Occasional updates will be posted below on the snow and rain event affecting the region over the next day. The latest updates, along with the latest available snow reports, will be at the top of this post. Radar images are from the Pennsylvania State University e-Wall.
Links: Yesterday’s Forecast | 8-Day Forecast | Twitter | Facebook
8:10 PM: Snow Tapers Off; Warmer Pattern On The Way
As the baroclinic zone continued to progress south throughout the day, snow gradually decreased in intensity by the mid to late afternoon hours, and as of 7 PM, only scattered snow showers remain with the steady snow having shifted south into Virginia. Preliminary snow accumulation reports suggest that 2 to 5 inches accumulated in southeast NY, 3 to 6 inches in northern NJ north of the I-80 corridor into coastal CT, and 4 to 8 inches in NYC and Long Island into the rest of New Jersey.
As of 4 PM, Central Park recorded 7.0 inches of snow, bringing the March snowfall to date to 13.6 inches, marking Central Park’s 12th snowiest March on record dating back to 1869, and the snowiest March since 1967. Additionally, Central Park brings its seasonal snow total to 42.0 inches, which is remarkable considering only 1.0 inch accumulated in December. Prior to this winter, in Central Park’s 145 recorded winter seasons, 43 winters had 1 inch or less in December; out of these years, only 5 winters (11.6%) recorded near or over 40″ of snow during the entire season, with the last such occurrence during 1977-78, and the average winter snowfall for Decembers with 1 or less inch of snow is only 19.8″, much lower than the 28.6″ average of all winter seasons in Central Park.
Warmth Returns: Unlike previous events, however, the latest 8-Day Forecast shows no additional snow over the next week. In fact, after another cold Friday, temperatures begin to steadily trend upwards, returning into the 40s and possibly even the low 50s in spots by next week, as the upper level flow in the northern US trends increasingly zonal. This warm trend can be partly attributed to an increase in tropical forcing over the equatorial Pacific Ocean, as convection associated with the MJO, which has been recently weak and centered near the phases 7-8 regions which are indicative of a trough and colder temperatures in the eastern US, is projected to re-emerge near Indonesia, indicating a phase 4 of the MJO which is often correlated with near to above average temperatures in the eastern US. There are, however, signs that the warmth will struggle to fully build into the region, as model guidance often exaggerates the eastward expansion of ridges in the spring, with a more pronounced northwesterly flow than modeled keeping parts of the region near the edge of the colder air masses to the east, and the longer range models continue to show occasional surges of cold temperatures beyond next week. More information on the longer range outlook will be posted with a more detailed analysis on Friday or Saturday, while daily updates to the 8-day outlook will continue in the meantime.
12:00 PM: Still Snowing
The baroclinic zone has continued to progress slower than modeled even as of last night, and a widespread axis of moderate to locally heavy snow remains nearly stalled from southern Pennsylvania into New Jersey and coastal New England. The persistence of strong upward vertical motion associated with the aforementioned mid-level frontogenesis continues to produce moderate to heavy snow, with the heaviest snow in the area generally over northeast NJ, NYC and Long Island, where radar reflectivity continues to depict returns over 20-25 dBZ. The high-resolution model data is accordingly trending slower with the ending time of the snow, and storm total accumulations may end up within the 4-8 inch range across NYC and Long Island and slightly lower over northeast NJ.
As previous updates have noted, the southward push in the baroclinic zone is associated with a surge of cold and dry air from the north, and locations near the northern end of the precipitation shield, particularly over northwest NJ and southeast NY, are only recording light snow with little accumulations despite the regional radar mosaic above depicting heavy snow bands overhead. As these locations are relatively far from the nearest radar sites in Upton, NY and central NJ, the radar beams only reach the higher levels of the atmosphere, where steadier snow may be falling, but is likely evaporating closer to the surface due to dry air. Based on the above and the latest available snow reports from the NWS, these locations appear to be on track with last night’s forecast at this time.
8:30 AM: Widespread Snow Continues Today
Since the previous forecast update, the steady moderate precipitation associated with the baroclinic zone has spread throughout the area, initially falling as rain with temperatures lingering in the mid 30s to low 40s. A gradual changeover to snow from NW to SE occurred towards 12-3am inland of NYC and 3-5am from NYC and farther south and east, with steady periods of light to moderate snow since then. Latest preliminary reports suggest at least 1 to 3 inches of snow through 7-8 AM this morning, with temperatures currently in the low 30s for most locations.
The latest regional radar imagery posted to the left depicts widespread moderate snow throughout the area, with a narrow band of heavy snow extending through central NJ into southern parts of NYC, aligned closely to the axis of maximum 700 hPa frontogenesis. As the baroclinic zone continues to gradually shift southeast, the precipitation shield will slowly follow along, with the heavy snow shifting south of the area while steady light to moderate snow continues through at least 3-6 PM before ending from north to south. Last night’s snow accumulation forecast remains unchanged at this time.
9:50 PM: Rain Continues This Evening, Snow Expected After Midnight
Observations: As yesterday’s update discussed, a strong baroclinic zone is setting up near the region, highlighted by a significant contrast in temperatures ranging from the 20s in central Kentucky to the 60s in western North Carolina, accompanied by a powerful upper level jet streak and approaching shortwave trough providing widespread synoptic ascent and producing widespread moderate to heavy precipitation along and north of the baroclinic zone. As the trough axis slowly approaches from the west, its associated cold air mass continues to be gradually advected eastward, with the east push of cold and dry air gradually shifting the baroclinic zone and accordingly its precipitation field to the southeast.
Even though there is no well-defined surface low pressure center, the setup is nonetheless favorable for heavy precipitation, with significant upper-tropospheric divergence due to the powerful jet streak surpassing an impressive 180 to 200 knots at the 250 hPa pressure level, as well as cyclonic vorticity advection ahead of the approaching shortwave trough, factors which both favor upward vertical motion and precipitation, with moisture from the southern US transported into the region by the strong southwesterly flow aloft along the frontal boundary. The latest regional radar imagery above depicts an elongated band of heavy snow just north of the rain/snow boundary, with steady light to moderate snow to the north and a sharp cutoff in the northern fringe of the system in Indiana and Ohio.
Following yesterday’s wintry mix event, largely forced by a strong southwesterly flow which transported a much warmer air mass into the region, temperatures peaked in the low to mid 40s throughout most of the area with localized spots of upper 40s; for parts of the area, this was the warmest day since early January, following the near historic cold pattern in February notable for its low temperatures but especially its prolonged duration. With persistent cloud cover and winds above 5 mph maintaining a mixed layer near the surface with little cold air advection occurring, however, temperatures have been very slow to cool down this evening, and remain in the upper 30s to low 40s range for most locations as of 9 PM. The rate of cooling overnight will be an important factor to determining snow accumulations later tonight.