENT...N/S OR NE/SW BANDS OF STRONG 925-850 MB THETA-E
CONVERGENCE WITHIN A LARGE AREA OF STEEP 850-500 MB LAPSE RATES
IN EXCESS OF 6C/KM THAT WILL LIKELY LEAD TO SOME SLOW-MOVING/CSI
BANDS OF HEAVY SNOW.

INITIAL PRECIP TYPE WILL BE WET SNOW OR A WINTRY MIXED-BAG MONDAY NIGHT.
AS DEEP LAYER COOLING OCCURS TUESDAY INTO TUESDAY NIGHT...PRECIP
TYPE BECOME PREDOMINANTLY SNOW.

 

[Eskimo Joe]

If only we we have some decent blocking, this would be a killer event.

[I-83 BLIZZARD]

They are without a doubt unusually bullish with the probability of snow. This will be interesting for elevated areas. I'm elevated but as far south as one can be in this region. I still expect 90% rain, but you never can tell in a complicated setup like this.

[cfbaggett]

Amazing how level-headed this forum is, almost to the point of being obtuse to what is staring PA in the face this week. The very best, and I mean by far the very best, weather model in the world is showing an intense closed 700 mb low hovering near Philly between hour 60 and hour 168. 5 days! For that reason alone CTP has every reason to be uncharacteristically bullish on this storm and sound warning alarms well in advance. Synoptically, what the Euro is depicting is about as good as it gets. And why wouldn't we trust the Euro? The US models aren't even second-stringers or junior varsity in comparison to the Euro. The Euro saw this thing 5 days ago and the GFS has still barely caught on. The same situation existed with the pre-Thanksgiving storm. The GFS was so bad with that storm that not a single of its ensembles saw it as a possibility just 3 days in advance. So I say kudos to CTP for leaning toward the Euro.

 

Sure temps are marginal, exact track, banding, etc., etc., etc. Time and luck will sort all that out.

 

But for now the potential is there, and that's enough to keep me excited. Euro ensemble snow means for State College: 0Z 6th: 4.5", 12Z 6th: 6.5", 0Z 7th: 8". Huge spread between 1" and 30". There's potential for nothing or overwhelming amounts of snow. No one knows, but it's ok to be excited about what's really an amazing weather event that is unfolding this week.

[MAG5035]

The 12z Canadian model is as far into PA as i've seen it recently, to the point that the central third is snow and the eastern third is rain. The animation was in the midst of going on 6-8 hours and counting of moderate snow before it switched from the RGEM to the GGEM after 48 hours.. then it kinda jumps northeast a bit. Had some reasonable backlash as well. 

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

[2001kx]

Amazing how level-headed this forum is, almost to the point of being obtuse to what is staring PA in the face this week. The very best, and I mean by far the very best, weather model in the world is showing an intense closed 700 mb low hovering near Philly between hour 60 and hour 168. 5 days! For that reason alone CTP has every reason to be uncharacteristically bullish on this storm and sound warning alarms well in advance. Synoptically, what the Euro is depicting is about as good as it gets. And why wouldn't we trust the Euro? The US models aren't even second-stringers or junior varsity in comparison to the Euro. The Euro saw this thing 5 days ago and the GFS has still barely caught on. The same situation existed with the pre-Thanksgiving storm. The GFS was so bad with that storm that not a single of its ensembles saw it as a possibility just 3 days in advance. So I say kudos to CTP for leaning toward the Euro.

 

Sure temps are marginal, exact track, banding, etc., etc., etc. Time and luck will sort all that out.

 

But for now the potential is there, and that's enough to keep me excited. Euro ensemble snow means for State College: 0Z 6th: 4.5", 12Z 6th: 6.5", 0Z 7th: 8". Huge spread between 1" and 30". There's potential for nothing or overwhelming amounts of snow. No one knows, but it's ok to be excited about what's really an amazing weather event that is unfolding this week.

cfbagget you in the state college area?

[cfbaggett]

If only we we have some decent blocking, this would be a killer event.

Why do we have to have blocking? Why can't the low simply cutoff like the Euro is showing?

[cfbaggett]

cfbagget you in the state college area?

Yes, I am in Boalsburg. 4th year grad student at PSU... I am an older student with a wife and 4 kids. I am living the dream here in State College where it actually does snow consistently. I grew up in TN.

[heavy_wx]

If only we we have some decent blocking, this would be a killer event.

 

How do you mean? The pattern actually becomes quite blocky as the mid-level low cuts off from the northern stream flow, the degree to which this happens depends on which model you look at.

 

Lower tropospheric temperatures are not all that cold preceding the development of this cyclone. That introduces rain for lower elevations and those closer to the coastal plain.

[cfbaggett]

The 12z Canadian model is as far into PA as i've seen it recently, to the point that the central third is snow and the eastern third is rain. The animation was in the midst of going on 6-8 hours and counting of moderate snow before it switched from the RGEM to the GGEM after 48 hours.. then it kinda jumps northeast a bit. Had some reasonable backlash as well. 

 

http://collaboration.cmc.ec.gc.ca/cmc/cmdn/pcpn_type/pcpn_type_gem_reg.html

Yep, the RGEM/GEM gets the job done... surface low over the Delmarva at hour 48. That initial pulse of ppt into central PA looks quite similar to the Euro now.

[canderson]

If I see accumulating snow I'll buy anyone who can get to a bar in hbg next week a beer.

[heavy_wx]

Amazing how level-headed this forum is, almost to the point of being obtuse to what is staring PA in the face this week. The very best, and I mean by far the very best, weather model in the world is showing an intense closed 700 mb low hovering near Philly between hour 60 and hour 168. 5 days! For that reason alone CTP has every reason to be uncharacteristically bullish on this storm and sound warning alarms well in advance. Synoptically, what the Euro is depicting is about as good as it gets. And why wouldn't we trust the Euro? The US models aren't even second-stringers or junior varsity in comparison to the Euro. The Euro saw this thing 5 days ago and the GFS has still barely caught on. The same situation existed with the pre-Thanksgiving storm. The GFS was so bad with that storm that not a single of its ensembles saw it as a possibility just 3 days in advance. So I say kudos to CTP for leaning toward the Euro.

 

Sure temps are marginal, exact track, banding, etc., etc., etc. Time and luck will sort all that out.

 

But for now the potential is there, and that's enough to keep me excited. Euro ensemble snow means for State College: 0Z 6th: 4.5", 12Z 6th: 6.5", 0Z 7th: 8". Huge spread between 1" and 30". There's potential for nothing or overwhelming amounts of snow. No one knows, but it's ok to be excited about what's really an amazing weather event that is unfolding this week.

 

As currently depicted by the 00z Euro, the initial low takes a track too far east for those outside of northeast PA to see much snowfall by 00-06z Wednesday. As that low weakens off of the NJ coast, we get some decent 700 mb frontogenesis that weakens with time in central PA. That could produce a band of enhanced snowfall at that time. After that period, a secondary low intensifies at the surface and retrogrades into LI (also as the 500 mb low cuts off). This produces more snowfall in central PA, due to the more favorable thermodynamics associated with the mid-level low, the increased moisture transport from the Atlantic and the intermittent mid-level vorticity advection.

 

At this time, though, it doesn't look all that likely that central PA, especially the State College area sees excessive amounts of snow with this. I think we need to see guidance somehow take the storm farther inland initially, where the best dynamics with this system occur.

[pawatch]

Would someone give us an update to what the Euro is showing.

Thanks

[MAG5035]

Amazing how level-headed this forum is, almost to the point of being obtuse to what is staring PA in the face this week. The very best, and I mean by far the very best, weather model in the world is showing an intense closed 700 mb low hovering near Philly between hour 60 and hour 168. 5 days! For that reason alone CTP has every reason to be uncharacteristically bullish on this storm and sound warning alarms well in advance. Synoptically, what the Euro is depicting is about as good as it gets. And why wouldn't we trust the Euro? The US models aren't even second-stringers or junior varsity in comparison to the Euro. The Euro saw this thing 5 days ago and the GFS has still barely caught on. The same situation existed with the pre-Thanksgiving storm. The GFS was so bad with that storm that not a single of its ensembles saw it as a possibility just 3 days in advance. So I say kudos to CTP for leaning toward the Euro.

 

Sure temps are marginal, exact track, banding, etc., etc., etc. Time and luck will sort all that out.

 

But for now the potential is there, and that's enough to keep me excited. Euro ensemble snow means for State College: 0Z 6th: 4.5", 12Z 6th: 6.5", 0Z 7th: 8". Huge spread between 1" and 30". There's potential for nothing or overwhelming amounts of snow. No one knows, but it's ok to be excited about what's really an amazing weather event that is unfolding this week.

 

That's just it, this has the potential to bury folks that end up being in the right spot, wherever that may be. It could be further northeast as it seems the most likely scenario at this point, or it could be right in Central PA. The strong 1040+ high up north coupled with the developing coastal low is going to create a tremendous easterly fetch off the Atlantic, the heavy QPF will likely be there. I'd keep an open mind with this anomalous setup. 

 

I can't believe I out  'd JB with mentioning this having a bit of December '92 feel yesterday (he mentioned it on twitter this morning). But there are some similarities I see with that event (cut off low and big high creating a major easterly fetch), which was why i posted the Ewall reanalysis link yesterday. This was additionally an extremely marginal event as well. Harrisburg saw mainly rain.. while some parts of the south central part of the state saw amounts that rivaled or exceeded the 93 storm later that winter. The track was somewhat different than how this current event is being progged though, exploding and closing off further southwest. 

[2001kx]

Yes, I am in Boalsburg. 4th year grad student at PSU... I am an older student with a wife and 4 kids. I am living the dream here in State College where it actually does snow consistently. I grew up in TN.

 

[cfbaggett]

12Z Euro is coming in further west and stronger with a surface low centered over the Delmarva coast at hour 48. Heavy ppt banding up I-99.

 

At hour 54, 998 low over Cape May, NJ. Intense banding continues over central PA.

 

At hour 60, banding shifts east, but not as east as 0Z run. 995 low just to the SE of NYC.

 

At hour 66, 996 low over Brooklyn. Band is weakening but shifts back west a little.

 

At hour 72, 999 low on I-80 in central, NJ. Snowing light to moderately in central PA. Banding isn't as obvious but is probably present. About 1.1" qpf has fallen in State College, some wiggle room, tight gradient about 30 to 50 miles west.

[Eskimo Joe]

Why do we have to have blocking? Why can't the low simply cutoff like the Euro is showing?

Blocking (-NAO in combination with 50/50 low) forces the storm track offshore, thus keeping PA on the cold side of the storm.  It also ensure amply cold air throughout the column which produces snow.  If you look at the latest version of the Canadian, the high is poorly positioned ahead of the storm and easily gets shoved out of the way of the storm.

[cfbaggett]

Blocking (-NAO in combination with 50/50 low) forces the storm track offshore, thus keeping PA on the cold side of the storm.  It also ensure amply cold air throughout the column which produces snow.  If you look at the latest version of the Canadian, the high is poorly positioned ahead of the storm and easily gets shoved out of the way of the storm.

Climatologically, the best track is not offshore for central PA... certainly offshore is better for east PA. Central PA prefers inside Hatteras and over the Delmarva. IMO, blocking is extremely overrated. For example, the '93 superstorm occurred during a weak +NAO. And what about the pre-Thanksgiving storm? Again a +NAO. -NAOs are good for cold, for sure... but the cold can overwhelm.

 

This event is an anti-cyclonic wave-breaking event that is occurring just in the right place. In fact, this event will actually help build an increasingly +NAO.

[cfbaggett]

As currently depicted by the 00z Euro, the initial low takes a track too far east for those outside of northeast PA to see much snowfall by 00-06z Wednesday. As that low weakens off of the NJ coast, we get some decent 700 mb frontogenesis that weakens with time in central PA. That could produce a band of enhanced snowfall at that time. After that period, a secondary low intensifies at the surface and retrogrades into LI (also as the 500 mb low cuts off). This produces more snowfall in central PA, due to the more favorable thermodynamics associated with the mid-level low, the increased moisture transport from the Atlantic and the intermittent mid-level vorticity advection.

 

At this time, though, it doesn't look all that likely that central PA, especially the State College area sees excessive amounts of snow with this. I think we need to see guidance somehow take the storm farther inland initially, where the best dynamics with this system occur.

Agree 100%. I'm just trying to get the point out that the potential is there and this talk of 0" and all rain by some posters is a little too much anti-hype for my taste and just as bad as if I said we were getting 30" this week. There's too much uncertainty. In any case, the 12Z has certainly upped the ante.

[Fozz]

Climatologically, the best track is not offshore for central PA... certainly offshore is better for east PA. Central PA prefers inside Hatteras and over the Delmarva. IMO, blocking is extremely overrated. For example, the '93 superstorm occurred during a weak +NAO. And what about the pre-Thanksgiving storm? Again a +NAO. -NAOs are good for cold, for sure... but the cold can overwhelm.

 

This event an anti-cyclonic wave-breaking event that is occurring just in the right place. In fact, this event will actually help build an increasingly +NAO.

 

For the LSV crowd (including me and Eskimo Joe), the lack of blocking will screw us over and we'll most likely get rained on. But I agree with you about central PA.

[canderson]

Agree 100%. I'm just trying to get the point out that the potential is there and this talk of 0" and all rain by some posters is a little too much anti-hype for my taste. The 12Z has certainly upped the ante.

Us in the valley have learned to never count on these workng out. This one especially, it'll be raining down this way unless the thermals drastically improve.

[NortheastPAWx]

So basically we need the ECM verbatim to get a decent snowfall.

[cfbaggett]

Us in the valley have learned to never count on these workng out. This one especially, it'll be raining down this way unless the thermals drastically improve.

I agree, even the 12Z Euro is quite marginal down in Harrisburg. I don't know what the other levels show, but at least at 850 hPa, you stay at 0C and below. Here at UNV it's -1C and below... marginal too.

[heavy_wx]

Agree 100%. I'm just trying to get the point out that the potential is there and this talk of 0" and all rain by some posters is a little too much anti-hype for my taste and just as bad as if I said we were getting 30" this week. There's too much uncertainty. In any case, the 12Z has certainly upped the ante.

 

I'm definitely looking forward to seeing the 12z Euro in more detail.

 

For the LSV crowd (including me and Eskimo Joe), the lack of blocking will screw us over and we'll most likely get rained on. But I agree with you about central PA.

 

I don't think that's so much due to a lack of blocking but more because there isn't a strong enough low-level ageostrophic flow from Canada.