Stormchaserchuck1

Back in the day, I made a daily index of all the strongest N. Hemisphere 500mb areas: 1. south NAO (north-central Atlantic) 2. North NAO- Greenland. 3. AO (arctic circle, although this one was rare), 4. EPO. 5. Gulf of Alaska. 6. PNA (Aleutian Islands). 7. WPO Bering Strait. I found that [1] the south-NAO had +temperature correlation in the Mid Atlantic and Southeast, and neutral to positive 500mb heights. AO was negative temps and heights, but moreso north, so a combination of those two is close to neutral for the Mid Atlantic.. average high temperature now is 40, so that's saying low 30s is probably the best case scenario. We know how those borderline events, with +NAO (south-based) or more recently -pna, we know how they trend from the medium to short range when a N. Hemisphere major index area is in a constant. They don't trend toward more snow... I'm a believer of the AO, but it's a short wavelength pattern, where we have some unfavorable things stacked directly underneath. Pacific isn't bad though, and it's mid Winter, when we average upper 10s to 20s snowfall/year.. so maybe we can squeeze in some snow.

No problem.. you're probably the only one who does a real discussion. Active precip jet is a bit atypical for a Weak Nina, huh?

AO is too far away. A neg 500mb NE of New Foundland is the reason why our H5 never goes negative for the threat(s).. I said earlier +NAO/-EPO is a big ice storm pattern, especially mid-Winter. I just think it's more of a setup for ice, although we may do a few inches on the front end.

See that pressure pattern of -500mb heights south of Greenland/Iceland vs +Heights off of Africa.. that's +nao. What you are looking at is -AO. When the negative 500mb moves south of New Foundland latitude.. that's -NAO, but north of that is +NAO. That latitude difference correlates with +temps in the Mid Atlantic and Southeast.

Any flakes in Baltimore?

NAO remains positive through Day 15.. You guys may say it's not, but what you are looking at is the AO. The NAO is actually SLP calculated between Iceland and the Azores. What's happening for the next 15 days is a "south-based +NAO", and I've run the maps, it goes with warmer than average conditions in the Mid Atlantic and Southeast. This is why 500mb never gets cold. I'm still of the opinion that the coming storms are mostly rain or ice.. we will do well if we exit this +NAO pattern with more than a few inches of snow total. +NAO/-EPO, which is modeled for some of the time, is correlated to icestorms.

Anything more than 2-3" with the pattern would be a blessing imo Usually in the medium-long range you want to see a negative-500mb trough. That it is mid-Winter makes a little less so, but I still don't trust borderline conditions at this timerange without +PNA or something stable like that, just based on experience from the last 10+ years. A big score of 6-12"+ would be an anomaly with the coming 500mb pattern.

I'll take 1" of sleet. Will probably look good Thursday morning with ice coated on everything.

I'm thinking models are too bullish.. We never have below average 500mb. https://www.meteo.psu.edu/ewall/ENSHGTAVGNH_0z/ensloopmref.html Hope I'm wrong.

The actual anomalies is what matters. Everything I've seen looks pretty neutral..

5800dm heights coming up for NW Russia in mid Winter! Looks to be about a +600dm anomaly, which I think is record breaking Loading area for -AO/-NAO later on.. let's see how that evolves/works out

5800dm Heights coming up for NW Russia in mid Winter! That's the H5 loading pattern area historically for -NAO several days later

Yeah, completely different 500mb from several days ago https://www.meteo.psu.edu/ewall/ENSHGTAVGNH_18z/ensloopmref.html EPS crushed it leading the way.. kind of a historic bust for the GEFS having >+300dm anomalies on the mean.. now the High pressure never centers over the N. Pacific ocean.. it's all Alaska or the Arctic circle.

End of the 12z GEFS run at Days 15-16 had Arctic blocking. That matches -EPO patterns And is a cold pattern at the surface in the eastern 2/3 of the CONUS Whether it verifies or not is another issue. Models have trended from predominantly -PNA pattern, to now -EPO in the last few days.

I used to climb up there in the Summer when it would go bear.. beautiful view of the green valleys around, but otherwise desolate. You can drive right up to 7,000', half way up the mountain. They are getting a train of moisture for the next 7 days.

Mount Shasta, CA, on top of the mountain, is expected to get 100" over 7 days.

That is a 1045mb High pressure in NNE when it starts snowing on the GFS run. If it trends weaker, will the storm come north?

Looks like 1" of QPF, 85-90% frozen here on the GFS.

Wow big ice storm for MD on the GFS!

SSWE occurring in 15 days would actually have the greatest effects on early March, -NAO. I get what you're saying though..

It was a big model shift at 500mb in the Pacific. In the Day 10+, I rarely see ensemble means going over +300dm (which is what it was showing in the Aleutian island/PNA region). That coupled, with what I believe is still a strong -PDO in the thermocline and negative ENSO subsurface, showing at least Weak Nina conditions, plus a record streak of 7-years of February -PNA, and I thought that was a good forecast going forward.. It seems the pattern we saw in Dec/Jan ends up having some staying power. Now models backed way off the -PNA ridge in the N. Pacific, but I wouldn't totally discount a trend back toward this in the coming days. It's actually very sensitive because the potential +precip pattern is currently projected to be very close to rain or snow in the Mid-Atlantic... if we see a resurgence of the -PNA the storms will go north and we'll get rain, if the EPS continues to lead they way and we have neutral PNA H5 anomalies and more -EPO, then we might be able to get some snow out of it. I'm still more excited about the wintery threat at our doorstep than the LR models right now.

-EPO/+NAO is the pattern.. Pacific has stronger input with our warm/cold temps. -EPO in mid-Winter can do it!

I'm not expecting any more than a dusting on the front edge.. in PA you might do 1". 850mb temps warm up real quickly though.. accumulating snow is mostly dependent on precip making it in real early Wednesday

0z NAM has 1-2" Wednesday for Cecil County and southern PA.. it also looks like a legit ice threat for northern MD

The PNA is such a huge area.. that trending from +300dm to +50dm or so, means that we can probably get snow mid Winter. -NAO I am still a little skeptical about, they might be overdoing the "no longer strong +AO" pattern of Stratosphere cooling turning into PV split.. it's still a neutral anomaly at 10mb, and historically warmings are 3:1 correlated to +time-to-the surface vs 0-time. Plus last Winter they showed so much of this pattern at days 10-15+, I think the fundamentals of -PDO and Weak Nina, although obviously weak this Winter so far, might still creep up there at the end. They may say the surface of PDO is neutral, but it's still strong -PDO in the subsurface/thermocline. Hopefully the 500mb pattern projected by models holds going forward, I actually hate -PNA in the Winter.