Jan 25

Jan 25, 2015: Nor’easter To Deliver Heavy Snow, Blizzard Conditions


Based on the latest analysis, no significant changes were made to the forecast. The 8-Day Forecast was slightly tweaked, with the next full update to be posted on Monday morning.

Forecast Highlights:

gfs_mslp_pcpn_frzn_neus_9Hardly 24 hours have passed since yesterday’s nor’easter produced widespread 4 to 8 inches of snow across the area, yet an even more powerful nor’easter is on track to target the region, targeting the northeast US from Monday night into Tuesday with heavy snowfall over 1 to 2 feet, near blizzard conditions and cold temperatures. Following the departure of this nor’easter, cold temperatures will persist through the remainder of the week (Image from Tropical Tidbits).

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Jan 25

Jan 25, 2015 Morning Update

Forecast Update: Major Snowstorm Expected on Monday, Tuesday

0z CMC valid at 0900 UTC Tuesday (4am EST), depicting a heavy snow band over the area, which would support at least over 16-20 inches of snow. Image from Environment Canada.

cmcOver the last two days, substantial shifts in the model guidance regarding the handling of a clipper system originating in the upper Midwest and Canada have resulted in a trend towards a nor’easter rapidly developing off the coast, producing significant snow totals upwards of 1-2 feet across the region, accompanied by strong winds to result in near blizzard conditions. The peak of the storm is expected to occur on Monday night, with otherwise periods of snow falling from late tonight through Tuesday afternoon.

There remain some uncertainties in the fine details, such as the positioning and trajectory of the upper level shortwave trough which will influence the positioning of the heavy snow banding and accordingly snow totals over the tri-state area; at least 8 to 14 inches of snow are expected in the event the heavy snow banding remains to the east, but should the heavy snow banding set up over the area, a scenario supported by the ECMWF and GFS, snow totals over 18-24 inches would occur across much of the tri-state area from northeast NJ on eastward.

An in-depth forecast analysis is currently in progress and will be posted by 2:00 PM, once the latest set of model guidance through the 12z ECMWF becomes available. In the meantime, the 8-Day Outlook has been updated with the latest forecast for the tri-state area.

Jan 24

Jan 24, 2015 Storm Updates

Occasional updates will be posted below on the prolonged rain, wind, flooding and snow event affecting the region this week. Radar images are from the Pennsylvania State University e-Wall.

Links: Yesterday’s Forecast | 8-Day Forecast | Twitter | Facebook


Saturday, January 24

5:30 PM: Last Round Of Rain/Snow; Tuesday Nor’easter Update

nerad25As of 5pm, the low pressure is situated southeast of Cape Cod and south of central Maine. The low pressure has been rapidly deepening over the last few hours with a minimum pressure near 979 hPa, and continues to track northeast towards Atlantic Canada.

Following a dry slot which persisted through much of the day, the low pressure has started to rapidly deepen, with deformation banding beginning to form to the west of the low over the area. Temperatures are still too warm to support snow for most of the area, although Connecticut and the rest of southern New England have changed over to snow, with parts of Long Island likely changing to a period of moderate snow later this evening as well before precipitation tapers off towards 7-8 PM.

In relatively quick succession, yet another major nor’easter is expected to affect the region on Tuesday, but is expected to have more significant impacts across the region with heavy snow, wind, and blizzard conditions for parts of New England. Snow totals over 12-24 inches of snow are possible over parts of the region, but with uncertainty regarding whether this axis sets up over eastern New England or over the NYC tri-state area. For now, the 8-Day Forecast has been updated with a preliminary and likely conservative estimate of potential snow totals, which will be updated again on Sunday morning following tonight’s set of model runs.


11:10 AM: Precipitation Tapers Off; Another Nor’easter Next Week?

11amradAs of 10am, the low pressure is situated south of Long Island and east of Delaware. Minimum pressure is near 992 hPa, and the low pressure continues to steadily deepen while tracking northeast.

As can be seen in the regional radar mosaic to the left, the main precipitation shield associated with the warm air advection has departed the area, with scattered rain and snow showers lingering. Little precipitation is expected through at least 4-5 PM, when deformation banding will attempt to develop in the back-end of the system as the low pressure rapidly deepens. This will occur too late to produce significant snow in the northeast US region, but with additional light snow likely mainly east of NYC, possibly moderate over Connecticut and eastern Long Island, before tapering off by 7-8 PM.

Dry conditions will return for Sunday, but may not last for long. An Alberta Clipper system on Monday is trending increasingly slower and amplified on the model guidance, which may result in the formation of yet another major nor’easter on Tuesday with the potential to produce additional widespread snow and wind. Details remain uncertain at this time as this trend in the model guidance is still underway, although this potential will continue to be monitored, and a separate forecast update will be posted later this afternoon.


8:00 AM: Heavy Snow Moving Out; Ice, Rain Continue

nerad25As of 7am, the low pressure is situated south of NYC and east of southern Maryland. Minimum pressure is near 997 hPa, and the low pressure is steadily deepening while tracking northeast.

Precipitation began toward 12-2 AM across most of the area, and with the aid of strong warm air advection and frontogenesis to the south of the area, bands of moderate to heavy snow quickly overspread the area and continued throughout the early morning hours. With warmer temperatures having spread in aloft, precipitation type changed over to rain along and east of the I-95 corridor, with freezing rain and snow continuing farther inland.

As of 8 AM, at least 4 to 8 inches of snow accumulated across northern New Jersey, southeast New York and southern Connecticut, with the highest totals near 6-8 inches over Bergen, Passaic and Sussex counties, where snow rates approached 2″/hour accompanied by higher than forecast snow ratios. At least 3 to 5 inches of snow accumulated in NYC, with 2 to 4 inches in Long Island.


Forecast Update: As mentioned with yesterday’s forecast analysis, however, this system is still currently dominated by the southern branch of the jet stream, with a lack of a closed mid-level low and deformation banding to the northwest of the low, and a surge of drier air aloft will expand into the area with drier conditions through the late morning hours once the current round of WAA-driven precipitation tapers off by 9-10 AM.

Yesterday’s update also mentioned remaining uncertainty concerning the second half of the storm this afternoon, once the low pressure begins to rapidly deepen with a closed mid-level low and a developing cold conveyor belt and deformation banding to its northwest. The high resolution model guidance has yet to reach a consensus, although the heavy snow scenario appears to be an outlier. As colder temperatures filter back in from the north, a changeover to snow is likely towards 3 to 6 PM from west to east, with additional periods of light snow for most locations and potentially moderate snow over Connecticut and eastern Long Island, where over an additional 1 inch of snow is possible this evening.

Jan 23

Jan 23, 2015: Nor’easter To Produce Snow, Ice Tomorrow

Forecast Highlights:

nmmSeveral nor’easters have affected the northeast US this winter season, most notably on November 26-27, but none have targeted the I-95 corridor with substantial snowfall thus far. A nor’easter currently developing near the Mid Atlantic region is expected to produce the first moderate snowfall of the winter for the area, as periods of moderate to heavy snow produce several inches of accumulation tonight followed by a messy wintry mix on Saturday.

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Jan 22

Jan 22, 2015: Snow on Saturday, Monday

Forecast Highlights:

rgemFollowing a relatively cool pattern but with a notable lack of snowstorms, two snow events are forecast to affect the northeast US in the next few days. Continuing the theme from the last few months, the heaviest snowfall is not expected to affect the area, although at least light to potentially moderate snow accumulations are likely with both events, followed by a surge of cold temperatures into the region in the wake of Monday’s storm.

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Jan 21

Jan 21, 2015 Update: Light Snow Tonight


The 8-Day Forecast page has been updated with the latest forecast, including preliminary snow totals for the next two snow events.

4:15 PM Update: Light Snow Tonight, More On The Way

nerad25The latest regional radar, posted to the left from PSU e-Wall, depicts the development of a strong coastal low pressure off the Mid Atlantic coast, associated with strong forcing and upward vertical motion ahead of a shortwave trough. This strong upward vertical motion is accordingly resulting in heavy snow bands over southern New Jersey, Pennsylvania and Maryland, where 2 to 4 inches of snow have been reported in some spots, but is also enhancing subsidence to the north over the NYC tri-state area, where a very dry air mass remains in place with dew points only near 3 degrees in NYC, aiding in preventing snow from spreading north into the area.

While the heavy snow will remain to the south, additional light snowfall over Pennsylvania will continue to spread east into the area mainly between 7 PM and 1 AM, with up to 1/2 inch of snow expected north and east of NYC and up to 1 inch over northern NJ, NYC and Long Island. Depending on the northern extent of the heavier banding, totals may approach 2 inches in eastern Long Island and central New Jersey.

Drier conditions will return for Thursday, but with more snow on the way; a strong nor’easter is projected to impact the region with snow, rain and potentially ice on Saturday, followed by another potential nor’easter towards next Monday and Tuesday. A detailed forecast analysis will be posted on Thursday morning; in the meantime, the 8-Day Forecast page has been updated with the latest preliminary outlook for these two events.

Jan 16

Blog Notice

Wednesday, 1/21/15 Update:

In anticipation of the numerous snow events over the course of the next 7-10 days, the 8-Day Forecast page will be updated this afternoon by 2:30 PM. Daily forecast discussions will resume on Thursday, 1/22/15.



Tuesday, 1/20/15 Update:

Periods of light snow are expected on Wednesday evening, with up to 1 inch of snow possible, potentially up to 2 inches towards eastern Long Island and south of NYC.

Some model guidance is indicating the potential for a major nor’easter on Saturday, 1/25. If this potential continues to receive support, a forecast update will be posted on Thursday. Otherwise, no updates will be posted through the remainder of this week. I apologize for any inconvenience due to the recent lack of updates.


Original Post on 1/16/15:

The blog will not be updated over the next few days. More information will be posted early this week on when updates will resume. I apologize for any inconvenience.


Jan 15

Jan 15, 2015: Rain Possible on Sunday

Forecast Highlights:

gfs_mslp_pcpn_frzn_neus_13Another surge of cold temperatures is anticipated for Friday night into Saturday with lows back into the single digits across interior locations, but with a warming trend expected by early next week as a developing coastal low pressure produces potentially heavy rain for parts of the area on Sunday, followed by a moderated cool air mass and the possibility of some midweek snow.

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Jan 11

Jan 11, 2015: Ice Tomorrow, Warmer Pattern Ahead

Forecast Highlights:

rgemThe cold pattern which has persisted over the last week will begin to gradually moderate, beginning with a freezing rain event tonight into Monday morning which will impact the morning commute with hazardous road conditions before a changeover to plain rain by the afternoon hours. Another brief cool down is expected on Tuesday with high temperatures in the 20s and lows in the single digits and 10s, followed by a gradual warming trend into the late week with high temperatures possibly returning into the mid 40s by next weekend.

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Jan 09

Jan 9, 2015 Update: Heavy Snow In Long Island

9:40 AM: Snow Tapers Off, Over 2 Inches In Long Island

1.9_1315Over the last several hours, a band of moderate to locally heavy snow associated with a clipper system passing to the north of the area progressed eastward, producing a several hour period of accumulating snowfall from 4-6 AM inland, 6-8 AM over the immediate NYC area, and from 8 AM onwards east of NYC. Preliminary reports as of 9:30 AM indicate that 1 to 2 inches of snow accumulated across most of the area, with the heaviest snowfall having occurred over Queens, Nassau and western Suffolk county, where snow totals significantly exceeded the forecast with widespread reports of 2 to 3 inches of snow.

Upper-level forcing was sufficient for persistence of the heavy snowfall rates into the area, accompanied by modest mid-level frontogenesis and upper-level divergence ahead of a powerful jet streak, factors which both favor upward vertical motion and accordingly precipitation. The high-resolution model guidance has indicated the potential for a moderate band of snow especially near and north of NYC over the last two days, but underestimated the snowfall rates and accordingly was too low with accumulations, which were generally forecast up to 1/2 inch in Long Island and up to 1 inch north of NYC.

The snow will continue to taper off over the next hour, with clearing skies expected later in the day as temperatures rise into the upper 20s to mid 30s followed by another surge of cold temperatures tonight into Saturday.

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