December 16-17, 2020 Winter Storm Obs/Nowcasting

[BristowWx]

1 minute ago, snowmagnet said:

I was stuck at 32.5 for several hours. Finally around 31 now.  It still is raining, but sounds a bit more icy, maybe changing over a bit. 

Yeah didn’t think this would be much ZR but there are trees hanging down everywhere here.  Can’t buy a flake however since about 1.  

[notvirga!]

Based on others obs sounds like we’ll go back to sleet here too before too long. Fingers crossed. 

[LeesburgWx]

Sounds like pouring rain in the summer outside but it is sleet. Not sure the changeover to snow will happen in tile. Back edge is approaching very fast

[DDweatherman]

1 minute ago, jayyy said:

That ULL catches the coastal quick enough and I think our area sees an additional 3” or so

You’d think with almost all models hitting on that now at <6 hrs lead time, we should get a couple inches... and it would dump pretty good with the ULL. 

[Ruin]

Just now, ldub23 said:

Seems  like the dry slot and warm nose always goes further  north and west than expected. Alot  of TWC reporters not  in snow.

yeah sadly funny thing is some one called me out saying i was lying about the dry slot.

[ErinInTheSky]

It’s a sleet blizzard (slizzard?) outside. Germantown.

[Thanatos_I_Am]

2 minutes ago, A777 said:

Heavy sleet in NW Rockville

Can confirm near town center. Pingers rattling on the window. Can we squeeze some snow to cover the sidewalks after the tropical downpours earlier?

[caviman2201]

Something I'm not understanding... maybe someone smart can explain it to me.  According to SPC Mesoanalysis, the SLP has basically taken a perfect track - the kind of track that had models spitting out ridiculous totals for us even along I95. The models (at least the runs over the past 24h) seemed to have nailed the event for I95 - quick thump, quick changeover, rain rest of the event, 1-3".  What I'm not understanding is that the models came to that conclusion based on an SLP that tracked basically right over Delmarva.  The SLP didn't do that - its at least 25-50 miles east of all guidance but we still ended up with the same result.

Am I missing something?

[midatlanticweather]

Flipping now. 

[poolz1]

Mod snow...large flakes.

[mattie g]

Raining in Burke. Dang...just a little coating to end the day would be nice.

[Mimiof2]

Sharpsburg, MD 420' ASL

9:30pm 24 degrees and snowing. It's not pouring but its snowing a good clip. I believe we changed over from sleet about 9pm. I guesstimate we got maybe 1/8 of an inch in sleet accumulation.

Hoping that its starts puking snow again!

 

[40/70 Benchmark]

How did DC and Baltimore do?

[LP08]

Back down to 32 after a high of 32 in N. Arlington.  “Hearing” the rain now so some sleet is in there.

[mattie g]

1 minute ago, mattie g said:

Raining in Burke. Dang...just a little coating to end the day would be nice.

Scratch that - it’s all sleet now.

[ravensrule]

Just now, 40/70 Benchmark said:

How did DC and Baltimore do?

DC got about an inch and Baltimore got between 2-3.5”

[PWC Split]

1 minute ago, 40/70 Benchmark said:

How did DC and Baltimore do?

Hopefully you get as much snow as DC and Baltimore did.

[Yeoman]

2 minutes ago, 40/70 Benchmark said:

How did DC and Baltimore do?

12" lollies

[psuhoffman]

8 minutes ago, DDweatherman said:

And as @psuhoffman said the NAM was out, it throws us some snow tonight on the 0z.

I wrote that up before any 0z guidance came out...the 12k did jump on board...not to the extent of the euro and rgem/hrdps but a significant move to that camp.  The 3k still wants none of it.  It took a tiny step, it sees it now...but it develops the banding to our northeast in PA.  That is very possible...but so is the euro idea...or anything in between.  The 12k NAM is also warmer...more of if would be mix...but that is a function of it not developing as robust a banding signature to cool the column.  

[MDphotog]

17 minutes ago, LP08 said:

I have family in Scranton, they have travel emergency notices going to their phones.  I hope to be getting pics tomorrow morning.

I can believe it, check out google maps traffic, that is a lot of interstate closures in that area.

[jayyy]

5 minutes ago, caviman2201 said:

Something I'm not understanding... maybe someone smart can explain it to me.  According to SPC Mesoanalysis, the SLP has basically taken a perfect track - the kind of track that had models spitting out ridiculous totals for us even along I95. The models (at least the runs over the past 24h) seemed to have nailed the event for I95 - quick thump, quick changeover, rain rest of the event, 1-3".  What I'm not understanding is that the models came to that conclusion based on an SLP that tracked basically right over Delmarva.  The SLP didn't do that - its at least 25-50 miles east of all guidance but we still ended up with the same result.

Am I missing something?

850 low never closed off, allowing warm air to scream north. It’s early winter, barely below freezing, with relatively warm ocean waters compared to deep winter. If we had a closed 850 low south of here, this was an easy 12+ area wide  

[DDweatherman]

Just now, psuhoffman said:

I wrote that up before any 0z guidance came out...the 12k did jump on board...not to the extent of the euro and rgem/hrdps but a significant move to that camp.  The 3k still wants none of it.  It took a tiny step, it sees it now...but it develops the banding to our northeast in PA.  That is very possible...but so is the euro idea...or anything in between.  The 12k NAM is also warmer...more of if would be mix...but that is a function of it not developing as robust a banding signature to cool the column.  

With the changeover coming W to E just west of us now, I’d favor better thermals occurring. Does the current swath now basically pivot to the NW/SE orientation? Or are we refiring more Precip again. 

[MN Transplant]

4 minutes ago, caviman2201 said:

Something I'm not understanding... maybe someone smart can explain it to me.  According to SPC Mesoanalysis, the SLP has basically taken a perfect track - the kind of track that had models spitting out ridiculous totals for us even along I95. The models (at least the runs over the past 24h) seemed to have nailed the event for I95 - quick thump, quick changeover, rain rest of the event, 1-3".  What I'm not understanding is that the models came to that conclusion based on an SLP that tracked basically right over Delmarva.  The SLP didn't do that - its at least 25-50 miles east of all guidance but we still ended up with the same result.

Am I missing something?

The exact position of the surface low didn’t end up mattering as much as the upper air features.  The 850 low, which is both broad and late developing, is basically over DC allowing the warm air to flood in.  We always want an 850 track to the south of DC by a fair margin.

[40/70 Benchmark]

3 minutes ago, Yeoman said:

12" lollies

I am honored to have been trolled by Yeoman lol

[ErinInTheSky]

3 hours ago, leesburg 04 said:

You ain't kidding too bad 5 people have felt it important to tell us it ain't happening 

Holy crap that gives me like 6-8" in Germantown.

[DDweatherman]

1 minute ago, DDweatherman said:

With the changeover coming W to E just west of us now, I’d favor better thermals occurring. Does the current swath now basically pivot to the NW/SE orientation? Or are we refiring more Precip again. 

Check that, now back to snow mixed in down in Westminster even before the good returns move back in. 

[40/70 Benchmark]

4 minutes ago, PWC Split said:

Hopefully you get as much snow as DC and Baltimore did.

If I don't, you'll find me tits up in the Merrimack river.

[WinterWxLuvr]

Think the dance has ended for us. Looks like from the motion on the radar that the low is really starting to scoot east.

[MDphotog]

2 minutes ago, jayyy said:

850 low never closed off, allowing warm air to scream north. It’s early winter, barely below freezing, with relatively warm ocean waters compared to deep winter. If we had a closed 850 low south of here, this was an easy 12+ area wide  

Is that why we didn’t see the usual pivot and spin on radar typical for winter storms? Or is that more of a different kind of storm?

[ErinInTheSky]

People are skidding all up and down Blunt Road near me and it's so unfortunate. That road is a car trap any time we have frozen precip.

Also: Am I the only one that is fine with sleet fests? Like, seeing sleet just filled my heart with joy after the last 3-4 hours of rain. Getting a lot of sleet seems to add some good staying power. One of my most memorable storms was... was it 2017? With the absolute epic sleet bomb 3.5" of sleet in Gaithersburg.