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WxUSAF

December 16-17, 2020 Winter Storm Obs/Nowcasting

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9 minutes ago, JakkelWx said:

Yeah this model run worked out REAL well for us

gem_mslp_pcpn_frzn_neus_22.png?width=778&height=586

That model run ran 5 days before the storm. 
 

Rule of thumb... you never want to be in the jackpot With a Miller a 4 to 5 days out. Nine times out of 10, the storm is coming north. 
 

Don’t get me wrong, I was rooting for this too. Just never seemed realistic given the time of year. This had the interior written all over it. This was a classic pre winter nor’easter. 
 

this run also depicted the 850 low closed to our south, with NE winds. That Never materialized. We were an 850 low closing away from seeing 12-24 area wide 

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While we/Columbia seem to do OK compared to many here, living in Columbia creates it's own sort of snow neurosis:  Too far south and east to benefit from the higher 400'-800' elevations and generally colder climo 30 miles to the N and W; too close to the Bay influences for situations like yesterday; and just barely west of the usual -- and seemingly very real - -"fault line and I-95" higher snow forecast cutoffs.   OTOH, we do sometimes get the MoCo-HoCo deathbands. 

Plus, it's a nice place to raise kids!

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48 minutes ago, PhineasC said:

I wasn’t forecasting for Upstate NY 

The storm trended north. They got the part that was supposed to be over our area 3 days ago when you made that point. The problem limiting snow wasn’t moisture it was track and lack of closing off of the mid level low. It had plenty of juice. 

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10 minutes ago, MillvilleWx said:

Definitely learned some things with this storm. I tried to be even keeled, but once again, I got bit some on the warm air intrusion in the boundary layer. I wrote a tweet thread about it. My estimates were still okay, for the most part. My high ends needed to be trimmed some out west. I’m glad almost everyone in here got some snow though. I certainly miss it and being back home for these events.
 

 

 


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Great thread!  A lot to analyze in hindsight.  I'm not sure any modeling system can claim victory for this event, but several did have some important pieces to add to the forecast puzzle.  GFS was pretty bad overall...  GGEM was the first I think to sniff out that the primary low would form along the SE coast and not be in the OH Valley and then jump to the NC/VA coast.  Euro did overall a pretty good job being on the western edge of the guidance and consistently showing a lot of mixing, even when the GFS/GGEM were snow bombs for us.  NAM did well even from long range with the very expansive area of mixing and rain.  I'm not sure the NAM did well on the track in hindsight, but it definitely was value added.  And actually the HRRR did surprisingly well from range with the WAA thump.  NAM, particularly 3k NAM, missed that entirely even from 6hrs out.  

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2 minutes ago, psuhoffman said:

The storm trended north. They got the part that was supposed to be over our area 3 days ago when you made that point. The problem limiting snow wasn’t moisture it was track and lack of closing off of the mid level low. It had plenty of juice. 

That is a "right for the wrong reasons" post. I said we would not have huge HECS-level precip totals and we didn't. I never said that some place 400 miles away wouldn't get good totals. LOL I am not verifying my forecast across half the damn country like HM does...

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Also, the GEM model is almost always one of the coldest solutions. If the GEM isn't showing snow, then it's probably not happening, but it often over does the cold. It doesn't mean it's always wrong, but as other people have mentioned, you can generally rely on a move NW, or at least a slightly warmer solution to ultimately verify.

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9 minutes ago, MillvilleWx said:

Definitely learned some things with this storm. I tried to be even keeled, but once again, I got bit some on the warm air intrusion in the boundary layer. I wrote a tweet thread about it. My estimates were still okay, for the most part. My high ends needed to be trimmed some out west. I’m glad almost everyone in here got some snow though. I certainly miss it and being back home for these events.
 

 

 


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Nice thread.  Another one of the storms where warning signs showed on one or two model runs a few days out but because the overall trend wasn't a total disaster it was assumed they were outliers.  Mesos came along and said there was something to those bad runs.  Thats why they exist.  To nail down the small stuff because for as good as globals are they can't get specific local dynamics nailed down until the storm forms and gets going.

 

All i know is that the power of warm layers cannot be denied and when they are modeled they will perform.  At least IMBY.  Blame warming oceans or whatever.  Until we get a Krakatoa I will just assume snow will be more and more difficult to get DC east.

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2 minutes ago, [email protected] said:

While we/Columbia seem to do OK compared to many here, living in Columbia creates it's own sort of snow neurosis:  Too far south and east to benefit from the higher 400'-800' elevations and generally colder climo 30 miles to the N and W; too close to the Bay influences for situations like yesterday; and just barely west of the usual -- and seemingly very real - -"fault line and I-95" higher snow forecast cutoffs.   OTOH, we do sometimes get the MoCo-HoCo deathbands. 

Plus, it's a nice place to raise kids!

Ha, exactly.  

We definitely don't have the climo of the cities and the airports, but we get fringed by the "N/W suburb" events usually.  But being above the fall line, even barely, is noticeable in situations like this.  We doubled BWI's snowfall and it's only ~15mi away.  

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3 minutes ago, psuhoffman said:

The storm trended north. They got the part that was supposed to be over our area 3 days ago when you made that point. The problem limiting snow wasn’t moisture it was track and lack of closing off of the mid level low. It had plenty of juice. 

Funny thing is from that crazy Canadian run is that the low pressure didn’t end up far from that.  It was the upper levels not letting this wrap up.

Tell ya this though ... we keep getting the storm track we’ve had for the past few months we are gonna be golden.

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Just now, WinterWxLuvr said:

Funny thing is from that crazy Canadian run is that the low pressure didn’t end up far from that.  It was the upper levels not letting this wrap up.

Tell ya this though ... we keep getting the storm track we’ve had for the past few months we are gonna be golden.

Feels like there might be enough cold air around this year to cash in from time to time.

Alot better than last year. Most of the times was a close the blinds type of pattern

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Great thread!  A lot to analyze in hindsight.  I'm not sure any modeling system can claim victory for this event, but several did have some important pieces to add to the forecast puzzle.  GFS was pretty bad overall...  GGEM was the first I think to sniff out that the primary low would form along the SE coast and not be in the OH Valley and then jump to the NC/VA coast.  Euro did overall a pretty good job being on the western edge of the guidance and consistently showing a lot of mixing, even when the GFS/GGEM were snow bombs for us.  NAM did well even from long range with the very expansive area of mixing and rain.  I'm not sure the NAM did well on the track in hindsight, but it definitely was value added.  And actually the HRRR did surprisingly well from range with the WAA thump.  NAM, particularly 3k NAM, missed that entirely even from 6hrs out.  

Nice thread.  Another one of the storms where warning signs showed on one or two model runs a few days out but because the overall trend wasn't a total disaster it was assumed they were outliers.  Mesos came along and said there was something to those bad runs.  Thats why they exist.  To nail down the small stuff because for as good as globals are they can't get specific local dynamics nailed down until the storm forms and gets going.
 
All i know is that the power of warm layers cannot be denied and when they are modeled they will perform.  At least IMBY.  Blame warming oceans or whatever.  Until we get a Krakatoa I will just assume snow will be more and more difficult to get DC east.


Thanks for the feedback guys. It was definitely a tough forecast to nail down. There wasn’t a classic phase of the streams that can make things a little easier to track in traditional Miller A events. This was a hybrid with a further north close off at 7H and that really hurt the chances for a bigger storm, along with the boundary layer warmth.

The HREF is amazing and it’s now got 3 storms I’ve used it for nailed down inside 24 hrs. I think that’s something to monitor for down the road. I’ll be a little more cautious with these kinds of setups for now on. You live and learn. It was fun to track. Wish I could’ve been up during normal people hrs, but what can you do lol


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Just now, WinterWxLuvr said:

Funny thing is from that crazy Canadian run is that the low pressure didn’t end up far from that.  It was the upper levels not letting this wrap up.

Tell ya this though ... we keep getting the storm track we’ve had for the past few months we are gonna be golden.

I agree. It APPEARS that storms want to keep taking a great path off the Carolina / VA coast to our SE. The pattern moving forward, especially from Christmas through January 10th, looks conducive for more of the same. 

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1 minute ago, Fozz said:

It’s one of the seemingly rare times that Worcester gets the dry slot.

Classic. Lift to the NW and SE is so strong, air is sinking over central MA. That band in NW MA into NH produced 5” per hour snowfall outside Albany. 

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43 minutes ago, PhineasC said:

If I was posting this in the Upstate NY forum your response would make more sense. Why should I give a single shit what happened up there?

There wasn’t a lot of hype for our area imo. Most of us knew what to expect. 

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Spent about 3 hours real early shoveling with Jebman and finally got out and all side roads are completely snow packed up here . This storm will probably be the subject of numerous studies in the coming years .

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1 hour ago, WxUSAF said:

Latest LWX totals, including my morning report:

 

https://mesonet.agron.iastate.edu/wx/afos/p.php?pil=PNSLWX&e=202012171312

 

Only a few 10"+ reports.  Seemed like the far N/W zones mostly ended up with 7-10".  

Over the years that Miller’s report a couple miles east of me (they are about 200 feet lower) aligns with my snow depth at the end of storms better then snowfall.  Sometimes the two are the same but sometimes when snow came in different parts with lots of mix and compacting they can be a bit off and their total almost always matches my depth. 

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53 minutes ago, WinterWxLuvr said:

Funny thing is from that crazy Canadian run is that the low pressure didn’t end up far from that.  It was the upper levels not letting this wrap up.

Tell ya this though ... we keep getting the storm track we’ve had for the past few months we are gonna be golden.

The trough was a tad too far north and negatively tilted(too soon), and with that the 850 mb low tracked overhead, and the surface low was tucked in real close. Had it evolved the same way, but a bit later/further SE, better outcome.

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3 hours ago, HighStakes said:

Total was 10.5. Got really windy so accurate measurements were difficult during part 2 overnight. May have been more because it snowed until 3-3:30 but I'll go with 10.5. Have to see how that compares to area reports.

My depth is a little over 8” because the initial 7” of powder compacted down to 5” of cement after the ice.  I measured an inch of sleet and snow mix during the mess period.  After that it was impossible to get an accurate measure but 2.5” seems about right. It snowed for several hours. It all blew into drifts up here. Your total seems right to me. This was a tough one to get an accurate total. 

59 minutes ago, PhineasC said:

That is a "right for the wrong reasons" post. I said we would not have huge HECS-level precip totals and we didn't. I never said that some place 400 miles away wouldn't get good totals. LOL I am not verifying my forecast across half the damn country like HM does...

The post I responded to 3 days ago and that I am referencing now was specifically about you implying guidance wasn’t showing enough moisture for 20” totals.  At that time most guidance was putting out 2”+ QPF across our area in the deform zone. That zone shifted north. The argument you were making was not that the deform was going to shift north due to a future model trend. You were specifically questioning whether the qpf on guidance AT THAT TIME supported big totals. They obviously did because that zone and the 2” qpf area shifted to northern PA and that area got 30”+. I doubt we get the ratios here they got even if it had not trended north but 20” in our area certainly wasn’t crazy had the storm not trended north. 

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