December Medium/Long Range Discussion

[psuhoffman]

@WxUSAF I’m not saying an inside runner isn’t a legit fear here.  Even up here that’s my fear. I don’t see any way this gets suppressed south. The trough goes neutral and starts to lift pretty far west. The whole flow is amplified. The block/50-50 are anchored a little north of the examples where we see something squashed to our south. Imo this is going to be a hit or too far north and rain. I feel pretty good about this ATT but still a long ways to go.  But you know me if there is an “oh no it’s all falling apart” moment I will be the first on here warning about it. The 12z EPS wasn’t that imo. 

[MillvilleWx]

Night crew check in after 6 hrs of sleep (Will be heading back to bed shortly)

Few thoughts gazing through things:

1. Initial thoughts holding with regards to ptype and where the best spots look to be. Fall line and west should remain majority snow unless we see a more amplified surface reflection. EPS showed more mixing out to even I-81, but if you look closely at the low clusters, everything that was inland was sub 990 with some at the low to mid 980’s. Remember the ptype algorithm is a smoothed mean that takes into account ALL members of the ensemble package. Even a few over amped members can skew the mean warm and could correct later in time as we get closer and filters the noise.

2. The confluence signature is becoming a positive feedback here with a classically aligned height pattern to our north that will pay dividends. High pressure over Quebec is consistently modeled around 1036-1038, which is solid for a snow event west of the fall line, so long as the low doesn’t over amplify.

3. Snow maps are fun, but best to look at QPF charts and base soundings. One of the bog things to look for in this storm is the CCB action on the final half of the system. Primary 8-10:1 caveats aside for areas along and west of the fall line for the first half of the storm, but this will have 15-20:1 potential within the deformation axis as 7H frontogenic progs have been off the charts across central MD, NoVa, Panhandle WV, into SoPA. There will be a nose of + theta-E advection when this begins to wrap as it crosses OCMD latitude. Where that points will be key in determining who gets the love on the back half. Even so, it’ll slowly gain latitude and sweep through to the east, so the ending of the system could be epic for many. It’s very classic in a Mid Atlantic MECS.

4. All that said, the typical Rt15 on west crew is in the best shape with elevated areas along Pars Ridge to Mappy sitting in a solid area due to elevation and mesoscale tendencies with bombing surface reflections. The lack of dry NW winds on the back half of the storm signify an expansive qpf shield is likely with this event, so even out to the mountains should see some love. Hancock on east is the best areas with some upslope component likely out near Garrett.

5. Sleet will undoubtedly occur for areas in the Blue Ridge in VA once south of Front Royal, but they could get smacked before a change over as southerlies scream out with the low reflection moving north.

6. Anyone who knows their climo should weight it in the result. You know your tendencies and nothing in this storm suggests a sway from the norm. A stronger high around 1040 would be what causes the mentality to shift, but it’ll likely fall short.

Now if you’ll excuse me, I’m gonna go back to sleep and I’ll be back on the night shift tonight to add more tired thoughts to this event. Be happy y’all. There’s a storm brewing!


.

[H2O]

Millville ftmfw

[Eskimo Joe]

10 minutes ago, MillvilleWx said:

Night crew check in after 6 hrs of sleep (Will be heading back to bed shortly)

Few thoughts gazing through things:

1. Initial thoughts holding with regards to ptype and where the best spots look to be. Fall line and west should remain majority snow unless we see a more amplified surface reflection. EPS showed more mixing out to even I-81, but if you look closely at the low clusters, everything that was inland was sub 990 with some at the low to mid 980’s. Remember the ptype algorithm is a smoothed mean that takes into account ALL members of the ensemble package. Even a few over amped members can skew the mean warm and could correct later in time as we get closer and filters the noise.

2. The confluence signature is becoming a positive feedback here with a classically aligned height pattern to our north that will pay dividends. High pressure over Quebec is consistently modeled around 1036-1038, which is solid for a snow event west of the fall line, so long as the low doesn’t over amplify.

3. Snow maps are fun, but best to look at QPF charts and base soundings. One of the bog things to look for in this storm is the CCB action on the final half of the system. Primary 8-10:1 caveats aside for areas along and west of the fall line for the first half of the storm, but this will have 15-20:1 potential within the deformation axis as 7H frontogenic progs have been off the charts across central MD, NoVa, Panhandle WV, into SoPA. There will be a nose of + theta-E advection when this begins to wrap as it crosses OCMD latitude. Where that points will be key in determining who gets the love on the back half. Even so, it’ll slowly gain latitude and sweep through to the east, so the ending of the system could be epic for many. It’s very classic in a Mid Atlantic MECS.

4. All that said, the typical Rt15 on west crew is in the best shape with elevated areas along Pars Ridge to Mappy sitting in a solid area due to elevation and mesoscale tendencies with bombing surface reflections. The lack of dry NW winds on the back half of the storm signify an expansive qpf shield is likely with this event, so even out to the mountains should see some love. Hancock on east is the best areas with some upslope component likely out near Garrett.

5. Sleet will undoubtedly occur for areas in the Blue Ridge in VA once south of Front Royal, but they could get smacked before a change over as southerlies scream out with the low reflection moving north.

6. Anyone who knows their climo should weight it in the result. You know your tendencies and nothing in this storm suggests a sway from the norm. A stronger high around 1040 would be what causes the mentality to shift, but it’ll likely fall short.

Now if you’ll excuse me, I’m gonna go back to sleep and I’ll be back on the night shift tonight to add more tired thoughts to this event. Be happy y’all. There’s a storm brewing!

Thank you so much for your continued analysis in this forum from afar. It's always appreciated.

[CAPE]

Just updated AFD from Mount Holly-

The latest guidance has trended a little slower with the low, which could potentially lead to more snow as more precipitation could fall coincidentally with the cold air. The models are in good agreement with the location of the high moving across southeast Canada Tuesday night into Wednesday, which will set up the cold air across the region. By Tuesday night and Wednesday, an area of low pressure is forecast to move up the southeast coast into the Mid Atlantic region, then continue to our east and out to sea Wednesday night into Thursday. The current track from the model guidance keeps the low near the coast as it passes by. This will bring precipitation to the entire forecast area, possibly starting as early as Wednesday morning, and continuing through the day into Wednesday night. With the current track, the forecast is for snow to start virtually everywhere Wednesday morning, before a mix and/or change to rain begins to lift northward into portions of southern/central Delaware and Maryland, as well as southern/eastern New Jersey; just south and east of the I-95 corridor. Along and north of the I-95 corridor, the forecast is for snow during the duration of the event. Eventually by Wednesday evening and overnight, cold air will move back in for all places, and everyone could change back over to snow where it changed to a mix or rain during the day. The precipitation types will be dependent on the track of the low and thermal profiles, so this could all change in the coming days. Although we do not have specific snowfall amounts forecast yet, all guidance is pointing to a significant snowfall accumulation for eastern Pennsylvania, much of New Jersey, northern Delaware and northern Maryland.

[WxUSAF]

Thanks @psuhoffman and @MillvilleWx for the analysis! Onto hopefully happy hour

[LeesburgWx]

17 minutes ago, MillvilleWx said:

Night crew check in after 6 hrs of sleep (Will be heading back to bed shortly)

Few thoughts gazing through things:

1. Initial thoughts holding with regards to ptype and where the best spots look to be. Fall line and west should remain majority snow unless we see a more amplified surface reflection. EPS showed more mixing out to even I-81, but if you look closely at the low clusters, everything that was inland was sub 990 with some at the low to mid 980’s. Remember the ptype algorithm is a smoothed mean that takes into account ALL members of the ensemble package. Even a few over amped members can skew the mean warm and could correct later in time as we get closer and filters the noise.

2. The confluence signature is becoming a positive feedback here with a classically aligned height pattern to our north that will pay dividends. High pressure over Quebec is consistently modeled around 1036-1038, which is solid for a snow event west of the fall line, so long as the low doesn’t over amplify.

3. Snow maps are fun, but best to look at QPF charts and base soundings. One of the bog things to look for in this storm is the CCB action on the final half of the system. Primary 8-10:1 caveats aside for areas along and west of the fall line for the first half of the storm, but this will have 15-20:1 potential within the deformation axis as 7H frontogenic progs have been off the charts across central MD, NoVa, Panhandle WV, into SoPA. There will be a nose of + theta-E advection when this begins to wrap as it crosses OCMD latitude. Where that points will be key in determining who gets the love on the back half. Even so, it’ll slowly gain latitude and sweep through to the east, so the ending of the system could be epic for many. It’s very classic in a Mid Atlantic MECS.

4. All that said, the typical Rt15 on west crew is in the best shape with elevated areas along Pars Ridge to Mappy sitting in a solid area due to elevation and mesoscale tendencies with bombing surface reflections. The lack of dry NW winds on the back half of the storm signify an expansive qpf shield is likely with this event, so even out to the mountains should see some love. Hancock on east is the best areas with some upslope component likely out near Garrett.

5. Sleet will undoubtedly occur for areas in the Blue Ridge in VA once south of Front Royal, but they could get smacked before a change over as southerlies scream out with the low reflection moving north.

6. Anyone who knows their climo should weight it in the result. You know your tendencies and nothing in this storm suggests a sway from the norm. A stronger high around 1040 would be what causes the mentality to shift, but it’ll likely fall short.

Now if you’ll excuse me, I’m gonna go back to sleep and I’ll be back on the night shift tonight to add more tired thoughts to this event. Be happy y’all. There’s a storm brewing!


.

Great write-up! Point #3 is what I will be watching for. During the 2016 blizzard, immediate DC dry slotted for much of the day before the major CCB rolled through, and it was epic! However, I watched from my Pentagon City Apartment while Loudoun West was getting pummeled under it for hours. It is why I "only" got 18" while my current home here in leesburg ended up with 35-38". High ratio heavy snow is where it's at and I hope this storm can pull some surprises in that regard.

[stormtracker]

What’s wrong with y’all?  Nobody is extrapolating the NAM. 

[mappy]

Just now, stormtracker said:

What’s wrong with y’all?  Nobody is extrapolating the NAM. 

lol

[mappy]

27 minutes ago, MillvilleWx said:

Night crew check in after 6 hrs of sleep (Will be heading back to bed shortly)

Few thoughts gazing through things:

1. Initial thoughts holding with regards to ptype and where the best spots look to be. Fall line and west should remain majority snow unless we see a more amplified surface reflection. EPS showed more mixing out to even I-81, but if you look closely at the low clusters, everything that was inland was sub 990 with some at the low to mid 980’s. Remember the ptype algorithm is a smoothed mean that takes into account ALL members of the ensemble package. Even a few over amped members can skew the mean warm and could correct later in time as we get closer and filters the noise.

2. The confluence signature is becoming a positive feedback here with a classically aligned height pattern to our north that will pay dividends. High pressure over Quebec is consistently modeled around 1036-1038, which is solid for a snow event west of the fall line, so long as the low doesn’t over amplify.

3. Snow maps are fun, but best to look at QPF charts and base soundings. One of the bog things to look for in this storm is the CCB action on the final half of the system. Primary 8-10:1 caveats aside for areas along and west of the fall line for the first half of the storm, but this will have 15-20:1 potential within the deformation axis as 7H frontogenic progs have been off the charts across central MD, NoVa, Panhandle WV, into SoPA. There will be a nose of + theta-E advection when this begins to wrap as it crosses OCMD latitude. Where that points will be key in determining who gets the love on the back half. Even so, it’ll slowly gain latitude and sweep through to the east, so the ending of the system could be epic for many. It’s very classic in a Mid Atlantic MECS.

4. All that said, the typical Rt15 on west crew is in the best shape with elevated areas along Pars Ridge to Mappy sitting in a solid area due to elevation and mesoscale tendencies with bombing surface reflections. The lack of dry NW winds on the back half of the storm signify an expansive qpf shield is likely with this event, so even out to the mountains should see some love. Hancock on east is the best areas with some upslope component likely out near Garrett.

5. Sleet will undoubtedly occur for areas in the Blue Ridge in VA once south of Front Royal, but they could get smacked before a change over as southerlies scream out with the low reflection moving north.

6. Anyone who knows their climo should weight it in the result. You know your tendencies and nothing in this storm suggests a sway from the norm. A stronger high around 1040 would be what causes the mentality to shift, but it’ll likely fall short.

Now if you’ll excuse me, I’m gonna go back to sleep and I’ll be back on the night shift tonight to add more tired thoughts to this event. Be happy y’all. There’s a storm brewing!


.

Thanks for the write up friend. Enjoy your snooze 

[Scraff]

Just now, stormtracker said:

What’s wrong with y’all?  Nobody is extrapolating the NAM. 

Too busy extrapolating the CRAS. 
 

[Thanatos_I_Am]

Been out of the game for a while.. any reason nobody mentions Para-GFS on TT?

[NorthArlington101]

1 minute ago, Thanatos_I_Am said:

Been out of the game for a while.. any reason nobody mentions Para-GFS on TT?

I honestly don't know what to make of it. Runs once a day and by the time it comes out it's always old guidance. Makes it tough to to discuss!

[AmericanWxFreak]

1 minute ago, Thanatos_I_Am said:

Been out of the game for a while.. any reason nobody mentions Para-GFS on TT?

Because it's west and warm. Shhhhh

[BristowWx]

3 minutes ago, stormtracker said:

What’s wrong with y’all?  Nobody is extrapolating the NAM. 

Seems like the EPS was a buzzkill.  Like waking up after an all nighter and wondering if something looks infected on your body. 

[H2O]

5 minutes ago, stormtracker said:

What’s wrong with y’all?  Nobody is extrapolating the NAM. 

It runs right up I-95. Torch

[H2O]

6 minutes ago, Thanatos_I_Am said:

Been out of the game for a while.. any reason nobody mentions Para-GFS on TT?

I would but I don’t want DT to yell at me with massive large font which denotes yelling

[BristowWx]

2 minutes ago, H2O said:

It runs right up I-95. Torch

You had me.  I looked with a nervous click.

[stormtracker]

1 minute ago, H2O said:

I would but I don’t want DT to yell at me with massive large font which denotes yelling

Just be glad his map didn’t put you in the Phantom Zone like Mapgirl was.  

[BristowWx]

Almost game time.  Biggest HH run since I was born.  Break out the JWB

[H2O]

2 minutes ago, stormtracker said:

Just be glad his map didn’t put you in the Phantom Zone like Mapgirl was.  

Kneel before Zod

[mappy]

2 minutes ago, stormtracker said:

Just be glad his map didn’t put you in the Phantom Zone like Mapgirl was.  

I had no category  

[PhineasC]

Maybe just a New England thing, but the para-GFS is always warm, just like the ICON. It frequently shows my place in Northern NH mixing with rain.  Something is wrong with the thermals on both of those models. I wouldn't get hung up on them.

[Ji]

10 minutes ago, AmericanWxFreak said:

Because it's west and warm. Shhhhh

TT only has the 00z version

[psuhoffman]

@WxUSAF just quick visual evidence of what I said. The edges tightened some due to some outliers falling off.  But look at the 50% prob of 6” line runs. Almost identical at 12z to 0z. The probabilities of the 2 camps hasn’t changed much. 
0z

12z

[Ji]

is DT really not coming back?

[Snowchaser]

1 minute ago, psuhoffman said:

@WxUSAF just quick visual evidence of what I said. The edges tightened some due to some outliers falling off.  But look at the 50% prob of 6” line runs. Almost identical at 12z to 0z. The probabilities of the 2 camps hasn’t changed much. 
0z

12z

i'll take 30-40% for 6+ 

Congrats PA!

[PhineasC]

2 minutes ago, Ji said:

is DT really not coming back?

This is like the 30th time he has stormed off the boards. Can't worry about it.

[HighStakes]

3 minutes ago, Ji said:

is DT really not coming back?

He'll be back in 2 years for a day or two then repeat the cycle 2 years from then.

[CAPE]

Yeah, who really cares.