February 7th Storm Threat Discussion/Obs

[WinterWxLuvr]

Who has the 20:1 map?

[ovechkin]

Serious question from a novice and my apologies in advance for my ignorance. 
I see what the models are projecting, and get there will be low dews and can calculate a wet bulb.  Yet, with temps on Saturday around 50 during the day, clouding up during the evening, and the inability in the immediate metro to cool down even to forcasted lows most nights (supposed to be 35 last night and never dropped below 40, and even last Friday night during the “very cold” stretch barely  ducked under 25,) how will this ever be cold enough to support accumulating snow?  I have seen dynaimc heavy snow accumulate at 34-35. I get it. But how can we be sure it won’t be just cloudy at 42 heading into the event in the immediate metro? Is just robust dynamic cooling? Again, sorry if this a stupid question. 

[mappy]

2 minutes ago, IronTy said:

That's a sign, lock it in.  

snow depth is probably the better one to use. 

[WesternFringe]

3 hours ago, Wentzadelphia said:

Before the last event on our Philly forum Tony (rainshadow) posted the model that’s supposed to be replacing the NAM soon. I forget what it’s called, but it did an amazing job. I think it begins with a C but idk lol. I’ll see if I can get a snow map off its recent run.
 

I found it...

so supposedly this will be the model replacing the NAM. This was its forecast before the last event

So, what is it showing now?  You have a link?

[snowfan]

1 minute ago, mappy said:

snow depth is probably the better one to use. 

Weenie slayer lol.

[osfan24]

4 minutes ago, BTRWx's Thanks Giving said:

I'm surprised they look the same! Ttb depth map only shows 3-4" for D.C.

Pivotal Kuchera looks way different. Highest amounts are around 6-8 inches. DC is like 4-5.

[mappy]

Just now, snowfan said:

Weenie slayer lol.

[Baltimorewx]

29 minutes ago, snowmagnet said:

Thank you for that - good to temper expectations.  Since temps are an issue, do you see this having a big impact on roads Sunday?  It sounds like it will be coming down pretty fast, but I’m wondering about accumulation on surfaces.  

I think it could coat the roads up pretty good if it comes down hard enough, even at 32-33 temps in early morning. But once it lets up, melting will occur quickly. So this will be one of those events where it’s impactful while it’s going, but once it’s done it’s done. Travel Sunday afternoon for the game should be fine 

[blueberryfaygo]

3 minutes ago, mappy said:

snow depth is probably the better one to use. 

 

IDK if this is the case.. the red taggers are talking about "saturated dendritic growth layers" and getting everyone excited.. this could be an over performer when it comes to ratios.. 

[The Ole Bucket]

Sorta now feels like we might have it where we want it since we'd anticipate further northwest movement...

 

Might have to start picking out which hat to eat.

[CAPE]

9 minutes ago, WinterWxLuvr said:

Who has the 20:1 map?

I will go with 10:1 initially, then ending up at 6:1 late Sunday morning/early afternoon. Probably ends as light rain here as advertised.

[mappy]

Just now, blueberryfaygo said:

IDK if this is the case.. the red taggers are talking about "saturated dendritic growth layers" and getting everyone excited.. this could be an over performer when it comes to ratios.. 

i highly doubt that the lower eastern shore will see a foot of snow out of this. but okay. 

[chris21]

5 minutes ago, ovechkin said:

Serious question from a novice and my apologies in advance for my ignorance. 
I see what the models are projecting, and get there will be low dews and can calculate a wet bulb.  Yet, with temps on Saturday around 50 during the day, clouding up during the evening, and the inability in the immediate metro to cool down even to forcasted lows most nights (supposed to be 35 last night and never dropped below 40, and even last Friday night during the “very cold” stretch barely  ducked under 25,) how will this ever be cold enough to support accumulating snow?  I have seen dynaimc heavy snow accumulate at 34-35. I get it. But how can we be sure it won’t be just cloudy at 42 heading into the event in the immediate metro? Is just robust dynamic cooling? Again, sorry if this a stupid question. 

Where are you located in DC? I got down to 36.7 last night in NW, you didn’t get below 40. Luckily, it’s early Feb so we are in prime climo for these types of events. I would be far more worried about what you are referring to of this event was in March. Most of the models indicate heavy precipitation with cold air aloft creating an ideal situation for dynamic cooling. Most models show temps of 31-33 during the heavy snow.

[DDweatherman]

Well other than the 12k NAM @ 6z, the rest of the suite came in more amped and more NW overall. The RGEM and Euro both showed nice moves. 

[Baltimorewx]

1 minute ago, mappy said:

i highly doubt that the lower eastern shore will see a foot of snow out of this. but okay. 

Yeah nobody’s getting a foot. But up to 5-6” I guess is possible in the heaviest precip locations where it’s still cold enough. 

[chris21]

8 minutes ago, mappy said:

snow depth is probably the better one to use. 

The snow depth map could be right, but in general I have found that product to be pretty atrocious with verification. 

[mappy]

Just now, chris21 said:

The snow depth map could be right, but in general I have found that product to be pretty atrocious with verification. 

then feel free to hug the weenie snow maps  

[Ravens94]

It certainly seems possible for a stripe of 6-10 looking at the individuals in the GFS there are some pretty big hitters in there. 

[ovechkin]

5 minutes ago, chris21 said:

Where are you located in DC? I got down to 36.7 last night in NW, you didn’t get below 40. Luckily, it’s early Feb so we are in prime climo for these types of events. I would be far more worried about what you are referring to of this event was in March. Most of the models indicate heavy precipitation with cold air aloft creating an ideal situation for dynamic cooling. Most models show temps of 31-33 during the heavy snow.

On call last night at the VA ( North Capitol and Michigan.)  I guess I’m just worried the models bust on temps. Hope they are correct. Will be a great event if they are right! 

[Negnao]

6z Eps > 3 inch probability 

  

[GATECH]

11 minutes ago, ovechkin said:

Serious question from a novice and my apologies in advance for my ignorance. 
I see what the models are projecting, and get there will be low dews and can calculate a wet bulb.  Yet, with temps on Saturday around 50 during the day, clouding up during the evening, and the inability in the immediate metro to cool down even to forcasted lows most nights (supposed to be 35 last night and never dropped below 40, and even last Friday night during the “very cold” stretch barely  ducked under 25,) how will this ever be cold enough to support accumulating snow?  I have seen dynaimc heavy snow accumulate at 34-35. I get it. But how can we be sure it won’t be just cloudy at 42 heading into the event in the immediate metro? Is just robust dynamic cooling? Again, sorry if this a stupid question. 

You kinda answered your own question, we will wet bulb down, but the real answer is to look upstairs, look at the surface temp at DCA in this sounding from DCA, looks to be below 32 at  anything above 1000mb.  Heavy rates and you get a beat down, light rates and it’s snow/rain or rain.   Your concerns are all valid though, we have seen many a marginal situations bust, and a few boom.  Learn to read soundings and skew-t charts, will be super helpful! 

 

 

[IronTy]

13 minutes ago, blueberryfaygo said:

IDK if this is the case.. the red taggers are talking about "saturated dendritic growth layers" and getting everyone excited.. this could be an over performer when it comes to ratios.. 

What's the canadian say?  It seemed to have a lot of dendritic growth for last weekend's storm...

[blueberryfaygo]

15 minutes ago, mappy said:

i highly doubt that the lower eastern shore will see a foot of snow out of this. but okay. 

Thats our Snow Mappy.. you know how these things trend in the last 48

[ForestHillbilly]

15 minutes ago, Baltimorewx said:

Yeah nobody’s getting a foot. But up to 5-6” I guess is possible in the heaviest precip locations where it’s still cold enough. 

Eternally the optimist!

[blueberryfaygo]

10 minutes ago, Negnao said:

6z Eps > 3 inch probability 

  

oh shit.. thats legit.. none of the events this year looked that good inside of 48 hours.. 

[The Ole Bucket]

One of our local mets with the pretty obvious call. Now just have that drift a little northwest like we expect.

[MillvilleWx]

2 hours ago, CAPE said:

If those areas are prime, my yard should be. I usually do better than those areas in marginal temp events because I am further E/NE and away from any moderating influences from the bay.

What do you figure the liquid/snow ratios will be? Even if there is good lift through the DGZ, the lower level temps are super marginal, so I would think maybe 7:1?

I'm thinking 8-10:1 given the mid-level frontogen involved with the wave. The s/w is still fairly prolific on guidance right now and there's going to be significant large scale ascent from the 25H jet amplifying to the north. I think one of the things the globals are not going to pick up on is that meso banding is all but a given with the current 7H progs. The 7H fronto AND 85H fronto will actually work in your favor, so you'll have deeper boundary layer lift compared to areas north and west. They have the mid-level fronto, but eastern shore will likely cash on both, which is why I like your spot, Easton, Kent Island, down to Cambridge as the local jack with central DE as another good spot pending the northern latitude push of the surface low along the coast. I'm rooting for you!

[Ravens94]

Not trying to make a entire discussion about the SREF but using SPC maps it's further NW and appears wetter for sure

[JakkelWx]

2 minutes ago, MillvilleWx said:

I'm thinking 8-10:1 given the mid-level frontogen involved with the wave. The s/w is still fairly prolific on guidance right now and there's going to be significant large scale ascent from the 25H jet amplifying to the north. I think one of the things the globals are not going to pick up on is that meso banding is all but a given with the current 7H progs. The 7H fronto AND 85H fronto will actually work in your favor, so you'll have deeper boundary layer lift compared to areas north and west. They have the mid-level fronto, but eastern shore will likely cash on both, which is why I like your spot, Easton, Kent Island, down to Cambridge as the local jack with central DE as another good spot pending the northern latitude push of the surface low along the coast. I'm rooting for you!

woot woot!

[osfan24]

2 minutes ago, Ravens94 said:

Not trying to make a entire discussion about the SREF but using SPC maps it's further NW and appears wetter for sure

People dog on the SREF's all the time, but if you don't pay attention to the ridiculous members (which is pretty obvious when you look at the charts), it's pretty accurate and gives you a great idea of what to expect. It did a really nice job with our last storm at least for my area.