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March 13-14 Storm Nowcasting/Obs


nj2va

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12 minutes ago, clskinsfan said:

Just went out and shoveled the dreaded snow plow mountain at the bottom of my driveway. This is some heavy ass wet snow. Serious compaction going on. I am going to call it 7.5 inches for the event. Probably had a little more at some point. Expecting an iceberg at the bottom of the driveway in the morning.

31/27 overcast

 

This snow is extremely heaving considering temps were in the 20's from about 10pm on.  Probably less than 10-1

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HRRR had terrible runs regarding snow accumulation, as late as the 2z run I remember it putting down about 12-15" for my area (weatherbell accumulation), bizarre that I don't remember models showing any Sleet potential until about 3 days out, it was strictly rain or snow. Tough to say what model performed the "best", but I would say RGEM because it was the best with Upper Levels and Surface, UKMET performed good too but surface was colder than modeled.

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As I promised in the banter thread, I would do a quick after action write up. So, here's what I got right. QPF was way underpredicted by the models, as expected things phased sooner, and we were certainly not too far south for this Miller B. Had the low been just 75 miles east, this would've been a much different storm for everyone. I expected the low to develop more along the gulf stream, since that seemed to be the usual location that lows want to jump considering all other factors being equal. Here is what I missed. The lack of a full phase and instead an energy transfer really hurt us. By staying disconnected from the main h5 low, the shortwave was not given enough room to amplify. The storm was and continues to be warm air advection dominant. A strong CCB never really got going (good prediction by the models until well in to NE PA/NY). Even there, it is not as impressive a CCB as many other large storms. The other thing that both myself and the models missed was the lack of blocking contributing to the fast movement. This is going to significantly cut down on totals and I will be surprised to see any reports over 20 inches. As far as what could've saved us in the mid levels is a stronger, more consolidated vort. Probably the biggest lesson I've learned from this storm is a good dynamic snow is entirely driven by h5. A 990 low off OC is great, but when you don't have a sharp vort, there will be a lot of warm air intrusion at the mid levels. A stronger 850 low could've helped here too.

Sent from my HTC 10 using Tapatalk

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Anyone interested in post-storm analysis threads for anomalous events? Booms/busts, surprise squalls, early/late season stuff, hecs (when they happen).

I can already see this particular event as a good case study!  

- having no blocking high in place matters (especially early and late season)

- snow maps only support reality when ratios match (32 degree snowflakes are not the same as 20 degree snowflakes and sleet never has as high ratios as pure snowflakes)

- model trends are important (globals were trending badly (warmer) late in the game within the last 36 hours or so, even though short range guidance was improving (colder) with their late frames (later frames shouldn't be trusted as often)

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11 minutes ago, vinylfreak89 said:

As I promised in the banter thread, I would do a quick after action write up. So, here's what I got right. QPF was way underpredicted by the models, as expected things phased sooner, and we were certainly not too far south for this Miller B. Had the low been just 75 miles east, this would've been a much different storm for everyone. I expected the low to develop more along the gulf stream, since that seemed to be the usual location that lows want to jump considering all other factors being equal. Here is what I missed. The lack of a full phase and instead an energy transfer really hurt us. By staying disconnected from the main h5 low, the shortwave was not given enough room to amplify. The storm was and continues to be warm air advection dominant. A strong CCB never really got going (good prediction by the models until well in to NE PA/NY). Even there, it is not as impressive a CCB as many other large storms. The other thing that both myself and the models missed was the lack of blocking contributing to the fast movement. This is going to significantly cut down on totals and I will be surprised to see any reports over 20 inches. As far as what could've saved us in the mid levels is a stronger, more consolidated vort. Probably the biggest lesson I've learned from this storm is a good dynamic snow is entirely driven by h5. A 990 low off OC is great, but when you don't have a sharp vort, there will be a lot of warm air intrusion at the mid levels. A stronger 850 low could've helped here too.

Sent from my HTC 10 using Tapatalk
 

You just beat me to it!  I highly suggest a thread for these... :)

eta: I have never had the honors to start o a thread, so I'm going to try this idea out by compiling similar comments!

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I had mentioned Sunday that the GFS ran too cold in NC in the early January storm and voiced concerns that it would be too cold again.   It often misses those warm layers and shows too much of a rain/snow transition without enough sleet and/or freezing rain in between.     The 3 km NAM parallel nest ptype forecast from 12z yesterday was pretty decent.   I dismissed the idea of some freezing rain, but it was right.

gfs_mslp_pcpn_frzn_neus_4.png

nam3km_mslp_pcpn_frzn_neus_24.png

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1 minute ago, BlizzardNole said:

Up to 36 in Germantown - hoping the sun pops out and we break 40.  I just wish my driveway faced south or west instead of NE.  I ain't shoveling that.

Here's hoping for a big SE ridge soon.

 

You don't want to. I just did and it's barely even snow, it's like shoveling ice chunks.

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6 minutes ago, WxUSAF said:

Nice flakes all of a sudden.

Ditto. Same in southern olney; it'll probably taper soon.

 

I measured ~4.5 of sleet/snow with an old ruler. After the sleet changeover, we didn't see any real snow until this. 

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7 minutes ago, supernovasky said:

You don't want to. I just did and it's barely even snow, it's like shoveling ice chunks.

I have a bad back and won't even attempt it, but I do have a little snowblower.  Since my driveway is small -- approx 20 feet by 20 feet -- I just have one of those little cord-powered blowers.  I'm gonna go ahead and see what it does later.  LOL it might not even bite into it, we'll see.

 

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18 minutes ago, high risk said:

I had mentioned Sunday that the GFS ran too cold in NC in the early January storm and voiced concerns that it would be too cold again.   It often misses those warm layers and shows too much of a rain/snow transition without enough sleet and/or freezing rain in between.     The 3 km NAM parallel nest ptype forecast from 12z yesterday was pretty decent.   I dismissed the idea of some freezing rain, but it was right.

gfs_mslp_pcpn_frzn_neus_4.png

nam3km_mslp_pcpn_frzn_neus_24.png

Nice analysis. That bottom image is literally spot on for everyone and everything that occurred. It looks exactly like the radar looked at that time.

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The weather always humbles you when you think you have it figured out.  I'm just a weenie but if someone told me we would have a 994, deepening and riding the beaches from VA Beach northward, I would say Bench Mark!  At least for my area that track is a bench mark...Couldnt get consistent rates above 1"/hr.  I was really looking forward to something dynamic out this way as usually those dynamics stay to my east. 

 No mix here and a final measurement of 8.5".

 

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