Mar 31

Mar 31, 2015: March Begins, Ends With Snow

Forecast Highlights:

wrf-nmm_ref_frzn_neus_23March has been a notably snowy month in the tri-state area, currently ranking as the 7th snowiest March on record in Central Park, accompanied by below normal temperatures but to a much lesser extent than February. The month is set to end on the same note as it began for parts of the region, with a low pressure producing mostly rain for eastern regions but heavy wet snow over Pennsylvania into northwest NJ.

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Mar 27

Mar 27, 2015: 60s Yesterday, Snow Tomorrow

Forecast Highlights:

wrf-nmm_ref_frzn_neus_26The major temperature swings typical of spring are once again occurring, as following a warmth spike yesterday with temperatures surging into the 60s in parts of the area, a cold air mass will overlap with a developing low pressure offshore to produce widespread snow over southern New England into Long Island on Saturday. A gradual warming trend is likely into next week, building up to a potentially significant warmth surge ahead of a cold front next Friday. (Image from Tropical Tidbits)

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Mar 25

Mar 25, 2015: Rain, T-Storms Likely Tomorrow

Forecast Update: Rain, T-Storms Likely on Thursday

18z NAM hour 24, valid at 1800 UTC Thursday, 3/26 (2 PM EDT), depicting scattered heavy showers and thunderstorms over the tri-state area with an approaching low pressure to the west. Image from Tropical Tidbits.

nam4km_ref_neus_8After a relatively inactive week, with a period of cold temperatures, rain and possibly snow return into the forecast for the late week into Saturday, possibly accompanied by warm temperatures for southern parts of the area. A developing low pressure over Oklahoma, currently triggering the first major severe weather outbreak of the month after a nearly month-long stretch of no tornado reports in the US, will continue to quickly progress northeast, remaining relatively weak due to a lack of broad synoptic forcing but nonetheless producing widespread precipitation north of a strong baroclinic zone.

Thursday Afternoon: The low pressure is expected to track through Pennsylvania on Thursday afternoon with its warm front slowly crawling north through central NJ, with a very warm air mass to its south as temperatures surge into the 60s and 70s. To the north of the warm front, over the tri-state area, a shallow cold air mass will linger near the surface, with temperatures remaining in the 40s and low 50s through the early afternoon, but with a strong southwesterly low-level jet streak advecting a warm and moist air mass aloft, where sufficient elevated instability is modeled to result in elevated convection, and accordingly locally heavy rain and thunderstorms, despite the colder surface temperatures. This activity is likely to be centered towards the 12 to 5 PM time frame, with the heaviest rain likely towards Long Island where over 1/2 to 1 inch of rain is possible by the evening hours.

Thursday Evening-Night: Following this activity, the warm front associated with the approaching surface low pressure is expected to progress north into the area, but the northward extent is somewhat uncertain as model guidance typically exaggerates the northward extent of warm fronts in similar synoptic setups in the spring. Unlike the GFS and ECMWF, which depict widespread temperatures in the upper 50s and 60s up through the central Hudson Valley region, the NAM model depicts the warm front struggling to expand north of NYC until about 5-7 PM, when temperatures briefly rise into the mid 50s to low 60s throughout the area ahead of the cold frontal passage. This scenario is more typical of past analogs and appears to be more reasonable at this time. The cold front is likely to move through between 8 PM to 12 AM from west to east, with temperatures sharply dropping into the 30s to low 40s and scattered showers and thunderstorms continuing through about 12-2 AM.

Friday & Beyond: Another trough is expected to amplify over the region by the weekend, bringing colder temperatures back into the picture with high temperatures struggling past the upper 30s on Saturday and Sunday. While significant cyclogenesis will occur too far offshore for significant impact with the trough axis too far east, some models are hinting at a potential inverted trough setup which may produce some light snow in eastern parts of the area on Friday night into Saturday. A more detailed update will be posted on Thursday morning.

Mar 20

Mar 20, 2015 Storm Updates

Occasional updates will be posted below on the snow event affecting the region today. The latest updates, along with the latest available snow reports, will be at the top of this post. Radar images are from the National Weather Service.

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


Saturday, March 21
10:30 AM: Snow Tapers Off in Connecticut, Long Island

northeast (2)As of 8 AM, the coastal low pressure which developed offshore last night continues to slowly deepen with a minimum pressure near 1004 hPa. The low is located well southeast of Cape Cod and will continue to deepen over the next day as it tracks towards Nova Scotia.

Following yesterday afternoon’s update, snow intensified on the back end of the system with widespread moderate to heavy snow for most places, but generally tapered off by 8-10 PM with scattered freezing drizzle and snow showers persisting east of NYC overnight. A separate vorticity maximum approaching from the Great Lakes is beginning to interact with this system offshore, which will eventually initiate rapid deepening of the low pressure offshore, although the redeveloped precipitation shield is more robust than modeled, with widespread light to moderate snow persisting over Long Island and Connecticut. This snow will generally taper off towards 11 AM to 12 PM, although may not accumulate to much as temperatures continue to rise and snowfall rates may not be intense enough to offset the melting rate.

Based on preliminary storm reports, snow totals so far are within the 2 to 4 inch range over southeast NY, eastern CT and interior CT, which is near to slightly below the forecast amounts; snow totals were higher than forecast over central NJ into Long Island and coastal Fairfield county, where snow accumulations were generally in the 4.5 to 7 inch range. Totals were near the forecast amounts over northern NJ and NYC, with 3 to 5 inches.


Friday, March 20
3:45 PM: Snow Lighter Than Expected for Some

northeastAstronomical spring is starting across the region with yet another snowstorm, but with less snow for parts of the area than others. The latest regional radar imagery continues to depict widespread snow across the region, but with lighter snow rates persisting over northern NJ north of the I-80 corridor into southeast NY and southern CT.

The lighter snow rates over most of the area are partly associated with the stronger synoptic forcing and upward motion focused over central NJ, where heavy snow continues to fall with over 3-4 inches in some locations as of 3 PM, with subsidence, or sinking air, to the north of the heavier snow over most of the tri-state area resulting in lighter snow rates and smaller flakes. Another issue, however, is the stubbornly dry air mass, with relative humidity only at 19% in Central Park last night as dew points remained in the single digits. The atmosphere took longer to moisten up than anticipated, with a longer period of snow evaporating before reaching the ground. These factors contributed to result in lighter snow rates, which struggled to accumulate at the onset given the warm surface temperatures coming off of the recent relatively warm pattern, and in some locations snow has yet to accumulate on paved surfaces.

Snow will continue to gradually wind down over the next several hours as a coastal low pressure quickly forms offshore with enhanced subsidence over the tri-state area, mostly tapering off by 8-11 PM. Last night’s forecast update noted a risk of less snow than forecast north of NYC; this appears to be the case for some locations, and parts of northern NJ, NYC and eastern Long Island may struggle to surpass 2-3 inches for a storm total. Farther south, steady moderate to heavy snow continues over central NJ into parts of NYC and western Long Island, where 3 to 5 inches of snow are still on track.

Mar 19

Mar 19, 2015: Astronomical Spring Starts With More Snow

Forecast Highlights:

wrf-nmm_ref_frzn_neus_31Regardless of the definition of spring, whether meteorological (3/1) or astronomical (3/21), the onset of spring will have been highlighted by snow. Even though temperatures are not nearly as cold as they have been during February, a sufficiently cold air mass will linger to result in widespread snow throughout the region on Friday, accumulating to over 2-4 inches for most locations. Cold temperatures will briefly return on Sunday, but with a warming trend otherwise expected by next week.

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Mar 19

Mar 18, 2015: Snow Returns On Friday

Forecast Highlights:

rgem2Meteorological spring on March 1st began with a moderate snowstorm, and the beginning of astronomical spring on March 21st may not be much different. The back-loaded winter of 2014-15 continues after a temporary interruption, with a relatively weak system expected to produce light to moderate snow over Pennsylvania, New Jersey and southern New York on Friday. Cold temperatures will persist through the weekend, but with a gradual warming trend towards next week.

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Mar 15

Mar 15, 2015: Cool Temperatures Persist This Week

Forecast Highlights:

nerad4Signs of winter continue to linger over parts of the region, as following a relatively warm week, a strong upper level low near the region has resulted in widespread rain yesterday and additional snow in Boston today. Temperatures will briefly warm up on Monday into the mid 40s to low 50s for most locations, but with a colder air mass returning following a frontal passage on Tuesday, with temperatures on Wednesday struggling to rise past the mid 30s.

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Mar 09

Mar 9, 2015: Warmth Continues, Some Rain Expected

Forecast Highlights:

temp25A more typical spring-like pattern continues to gradually emerge, with temperatures today having soared into the low to mid 50s for the first time since early January. Mild temperatures will continue through Wednesday along with some rain on Tuesday evening and night, but with cooler temperatures lingering near the region accompanied by additional rain and/or snow on Friday night into Saturday.

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Mar 04

Mar 4-5, 2015 Storm Updates

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

3.6.15_0015As 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.


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Mar 03

Mar 3, 2015: Snow, Ice Return Tonight & Thursday

Forecast Highlights:

rgemMarch continues with the cold and snowy pattern from the end of February, with several inches of snow having accumulated across the area on Sunday. Additional light to moderate snow and ice is expected this afternoon, followed by a changeover to freezing rain and rain later tonight and another wave of snow on Wednesday night. More prolonged dry conditions will return for the remainder of the week, however, with no additional snow expected.

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