A light snow event affected the region today, with snow accumulations up to 1 inch for most areas and locally 2 inches in some spots. Temperatures briefly warmed into the 20s, but will return into the 10s for Sunday. Above-freezing temps will briefly return on Monday before temperatures crash into the single digits and 10s for Tuesday and Wednesday. The cold will gradually moderate for the late week with temperatures likely to return into the 30s, with no additional cold surge in sight for the near future (image credit: PSU e-Wall).
Tonight – Monday: Slightly Warmer, Snow North of NYC
While the main precipitation shield has moved out of the area, the arctic front continues to approach from Pennsylvania, and is expected to move through around 2am. Until then, temperatures will remain steady in the mid 20s to near 30 degrees, with temperatures afterwards crashing into the single digits north and west of NYC and the low-mid 10s for NYC, Long Island and coastal CT. A strong shortwave trough associated with a strong piece of the polar vortex over southern Canada will swing through the region tonight into Sunday, leading to a cold air mass quickly moving through with temperatures at the 850 millibar layer, or about 1 kilometer above ground level, falling to near -20C, supporting temperatures on Sunday peaking in the upper 10s to low 20s with partly sunny skies and a breezy west wind at 10-20 mph, leading to wind chills in the 0 to -10 degree range in the morning.
The first round of cold will be short lasting as a stronger shortwave enters the Midwest US, forcing a quick rise in heights aloft with a southwesterly flow in the low levels as a relatively strong clipper-type low pressure system tracks over northern Michigan into southern Canada. This will lead to temperatures rising overnight, reaching the mid 20s to low 30s by 5am on Monday. The system will be moisture starved, only producing scattered snow showers north of the area on Sunday night. With the southwesterly flow continuing, temperatures will briefly spike into the low to mid 30s on Monday morning into the early afternoon hours, marking the first time temperatures were above freezing in a week, since January 20. As the cold front moves through in the afternoon, temperatures will begin to fall into the mid 20s by the evening for western parts of the area with a strengthening westerly wind. The frontal passage will also lack moisture and thus widespread precipitation, although there have been some signals for potential snow showers along the front on Monday afternoon which will be monitored; should this verify, any accumulations are expected to remain minimal.
Tuesday – Wednesday: Final Cold Outbreak of January
18z GFS at hour 42, for 12z Monday (7am), from the Pennsylvania State University e-Wall, depicting the cold front moving through the area and the arctic cold blast entering the Midwest US.
The final arctic cold outbreak of the cold January 2014 will occur between Monday and Wednesday, as a strong northerly flow over the Midwest behind the Monday shortwave will allow for the frigid temperatures in Canada to spill into the Midwest and Great Lakes regions somewhat similarly to January 7, which was anomalous by itself, with widespread temperatures below -10 to -20 degrees expected to cover much of the north central US again, along with dangerously cold wind chills below -40 degrees spreading as far southeast as Chicago. Unlike that outbreak, however, the core of the cold will not extend into the northeast US region; the trough axis will remain positively tilted and will be slowly to push east through the region, giving the cold air mass time to moderate as the upper level low over Canada begins to retreat to the NNE.
Despite not being as cold as early January, the air mass will still result in some of the coldest temperatures of the winter in the area for Tuesday and Wednesday. A relatively tight pressure gradient is expected to set up, leading to a breezy west-WNW wind at 10-20 mph for Monday night into Tuesday. Lows are expected to fall to near zero in interior northwest areas, mid 0s in the north/west suburbs of NYC and southern CT and the upper 0s to low 10s elsewhere, which along with the winds will lead to wind chill values between -5 and -15 degrees for Tuesday morning. Highs are only expected to peak in the low to mid 10s inland and the mid to possibly upper 10s for the rest of the area during the day, which despite not being as cold as January 7 is still nearly 20 degrees below average. Winds will generally decrease by the afternoon and evening as temperatures overnight fall to similar values to those of Monday night, if not 1 or 2 degrees colder, with partly sunny skies continuing on Wednesday as temperatures slightly rise into the mid 10s to near 20 degrees for highs.
Thursday – Beyond: More Sustained Warm-Up; Watching Early February
A more sustained warm up will begin on Thursday as the strong high pressure expands into the region and then to the east, with a southwesterly flow resuming ahead of a weak approaching cold front. As with today, despite a strong southwesterly flow with winds at 10-20 mph, the cold air will be firmly entrenched over the region, leading to temperatures warming up only into the mid 20s to near 30 degrees for highs, although unlike today no widespread precipitation is expected at this time. Behind the front, however, no arctic air mass will follow; changes in the synoptic pattern over North America will be underway by this time frame, most notably featuring the collapse of the ridge over the western US and northeast Pacific which has remained in place since at least January 14 and was responsible for further worsening the drought conditions over California. With a lack of strong ridging to aid in significant southward displacement of cold air, along with a weaker upper level low in Canada with temperatures not as cold as those currently in place, the colder temperatures will remain north of the US/Canada border behind the front, with temperatures in the area expected to warm up above freezing on Friday into the low to mid 30s.
The next uncertainty in the outlook is towards early February, when the potential exists for the next widespread storm system to affect the region; this time frame especially needs to be monitored with the Super Bowl held in East Rutherford, New Jersey on Sunday, February 2. Quickly looking through the latest model guidance, the GFS and ECM depict a moderate snow to rain system on Saturday with drier conditions and slightly chilly temperatures for Sunday, while the CMC keeps a light snow event south of the area on Sunday with a more significant system approaching by next Tuesday. As the key players for any potential storm in this time frame are most likely still in the poorly sampled Pacific and Canada regions, with a lack of data sampling for the model guidance to ingest, additional changes are expected for this time frame over the next few days, although the overall synoptic pattern, including the likely return of ridging into the southeast US and troughing in the western US potentially resulting in a gradient-type pattern, along with a cold air mass in the northern US not nearly as cold as the current temperatures but enough to potentially support snow as a precipitation type, supports signals for a storm potential around the first 4-6 days of February, which will continue to be monitored with future updates.