Summary: Given high uncertainty, using the NBM (National Blend of Models) is usually a good place to start when there is quite a bit of model spread, as we have now and which is not a surprise since we're still 4 days from the event, which looks like it'll be from the wee hours Monday morning into the afternoon, with temps in the 20s for the whole event, so accumulations on all untreated surfaces would be expected, which could make the Monday am rush difficult. The NBM shows 1-2" along and N of 80 (including NYC) increasing as one goes south to 3-4" along 276/195 and more south of there, which would mean 2-3" for most of CNJ. Snow fans would certainly take that, considering things were looking like <1" for most folks N of 276/195 until this evening's shift north in the precip/snow shield seen on most models. <1" and 4-6" are still on the table for areas between 276/195 and 78.
Details: Been talking about this threat in the pattern thread for a few days, but now that we're about 4 days away from the event, figured it was time for a thread. Uncertainty is fairly high on snowfall amounts, given that the main system is still in the Pacific Ocean and the setup is a sensitive one, since this will be what is known as a SWFE (southwestern flow event) with a storm traveling mostly west to east across the country putting down significant snow (and mix to rain south of the track) north of the track as the SW flow of moist air from the south is thrown into the well-entrenched cold air north of the track; this is not a coastal low/nor'easter coming up the Atlantic coast. As a result of the expected track being a bit south of here and the influence of the tropospheric polar vortex (TPV) to our north possibly suppressing moisture to our south (confluence), areas N of 276/195 are on the northern edge of the precip/snow meaning there is a wide range of potential snowfall amounts as mentioned above, with amounts quickly decreasing as one goes north.
Through much of last night and today, most of the models weren't showing that much snow for our area, but that started changing with the 18Z Euro, which brought moderate snow much further north into our area and since then just about every model at 0Z tonight is showing at least a bit of snow for our area with some showing a few inches or more, which is why the NBM is showing the minor (1-2" to moderate snowfall (2-4") I mentioned in the thread title. Still a long way to go and we could trend back downward to an inch or less for most or upward to several inches for everyone or kind of stay on track. Note that for much of VA/MD/DE and SNJ (south of Wilmington to AC) 4-8" are looking somewhat likely. One other factor to consider is that temps should be in the 20s throughout the event (wee hours of Monday through Mon afternoon, although we could still see a shift of 4-8 hours in precip timing), so any snow that falls should accumulate easily, meaning impacts, especially on the morning rush hour on a Monday after a holiday week for many, could be significant if we get more than 1-2" (and even 1-2" would have some impact). Also, note that the NWS as of their 4 pm update was less optimistic for snow vs. what I've posted, but that was before they had seen the model shifts, so I'd expect them to be more bullish at 4 am.
https://www.weather.gov/phi/
Details: Been talking about this threat in the pattern thread for a few days, but now that we're about 4 days away from the event, figured it was time for a thread. Uncertainty is fairly high on snowfall amounts, given that the main system is still in the Pacific Ocean and the setup is a sensitive one, since this will be what is known as a SWFE (southwestern flow event) with a storm traveling mostly west to east across the country putting down significant snow (and mix to rain south of the track) north of the track as the SW flow of moist air from the south is thrown into the well-entrenched cold air north of the track; this is not a coastal low/nor'easter coming up the Atlantic coast. As a result of the expected track being a bit south of here and the influence of the tropospheric polar vortex (TPV) to our north possibly suppressing moisture to our south (confluence), areas N of 276/195 are on the northern edge of the precip/snow meaning there is a wide range of potential snowfall amounts as mentioned above, with amounts quickly decreasing as one goes north.
Through much of last night and today, most of the models weren't showing that much snow for our area, but that started changing with the 18Z Euro, which brought moderate snow much further north into our area and since then just about every model at 0Z tonight is showing at least a bit of snow for our area with some showing a few inches or more, which is why the NBM is showing the minor (1-2" to moderate snowfall (2-4") I mentioned in the thread title. Still a long way to go and we could trend back downward to an inch or less for most or upward to several inches for everyone or kind of stay on track. Note that for much of VA/MD/DE and SNJ (south of Wilmington to AC) 4-8" are looking somewhat likely. One other factor to consider is that temps should be in the 20s throughout the event (wee hours of Monday through Mon afternoon, although we could still see a shift of 4-8 hours in precip timing), so any snow that falls should accumulate easily, meaning impacts, especially on the morning rush hour on a Monday after a holiday week for many, could be significant if we get more than 1-2" (and even 1-2" would have some impact). Also, note that the NWS as of their 4 pm update was less optimistic for snow vs. what I've posted, but that was before they had seen the model shifts, so I'd expect them to be more bullish at 4 am.
https://www.weather.gov/phi/
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