AM All Zones Update: Major Snowstorm Underway for Much of the Region

An area of snow, sleet and rain overspread the region overnight. Precipitation started as some sleet and rain in some areas, because temperatures at the surface and aloft were warmer. But as low pressure strengthens near the Delmarva coast, the airmass will be turning colder with increasing northerly winds this morning. This cause precipitation will changeover to snow in all areas by 8am. It has already changed over to all snow from C NJ and north as of 7am.

Then snow will be moderate to heavy at times for rest of this morning through the region. Temperatures will be dropping into the 20s. So this snow will begin accumulate more rapidly on roadways this morning and reducing visibilities.

Near-term model guidance continues to indicate some extremely intense frontogenesis and lift over the region this morning . This will likely cause some deformation banding with very heavy snowfall rates between 2” to 3” per hour. Some slanted instability indicated on model skew-t soundings, may also support some thundersnow and even higher than 3″ per hour snowfall rates.

NAM model showing intense frontogeneis moving through NYC metro region around 14z (9am) today.

NAM model showing intense frontogeneis moving through NYC metro region around 14z (9am) today.

Also, a tight pressure gradient with some instability could lead to strong winds — gusting to between 30-40mph — over many parts of the region today. Over Long Island winds could gust to between 40-50mph, as stronger 850mb jet moves over that region later today. As a result, a Blizzard Warning has been issued for all of Long Island.

Snow will begin ending from west to east over the Western parts of the region during early to mid-afternoon hours, as low pressure beings moving further offshore. However eastern areas, especially Long Island and Connecticut could see more moderate to heavy bands move through this afternoon region underneath a developing CCB (cold-conveyor belt).  Snow ratios may also increase by early this afternoon, with colder temperatures aloft and stronger omega (upward motion) in the region where the snow flakes are forming. This will result in higher snowfall accumulations for those areas.

All snow should end everywhere by this evening, with skies clearing overnight. Even colder air will arrive behind this storm with temperatures dropping into the teens in many areas and perhaps some isolated single digits well in the interior. Tomorrow will remain very cold, despite more sunshine. The new snowpack over the region will prevent temperatures from rising higher than the upper 20s or lower 30s. A weak low area of pressure passing to the north with a warm front approaching the region, may produce a period of light snow Friday night, especially for northern zones.

SNOWMAP_FINAL_FEB8

Then higher mid-level heights will allow for some moderating temperatures this weekend. But another storm system may produce precipitation over the region on Sunday. This time, however, we’ll have a warmer airmass, so this will likely be mostly rain. But some sleet or freezing rain possible over Interior, especially with more snowpack keeping temperatures colder.

We will continue to monitor this storm throughout the day, with more individual zone updates likely to cover mesoscale banding or conditions in parts of the region.