Posts

Cold front arrives Saturday, watching two light snow events around Christmas

Improving conditions Saturday, watching a system to our west on Sunday night

After the passage of a cold front this morning, temperatures are falling and wind gusts are picking up. Clouds will also be diminishing throughout the day as well, allowing for mostly clear skies to overtake the region by the mid/late afternoon hours. The combination of these factors will mean that today will be much cooler than the previous couple of days, but not quite “cold”. After the passage of the cold front, most of the area should see temperatures drop into the middle to upper 30’s, with some 40 degree readings possible along the coast. Conditions will remain calm and clear for the remainder of the day, with any residual gusty winds dying down tomorrow evening. This should allow for temperatures to drop back into the upper 20’s and lower 30’s tomorrow night, which is right around normal for this time of year.

Sunday should start off as an excellent day, with sunny skies and temperatures in the lower to middle 40’s across the entire forecast area. However, we will have to watch a shortwave trough off to our west that will be moving through the Ohio Valley by Sunday evening. Model guidance diverges significantly on the exact evolution of this system, but there is a low chance that this system is able to cause an area of light rain/snow to develop over portions of the Mid-Atlantic and Northeast late Sunday and into the very early morning hours on Monday. This system will be moving very quickly from west to east, will not have a lot of moisture associated with it, and the airmass it will be moving into will be quite marginal for snow. It appears that any potential for anything outside of a brief coating of snow is quite low, and this system should not cause significant travel issues overnight Sunday and into the very early morning hours of Monday before moving off the coast by daybreak Monday.

NAM Simulated Radar

This afternoons NAM model showing an outside chance for a potential light rain/snow event Sunday night/Monday morning

Another weak system passes through Wednesday, conditions go downhill once again late next week 

Conditions should be quite pleasant for much of the area on Tuesday (Christmas Day), with mostly sunny conditions and highs in the upper 30’s to lower 40’s expected. Calm and cool conditions should last throughout the entire day, with lows eventually dropping down into the middle to upper 20’s-with coastal locations likely in the lower 30’s. By the time we head into the overnight hours, our attention turns to the Ohio Valley once again. Yet another moisture-starved northern stream shortwave trough will be quickly moving from west to east, possibly causing an area of very light rain and snow showers to develop from west to east Christmas night and into the very early morning hours of Wednesday. Once again, due to the quick-moving nature of this system and the marginal airmass in place, any accumulation potential will be very low for the New York metro area.

A large area of high pressure will begin to build over much of the east on Wednesday as the next major storm system begins to build over the Plains states. This system looks to take a track predominately up over the middle of the country, which should once again drag a warm/moist airmass from the south and up into the Northeast. Though this system is still a week out, there appears to be a heightened threat of yet another dreary and wet end to the week next week across much of the eastern half of the country.

ECMWF 850mb Winds/Temps

This afternoons ECMWF model showing another exspansive storm system moving off to our west, bringing unsettled and above-average conditions to much of the East

We’ll have an update on the potential light snow events and any other threats that may arise by the later half of this weekend! 

Have a great Holiday Weekend! 

 

Steve Copertino

Flooding rains likely to impact holiday travel Friday

Briefing: Heavy rain and possibly flooding concerns Thursday/Friday, colder and calmer pattern will follow…

This morning (Thursday) will start off quite cool with temperatures in the upper 20’s to middle 30’s across much of the New York metro area with a few passing mid to high-level clouds for the AM commute. Calm, clear, and cool conditions should last throughout the majority of the day as a large and highly-anomalous upper level trough amplifies over the Southeastern states. As this system amplifies and strengthens off to our south, the low-level flow will gradually shift from southwest to due south, causing a much warmer and increasingly moist airmass to creep northward. Overcast and some spotty showers will be possible by the PM commute, especially for locations south of the city.

Read more

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.

7-day Weekly Planner

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.

3km NAM simulated radar

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.

12z ECMWF PWATS

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

Friday Overview: Showers into Saturday, turning cooler and windy

Cooler and unsettled has arrived late this week, as anticipated. This morning showers are moving northward with moderate to heavy downpours, over Eastern NJ, NYC metro and into Lower Hudson Valley. These showers will move north of region by early this afternoon. But more showers could developing later this afternoon and evening as a cold front and a wave of low pressure developing along it approaches the region. Some locally moderate to heavy downpours with possible with any showers. But some subsidence between the cold front and another system offshore, will likely keep showers from becoming more widespread over region and could cause clouds to break for more sunshine this afternoon. This will help temperatures rise into the lower to mid 70s this afternoon, over much of the region.

Read more