Discussion: I think it is best to address the January 31-February 3, 2021 winter storm by the phases they were laid out in our initial Jan 30 forecast article:
Phase I: The Onset
We had a very cold air mass over the entire Mid-Atlantic/Northeast US heading into this system. If you can remember, last Thursday’s coastal missed to the S of NJ but allowed some Arctic air to spill in behind it for this past weekend. The primary surface low tracked in from the W to about the Cincinnati/N KY area. The warm front from this primary advanced towards NJ on Sunday while warmer moisture from the warm sector hopped the warm front into the slowly retreating Arctic air. The isentrophic process allows the moisture to pass through without the heat. We therefore saw a front-end burst of snow during Sunday PM hours, mostly affecting SNJ. The warm front then came to a stall across SNJ early Monday morning. The primary low transferred to a secondary coastal low off OBX/VA latitude later Monday morning.
Phase II: The Warm Push
Once the coastal took over, it advanced the warm front further into SNJ from the SE. This changed most people over to rain SE of I-95. Areas NW of I-95 just continued to snow as the main snow band of the system. The 850mb and 700mb lows were slow to follow the sfc low during this phase. For this reason, the sfc low was due east of NJ, pulling cold air from the N/NE but the mid-level lows were still fetching warmer E air N of their cyclonic centers. This created a shallow above-freezing layer between 700mb and 850mb that extended into parts of CNJ and even NENJ at times. This layer became trapped beneath the cold conveyor belt and hovered over the state like a flying saucer. This was the reason for whatever periods of sleet you saw NE of the surface line of freezing…and also why SENJ saw the sleet period extended into Tuesday morning. But either way, the wintry/non-wintry aspect of the system generally kissed the I-95 corridor on Monday and then retreated back to the SE for all expect coastal regions of Ocean County and S through SENJ (back to Cumberland). These areas went back to sleet but not back to snow for the rest of Monday and most of Tuesday morning. NNJ and much of CNJ continued to Kaboom under the heavy snow band. Dude where’s my car criteria was met Monday night as 24-inch snow reports/pics were coming in. Winds roared and tidal planes rose as they do with any coastal storm system. A few locations might have reached into the low-end major flooding stage with most areas seeing solid moderate.
Phase III: The Backside
Once all lower-level layers were stacked near the sfc low (due E of NJ), all levels continued to cool. This set up the backside of the departing mid-latitude cyclone known as the deformation zone. WNJ saw this first from early Tuesday morning through…aww heck it’s still flurrying over there now lol. But Tuesday morning was a big accumulation filler for SWNJ. SENJ was slower to see this later Tuesday into…aww heck it’s still flurrying here too. WNJ saw more of a N to S train of solid wintry precip and accumlations. ENJ saw/is still seeing broken precip with less accumulation potential because the low has transferred away. Today the snow showers are still around but finally tapering. Most of this is because of the 500mb low providing lifting near the 700mb moisture stream around the backside of the 700mb low. Once the last flurries taper off we can close the books on this historic snowfall (for NNJ), Kaboom (for NNJ and CNJ) and light snow/heavy wind event (for SNJ).
We obviously verified in the NNJ jackpot zone C likely around Monday evening (middle of Phase II). The low end of expected ranges were met for Zones E and F (SNJ up to about central Burlington/Ocean) mostly from the Sunday PM onset (Phase I). Per the NWS official storm total report, the W side of zones D and E were caught up with Tuesday morning’s WNJ train. Zone D was the most uncertain zone, especially for points E points near the ocean. I did see official reports of 8.5 and 7.8 in the Whiting/Jackson area but most other reports fell short of the expected 8-12 in that location (N Ocean County/SE Monmouth. The jackpot band simply didn’t expand far enough into SCNJ and a lot of those areas dealt with periods of sleet. I also feel like at least a few SNJ inches were wasted by snow trying to fall and accumulate during the warmest part of the day. I’m not blaming sun angle. Just that noon to 3pm is the warmest part of the day…when much of SENJ were battling marginal temp issues. The extreme SENJ coast didn’t fall back below freezing until after sundown last night (Tuesday).
I don’t ever issue a forecast map thinking it will 100% verify. We take our best guess with the most evidence collected prior to and put it out there in the interest of public safety. This map, however, verified in probably 90% of the state. I am very happy about this. But this is not to say that I do not feel your snow lover pain in the SNJ areas robbed of snow potential. I am right there with you. Just know that there are 4-6 weeks of wintry potential left in the core of the season and the pattern looks to remain very active. In the baseball game analogy, it’s probably the bottom of the 6th inning of snow season. For NNJ/CNJ, congrats on the grand slam! Otherwise thank you all for your kind words, patience (during times of frustration), and all that you endure during an event like this.
We’ll stay cold and dry through Thursday evening in a trough of stale cold air mass. I say stale because it’s not true Arctic air, more of a statewide high 35-40 lows in the 20s situation. This trough will be reinforced by weak high pressure until that high is E of NJ on Thursday. We’ll then see a transient (24-hour) weak ridge move through between Thursday PM and Friday PM, creating a period of slightly milder conditions. The most immediate signal is a weak and quick moving disturbance on Friday. A low will track through Canada and cut through the N Great Lakes, dragging a secondary low-reinforced cold front through NJ on Friday. This would likely only produce light-to-moderate wintry precipitation for NWNJ (N of I-78/NW of I-287). The lower 2/3 of NJ would likely see all rain with maybe an icy transition for WCNJ/NENJ. And this might be too generous cold wise for the solution. Either way, not a big deal wintry-wise except for may the higher elevations.
Once the front is through (by Friday night), conditions should return to a stale cold feel that will stay in place through the next general winter storm signal (Sunday-Tuesday Feb 7-9). At this point there are two streams of upper-level energy expected to pass by closer together in that time frame. One to our N through the Great Lakes and the other through the SE US. The closer these two streams interact, the better the chance for another snowstorm in the Feb 7-9 period. Up until last night, the Euro was bullish in interaction and therefore suggesting the storm at the surface. It has since backed off, but other models are starting to pick up on it. I recommend not paying attention to the surface solutions. They will fall in line with whatever the upper level energy does. To see the storm come into fruition, we need the geopotential heights to rise along the east coast ahead of the system Sunday morning. This would allow the southern stream to come N and produce the phase. If the east coast geopotential heights are flat Sunday morning then the two waves will likely pass to the N and S of us from W to E as weak disturbances. So I will be watching that period (Feb 7-9) very close and still believe it’s a strong storm signal. You’ll probably see surface model run solutions hop back and forth between storm and no storm. I wouldn’t commit to serious tracking unless it is showing with agreement through Thursday overnight data. After that, most model guidance has some kind of disturbance floating through the east coast every 3-5 days as far as I can see into February. So we remain very active with some of the coldest air yet plunging into the N/C US and Great Lakes. There will be a lot of energy rounding that general flat but very cold trough of polar vortex lobe energy.
In English: This recent winter storm produced historic snowfall for NNJ, a major snowstorm for most of CNJ, and a light snow/mix/high wind event for most of SNJ. We now turn towards a nuisance system Friday, maybe cold enough for light wintry action in NWNJ, followed by a strong winter storm signal IMO for the Sunday-Tuesday (Feb 7-9) period. I expect surface model output to flop around a bit more these next few days. If it looks good on Friday morning I’ll run with it. If it looks beat, we’ll toss it. From now until then, it’s just a signal being monitored. Everyone have a great rest of your Wednesday. I’ll check back in tomorrow with more detail about Friday’s system and anything new about Sunday. Be safe! JC