CAPE

The first period of interest imo is still centered on Jan 3. As advertised, a temporary reshuffle of the Aleutian ridge shears off a vortex lobe and sends it southeastward, relaxing the western US trough, bringing colder air east/south and flattening the SE ridge for a time. Our region should be on the colder side of the boundary and there will be a chance for a wave or 2 to track along it. Beyond that the trough digs in out west again, but some signs of favorable change again towards day 15.

I posted about the weakening Okhotsk vortex advertised on guidance this morning. It clearly plays a big role in sustaining a strong NPAC blocking ridge(wave breaking), so some weakening should occur if that trough dissipates. Seeing that in the ens means now, and in response the western US trough looks less 'diggy' and seems to broaden and expand eastward some with time. I am still not sure this is going to make a huge difference here without a shift in the tropical forcing further away from the MC. We really need the ridge to weaken a tad, shift east some, and ideally expand poleward into the EPO domain. It's a real pain in the ass. Seeing some slight improvement advertised on the means but difficult to say how meaningful/sustainable it ends up being wrt to sensible weather here. In addition the negative NAO is looking somewhat less impressive in the LR. It's a wait and see game as usual when we have a pretty shitty pattern in place.

The main piece of energy tracks way NW, and it becomes a weak strung out mess as it moves east. Best chance of seeing anything 'significant'- frozen or otherwise- would probably be in the western part of our region, and mostly further north. Might not see anything from the metros point east.

A half dozen or so GEFS members have frozen for our area Jan 3-4 timeframe. It's a decent setup as advertised for a light to moderate event.

Yes. If that trough dissipates, the Pac ridge should weaken some, and heights can build more into the EPO domain. We will see how sustainable this is if it plays out this way.

Go Canada. Looks like a TPV lobe migrating southward as well.

The Okhotsk vortex that has been enhancing/sustaining the strength of NPAC ridge weakens dramatically towards the end of the GEFS run, and heights build a bit more over AK and poleward(-EPO). If that is real it would allow the western US trough to broaden and shift eastward some. Canadian ens looks even better than the GEFS at the end of its run. EPS wants to mostly keep the trough out west, although it is expanding eastward at the end.

A little pre holiday (fantasy) cheer.

Oh shit, yeah.

^Above my pay grade, but 86-87, 09-10, or 14-15 would work for me.

Utopias Barrel Aged WWS for HH. Its basically Friday for the next 3 days.

This is from late Feb 2015 taken from Terrapin Park, east side of the bridge. Have not seen anything close to this since.

In this thread when there is not much to see in the shorter range, we are mostly left with discussion/conjecture centered on progression of the longwave pattern in the long range. Analysis of a LR ensemble mean plot for a given timeframe over multiple model cycles can provide indications about the evolution of the overall pattern. Big picture stuff with plenty of uncertainty obviously.

And ofc the cold typically comes via a -AO, or in the absence of that something like 2014 with the -EPO. The -NAO (esp during a Nino with a legit stj) enhances the odds of a storm tracking underneath and just off the coast, plus keeps a N/NE wind component during a coastal storm. This is critical for significant snow in the lowlands, not so much for places further inland, esp the western highlands where there are microclimates with mechanisms like NW flow/upslope that also provide snow.

Maybe the best article ever written about the various teleconnections and their importance for snow in DC, by Wes Junker. https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/11/12/what-the-different-weather-patterns-might-mean-for-snow-this-winter/ Lots of good info and plots/graphs, but for those who don't want to take the time to read it-

I mentioned this yesterday, but this window looks somewhat interesting for a possible modest wave moving along the boundary to our south.

Light rain and 37 here. Another few hundredths maybe? 0.62" for the month.

2013-14 was a cool winter but also pretty rare in that it was EPO/WPO driven and the AO/NAO was predominately positive, and we had plenty of luck with timing of the smaller events. Bigger events mostly cut. 2015 was fun once we got to mid Feb, but literally nothing for more than 2/3 of met winter for the lowlands. Those winters were also back before clippers became seemingly 'extinct' which is something you have noted of late. I would guess if we see a close repeat of the big -EPO setup again(with +AO) it would be generally frustratingly dry and cold in between rain/slop with any wave that amplified.

Should also include ENSO state to get a complete picture, and maybe EPO phase. From this plot you can clearly see the importance of -AO though.

LC2 = cyclonic wave breaking equatorward P2 = anticyclonic wave breaking poleward

Thanks, good post. In the bolded, you meant Nino favors stj, not Nina. And yes that is a major factor at our latitude to get bigger storms, and that's the big difference- in a Nino with an active stj we can score a big event or 2, and the winter as a whole is not necessarily even very cold. Combined with a -AO/NAO, we get the opportunity for a much more favorable storm track to maximize chances. 2009-10 was just cold enough with the -AO/NAO plus the active southern jet.

A -EPO can deliver some big cold yes, but also can be dry. In conjunction with a +AO/+NAO, amped storms have the tendency to cut NW. -AO has the strongest correlation to significant snow for the DC area.

-AO is king. -NAO typically occurs concurrently. Tough to beat for cold/snow in these parts. We can do fine with a -PNA, and some of our best storms have occurred with the PNA negative, but not severely so, like we can tend to see in a Nina. I would guess the -AO/NAO and -PNA combo mostly produces in a Nino winter for the DC area, but psu is the man to confirm or debunk that.