Jan 6/7 "Event" and obs

[jayyy]

6 minutes ago, SnowGolfBro said:

The GFS certainly thinks so. Maybe the model is just simplifying things. Big blob of precip headed our way, cold enough = snow! If only it were that easy

Perhaps it is… so long as the MSLP stays in tact and tracks SW to NE to our south. Man, oh man, that’d be nice 

[osfan24]

17 minutes ago, Interstate said:

The CMC is going to nice

 

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

Certainly wouldn't kick it out of bed.

Seems to snow hard over 95 for several hours.

[WinterWxLuvr]

18 minutes ago, Interstate said:

The CMC is going to nice

 

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

Not sure I agree

[Snowchaser]

About to start my journey to Snowshoe for this one. Hopefully the roads are snow covered 

[WinterWxLuvr]

4 minutes ago, NorthArlington101 said:

HDRPS pretty decent.

By what standard?

[NorthArlington101]

1 minute ago, WinterWxLuvr said:

By what standard?

mine 

12z CMC

[SnowGolfBro]

7 minutes ago, jayyy said:

Perhaps it is… so long as the MSLP stays in tact and tracks SW to NE to our south. Man, oh man, that’d be nice 

That’s really the unicorn solution for us right now. Get the precip to come in from SW to NE and hold on a couple extra hours before the coastal takes over.

[jayyy]

1 minute ago, Bob Chill said:

Globals are too broad brush for narrowly defined sensible wx in the short range. Euro has the resolution but it's still a global. OTOH- mesos try to be "too accurate" with exact placement of subtle variations of qpf/bands etc. I know you know this but just reminding everyone that all decent models are useful in the short range but no one model is deadly. Just blend and apply climo. Rarely fails. 

Precisely! Each model has its relative strengths and weaknessess and some do better in a given setup, but there’s no model we can point to as gospel here or in any setup really.   

If the NAM GFS Euro HRRR RGEM show 1”, 2”, 3”, 4”, and 5” in your backyard  respectively — I’d say 2-3” is pretty good bet. We of course all want to lean on the snowiest solution in any setup, but how often does that pan out?  We typically see one model nail track, another model nail thermo profile, etc.

Find a reliable model blend and know your climo. Good rules of thumb for sure. 

[mappy]

5 minutes ago, NorthArlington101 said:

mine 

12z CMC

#mappyjackpot

[osfan24]

4 minutes ago, NorthArlington101 said:

mine 

12z CMC

Eh, it's fine I guess, at least for those of us just west of Baltimore. But not great for everyone else. Certainly looked better just looking at the animation. Would have expected some totals around half a foot with what looked like very heavy rates for a few hours.

[Wetbulbs88]

5 minutes ago, Bob Chill said:

Globals are too broad brush for narrowly defined sensible wx in the short range. Euro has the resolution but it's still a global. OTOH- mesos try to be "too accurate" with exact placement of subtle variations of qpf/bands etc. I know you know this but just reminding everyone that all decent models are useful in the short range but no one model is deadly. Just blend and apply climo. Rarely fails. 

Obvious but true, and we tend to forget it. I hate to be a debbie downer but in situations like these, we tend to underperform. Not saying that will happen, but I'm looking for 1-3" here. You never know--either the WAA can remain stronger for longer, or the coastal can develop earlier than expected. But when you're trying to thread that needle, you're trying to thread that needle. Then you're trying to catch a decent band either way.   

[BristowWx]

8 minutes ago, Bob Chill said:

Globals are too broad brush for narrowly defined sensible wx in the short range. Euro has the resolution but it's still a global. OTOH- mesos try to be "too accurate" with exact placement of subtle variations of qpf/bands etc. I know you know this but just reminding everyone that all decent models are useful in the short range but no one model is deadly. Just blend and apply climo. Rarely fails. 

So when one model "nails it" its really more luck than it being that good.  Makes sense. 

[nj2va]

15z HRRR looks great for Davis/Deep Creek.  12"+....great for the ski resorts.  Fozz will have good time.

[EastCoast NPZ]

40 minutes ago, Weather Will said:

WB 12Z GFS

Looks perfectly reasonable 

[Interstate]

2 minutes ago, osfan24 said:

Eh, it's fine I guess, at least for those of us just west of Baltimore. But not great for everyone else. Certainly looked better just looking at the animation. Would have expected some totals around half a foot with what looked like very heavy rates for a few hours.

Yeah me too... but remember us west and north of Baltimore missed out on Monday... so there is that.

[Wetbulbs88]

 

1 minute ago, EastCoast NPZ said:

Looks perfectly reasonable 

I'd wager it's too generous. 

[WinterWxLuvr]

2 minutes ago, nj2va said:

15z HRRR looks great for Davis/Deep Creek.  12"+....great for the ski resorts.  Fozz will have good time.

Lol I have decided I will only look at the hrrr out to one hour. That means it will have already happened 

[MN Transplant]

16z HRRR will be the first run that has the entire storm within the 18 hours.  The 15z is a minor improvement on the 12z, taking the <0.10" QPF amounts off the table.

[aldie 22]

1 minute ago, MN Transplant said:

16z HRRR will be the first run that has the entire storm within the 18 hours.  The 15z is a minor improvement on the 12z, taking the >0.10" QPF amounts off the table.

> or <

[RevWarReenactor]

4 minutes ago, Wetbulbs88 said:

Obvious but true, and we tend to forget it. I hate to be a debbie downer but in situations like these, we tend to underperform. Not saying that will happen, but I'm looking for 1-3" here. You never know--either the WAA can remain stronger for longer, or the coastal can develop earlier than expected. But when you're trying to thread that needle, you're trying to thread that needle. Then you're trying to catch a decent band either way.   

 

On the HRRR the WAA is angled in a way where it snows in NH before it snows in DC. Not a great sign. See that before and it doesn't end well.  By the time its in the I-95 corridor, its weak, and the coastal has taken over giving Coastal southern Del and Coastal NJ the snow leaving a hole. Its very plausible.

I'm thinking 1-2 for I-95, anything else would be a bonus.

[Warm Nose]

O/U remains 3" it seems like. Shifts between now and then but we'll just have to nowcast.

[jayyy]

2 minutes ago, SnowGolfBro said:

That’s really the unicorn solution for us right now. Get the precip to come in from SW to NE and hold on a couple extra hours before the coastal takes over.

Indeed. How many times have we said “the initial slug of precip came in faster / heavier than modeled” or “we were a few degrees colder than modeled due to heavier precip than expected at the onset” after a marginal event was over?
 

It certainly happens. Will it happen here? Maybe. Hard to know. We should get an idea pretty early on regarding how much of that precip is getting eaten up as it crosses the Apps. But it’s DC to Baltimore’s (central MD) best shot at seeing the higher end totals being depicted by the Canadian and GFS - as the likelihood the coastal gets going early enough to throw Atlantic moisture into the CWA is very low (models see that happening in southern New England - not anywhere near our latitude)

The 4-5” being depicted near Baltimore could just be the obvious shortcomings of using global models this close to an event with this type of setup, but it’s still possible if the initial energy manages to hold together for a few extra hours.

That’s why it’s best that we blend models at this juncture, which is why I think NWS’s 2-4” with 5-6” lollies area-wide is a very reasonable forecast for most. 

[MN Transplant]

14 minutes ago, leesburg 04 said:

> or <

edited!

[Ravens94]

HRRR shows a NE wind for quite awhile when the snow is along the apps you would think it would be saturated enough east to snow vs a NW component 

[jayyy]

One thing is for sure - some places will get 1-2”, while others relatively nearby see 3-4-5”. Nature of the beast when you’re banking on banding and WAA.  Could very well see dc metro at 1-2” with Baltimore hitting 3-4” in this setup. Or both see 1-2” with 3-6” totals to the NW and NE of both metros. That line is very fine in these setups and often comes down to very minute differences in timing, track, thermals, etc. 

If you stick with 2-4” as the general forecast, it’ll likely verify for 90% of the CWA. Nowcasting is when we’ll be able to verify where the lollies / jackpot zones setup. Somebody expecting 6” will see 1-2” and somebody expecting 1-2” will see 6”. That's how these setups almost always pan out. We use previous setups to make our best educated guess on where that occurs leading up to the event, but we won’t know until it happens. 

[Scraff]

So how’s our dusting shaping up? 

[jayyy]

2 minutes ago, Scraff said:

So how’s our dusting shaping up? 

Relatively clueless on whether or not the DC to BAL corridor will see 1” or 6” within 12 hours of a storms onset. You know… the usual. 

[psuhoffman]

1 hour ago, WinterWxLuvr said:

Same here. GFS showed a better northern edge that turned out to be pure fantasy.

Gfs doesn’t have the resolution or the physics to resolve fine details like banding and sharp edges due to subsidence around banding. It smoothed everything which gives a too expansive representation of precip along sharp edges. 

43 minutes ago, WxUSAF said:

RGEM in camp 2

It’s very subtle, one of those things where we’re right near a critical mass switch flip and models can’t decide which side we end on, but the deciding factor seems to be how much energy transfers to the coastal v simply amplifying the primary associated with the SW. 

Runs that key on a quicker transfer and amp the coastal more v the primary less, cause 2 effects. It interferes with the south and easterly flow around the primary cutting off better moisture transport. And it develops a more intense deform band along the coastal front sooner which puts a subsidence zone over our area. 
 

The models that amplify the primary more and coastal less delay that process, or in the case of the Gfs simply never really develop the secondary and just have the primary amplify and merge with the secondary, so the initial band intensifies after the mountains as it crosses our area aided by a nice southeast moisture influx from the primary.  

35 minutes ago, Bob Chill said:

Globals are too broad brush for narrowly defined sensible wx in the short range. Euro has the resolution but it's still a global. OTOH- mesos try to be "too accurate" with exact placement of subtle variations of qpf/bands etc. I know you know this but just reminding everyone that all decent models are useful in the short range but no one model is deadly. Just blend and apply climo. Rarely fails. 

I tend to like to use the euro for Synoptics like where to expect a feature then the higher resolution models for what the exact details of said feature will look like. That’s not 100% and I definitely factor the Gfs and other data into it and can nudge the euro representation one way or the other but that method has served me pretty well as a “starting point” from which to build on in the past. 

[NorthArlington101]

UKIE is (a bad model and cannot be trusted) but is on the team of having the screw zone being closer to PHI.

 

[psuhoffman]

9 minutes ago, jayyy said:

One thing is for sure - some places will get 1-2”, while others relatively nearby see 3-4-5”. Nature of the beast when you’re banking on banding and WAA.  Could very well see dc metro at 1-2” with Baltimore hitting 3-4” in this setup. Or both see 1-2” with 3-6” totals to the NW and NE of both metros. That line is very fine in these setups and often comes down to very minute differences in timing, track, thermals, etc. 

If you stick with 2-4” as the general forecast, it’ll likely verify for 90% of the CWA. Nowcasting is when we’ll be able to verify where the lollies / jackpot zones setup. Somebody expecting 6” will see 1-2” and somebody expecting 1-2” will see 6”. That's how these setups almost always pan out. We use previous setups to make our best educated guess on where that occurs leading up to the event, but we won’t know until it happens. 

If you want to look smart say 2-5 everywhere.  90% will verify. When in reality we know there is likely to be a zone of 3-6 with a zone of 1-3 but placing those exact bands is risky and really just an educated guess.