A cool air mass remains in place over the region, with highs in the upper 40s-low 50s along with isolated reports of flurries/graupel yesterday. A strong cold air mass will enter the region on Monday night, bringing isolated rain/snow showers and much colder temperatures for the middle of next week, struggling to climb above 40 degrees for highs. A moderation in temperatures is expected for the late week, but this fall’s dry pattern continues with no widespread precipitation in sight until beyond the 8-10 day range.
Tonight – Monday: Seasonably Chilly
The current pattern consists of a progressive and relatively zonal flow aloft, with cool air masses quickly moving in and out. The region is currently under a departing trough, with an approaching shortwave trough over the Great Lakes bringing another cooler air mass behind it. The region will be in between these cool air masses tonight into tomorrow as a low pressure quickly tracks east through southern Canada, producing scattered rain/snow showers today and tonight to the north of the area, with a brief warm up on Sunday as the second cool air mass starts to enter. This air mass will be short lasting as well, barely lasting for 24 hours as a southwesterly flow resumes on Monday with highs reaching the low 50s for most of the area.
Temperatures today are expected to peak in the upper 40s to low 50s with partly to mostly cloudy skies as scattered rain/snow showers stay to the north of the area. Temperatures tonight are expected to fall into the mid 30s inland and upper 30s for the rest of the area except for NYC, which is likely to stay in the low 40s. Temperatures will briefly warm up into the low to mid 50s on Sunday with a breezy west wind at 15-20 mph, with colder temperatures overnight falling into the low to mid 30s away from NYC and the coast. Mostly sunny skies are expected for both Sunday and Monday, with highs on Monday slightly falling into the low 50s.
Tuesday – Thursday: Much Colder, Isolated Rain/Snow Showers Possible
A strong cold air mass will enter the northern US on Monday, entering the area on Monday night into Tuesday as a strong but moisture starved cold front moves through. This cold front is expected to produce isolated rain/snow showers on Monday night into Tuesday morning, with the highest probability of snow showers towards northern parts of the area and into New England. The previous forecast noted that some models have been showing the potential for a midweek storm, but given the progressive flow that such a significant storm was unlikely to materialize; over the last day, the model guidance trended towards a more progressive trough that remains positively tilted as it moves off the coast, potentially splitting into a cutoff low well to the south and east which does not develop into a significant storm until well offshore. The ECMWF was the last model to back away from the storm, still showing a major snowstorm as recently as the 0z run yesterday. As this is still several days away, the models are expected to change with the smaller details; the possibility is there for a somewhat further west storm track than currently modeled, but a major storm remains unlikely based on latest indications and the 7-day forecast continues to reflect dry conditions aside from Tuesday’s cold front.
There is high confidence in the temperature aspect of next week’s forecast, however, as the strong cold air mass brings the coldest temperatures so far this fall with 850 millibar temperatures near -10C. The coldest temperatures are expected on Tuesday and Wednesday, with highs only reaching the mid-upper 30s inland and upper 30s-low 40s for the rest of the area, and overnight lows falling into the low 30s in NYC and 20s elsewhere, perhaps into the upper 10s for interior locations.