January 6-7 Storm Discussion: we’re due?

[Chris78]

1 minute ago, EastCoast NPZ said:

It has snow, but a fraction of what we were looking at even yesterday.   For days straight we were looking at 1.5" precip area-wide.

Hopefully it was just a blip at 6z but precip cut in half for our areas on both the GFS and Euro. 

That probably effects temps with not getting the evaporational cooling / wet bulbing we would get from a wall of precip moving in from the Southwest.

Fingers crossed the QPF is back at 12z

[ers-wxman1]

16 minutes ago, EastCoast NPZ said:

Goodness, this thing has trended the wrong way.  Has anyone ever seen a major storm consensus on all guidance at D5 degrade like this?  I know they've busted at gametime,  but to see this storm universally morph on guidance in the medium range like this? 

Wrote about this yesterday. It is a mistake just to look at the model output, QPF etc. Analyze the scenario from the top down. 500/700/850. Are you seeing any features that align with known weather patterns that generate heavy snow across our area? Ridging out west, 850/700/500 energy is closed, deepening as it swings to our south? Strong high to the north? Blocking? Also with the CAD…what kind of air mass is being dammed? Nowhere in the northern tier do we see wind chill or extreme temperature headlines. These are flags. It’s been mild.

The big difference last night on the 00z I saw was the 850 low became closed and stronger with the vort passage, while the high became stronger, and more dynamics, ridging hinted over the western U.S. that amplifies things enough to deepen the surface low in the right spot, however this isn’t slam dunk. It’s all marginal and not dealing with a textbook winter storm here, so any minor shift in these subtle features will significantly alter snowfall amounts. That is what is happening. It’s simply not the ideal pattern. It would be a heavy front end thump then hope for wrap around as it winds up offshore before subsidence kicks in. Many moving parts. Strong SW upper flow makes this fast moving system, rely on front end WAA. Thermals also marginal, no good source to fuel this. These types of systems are a nightmare to forecast, especially with regard to headlines and where to put them. 

 

 

[clskinsfan]

Us westerners might get more from the front end thump on Tuesday than the weak mess on Saturday.

[Ravens94]

First SREF plume for the storm does not include the entire duration.

BWI 

[WinterWxLuvr]

Waffling means uncertainty. It may not go our way but I seriously doubt we have seen the actual result forecast yet.

We need a stronger storm. To get it, we need that first sw to dig. To get that we need that trailing piece to back off. Just my views 

[WinterWxLuvr]

3 minutes ago, clskinsfan said:

Us westerners might get more from the front end thump on Tuesday than the weak mess on Saturday.

Without snow on the ground I doubt there would be a front end thump.

[WxUSAF]

My quick look at 6z euro was that it jumped back to that “worst of both worlds” scenario from 6z/12z yesterday with a stronger vortmax and more phasing, but not enough to get back to that strong storm scenario from 48-72 hours ago. It was a fairly big jump from 0z. We’ll see what happens at 12z!

[mattie g]

2 hours ago, WinterWxLuvr said:

What impresses me about the gfs is it’s rock steady consistency 

It's not just the GFS that's had these little blips.

[Chris78]

I pulled this from the PA thread but I would say the OP doesn't agree with its ensembles .  Pleasantly surprised to see this.

[baltosquid]

1 minute ago, Chris78 said:

I pulled this from the PA thread but I would say the OP doesn't agree with its ensembles .  Pleasantly surprised to see this.

A nice silver lining, just have to hope there's still room for the ensembles to be the leader here rather than the OP. Relatively close now...

[WxUSAF]

2 minutes ago, Chris78 said:

I pulled this from the PA thread but I would say the OP doesn't agree with its ensembles .  Pleasantly surprised to see this.

Oooohhh…that’s encouraging. Tossing 6z euro with extreme prejudice! 
 

[Newman]

6z RGEM at the end of its runtime, sticking close to its global counterpart. The NAM... just don't look at it unless you want disappointment

[Rhino16]

14 minutes ago, ers-wxman1 said:

Wrote about this yesterday. It is a mistake just to look at the model output, QPF etc. Analyze the scenario from the top down. 500/700/850. Are you seeing any features that align with known weather patterns that generate heavy snow across our area? Ridging out west, 850/700/500 energy is closed, deepening as it swings to our south? Strong high to the north? Blocking? Also with the CAD…what kind of air mass is being dammed? Nowhere in the northern tier do we see wind chill or extreme temperature headlines. These are flags. It’s been mild.

The big difference last night on the 00z I saw was the 850 low became closed and stronger with the vort passage, while the high became stronger, and more dynamics, ridging hinted over the western U.S. that amplifies things enough to deepen the surface low in the right spot, however this isn’t slam dunk. It’s all marginal and not dealing with a textbook winter storm here, so any minor shift in these subtle features will significantly alter snowfall amounts. That is what is happening. It’s simply not the ideal pattern. It would be a heavy front end thump then hope for wrap around as it winds up offshore before subsidence kicks in. Many moving parts. Strong SW upper flow makes this fast moving system, rely on front end WAA. Thermals also marginal, no good source to fuel this. These types of systems are a nightmare to forecast, especially with regard to headlines and where to put them. 

 

 

Top down forecasting! Very important technique to use for winter especially.

[mappy]

6 minutes ago, Chris78 said:

I pulled this from the PA thread but I would say the OP doesn't agree with its ensembles .  Pleasantly surprised to see this.

Zoomed in version

[Chris78]

1 minute ago, baltosquid said:

A nice silver lining, just have to hope there's still room for the ensembles to be the leader here rather than the OP. Relatively close now...

Going off of the NBM and Euro and GFS ensembles ( I think we can still use ensembles for today) west of the Fall line still has a great chance at a moderate event. Even all the way to 95 probably sees some snow.

It may not be the double digit storm that we were all hoping for a few days ago but it still could be decent.

[WinterWxLuvr]

6 minutes ago, Newman said:

6z RGEM at the end of its runtime, sticking close to its global counterpart. The NAM... just don't look at it unless you want disappointment

Damn that’s discouraging. I typically rely on the long range NAM for my forecasts.

[clskinsfan]

RGEM is actually a pummeling out here. 

[osfan24]

10 minutes ago, Chris78 said:

I pulled this from the PA thread but I would say the OP doesn't agree with its ensembles .  Pleasantly surprised to see this.

Is this really that encouraging for most, though? 3-4 inches on these 10:1 maps is likely to have almost zero snow depth given temps. We need this to be real thumpy.

[WinterWxLuvr]

Just now, clskinsfan said:

RGEM is actually a pummeling out here. 

It can’t be trusted as well. Only missed by about 45” in Balt a few years ago.

[NorthArlington101]

Just now, WinterWxLuvr said:

It can’t be trusted as well. Only missed by about 45” in Balt a few years ago.

if we're being technical that was it's high-res counterpart the HRDPS - but yeah, RGEM isn't a known winner either.

I know we've already shared the EPS mean -- below is the median. Wanted to make sure there weren't crazy outliers propping up the mean. Still looks solid enough.

[stormy]

Hmmm...... Saturday and Tuesday are now nearly tied!!  7.5" on Saturday and 6.9" on Tuesday.  10:1 GFS, ECM, GEM deterministic. Ensembles 3.8" Saturday, 4.5" Tuesday

[clskinsfan]

2 minutes ago, stormy said:

Hmmm...... Saturday and Tuesday are now nearly tied!!  7.5" on Saturday and 6.9" on Tuesday.  10:1 GFS, ECM, GEM deterministic. Ensembles 3.8" Saturday, 4.5" Tuesday

Yeah. Tuesday's thump is a beatdown as modelled:

[Chris78]

3 minutes ago, osfan24 said:

Is this really that encouraging for most, though? 3-4 inches on these 10:1 maps is likely to have almost zero snow depth given temps. We need this to be real thumpy.

I would consider it encouraging but everyone has there own interpretation. 

That's a pretty good indicator that it's going to snow. It may not be the double digit storm that has been shown from time to time but any snow is good snow. This might be the first plowablw snow in these parts in 2 years.

[NorthArlington101]

and FWIW - just because I think it's interesting to track how the newer-tech (not necessarily better, at all) models do - the SPIRE has held a 6-8"+ storm (kinda like the 00z GFS/CMC) sicne 00z yesterday. It only runs 2x a day.

[WxUSAF]

11 minutes ago, osfan24 said:

Is this really that encouraging for most, though? 3-4 inches on these 10:1 maps is likely to have almost zero snow depth given temps. We need this to be real thumpy.

Let’s not do this “it won’t accumulate” game for the 1081st time please. Could 10:1 be too high? Sure. But I will bet my retirement fund that if 10:1 shows 3-4” that falls in 6 hours, the snow depth won’t be 0.0”.

[rjvanals]

06z EPS Mean for 1 inch plus is 82% for DCA which is the highest it's been in the past 4 cycles. The 4 inch mean is holding steady the past few cycles around 30% for DCA. 

[WinterWxLuvr]

16 minutes ago, NorthArlington101 said:

if we're being technical that was it's high-res counterpart the HRDPS - but yeah, RGEM isn't a known winner either.

I know we've already shared the EPS mean -- below is the median. Wanted to make sure there weren't crazy outliers propping up the mean. Still looks solid enough.

I like your use of the median 

[Rhino16]

2 minutes ago, WinterWxLuvr said:

I like your use of the median 

Me too, it’s really what we should be posting.

[Terpeast]

LWX AFD if not already posted (from 3:50 am). Their office has been handling this storm better than any of the models  i applaud them for their restraint. 

They also slate the start of the storm during Friday night, which could help us with the temps.

 

A strong southern stream mid/upper-level trough over the Mid-South
Friday night quickly moves northeast as it phases into a flat trough
over the OH Valley/Mid-Atlantic on Saturday. At the surface, an
associated area of low pressure develops along the northern Gulf
Coast and very quickly moves across the Southeast states through
Saturday morning. The surface low becomes better organized as it
crosses eastern NC into far southeast VA, where it moves offshore
along the NC/VA border.

Precipitation overspreads the area from southwest to northeast
starting late Friday night into Saturday. Temperatures Friday night
are forecast to be below freezing for most of the area. However,
there is considerable uncertainty to the east of US-15 as easterly
winds advect in a warmer marine airmass and strong WAA ahead of the
surface low help to increase temps along/east of I-95. All that
being said, precipitation is likely to start out as snow west of US-
15 and a rain/snow mix along/east of US-15. As the morning
progresses, areas east of I-95 are most likely to transition to a
cold rain, with steady snow west of US-15, and a mix in between.

Having the surface high well to the north and weak onshore flow
proceeding the surface low are not generally favorable for
accumulating snow along I-95. Any chance to see higher snow totals
there will be dependent on higher precip rates and wet bulb effects
overcoming the marginal temperature profile.

Still, p-type is going to be highly sensitive to the track of the
low, with a tight rain-snow gradient likely. Significant snow
accumulations are most likely along/west of the Blue Ridge and
Catoctins. Where precip is more likely to be in the form of rain,
near and east of I-95, there is the potential for instances of
flooding. Continue to monitor the progress of this storm as the
weekend approaches.

 

[Warm Nose]

"When all else fails, rely on historical climo" seems to be the writing on the wall for this one.