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

[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. 

 

[87storms]

51 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. 

 

 

LWX mentioned in their disco this morning what one of my concerns was and that's an onshore/return flow prior to the system arriving.  That primary setup has been shown the last couple days with the hp moving off the mid-Atlantic.  I think that's going to make it difficult for areas further east.  Further west, we're gonna need to rely on CAD, but I could picture that being an issue, too, until you get to the higher elevations.  And I'm not saying this because I think I'm right, but I agree with you that (at least through my hobbyist tracking) that this wasn't a clean setup.  Hopefully, most of us can at least get some snow on the front end while the antecedent conditions allow for it...from there, roll the dice.

[psuhoffman]

47 minutes ago, WxUSAF said:

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

If you look at both the gefs and eps members there is a mix of all 3 possible outcomes.
 

A 0z gfs ggem type sweet spot solution. 

some phasing and a primary with a NW solution 

A weak washed out solution 

 

It’s not shocking to see the 6z ops pull out from any of these camps.  But it does seem the EPS as a whole took a step towards the option we want. All 3 camps still have support within the spread though. 

[87storms]

8 minutes ago, psuhoffman said:

If you look at both the gefs and eps members there is a mix of all 3 possible outcomes.
 

A 0z gfs ggem type sweet spot solution. 

some phasing and a primary with a NW solution 

A weak washed out solution 

 

It’s not shocking to see the 6z ops pull out from any of these camps.  But it does seem the EPS as a whole took a step towards the option we want. All 3 camps still have support within the spread though. 

I gotta think areas closer to the M/D line are in good shape...I'm actually not really even that concerned up here (though I probably should be lol).  I think it's the 95 corridor that is going to be the most challenging forecast.  I grew up in Silver Spring, so I know exactly what that's all about.

[clskinsfan]

NAM is a hot mess. Disaster run.

[Paleocene]

NAM'D

[konksw]

It’d be hard to describe what 12z NAM is showing as a storm at all…

[mattie g]

3 minutes ago, clskinsfan said:

NAM is a hot mess. Disaster run.

Looking forward to my drizzly Saturday evening.

NAM at 84...lol.

[87storms]

44 minutes ago, clskinsfan said:

NAM is a hot mess. Disaster run.

That follow-up wave is becoming the main show.  It's actually a hecs-level looking vort lol.  If we can get that to trend south, then it's game on.

[Alfoman]

2 minutes ago, clskinsfan said:

NAM is a hot mess. Disaster run.

Won't ever take Hours 60+ on the NAM with any sort of seriousness - but on that note, there was better confluence and slightly lower surface temps this run. 

[osfan24]

52 minutes ago, WxUSAF said:

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”.

I didn't mean it will literally be zero but my point was that it won't be anywhere near that, especially if the timing of afternoon into evening is accurate as opposed to more evening and overnight. I am well aware we can overcome warm temps if it snows hard enough, but I am not sure a half inch per hour is thumpy enough given all of the other mitigating factors for the metro area.

[RDM]

NWS posted a large swath of notices from Fredericksburg South for Hazardous Weather Outlook for Fri night/Sat.  Somewhat odd - nothing N of that. 

[Kmlwx]

Just now, RDM said:

NWS posted a large swath of notices from Fredericksburg South for Hazardous Weather Outlook for Fri night/Sat.  Somewhat odd - nothing N of that. 

That's a different WFO

[clskinsfan]

RGEM still really nice west of the fall line. Heavy snow for Loudoun. Good run.

[Warm Nose]

New Sterling discussion, SIAP.

 

.LONG TERM /SATURDAY THROUGH TUESDAY/...
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
preceding 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.

The coastal low tracks northeast and away from the area Saturday
night, then a reinforcing upper trough traverses the area on
Sunday. Some lingering rain and snow showers possible during the
first part of Monday north of I-66 and west of the Blue Ridge,
though conditions dry out quickly in the afternoon. Upslope
mountain snow showers continue into Sunday night.

[aldie 22]

2 minutes ago, Warm Nose said:

New Sterling discussion, SIAP.

 

.LONG TERM /SATURDAY THROUGH TUESDAY/...
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
preceding 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.

The coastal low tracks northeast and away from the area Saturday
night, then a reinforcing upper trough traverses the area on
Sunday. Some lingering rain and snow showers possible during the
first part of Monday north of I-66 and west of the Blue Ridge,
though conditions dry out quickly in the afternoon. Upslope
mountain snow showers continue into Sunday night.

Curious what part of Western Loudoun are you in....is it for real Western Loudoun or Ji's version of Western Loudoun? If it's for real Western then i think your area is in a pretty good spot for this one especially Round Hill on West

[winter_warlock]

3 minutes ago, clskinsfan said:

RGEM still really nice west of the fall line. Heavy snow for Loudoun. Good run.

Where are u getting longer range rgem?

[NorthArlington101]

2 minutes ago, winter_warlock said:

Where are u getting longer range rgem?

Nasty gradient... 10" in NW Arlington, 3" in SE. 

It's also still ripping at this point in DC.