Newman

Philadelphia averages 2.5" through November and December. The November storm this year dropped around 3.5". Even if no snow falls the rest of December, Philly will still be above average heading into January. The same goes for Allentown area. If I use ABE averages for my area, I should average 5.3" through November and December. I am at 8" for the season.

Actual snowfall on the NAM: However, north and west will definitely experience a bit of freezing rain and sleet if this is right:

If you are taking that map verbatim I wish you all the best. I'm not even going to waste my time trying to explain.

We went from 65 and torch this weekend to now sleet/snow mixing in for north and west:

Just to play around with, Member 18 on the GEFS shows 3 straight snowstorms around the Christmas time frame. First storm on the 23rd: 2nd storm on Christmas (biggest one): 3rd storm on the 28th:

A lot of models have the bias of holding back the trough in the west around the Rockies, but the EPS is notorious for it. Lowering thicknesses because of naturally colder temperatures due to high elevation correlate to lower average virtual temperatures, which lower thicknesses again, lowering average virtual temperatures again, creating a bias toward amplifying a trough over the Rocky Mountains. However, all you have to see is the AK ridging that correlates to a trough in the lakes/east. The 23rd to 31st time period will feature a storm for most of the Philly area IMO, likely west of 95. This look will produce a storm on the east coast. Wet or white TBD as we get closer.

The AK ridging will continue to grow in merit as we enter the latter half of December. The Aleutian low, however, will determine how it sets up. If it retrogrades far enough west we will have a much better look than if it stays put in the GOAK. Looking at the EPS, you can clearly see it correcting it's bias of dumping the negatives into the west coast and forcing a SE Ridge to pop. This isn't me wishcasting or anything. Do your own research and look back at this entire winter so far (and other winters for that matter) and you can clearly see how the EPS corrects over time from a trough out west to a trough in the east. The GEFS, and the GEPS to a lesser degree, have been schooling the EPS the past couple of weeks with regards to this pattern. The EPS was arguing for a 5-10 day period of warmth and now, what do you know, we're looking at a transient 3 day mild period, if that. Blocking will likely grow more likely as we get closer to Christmas as well with a SSWE likely. However, we're not going to see a huge 4-SD block, but rather a block just strong enough to hold down the SE ridge. I really like what I'm seeing after the 23rd. BTW, I wouldn't put too much stock into the MJO phases we're going to be going through. Although a phase 5 would argue for warmer east coast conditions, the MJO will be rather weak and the ENSO phase will likely override that. A P5 MJO in the current ENSO phase (Region 3.4 at .5C or higher) actually results in N to BN conditions in the east.

Thursday possibly some snow showers.

The Christmas time period is really intriguing me. Let's see how this looks a week from now. IMO we don't need high latitude blocking. In fact I'd much rather ride with a -EPO and +PNA. The key piece once we get towards the 20th is how the vortex in the NP acts. If it continues to sit in the GOAK then warmer temperatures will be much more likely than if it retrogrades west into the Bering Strait. Also, I'm hearing plenty of talk about the possible SSW that may take place towards the end of December and January. I'd like to caution that, if the SSW event does indeed come to fruition, it may not be a good thing. If the vortex gets displaced towards the Asian side of the pole, we may be wondering why we were jumping up and down for the event to take place in the first place. Also, the SSW may interrupt the entire evolution of our winter. I feel we are entering winter with plenty of upside already without a SSW. I'd take my chances rolling through winter without any stratospheric warming. Of course it could always help but, like I said, I'd rather hedge on the side of caution.

The trough is back in the east by the 23rd. The GOAK trough will retrograde west to the Aleutians, build the ridge west with it, and dump the trough into the east, aided by the MJO, AAM, and a more favorable NP Jet.

These snow showers are pretty nice right now. Snow sticking to everything with how cold it is:

A lot of times every model can be wrong with the northern extent of the precip shield. Sometimes the radar day of will give you an idea if there's any fighting chance. However, the NW confluent flow is likely going to eat up the northern shield, and if it doesnt, dry air and virga will be an issue with little forcing. I'm pulling for you guys in DC.

Here are some of Isotherm's thoughts. Let's not bridge-jump too soon. Everything's going to plan: Geopotential heights are likely to correct more positive over the PNA, NAO and southern AO domains as an ineluctable consequence of stratospheric alterations ongoing D10-12. By December 15th-16th, the geopotential structure alteration will have overspread most of North America and Greenland, as the stratospheric vortices are perturbed / displaced toward Eurasia. Robust w1 hit will impact the SPV via the felicitous tropospheric precursor pattern, and once the nascent blocking encompasses the NAO region, wave 2 will be enhanced again. This final follow-up w2 hit circa Dec 23-31 will be the primary opportunity to induce a technical SSW. I have thought that we'll come close, but near miss. Regardless, the tropospheric impacts will be quite significant. MJO should circulate should through p3, thereupon, rapidly losing coherency during passage in p4-5 by mid December. GWO should be back into/approaching phase 5 by about the solstice in my opinion. The momentum reversal processes are already beginning, as this negative/removal mini cycle will be efficiently overshadowed / dampened by the background, resuming +AAM state. +EAMT will increase in the coming week, with more rossby wave dispersion events and wly momentum injection. Classic walker cell forcing resumes again by the 18th, and we will see the retrogression of the GOAK trough into an Aleutian low position on or about December 20th/21st. As a consequence of which, temperatures neutralize/near normal by the 18th-19th, supportive of snow in the coastal Northeast as early as around the 18-20th, then cooler than normal air begins developing shortly following the EPO diminution via GOAK retrogression. December 20th-31st is colder than normal and active w/ an undercutting STJ, with SPV perturbation continuing. In other words, everything's on track. There are heterogeneous stances on initiation/timing among our colleagues here, but by and large, I see the disparities as fairly immaterial and we accord on the larger scale forcing mechanisms

Cutter on the 15th ushers in a better pattern, perhaps we can steal a storm around the 18th-20th, but the pattern fully matures around the 23rd and on into January.

12z RGEM: