Light wintry mix possible tomorrow, dreary weekend ahead

Good afternoon!

The cool and quiet conditions that have been with us for the past week or so continue over the Northeast this afternoon, with the only real changes being that cloudiness has increased in earnest and highs today are only slightly warmer than the previous couple of days. Despite temperatures running a few degrees above what they have been, we’re still seeing highs across the New York metro area in the upper 30’s to lower 40’s, with lower to middle 40’s over portions of Southern New Jersey. Conditions should stay rather cloudy this evening and overnight as a shortwave trough over portions of the Great Lakes continues to head to the east, dragging up warmer mid-level air from the south. Temperatures this evening should remain cool, but not nearly as cold as the past few nights thanks to the increased low/mid-level clouds limiting any potential for radiational cooling. Expect lows to generally stay in the upper 20’s to lower 30’s for most of the New York City area-with middle to upper 20’s well to the NW and middle to upper 30’s over portions of SNJ.

Weekly Planner for the next 7-days

Light wintry mix possible tomorrow morning/afternoon

During our previous update we introduced the possibility of a period of light snow/rain moving through the Northeast on Thursday, and since that time we have seen models become a bit more bullish on this event. The same shortwave moving through the Great Lakes this afternoon/evening will be over portions of PA/NY by early tomorrow morning, with light snow likely breaking out over Central Pennsylvania.

Though this shortwave is rather dry, it will be given small boost of moisture from relatively warm and moist air advecting into the Northeast. This should allow the small area of snow to sustain itself during its journey through Pennsylvania tomorrow morning, possibly reaching New Jersey by 7-9am. Once we get to around 10-11am, we should see precipitation expand into New York City and portions of Long Island. Given the limited dynamics/moisture available with this system in addition to very marginal surface temperatures, this system will not be an areawide snow producer. As of right now, it looks like locations mainly to the north of Trenton, New Jersey to NYC should begin as snow, but the same warm air advection that will be causing the precipitation will also help to gradually change precip over to light rain or a wintry mix from south to north.

Locations to the north and west of the immediate New York City area should have the best shot at staying mainly light snow for most of the morning/early afternoon, in addition to locations with greater elevations. While snow will likely be in the air tomorrow, the vast majority of the area should see issues with the snow sticking, outside of colder surfaces given the very marginal airmass. Additionally, snow growth a few thousand feet above the surface will be far less than ideal, meaning that snowflakes could be very small and malformed. This only further complicates any accumulation talk, but at this time a general coating to two inches is expected from Pennsylvania and into portions of NNJ/SNY (with the potential for locally higher amounts for elevated locations).

The timing of the precipitation ending will be highly dependent on when the shortwave outruns the best WAA (warm air advection), but this looks to be during the late afternoon hours. Any remaining precip during the late afternoon hours should change to a light wintry mix for the remainder of the area. All in all, this should not be a highly impactful system, but it could cause some slick road conditions, so please use caution when traveling tomorrow.

Loop of this afternoons NAM model showing the light snow/mix event for tomorrow morning and afternoon. Note how most locations around New York City end as rain.

Weekend storm likely to deliver wet and dreary conditions through Sunday

Back on Monday we mentioned the potential for heavy rain from an approaching upper level low over portions of the Southeast, however since that time the reliable computer models have trended weaker/more disjointed with this system as a whole. The result of a weaker system for the Northeast means that the strong low level jet that was forecast to occur over the East coast is now much less likely which severely limits the heavy rain/wind threat.

While we will likely see moderate to possibly locally heavy rain move into the area by Friday night and into Saturday morning, the risk for widespread heavy rain and potential flooding is now much lower. As the upper level low exits the coast on Sunday there will be the chance for some additional rainfall, especially along the coast. Interestingly enough, some models develop a coastal storm late Sunday and into Monday that could potentially extend the wet/unstable period a bit longer, but this remains quite uncertain at this time. We will continue to monitor the progress of this system as more details become clear in subsequent updates.

This afternoons ECMWF model showing a weaker/disjointed low level jet over portions of the East Coast early Saturday morning

We will have further updates on tomorrow light mix event and this weekends rain event by tomorrow! 

Have a great evening! 

Steve Copertino