WxUSAF

1 minute ago, Eskimo Joe said:

Just flipped back to all rain but my temp fell to 33. Really weird.

CC line has wobbled back north. Probably losing some of the best lift as the storm pulls away?

Just now, 87storms said:

pingers in bethesda.  kinda suprised by that, but i'm under a legitimate band, so might just be temporary.

CC line has jumped south so that fits.

1 minute ago, mappy said:

I don't know CC well enough to interpret correctly, so thanks for this.

It can be hard to interpret.  Definitely helps to orient yourself with direct surface obs for reference.  The CC product will be very useful Wednesday.

Snow line showing up very well on correlation coefficient radar product.  Looks like the line is along Harpers Ferry-Frederick-just west of mappy's house.  

1 minute ago, Ji said:

the NAM used to run to 48 hours probably for a reason

The 12K NAM was replaced by the 3k NAM several years ago for a reason.  The 3k is probably worth looking at starting with tomorrow's 12z run.

Repeat this week in prime climo season and it's the best week since Feb 2010 for most places.  Just sayin'.  

NWS take looks pretty good to my eyes

10 minutes ago, H2O said:

First, last, third, its all for fun call

 

 

Woohoo!  I'm in the "assload" zone!

5 days out: everyone sets unreasonable lower bound expectations based on the best model run

2 days out: everyone jumps when they realize it’s not going to be a HECS for them 

1 day out: most people accept reality and realize yes, it’s going to snow

4-8 hours out: radar hallucinations

1 day after: everyone’s happy and can’t wait to get the next storm 

every. Single. Time.

7 minutes ago, jayyy said:

Interested to see what the GFS/ICON/EPS/RGEM do at 12z. More concerned with the trend than the verbatim solution. 

I'm not convinced there's any trend at all. It's wobbling back and forth for the reasons I and others have laid out.  6z Euro wobbled left, 6z RGEM wobbled right.  And these moves are so small in reality, even if it did "trend" left for 4 runs, a bump right on tomorrow's 12z runs could easily happen that would put it right back where it started. This (and other reasons) is why snowfall forecasts always have ranges.  

1 minute ago, osfan24 said:

Not based on that above snowfall map. Woof.

At this range the Op runs are much prioritized and you really never should use ensembles snowmaps for prime forecasting methods.  I know we all look at them but it's not what ensembles are for.  Op Euro, GGEM, and GFS all give us a really nice storm.  It's going to wobble back and forth a little and then come down to mesoscale/microscale features in the end like it always does on final snow amounts.  But the goalposts have narrowed and stayed in place pretty much for the last 48-72 hours.  There's no primary to Cleveland or Miller B screw job on the way.  It's not suppressed or OTS.  It's a coast-running Miller A in mid-December.  Thermal gradient is more onshore than it would be in January-March due to the water temp and respectable, but unremarkable, cold airmass ahead of the storm.  Give me that basic information alone and I think I could give you a snow forecast that would be pretty reasonable for most of the area... 

1 minute ago, losetoa6 said:

Eps clustering tighter to the coast . Mean slp is centered just east of the Delaware bay.

Nice place for us.  

2 minutes ago, osfan24 said:

I keep hoping we see the Euro back off these NW pushes and get closer to the GFS solution. It will really make a huge difference for us. I've seen my totals around 16 inches on some runs with bigger totals not all that far NW of me but then closer to 8 on others with much smaller totals not that far to my SE.

Every model, even the GFS, has this baggy area of low pressure stretching from onshore to well offshore as it approaches and pass our latitude.  Where the "L" gets put on the surface map isn't always a fine science.  All comes down to how convection plays in (we really won't know this until tomorrow or Wednesday) and where the surface low starts to get stacked with the upper level energy. That later detail just keeps wobbling just onshore and just offshore.  

1 minute ago, MillvilleWx said:

For sure. This has Fall Line special written all over it. Massive increases the further north and west you go with this one. Then pinning down the CCB will be another fun task. That's where the real fun totals will come out. 

I really, really want that CCB.  Seems like the front half of the storm is pretty well set for MBY.  3-5" of snow+sleet.  

3 minutes ago, MillvilleWx said:

I never move from the Euro since it's got a great resolution and is good with large scale forcing mechanisms. The mesoscale is definitely not good for it, but that's where our short term guidance will come in play. It gets mixed more with other guidance for decision making and review for trends. GFS is in the same boat as the Euro since it has fairly similar properties for large scale ascent depictions.

Seems like we've seen 0z/6z euro runs bump NW and then 12z runs move SE.  All-in-all, these are ultimately small differences, even if this was 24hrs before start time, but it obviously makes a big difference to most of us in snow totals.  

Good thread from @tombo82685 on Twitter.  I wonder if the weaker s/w is a reflection of more complete sampling now that it's onshore? 

13 minutes ago, cbmclean said:

Please excuse the novice question, but what is "the benchmark"?

40N/70W is the classic location from the KU book for major east coast snow storms.  That's past our latitude, but when it's at the benchmark a storm is usually about to hit NYC and Boston.  

18 minutes ago, WxUSAF said:

18z EPS has the surface low in exactly the canonical spot, ~50mi off OCMD, at 6z Thursday.  Don't overthink things.  Use the ensembles the way they're supposed to be used for, not agonizing over 5-10mi wiggles in 10:1 snow maps.  Going forward now, we can start seeing mesoscale effects like thermal profiles and banding.  

After 6z Thursday it really doesn't gain much more latitude.  Just moves ENE out to sea.  That's very nice for us.  Better chance the CCB cranks overhead and then snows itself out as the storm moves away. Some of the runs where the CCB is much farther north into the Poconos and NY state had the storm moving toward the benchmark and farther NE.  

4 minutes ago, losetoa6 said:

Improving each run 

 

Light Accumulations starting to get into Howard and northern Montgomery 

Ha, that little dot in eastern Howard County is the higher terrain near Howard High School.  Gets up to 500-600' on that hill.  That's like 2-3mi from my house as the crow flies. 

18z EPS has the surface low in exactly the canonical spot, ~50mi off OCMD, at 6z Thursday.  Don't overthink things.  Use the ensembles the way they're supposed to be used for, not agonizing over 5-10mi wiggles in 10:1 snow maps.  Going forward now, we can start seeing mesoscale effects like thermal profiles and banding.  

Let's do this same thing again in a month with temps 5-10F colder please

2 minutes ago, DCTeacherman said:

That’s pretty good for around here.  Half the time we get a storm it melts within 12 hours. 

If there's any time to try and hold onto snow cover, it's 5 days before the solstice...

Mt. Holly hoisted watches

Just now, mappy said:

Zoomed in screenshot 

 

You just want all of us to see how you're in the 20"+ zone

3 minutes ago, Eskimo Joe said:

Wow @mappy, @psuhoffman, @losetoa6, and @HighStakes are smoked by the Euro. At least a foot.

Oops, you accidentally left me off the list!