Jump to content
  • Member Statistics

    17,586
    Total Members
    7,904
    Most Online
    23Yankee
    Newest Member
    23Yankee
    Joined

January 6-7 Storm Discussion: we’re due?


WxUSAF
 Share

Recommended Posts

4 hours ago, EstorilM said:

Wow this seemed like a lock for Northern VA, then again people always say you never want to be in the bullseye ~5 days out - all it can do is “trend” away from you lol. 

Skip to the end if you want the TLDR version

We weren't really "in the bullseye".  From 8+ days out guidance showed the potential but was all over the place with the track, as it will be from that range.  Once it started to lock in on the SW for a few runs around day 8 it was south of us.  Then as it caught onto the details it shifted north.  There were a couple random runs as that happened that might have jacked DC, but if you pulled back and looked at the average across all guidance over a whole day's of runs...NEVER was DC the bullseye for snow.  It shifted within one day from being south to north.  Then it settled down for a couple days where it showed DC dangerously on the south edge of snowfall with a WInchester to central PA jack.  That is NOT where we want to be 5-6 days out.  These things tend to trend north the last 100 hours 80% of the time.  Several red taggers said that the last few days.  The warning sings were there.  These are just basic model trend things.

Additionally there is the synoptic setup here.  There was no true block.  There is a 50/50 but everything is shifted east of ideal because the -NAO is very very east based.  We want that ridge centered closer to Greenland to Baffin not where it is.   The confluence is pretty far north here.  This isn't the right setup to stop the typical trends.  There are things that could prevent a storm from trending north the final 100 hours.  A crazy block like 2010.  Those storms didnt' budge the final 100 hours because they couldnt move north at all there was a wall of confluence over PA.  Another option would be a NS feature coming across the top suppressing the wave.  Not sure that's even what we wanted here, but the NS is pretty far north and there is no TPV in quebec for a lobe to rotate around like happened in 2014 and 2015 a few times to help suppress a wave without blocking.  

Not every snow event here follows the standard.  Flukes happen.  There is always a chance.  Even now maybe it trends a few degrees colder and places closer to the city get a thump snow Saturday.  Weirder things have happened.  But thinking this was a lock day 6 was crazy.  I was LOL at some of the posts making declarative statements from places well southeast of me when I was not even comfortable expecting snow up here frankly, knowing the setup and the typical correction in guidance from that range.  

TLDR version below

If you want to feel good about snow in the DC area from 5 days out you need a few things.  

1) Truly cold and deep antecedent airmass where the thermal boundary is well south of us as the wave gets its act together in the TN valley

2)A well placed 1030 or greater high

3) A STJ wave tracking at us from the SW, not the NW or not needing some crazy negative tilt system to bomb straight up the coast.  Something into the TN valley then transferring to the NC coast is the highest probability snow event here

4) Strong confluence where the flow turns somewhere just to our north, like in central or northern PA, not up in northern New England or Canada

5) a true blocking situation with a 50/50 locked in by a ridge to its north.

If you have all 5 of those features then I think its safe to feel optimistic about snow chances in DC from longer leads.  Absent those...I would NEVER feel good about snow until it was within like 48 hours because the more of those factors we lack the more we need lots and lots of other variables to go perfectly to compensate.  It won't be simple or easy.  

We really only had 1 of those this time...we had an ideal STJ wave and track.  And that does put is at least in the game for a fluke to work out absent other things.  But we didn't have all the other things needed to make this an "easy" win for DC.  

  • Like 5
  • Thanks 8
Link to comment
Share on other sites

The difference with the Can models, and to an extent the UKIE, is that they are much wetter. I guess that’s ok, but at least here, the last few systems have been drier in the actual than they were when modeled. The euro and gfs are really dry here. The NAM moistened up a bit over the 0z.

  • Like 1
Link to comment
Share on other sites

8 minutes ago, umdterps29 said:

What time frame is this through? Can you add through end of day Sunday if not already included? I'm curious as I'll be out at the mountain house. Thanks!

It’s free on pivotalweather. Deep Creek gets about 6” on the UK, after taking into account the stuff this morning. 

Link to comment
Share on other sites

8 minutes ago, jayyy said:


Imagine after all of this tracking and boom / bust concern it ends up being an areawide 2-5” storm for many emoji1787.png what’s kuchera have to say? 10:1 is generous.

If this verifies BWI will get double the snow as DCA.

Usually if one busts the other busts too.

Link to comment
Share on other sites

Pretty interesting to see all of the snowfall accumulation changes from run to run. Track remains mostly the same as Clskins alluded to, but the thermals are all over the place. We may really need to wait until Friday night to know what’s going on, once the airmass / high is actually in place and models aren’t just predicting what it’ll be like.

Link to comment
Share on other sites

2 minutes ago, jayyy said:

Pretty interesting to see all of the snowfall accumulation changes from run to run. Track remains mostly the same as Clskins alluded to, but the thermals are all over the place. We may really need to wait until Friday night to know what’s going on, once the airmass / high is actually in place and models aren’t just predicting what it’ll be like.

One thing is certain. It’s cold Sat morning. The dews are low. No sun, steady even heavy precip into that makes the cold hard to erode and warm.

  • Like 1
Link to comment
Share on other sites

7 minutes ago, WinterWxLuvr said:

Euro is better, closer to the GGM and UKIE 

More precip, little stronger, closer

Great track too if that matters at this point.. MYR to right around VA Beach. Can’t ask for better track. 

Link to comment
Share on other sites

So with the 6 hour wobbles and melancholy I am still at the same place I was Monday but now up to 85% probability of an area wide 3-6” from Camp Springs to Frederick 

I put out my checklist yesterday and will run that down item by item either late tonight or early Friday afternoon

Moving from models to temps and dew points is a stable idea from now and  forward .  Looks like T minus 46 hours to liftoff!

 

Link to comment
Share on other sites

1 minute ago, winter_warlock said:

Well that sucks lol

The fun part is that it keeps trending worse.  Best chance at this point is that either (a) the bleeding stops, and/or (2) cad is underdone.  The upper air pattern is not ideal.  Honestly, looking at it, I wouldn't even think we'd get snow from it, but luckily we have at least some residual cold air to work with.  It'll be interesting to see how the storm ultimately plays out, but I'd be ok with it just simply starting as snow at this point east of the Blue Ridge.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...