Central PA - Winter 2021/2022

[Blizzard of 93]

12 minutes ago, Itstrainingtime said:

Perhaps they feel like the icing issue combined with total snowfall will be more significant in those areas?

Regardless, it's not going to affect your ground truth either way.

True, & it really doesn’t matter much, but some people & businesses might say, “No Watch here, no big deal” because there is no Watch despite their actual current forecast.

I thought their main goal was to try to “protect life & property”?

[Voyager]

28 minutes ago, Blizzard of 93 said:

Again, based on this CTP map above, why no Watch for Dauphin county?!?

More snow than York and similar amounts to Adams & Cumberland!

It makes no sense.

Do they not realize where the capital city is located? A watch might get some folks attention?

It appears that they just said, "anything west of the Susquehanna gets a watch, anything east doesn't". I guess it's just the DMZ for this storm. I mean, it seems a bit lazy to me. Take Shamokin Dam and Sunbury, or Harrisburg and Enola for example. Both areas are in the 3-6 range and are practially neighbors divided by the river. Shamokin Dam (Enola) has a WSW and Sunbury (Harrisburg) do not.

[Itstrainingtime]

1 minute ago, Blizzard of 93 said:

True, & it really doesn’t matter much, but some people & businesses might say, “No Watch here, no big deal” because there is no Watch despite their actual current forecast.

I thought their main goal was to try to “protect life & property”?

I understand...just yesterday or the day before I raised a question about something that CTP had put out. But I immediately followed up with "they're the mets, I'm just an HR guy" or something like that. 

It might not make sense to us looking at their maps but there's a reason for it. 

[Blizzard of 93]

1 minute ago, Voyager said:

It appears that they just said, "anything west of the Susquehanna gets a watch, anything east doesn't". I guess it's just the DMZ for this storm. I mean, it seems a bit lazy to me. Take Shamokin Dam and Sunbury, or Harrisburg and Enola for example. Both areas are in the 3-6 range and are practially neighbors divided by the river. Shamokin Dam (Enola) has a WSW and Sunbury (Harrisburg) do not.

Great points

[Blizzard of 93]

1 minute ago, Itstrainingtime said:

I understand...just yesterday or the day before I raised a question about something that CTP had put out. But I immediately followed up with "they're the mets, I'm just an HR guy" or something like that. 

It might not make sense to us looking at their maps but there's a reason for it. 

You are right, but their other maps & products that they currently have out don’t agree with each other, hence my frustration.

[Blizzard of 93]

The 12z ICON had another Warning level snow run for Harrisburg & York on north & west.

 

[Itstrainingtime]

1 minute ago, Blizzard of 93 said:

You are right, but their other maps & products that they currently have out don’t agree with each other, hence my frustration.

So here's an honest question that maybe @MAG5035has some insight on - it does appear that it's possible that the impact could vary significantly from say Middletown to the NW part of the county. Both CTP and Mount Holly have counties broken down in watches and warnings. CTP breaks Centre, Lycoming, and I think Clinton into Southern and Northern during certain events. Might this storm be a good example to break Dauphin out? 

[Blizzard of 93]

Even if MDT only gets around 3 inches of snow, they will be at “normal” average snow through Monday’s date with a seasonal total near 10 inches. If MDT gets closer to the 5 or 6 inches of snow, then MDT will be a couple of inches Above normal by Monday!

[mahantango#1]

6 minutes ago, Itstrainingtime said:

So here's an honest question that maybe @MAG5035has some insight on - it does appear that it's possible that the impact could vary significantly from say Middletown to the NW part of the county. Both CTP and Mount Holly have counties broken down in watches and warnings. CTP breaks Centre, Lycoming, and I think Clinton into Southern and Northern during certain events. Might this storm be a good example to break Dauphin out? 

Yes there is a difference, based on prior events Peter's Mountain seems to be huge factor on these type of events. Peter's Mountain seems to divide the county on the weather. You can go from the upper end of the county with 3 in of snow but once past the mountain Harrisburg could have nothing. So it happens with thunderstorms in the summer also but not all the time. I truly believe the mountain has some involvement in the weather dividing Dauphin County.

[paweather]

1 hour ago, Blizzard of 93 said:

The only thing that matters to me…snow!

Good luck Blizz and everyone else get a win!

[CarlislePaWx]

I'm pretty sure that when the NWS totally restructured its zones to the county level (more than 15 years ago), if there was enough of a climatological difference in one portion of a county to the other, then that county was split up by name...ie northern/southern, coastal/inland, northwest/southeast, etc.  They will only issue differing forecasts within a county if it exists as a "split county".  There apparently is not enough difference in Dauphin to warrant a split...thus it's a "whole" county.

[Blizzard of 93]

These maps were issued recently by CTP.

Expected & High end snow maps 

[Voyager]

Well, Mt Holly put Carbon and Monroe Counties under a WSW, so now it's northern Dauphin and Schuylkill that separate watches from CTP and PHL north of Peter's and Blue Mountain respectively. Interesting...

[Cashtown_Coop]

10 minutes ago, Blizzard of 93 said:

These maps were issued recently by CTP.

Expected & High end snow maps 

Blizz93 you going with the 10%

[Cashtown_Coop]

Just noticed LWX forecasting more ice than CTP.  Low dews and wet bulbing holding temps down longer 

[MillvilleWx]

Here you go y'all on my breakdown of the event. I am low on the north side into your necks of the woods, but I can make a separate map later that will give a rough estimate, or I can give a breakdown by towns/regions later via text. Happy tracking!

3 minutes ago, MillvilleWx said:

Alright y'all. I think I have time to delve into some details on this event and my forecast will be the last thing I post if you want to jump to it, now's your chance!

Anyway, the setup is one that is complicated in the evolution, but the ground truth makes perfect sense meteorologically. Leading into the event, a cold HP over the top will deliver some pretty chilly air to the east coast with wedging down as far as northern GA. Traditionally, this would spell a pretty significant snow/ice storm for the piedmont and areas NW. There will be significant storm, but how we get there will determine the fate of the sub-forum. That fate will make some people sad, but it unfortunately is how it is and how we will roll, so lets dig in.

First off, a potent upper-low (ULL) is currently traversing the south plains into the Arklatex and will round the corner this evening and move through the Deep south. This ULL will be matured and ready to go as it moves eastward overnight into tomorrow morning prior to making the turn NE after it enters GA. Over the N Atlantic, a beast of a low pressure will meander for about 12-18 hrs before slowing pulling eastward due to limited blocking over Greenland. This will allow for spacing to occur to our NE and weak ridge extension from the Atlantic over New England. This allows our HP to the north to scoot eastward, generating an onshore pattern for later in the storms life cycle (More on that in a bit).

 

Off to the NW over Canada, a progressive shortwave trough will dig into the northern plains with eyes on the Midwest/OH Valley by Monday. This is what will cause a fair bit of commotion in the overall setup as the shortwave will "capture" the ULL over the east and begin to lasso it in place while tilting the trough negative as it wanders nearby. The associated surface low over the SE will motion to the north, then NW as the anchored 500mb presence will drive the low pressure towards the ULL as the features try to stack on top of each other, which is known as an occlusion.

While this is all happening, the low pressure along the Atlantic coast will bomb out on its journey north, generating a prominent low-level jet (LLJ) in the lower confines of the boundary layer (PBL). Remember that HP that moved out into the Atlantic, well that in tandem with the developing LLJ will couple to create a "fire hose" effect of warm, moist air within the 850-700mb layer in the atmosphere. Figure Below shows a 7 StDev u-vector component. That screams warm/moist air funneling due west off the Atlantic. This is caused by the tandem of the base of the HP off the coast and the counter-clockwise flow around our surface low. This is what will be aimed at the area during the storms life cycle as it moves into the region. In the very beginning of the storm, the antecedent airmass is still pretty cold with near to below 0C temps through the column above. The leading precip will help wet bulb temps a bit with an initial start as snow, but the vigor of the LLJ will allow for the warm air aloft to quickly notch above freezing with areas to the SE seeing the transition first. Due to the increasing pressure gradient pattern and slow warming of the PBL, winds will increase areawide, leading to a mixing out of the cold surface inversion layer in place. This is why temps on models appear to "jump" to near and above freezing despite the cold air that was in place. There is no refresh of cold air to lock into place, so the warmer air above is able to mix appropriately and nothing can fight it back. 

As the storm begins its occlusion phase, guidance wants to have the stacking phenomena occur pretty much overhead or very close by. ULL's are dynamic and a mature mid-latitude cyclone has multiple parts that make it tick. As the low becomes stacked and the phase between the Midwest shortwave and ULL occur, the storm will drift off to the NE given the lack of blocking and the region will be on the backside of the flow at all levels. A strong vort max on the base of the mean trough axis will pivot through on Monday AM with a potential to kick off some light to moderate snow showers before pulling NE due losing the areal ascent on the underside of the trough. Way out west in the mountains, a continuous westerly flow pattern found on the western flank of the low/trough pattern will induce a period of upslope snowfall under cold upper-level conditions, leading to a higher-ratio powder that occurs over the traditional spots in Garrett/Tucker counties in MD/WV respectively. This will add to the synoptically drive snowfall with the storm, putting those areas in the best chance to reach double digits, despite the fact they will likely mix with sleet/freezing rain for a time during the storms height at their latitude. 

Overall, this is still a pretty high profile event due to expected winds and widespread impacts from N GA up into New England. As fate would have it, it's just not a pure snow event due to the lack of reinforcing cold air and the positioning/magnitude of features that occur overhead. That's just meteorology for you, but one cool thing to take away is the satellite will be pretty incredible, and will fit the textbook of a classic Swedish Modeled Mid-Latitude Cyclone (Gotta love the Swedes for their expertise on this matter )

In any case, there will still be winter weather in the area, and here's my thoughts displayed. I utilized a blend of NBM interpretation and hi-res guidance as they begin to narrow down the goal posts in terms of precip/timing/temps. There's a MEDIUM confidence on this forecast as their could be a slight bust either way, so keep an eye on those short term trends tomorrow to see what could be occurring. For now, look for a wintry mess with all the trimmings. 

Second Call (Potentially Final outside Minor Adjustments)

 

[Blizzard of 93]

11 minutes ago, Cashtown_Coop said:

Blizz93 you going with the 10%

I think 4 to 6 inches of snow is reasonable for the Harrisburg & I-81 corridor.

[Voyager]

10 minutes ago, MillvilleWx said:

Here you go y'all on my breakdown of the event. I am low on the north side into your necks of the woods, but I can make a separate map later that will give a rough estimate, or I can give a breakdown by towns/regions later via text. Happy tracking!

 

One or both would be great, and thanks for the post and analysis! I'm sure I speak for all in that we appreciate what you (and Mag as well) do and bring to our subforum!

[Cashtown_Coop]

[Itstrainingtime]

25 minutes ago, Blizzard of 93 said:

I think 4 to 6 inches of snow is reasonable for the Harrisburg & I-81 corridor.

If MDT records 4" or more of snow, I will forever refer to you as the zen of LSV snow forecasting. I believe anyone expecting (not hoping, but expecting) those totals around Harrisburg will be greatly disappointed.

We shall see soon enough!

[Atomixwx]

And if MDT gets less than 4-6 he's a model hugger.

[canderson]

9 minutes ago, Cashtown_Coop said:

Rare to see such a discrepancy.  

[Cashtown_Coop]

1 minute ago, canderson said:

Rare to see such a discrepancy.  

Their snow maps are seamless.   Something to watch for sure 

[Cashtown_Coop]

@MillvilleWx

Thanks for the info.  Based upon your map, do you think the Catoctins up through South Mountain stand the highest impact with the locally higher ice.   2-4” of snow with .25” or more of ice plus wind would be a high impact  event 

[canderson]

8 minutes ago, Atomixwx said:

And if MDT gets less than 4-6 he's a model hugger.

Meh no one can be criticized or mocked for busting on this system (not saying anyone here does that just in general). 
 

I’ll be absolutely shocked if I get 4” snow out of this. Warm air nearly universally gets here quicker then forecast. But if the thump is heavy enough it very well might be 4-5”. Anything over that is lottery ticket stuff l.  

[Blizzard of 93]

15 minutes ago, Itstrainingtime said:

If MDT records 4" or more of snow, I will forever refer to you as the zen of LSV snow forecasting. I believe anyone expecting (not hoping, but expecting) those totals around Harrisburg will be greatly disappointed.

We shall see soon enough!

Not sure why it seems so lofty of a number considering several models not named the NAM and support from CTP?

We shall see what the actual numbers say on Monday.

[mahantango#1]

6 minutes ago, canderson said:

Rare to see such a discrepancy.  

Just like we'll maintained roads, the ice stops at the Pa. line.

[Bubbler86]

Hopefully someone has time to post or review the euro in 30 min? Curious.  

[Voyager]

13 minutes ago, mahantango#1 said:

Just like we'll maintained roads, the ice stops at the Pa. line.

From what I heard, it even stropped at the county lines. Word on the street was that Schuylkill County roads were really bad last Sunday, but as soon as you got out of Tower City (and the Skook) and into Dauphin County on 209 at least, the roads went from bad to pretty good.

[KPITSnow]

No matter what happens, I think someone should remind JB of his proclamation that the storm would slide off the Jersey coast.

That is why you don't make definitive calls, especially as a legitimate met, 5 days out.