Feb 7: Storm Recap + Next Wintry Signal

Written on 02/08/2021
Jonathan Carr

Storm Recap: Radiational cooling allowed last night’s low temperatures to dip below freezing across parts of SENJ. This seemed a little surprising but ended up not mattering. The low’s position and track provided warmer flow that rocked counterclockwise from S to NE between about 4am this morning and noon today. This allowed the sea surface temperatures, which are running a few degrees above average (~42F), to warmly influence the surface above freezing all the way to 95.

A warm 925mb layer moved in from the S and parked over CNJ/SNJ around dawn. This produced heavy rain downpours on above-freezing surfaces across much of SNJ. This layer collapsed below freezing as soon as the cyclonic winds rocked to the colder N/NE direction (about 9-10am). Rain changed to snow from NW to SE through the rest of SENJ by noon. All this time, a snow band parked under the best lifting just NW of 95 running from WCNJ into NENJ. NWNJ saw lighter snow.

From about noon until 3pm, the frontogenic forcing rates verified off the charts as the NAM properly modeled. The primary meso band generally moved from NW of 95 to SE of 95 (W to E) in this 3-hour window. I haven’t seen precip rates like that in a while. They were enough to take the surface down to freezing and allow accumulations at the warmest part of the day. It would have been in the low-to-mid 40s in SENJ without the dynamic cooling process. The battle between heavy cold precip rates and warm surface temps was for real. Accumulations ranged from C-2 along the immediate SENJ coast to about the 2-5 range for much of SNJ away from the ocean. Snow ratios for this area were likely less than 10:1. Areas just NW of 95 were able to reach the 5-8 range, especially into NENJ. Extreme NWNJ saw more of a 2-4 event being on the NW fringe of the shield.

Moving Forward: Tonight will be cold enough for any untreated wet surfaces to freeze statewide. Please use caution. Temps should struggle to rise above freezing tomorrow for an afternoon high before dropping back to a very cold Monday night. On Tuesday, milder temps and some rain could return to SNJ but a light-to-possibly significant snow graze is likely for NNJ. The snow rain line should set up from W to E somewhere between the I-78 and I-195 areas with NNJ elevations most favored for accumulations.

The general pattern remains favorable for supporting Mid-Atlantic US snow events. There’s blocking (-NAO), Arctic air spilling into the mid-latitudes (-AO), and nothing upstream that typically inhibits east coast snowstorms (neutral PNA and EPO). A daughter vort of the Polar Vortex, or PV love if you will, has pushed into the N/C US and northern plains out of Canada. This is the mid-latitude tropospheric propagation that stemmed from the stratospheric warming over the N pole. It’s just plunging into the C US not the E US. If it were plunging into us, it would simply suppress most storm systems to the S and we’d be stuck in dry near-record low temperatures.

Instead, the upper jet rounding the C US Arctic-filled trough should rise back up through the Mid-Atlantic US and keep a boundary nearby. This sets up a scenario with a very strong thermal and moisture gradient from N to S. Arctic dry air to the N of the boundary and moist mild air to the S. Key takeaway? Quality ingredients for a natural snowmaking machine. It could snow multiple times this week, especially through the weekend. And that’s just to kick off the general classic winter pattern that lasts until at least Feb 20. I only see one warmer surge in the Feb 14-15 period surrounding a transient warm sector/frontal passage scenario. It must be said however that because warm and moist air mass will exist S of the boundary, SNJ/SENJ/ECNJ will probably deal with more temperature issues for any lows that try to come north. Otherwise cold air should be in place for flatter systems and any SouthWest Flow Events (SWFE)

In English: The active wintry pattern should continue. Several events capable of producing snow are expected this week. The first being Tuesday for NNJ (rain for SNJ). Later in the week and weekend is uncertain. Some models are suggesting separate events, others more of a prolonged period of snow from Thursday through Sunday lol. Different latitude regions of NJ are targeted at various times. Let’s see how Tuesday’s NNJ snow event does and play it from there. I’ll probably do an article tomorrow afternoon with more details about Tuesday snow/rain lines and expected amounts. We can also take a closer look at the rest of the week. From now until Tuesday, temperatures should be below average (cold) with dry conditions. Have a great night and please be safe! JC