psuhoffman

5 days ago the GFS had a cutter with rain to Canada today. Instead there is a weak wave squashed to our southeast. Just pointing that out. Might be relevant.

I agree to an extent but like every setup it’s a matter of degrees. Problem is in DEC with warm SST even for Dec you need almost a perfect setup. You are right it wasn’t the PERFECT setup for a DC BIG snow and I never had DC pegged as the epicenter of that storm. I think 3-6 was my original thought from 72 hours. But at that time guidance had a better mid level pass/close and wasn’t picking up on that crazy mid level warm layer. The actual track was ok for a messy but significant snow. We get caught in the HECS look but most of DC snows aren’t HECS. That look was fine for a 3-6” to ice event in DC had other details gone better. A better mid level track or earlier phase and DC provably gets a few more inches before that warm layer blasts in...and maybe more on the back as a less westward intrusion takes less time to recover. So if the point is that look was not ideal for a HECS I totally agree. But it was a look that has lead to plenty of good solid snows in and around DC just not HECS level. If we can somehow avoid the spike to 50 dews on Thursday we could hold our pack. It’s like 8” of solid you can stand on it concrete with like 1.5 qpf content here. It won’t melt easy if we can avoid a complete torch somehow.

One reason the GFS is cutting the wave around New Years is how it’s handling the Xmas-28 period. Frankly all 3 globals have a different evolution but the other 2 end up with a massive 50/50 that sets up the Dec 30 on period. Euro bombs the Xmas system into that vortex then absorbs the Dec 30 wave to amplify it even more. CMC is weaker with Xmas wave and develops a weaker vortex but then amplifies the dec 28 wave and they phase into a monster vortex. End result is the cmc and euro have a massive vortex to our northeast to suppress the flow. Gfs is weaker with both waves and so does not. This is everything. to be clear “blocking” is a means to an end not the end. The actual effect of blocking that directly leads to our threats is the 50/50 feature. Blocking is important because ridging around the NAO domain forces systems to track and get stuck in the 50/50 region. It’s that feature, though, that sets up the confluence and suppressed flow across the eastern US that we need. If you look at all our big storms almost all had a NAO block. But the few exceptions had a well timed 50/50! As for the AO v NAO debate...it depends. The AO being - encourages a more expensive jet into the Conus and cold. Depending on other factors it can also promote some 50/50 assistance but not as effective as the NAO. If we have a cooperative PNA AO combo that works just fine. If there is a progressive pattern with open waves the AO can do just fine. Get the cold pressed south and let waves attack. Some of the 2014 systems worked that way. We did have a -AO just not a -NAO at times that winter. Those kinds of waves can work without a blocked up pattern. But if you want a big dog HECS storm you want the NAO/50/50 combo. That combo can also bully the whole pattern and compensate for warts in other places. so in conclusion Imo BIG snows are most correlated to the NAO/50/0 and just snow in general (be it 1” or 6”) is most correlated to the AO.

Para gfs is close on the 28.

The first storm after Xmas (the only one in range of worrying about yet) doesn’t cut. It gets shredded them redevelops as a miller b that misses us. Problem is the NS wave runs out ahead of the SS and gets shredded but it also flattens the heights and squashes the SS until it phases and comes together too late. We need the SS out in front so the NS can phase in to our south. Look at the h5 for most of our big snows (it’s on the climo thread) there is a trough near AK usually.

There used to be a great discussion archived by Gary Gray on all the models each day that week. The Euro was closest to reality but it’s kind of a myth that it nailed it. From his discussion it seemed the euro most of the week was further north and did get more snow then the American guidance into our area but it was by no means close to reality. I think NWS was splitting the difference with a 3-6” forecast between the American guidance that had barely anything in DC and the euro that showed like 6-10”. It did but it also trended weaker and strung out. A lobe of the tpv rotated on top of it and squashed the system. From 72 hours it looked like a 20” snowstorm in PA and it ended up a 4-8” snow in VA. It wasn’t really last minute though. The shift happened around 48 hours. I was up in PA that year and by the last 36 hours knew we were screwed.

Happy Anniversary @mappy

How do you hyperlink pictures? I used to use imgur but it stopped working.

Euro tries to cut a storm day 9 and block days nope. Forces a transfer from the Great Lakes to off SC lol.

@ErinInTheSky @MillvilleWx @Winter Wizard There is a lot of perception bias to this. But I do think globals underestimate mid level warm intrusions and that’s a BIG deal here. That factor alone probably does make us more prone to negative then positive busts. But those do happen also. Only they aren’t usually going to be going from 3” to 12+ at the last second. That’s kinda extreme. DC area doesn’t even get that many of those storms. And most of our negative rug pull busts aren’t that close to game time we just remember them that way. Even this storm the writing was on the wall 48 hours out that big totals were slipping away. We knew. The 1996 storm we didn’t know until 24 hours from first flakes it was going to be that big. It started snowing late evening Saturday and Friday the forecast was 3-6”. Then the 0z guidance shifted way north and Bob Ryan interrupted the 11pm news to say it was gonna be BIG and the rest is history. We knew this storm was going wrong before we knew that was going right! @HighStakes there was another storm in Feb 1996 that was a total shock. A miller B that was supposed to develop too late for our area. Night before the forecast was nothing and woke up in Herndon VA to 3” and heavy snow. Ended up with 8” and some places got 12”. There are some others you can add to the list below. More recently the Feb 2006 storm wasn’t really locked in until 48 hours out. There were hints on some runs (famously the JMA) but it was 48 hours that the majority of guidance caught on. And even this it outperformed the final forecasts. Did someone mention the Jan 30 2010 storm? The second Feb 2010 Storm wasn’t on guidance until 48 hours out. A lot of the 2014 storms didn’t appear until 72 hours and didn’t look big until 36-48 hours out. The early march storm looked north until about 48 hours out. Feb 2015 some places in MD for 12” when the forecast was 3-6 when the storm started. Jan 2019 was a pretty big +bust in your area One thing I’ve noticed I can’t remember any last minute big busts from a storm suddenly shifting way south. That just isn’t likely. It’s not as bad as it used to be but there is still a tendency for big storms to trend north some the final 48 hours. Add in their underestimate of warm layers and that combo makes up most of our last second busts.

There are theories that the warming SST profile overall in conjunction with some anomalies we didn’t used to see concurrently has muted typical enso response recently. I’m in the Frd camp that usually there is a lag to enso but it’s possible that the weaker then expected peak along with anomalous warm pools in other places like the north PAC mute the Nina response the same way the nino response was muted in 2019. On this we agree.

That vortex is keeping the central PAC ridge suppressed though. You’re right it’s preventing an epo ridge and cross polar flow but in runs that break that down the pac ridge pops and we end to with a trough in the west ridge east. I think I’ll take my chances with the WPO vortex and hope as Canada gets colder we can make die with N American domestic cold sources.

@CAPE this what you want?

@Ji when we get into January if we keep this pattern I think the cold problem wont be as big an issue as right now.

There is a shot around Xmas and then after New Years a big dump coming...it finds a way to miss us again with a Miller B first lol

I don't know... when we have pacific driven cold Decembers in a nina they tend to fade into a crappy January/February look. When the AO is this negative it tends to linger and reload through winter. That doesn't mean we are headed for 1996 or 2010...sometimes we still struggle in a Nina with a -AO to get EPIC results...it just skews us towards a more normal snowfall year v a dreg year...but that is assuming the STJ goes dormant. If that stays active...then who knows.

Active pattern...lots of chances...all too far out to know anything about details.

@Ji There is your threat around New Years on the GFS from that block...gets squashed this run. Details don't work out. A system crashes into the west coast and flattens the flow which doesn't allow things to amplify...but that is a detail that will change at that lead. But you can see with that block nothing is going to cut in that time period. Just need to get a healthy system to amplify during the window it creates.

@Ji ignore the surface...this was REAL close to something big here

@Ji CMC pops another coastal too late a couple days after xmas and has another piece of energy diving in right after that...active pattern. There would be opportunities.

Would help if that low off AK would back off just a TINY bit...but still that look probably WOULD give us chances and threats...then its up to the details again. Remember 2 weeks ago we saw the blocking up top several days before even a hint of a specific threat showed up. People were frustrated about that. I will take the pattern first...storm threats come if the pattern is right.

That looks like the 20 minute super cold front blizzard we got a few years ago It actually stripes us with 3-5" right through up the middle of our forum. I'm sure it will work out probably not...but we keep seeing chances in this pattern.

Oddly the anafront snow idea on xmas eve is on the GFS and CMC.

We still have not seen any arctic air yet looks like we get a brief shot around xmas...then after there is at least cold air around to tap. We have been paying for the god awful November still. It was so bad...one of the worst November's every...that it wasn't easy for the thermal profile of North America to recover.