Truisms for big snowstorms in our region that this blizzard followed

[gymengineer]

Here's a start-- please add other ones.

 

1) You never want to be on the southern side of the modeled heaviest snow zone. 

 

What helped me be at ease heading into the storm was that DC was smack-dab in the middle of the bullseye zone on the last collection of runs. Richmond flipped over early but thank goodness the snow the next day performed. 

 

Related to 1)-

2) The mix line always makes it further NW than the model consensus.

 

I escaped mixing in 2/5-6/10 and in this one, but it was a closer call than modeled. The 1/96 mix was unexpected. And of course, 2/03 was a surprise for mixing going into the far-north and west suburbs. 

 

3) Models are not going to get every part of a prolonged snowstorm correctly. But, the model consensus qpf ends up more-or-less verifying despite the changes. 

 

3/1/09 and 2/9-10/10 were classic examples, where it seemed a bust was imminent, but then the back end overperformed and the whole storm met the original forecast expectations. This storm had the dryslot punch up over eastern parts, but most in DC-Baltimore metro still met the forecast ranges.

 

4) If models are showing an extreme duration for precip, expect the back end to shut off sooner than depicted. 

 

Within 48-hrs of onset, we were still seeing model runs with snow falling in DC between 6Z and 12Z Sunday. 

[Amped]

The front end is sometimes a little slow, but the coma head usually over performs.

[HighStakes]

Unless an arctic surge is forecasted behind the storm you can always expect temps to bust on the high side for days following the storm. If your high is projected to be 32 the next day you can be assured you will be in the 40's. It seem as though this used to be the opposite years ago.

[gymengineer]

One more I forgot:

 

Unless we are specifically looking a modeled repeat of the January 1940 storm, there is no need for anyone in the NW zones to be concerned about a squished northern-edge Euro run. 

[Bob Chill]

Nw extent of juicy miller a's are always bigger than modeled. Sharp cutoffs are suspect unless there is strong confluence and big high pressure eating the edge.

[WinterWxLuvr]

One more I forgot:

Unless we are specifically looking a modeled repeat of the January 1940 storm, there is no need for anyone in the NW zones to be concerned about a squished northern-edge Euro run.

March 09 would beg to differ on that one. Leesburg got about 5" in that one and Winchester barely got a flurry. That's probably less that 30 straight line miles.

[WinterWxLuvr]

Nw extent of juicy miller a's is always bigger than modeled. Sharp cutoffs are suspect unless there is strong confluence and big high pressure eating the edge.

There's still a pretty sharp cutoff. It just matters where it sets up. Look 30 miles north of Harrisburg or NYC (I'm generalizing).....I'll bet in plenty of places in the last storm you can find 12" and 1" or less within a short distance of each other.

[gymengineer]

March 09 would beg to differ on that one. Leesburg got about 5" in that one and Winchester barely got a flurry. That's probably less that 30 straight line miles.

You're absolutely right. Hence it's truisms and not steadfast rules Everything posted this thread will have exceptions. 

[WinterWxLuvr]

You're absolutely right. Hence it's truisms and not steadfast rules Everything posted this thread will have exceptions.

You are correct. Those of use who live on that edge are more fearful of that cutoff than we are of anything else. Doesn't happen often but it does happen. You guys have to put our fear in perspective with your fear of mixing. At least if you mix, you got something.

[Kevin Reilly]

Usually after a blizzard 20" or more within a week expect a melt down...flooding rain event...or pattern reversal even if for only a short time.

[Amped]

Unless an arctic surge is forecasted behind the storm you can always expect temps to bust on the high side for days following the storm. If your high is projected to be 32 the next day you can be assured you will be in the 40's. It seem as though this used to be the opposite years ago.

Good one, noticed that too.

[Bob Chill]

There's still a pretty sharp cutoff. It just matters where it sets up. Look 30 miles north of Harrisburg or NYC (I'm generalizing).....I'll bet in plenty of places in the last storm you can find 12" and 1" or less within a short distance of each other.

I should have been more specific. Cutoffs will be north of models even at short range. The high was pretty weak compared to other storms. The big totals in PA and NY weren't that surprising

[gymengineer]

I should have been more specific. Cutoffs will be north of models even at short range. The high was pretty weak compared to other storms. The big totals in PA and NY weren't that surprising

This map shows it clearly---So the hi-res NAM was pretty spot on in the placement of the super-heavy totals poking into the NYC region, but then there's still the sharp cutoff to the north of the city. Meanwhile, the globals *and* the RGEM were nowhere nearly as aggressive with sending the 2"+ QPF that far north. 

 

[WinterWxLuvr]

I should have been more specific. Cutoffs will be north of models even at short range. The high was pretty weak compared to other storms. The big totals in PA and NY weren't that surprising

I agree. It is usually modeled too far south/east, early on especially. But it is a really scary thing to flirt with.

[Ian]

That map actually kinda sucks not sure why it looks like that. They have 6-12 over places that got like 1" in NW CT.

[winterymix]

I think David Ludlum was absolutely correct when he said that snowstorms pulse on and off.

Rarely does the intensity of snow remain stable and constant.

 

We surely experienced that pulsing with snowzilla.

 

Ludlum also talked about the January thaw.  He said that usually around the third or fourth

week of January, winter takes a break before the pattern reloads.

 

For those unfamiliar:

 

http://www.nytimes.com/1997/05/29/nyregion/david-ludlum-weather-expert-dies-at-86.html

[HighStakes]

That map actually kinda sucks not sure why it looks like that. They have 6-12 over places that got like 1" in NW CT.

Some of the NESIS maps don't always look that great either.

[hosj III]

Precip usually comes in sooner than models show. IIRC, Tuesday and Wednesday models started pushing the start time from 12z up toward 0z but at the last minute brought it back to 18z. Not a great example because the models still caught on in the end but a lot of forecasters had to bump the timing back and then forward again.

[gymengineer]

That map actually kinda sucks not sure why it looks like that. They have 6-12 over places that got like 1" in NW CT.

Hmm you're right. For the deep south it's completely wrong too. 

 

Edited to add: In case it wasn't clear from the lower right attributions, that map was the NCDC's map for the storm to use for their regional impact scale. Maybe a NESIS map will come out later, but they're pushing scales centered on other regions beyond the Northeast. 

[Ian]

Hmm you're right. For the deep south it's completely wrong too. 

 

Edited to add: In case it wasn't clear, that map was the NCDC's map for the storm to use for their regional impact scale. Maybe a NESIS map will come out later, but they're pushing scales centered on other regions beyond the Northeast. 

I think there's a built in distance calculation on points in these systems. It looks OK in the main area more or less. Can see as far as actual measurement points there's none in some of the areas on the edge http://gis.ncdc.noaa.gov/map/viewer/#app=cdo&cfg=rsi&theme=rsi

[MidlothianWX]

The weekend rule always applies.

 

I might be a little biased but I love that NESIS map (sans the issues Ian pointed out). The backside banding down this way really did bullseye Richmond.

[87storms]

The weekend rule always applies.

I might be a little biased but I love that NESIS map (sans the issues Ian pointed out). The backside banding down this way really did bullseye Richmond.

It really is bizarre. I don't think I recall a midweek HECS.

[Ian]

Agree with weekend rule. And others in general. We talk about mix a lot so I think no one assumes mix isn't an issue. For all the talk we didn't mix here. Did get a little close.

Also the N&W fringers will be annoying.

[clskinsfan]

The big ones always seem to be sniffed out better by the models in the long range. They just dont seem to sneak up on us anymore. 

[usedtobe]

Truisms for the big snowstorms.  Usually the rain snow line is nearby but not always (1979),  often there is a sharp cut off though usually it is a tad north and west of the guidance especially the euro.  The NAM was good going north with this storm but horrid with one of its similar north spreads during the Feb 5, 2010 event  That event if anything,  the northern extend got worse with time, UNV and NYC got hosed.  Overrunning precipitation often comes in earlier than forecast but a lot of peole are forgetting that early in the game the GFS was bringing snow into the region around the time of the morning rush. It backed off. 

 

I guess I'm saying I don't believe in absolute truisms. 

[WinterWxLuvr]

Agree with weekend rule. And others in general. We talk about mix a lot so I think no one assumes mix isn't an issue. For all the talk we didn't mix here. Did get a little close.

Also the N&W fringers will be annoying.

As are the mixers and drysloters.