Advisories were issued for up to 3" of snow today, from about mid-morning through mid/late afternoon; see map below. However with temps in the mid-30s there could also be some rain mixed in, especially at the immediate coast, plus those temps could limit snow accumulation in spots, although moderate to heavy snow will accumulate almost anywhere this time of year (very low sun angle). An inverted trough feature (often called NorLun Troughs, after the mets who first studied these phenomena; see link) has been showing up for days near/along the NJ coast and now the short term mesoscale models are showing this feature producing periods of moderate to possibly heavy snow for several hours in parts of Ocean and SE Burlington Counties.
https://www.mattnoyes.net/new_engla...-you-forecast-weather-associated-with-it.html
However, these features (like mesoscale t-storms) are notoriously difficult to predict with regard to placement and intensity, meaning parts of the advisory area could get very little snow and parts could get 2-3" (or even more - this is similar to the event that put down 4-8" of snow in Dec-2013 in the Philly area, including during an Eagles game). It's also possible that the axis of snow could shift 30-50 miles from where it's forecast now, so folks in Monmouth through Atlantic counties should at least pay attention to the radar today. This is all discussed in a very informative discussion from the NWS below.
By the way, the storm for Sunday/Monday still mostly looks like a miss out-to-sea, but the Euro jumped 100+ miles north in its track last night, bringing the northern extent of the snowfall from southern VA to DC through the DelMarVa, while other global models are close to that or maybe a little to the south of that. Being 5 days out, significant shifts north or south are still possible, especially as one of the main players is still way north in the Arctic in a poorly sampled area (so model inputs are less accurate, meaning outputs have greater uncertainty), so our area should still watch this, although at this point it still looks like a miss for anywhere north of DC.
National Weather Service Mount Holly NJ
300 AM EST Wed Dec 5 2018
NEAR TERM /UNTIL 6 PM THIS EVENING/...
For the vast majority of the region, it will be a dry, albeit cool
day. Temperatures are expected to be 10 to 15 degrees below normal,
with highs generally in the 30s across most of the region, although
higher terrain of the Southern Poconos and NW NJ will likely not get
above freezing.
For eastern NJ, however, the forecast is decidedly more complicated.
We are still expecting a surface trough associated with the off
shore low to dig back towards eastern NJ. At the same time, a mid
and upper level short wave trough will be propagating southeast
towards our region. A combination of synoptic scale lift from the
mid and upper level trough and mesoscale lift centered around the
surface trough axis will result in a likely narrow band of snow
showers from mid morning through late afternoon. There is an
increasing signal for mesoscale banding, including a narrow corridor
of frontogenesis at 925 and 850 mb. Even with some mesoscale
banding, this event is not likely to be a major snow producer (more
on snow amounts below), but it could result in a localized area of
advisory level impacts with slick roads and hazardous travel.
Locations affected: As mentioned above the band of snow showers will
likely be rather narrow centered on or near the surface/low level
trough axis. At this point, it looks like this is most likely to be
the southern half of Ocean County and southeastern Burlington
County. However, a change even 10 to 15 miles one way or the other
could result in significant differences in the impacts for any one
location. Especially in northeastern Atlantic County, where if the
trough sets up just slightly further south, they could have impacts
similar to southeastern Burlington.
Snow amounts: I am forecasting maximum amounts of 2 to 3 inches of
snow. Most models are depicting QPF amounts between 0.25 to 0.5
inches. However, the snow liquid ratios are going to be tricky with
this event. While banding normally results in higher ratios,
However, with the relatively mild air from the ocean this could
negate some of the higher ratios. Some of the near term ensemble
members of both the SREF and HREF have significantly higher amounts
than the forecast, but even the mean of the HREF tends to have a
high bias and some of these ensemble members may be using a static
10:1 ratio which is likely not going to be the case for much of this
event. Regardless of the exact snow amounts, within the narrow band,
hazardous/slick travel conditions are possible.
Headlines/hazard messaging: We had a hard time deciding on the best
way to message this as the area impacted will likely be much smaller
than a winter weather advisory usually covers, but it is not the
traditional definition of a snow squall (not expecting gusty winds,
and the period of snow could be a few hours compared with less than
an hour for most snow squalls) and thus the snow squall warning
seemed inappropriate. Therefore, decided to issue a small winter
weather advisory to cover inland Ocean (coastal areas of Ocean Co
are likely to see more of a rain and snow mix) and southeastern
Burlington Counties. Note though that even in the advisory area,
some locations may see little, if any snow, especially in far
northern Ocean County. Have also issued an SPS for the surrounding
zones (northwestern Burlington, Camden and Atlantic) to mention the
potential for impacts if the trough develops further south or digs
further inland.
https://www.mattnoyes.net/new_engla...-you-forecast-weather-associated-with-it.html
However, these features (like mesoscale t-storms) are notoriously difficult to predict with regard to placement and intensity, meaning parts of the advisory area could get very little snow and parts could get 2-3" (or even more - this is similar to the event that put down 4-8" of snow in Dec-2013 in the Philly area, including during an Eagles game). It's also possible that the axis of snow could shift 30-50 miles from where it's forecast now, so folks in Monmouth through Atlantic counties should at least pay attention to the radar today. This is all discussed in a very informative discussion from the NWS below.
By the way, the storm for Sunday/Monday still mostly looks like a miss out-to-sea, but the Euro jumped 100+ miles north in its track last night, bringing the northern extent of the snowfall from southern VA to DC through the DelMarVa, while other global models are close to that or maybe a little to the south of that. Being 5 days out, significant shifts north or south are still possible, especially as one of the main players is still way north in the Arctic in a poorly sampled area (so model inputs are less accurate, meaning outputs have greater uncertainty), so our area should still watch this, although at this point it still looks like a miss for anywhere north of DC.
National Weather Service Mount Holly NJ
300 AM EST Wed Dec 5 2018
NEAR TERM /UNTIL 6 PM THIS EVENING/...
For the vast majority of the region, it will be a dry, albeit cool
day. Temperatures are expected to be 10 to 15 degrees below normal,
with highs generally in the 30s across most of the region, although
higher terrain of the Southern Poconos and NW NJ will likely not get
above freezing.
For eastern NJ, however, the forecast is decidedly more complicated.
We are still expecting a surface trough associated with the off
shore low to dig back towards eastern NJ. At the same time, a mid
and upper level short wave trough will be propagating southeast
towards our region. A combination of synoptic scale lift from the
mid and upper level trough and mesoscale lift centered around the
surface trough axis will result in a likely narrow band of snow
showers from mid morning through late afternoon. There is an
increasing signal for mesoscale banding, including a narrow corridor
of frontogenesis at 925 and 850 mb. Even with some mesoscale
banding, this event is not likely to be a major snow producer (more
on snow amounts below), but it could result in a localized area of
advisory level impacts with slick roads and hazardous travel.
Locations affected: As mentioned above the band of snow showers will
likely be rather narrow centered on or near the surface/low level
trough axis. At this point, it looks like this is most likely to be
the southern half of Ocean County and southeastern Burlington
County. However, a change even 10 to 15 miles one way or the other
could result in significant differences in the impacts for any one
location. Especially in northeastern Atlantic County, where if the
trough sets up just slightly further south, they could have impacts
similar to southeastern Burlington.
Snow amounts: I am forecasting maximum amounts of 2 to 3 inches of
snow. Most models are depicting QPF amounts between 0.25 to 0.5
inches. However, the snow liquid ratios are going to be tricky with
this event. While banding normally results in higher ratios,
However, with the relatively mild air from the ocean this could
negate some of the higher ratios. Some of the near term ensemble
members of both the SREF and HREF have significantly higher amounts
than the forecast, but even the mean of the HREF tends to have a
high bias and some of these ensemble members may be using a static
10:1 ratio which is likely not going to be the case for much of this
event. Regardless of the exact snow amounts, within the narrow band,
hazardous/slick travel conditions are possible.
Headlines/hazard messaging: We had a hard time deciding on the best
way to message this as the area impacted will likely be much smaller
than a winter weather advisory usually covers, but it is not the
traditional definition of a snow squall (not expecting gusty winds,
and the period of snow could be a few hours compared with less than
an hour for most snow squalls) and thus the snow squall warning
seemed inappropriate. Therefore, decided to issue a small winter
weather advisory to cover inland Ocean (coastal areas of Ocean Co
are likely to see more of a rain and snow mix) and southeastern
Burlington Counties. Note though that even in the advisory area,
some locations may see little, if any snow, especially in far
northern Ocean County. Have also issued an SPS for the surrounding
zones (northwestern Burlington, Camden and Atlantic) to mention the
potential for impacts if the trough develops further south or digs
further inland.
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