… Synopsis … (2pm NYS radar loop)
- Extreme Cold!!! … 2pm Temps: 2° to 8° around the region
- Temps will climb between 10° and 20° tonight
- Heaviest Snow expected between now and 12am.
- Snowfall Rates 1-4”+ per hour
- Near zero visibility… white out conditions ??
- Dangerous to impossible travel
- End Time: 12AM- 5AM Monday
- Snowfall Accumulations:(See snow map)
- South of I-287: 8″ to 12″ (change to sleet 2pm to 4pm: 0.5″ to 2″ of sleet)
- South of I-84: 12″ to 16″ (mixing with sleet is a possibility)
- I-84 corridor on North: 16″ to 20″ (all snow – Localized totals up to 24”)
- Catskills: 20″ to 24″+ possible in highest elevations (localized 30” amounts across eastern facing slopes and ridges)
- Periods of light snow possible throughout the day on Monday with additional accumulations of a coating to 2″ (between sunrise and sunset)
Discussion
The National Weather Service discussion overnight started like this…
“A blockbuster snowstorm is setting up for eastern NY and western
New England.” …. and we agree 100%. A historic, major snowstorm unfolding at this hour, as snow pummels the entire Hudson Valley. Snowfall rates at this time are 1 to 3 inches per hour… with much of the region already reporting 6 to 12 inches of snow already. Computer guidance suggests another 8 to 12 inches is likely across the region between now and the end of this storm between 12am and 3am. There will be periods of light snow during the day on Monday, but it shouldn’t accumulate more than another dusting to an inch or two.
Now-cast Challenges
There are a couple forecast challenges related to the details (final snowfall accumulations)
Potential snow/sleet boundary …. we’re watching as a thin warm nose of air about 5,000 to 10,000 feet up, that will cause some areas to mix or changeover to sleet. No guidance takes this boundary further north than I-84… and most guidance keeps the boundary in Rockland & Westchester counties. This period of sleet will reduce final accumulations. Snowfall accumulations are forecast by location… but with this storm… it’s simple.
– Where you change over to sleet, final snowfall of 8″ to 16″ is expected. Totals are dependent upon how long you mix with sleet. If only for an hour or two, your totals are closer to 16″… if you change to sleet for 5 or 6 hours, totals closer to 8″ or 10″ are expected.
– Where you stay all snow… 16 to 24 inches is likely. It all comes down to snowfall ratios and amount of precipitation. We won’t be surprised if there are numerous reports around 20″ to 24″. The dynamics of this storm are so extreme, with bitter cold air and a river of moisture, that chances are guidance is slightly underdone.
Dry air rushing in… on the backside of this storm, dry air will race in, and try to shut off the snow early. Guidance has the snow lasting through midnight… but if that dry air is more aggressive than the data suggests, it could shut off as early as 9pm or 10pm in western areas. If that happens, final totals will be 2 or 3 inches less. But the final impacts will remain the same.
A historic, once in a decade storm is well underway… stay warm… stay safe… and use caution. more updates will follow this afternoon.
-Bill