Dec 29, 2013 Storm Updates

Occasional updates will be posted below on the heavy rain event affecting the region today. Radar images are from the Pennsylvania State University e-Wall.

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

 


Final storm rain totals in NYC:

Central Park – 1.20″ | LaGuardia – 1.20″ | JFK Airport – 1.19″


 

8:30 PM: Rain Ends Across Area

12.30_0115As of 8 PM, the coastal low pressure was located near southern Rhode Island, with a minimum pressure of 993 mb. The northern low pressure was located just north of the NY/Canada border with a minimum pressure near 1000 mb. The coastal low will continue to intensify tonight as it quickly tracks out of the region while absorbing the northern low pressure.

Since the last update, the rain has ended across the entire area, having moved out of far eastern CT around 7:30pm. Rain totals were generally between 3/4 to 1.5 inch, with the lowest totals further west and highest totals towards Long Island. Cloudy conditions persist across the area with temperatures generally in the upper 30s to low 40s. Long Island has been the exception, where winds briefly switched to the SE with gusts up to 20-35 mph as temperatures surged into the low-mid 50s, and will fall back quickly into the 40s and later the upper 30s tonight. Areas of fog with low visibility will continue in the short term, with visibility expected to improve later tonight with a breezy NW wind developing. Most locations will remain above freezing tonight preventing the development of black ice, although this may be a concern towards Sussex and Orange counties where temperatures may reach the freezing mark late tonight.

This is the last storm update for tonight. The next forecast update will be posted on Monday morning, focusing on the late week storm and its potential impacts in the area.

Thursday’s Storm Update: Today’s model runs were generally drier for the area, with the GFS and ECM depicting moderate-heavy snow to the north, heavy rain to the east, and generally less than 1/2 inch of liquid-equivalent precipitation over the area. Interestingly enough, the NAVGEM model, notable for having a progressive bias, is among the most amplified models with this system. Some trends to make note of are in the mid levels, where the GFS has been consistent in correcting towards a slower and stronger southern stream shortwave, previously having depicted it as too weak and shearing it out too quickly, a bias it has displayed with some storms over the last month. While additional slight changes are expected with the handling of the southern shortwave, additional uncertainty rests with the northern stream shortwave, which is expected to enter the northwestern US in about 48 hours.

There remains the potential for a more significant storm than currently modeled, in which case the heaviest snow would likely focus in the northeast US with mixed precipitation likely in the NYC area; at this time the 8-day forecast continues to reflect an 80% chance of snow in northern areas and mix in southern areas, with the new probability table further increasing the probability of precipitation. Stay tuned for more information on Thursday morning.

 

5:00 PM: Rain Moving Out

12.29_2115As of 4 PM, the coastal low pressure was located near southern NJ, with a minimum pressure of 998 mb. The northern low pressure was located near southeast Ontario with a minimum pressure near 1002 mb. The two system are on track to merge tonight as the coastal low continues to strengthen and track northeast.

The rain has moved through faster than expected, with the back end of the precipitation shield over eastern Pennsylvania and about to move through the area. Drying conditions are expected between 5-6pm over northern NJ/SE NY, 6-7pm in NYC, and 6:30-7:30pm in western Long Island/SW CT and 7:30-8pm in eastern Long Island/SE CT. Rain totals are expected to generally end up in the 3/4″ to 1.5″ inch range, which is within the forecast range. While a changeover to heavy wet snow has occurred over the higher elevations of the Northeast, given the timing of the rain and the temperature profiles, the entire area is expected to remain with plain rain for the remainder of the event, although a few back end flurries can’t be ruled out over far interior areas with any lingering light precipitation.

 

12:30 PM: Steady Rain Continues

12.29_1700As of 12 PM, the coastal low pressure was located near north central North Carolina, with a minimum pressure near 1006 mb. The northern low pressure was located near southern Ontario with a minimum pressure near 1004 mb. The coastal low will continue to intensify and track northeast as it absorbs the northern low later tonight.

Since the last update, steady rain has spread into the area, with the heavier rain currently in the eastern Mid Atlantic, making its way into the area. Most of the region continues to see plain rain, except for northern Pennsylvania which has had some mixing with snow. As the precipitation shield continues to spread north into the cold air present close to the US/Canada border, snow will develop across northern NY state and interior New England, with rain elsewhere, including the NYC area. Rain is expected to end towards 6-8pm, with at least 3/4″ to 1″ of rain expected for most locations with locally higher totals.

 

8:45 AM: Rain Approaching

12.29_1330As of 8 AM, the coastal low pressure was located near western South Carolina. Minimum pressure is near 1009 mb, and the low is steadily tracking northeast. The northern low pressure was located near northern Michigan with a minimum pressure near 1006 mb. The coastal low is expected to track just east of NYC later this evening while continuing to intensify as it begins to absorb the northern low.

As mentioned with yesterday’s update, the cold air remains bottled up north of the northern low pressure and its associated frontal boundary over coastal Maine, which is keeping precipitation type as rain throughout the coverage area of the coastal low. Rain is falling heavily at times with the subtropical moisture brought up with the system, with up to 1-3 inches of rain generally observed throughout the southeast US. Rain will begin to fall by 10-11am from SW to NE, peaking in intensity around 2-6pm and continuing through at least 8-10pm before ending. Rain totals of at least 3/4 to 1.25 inch are expected, locally up to 1.5 inch. Temperatures this morning have been warmer than expected following yesterday’s temperatures nearly 4-8 degrees warmer than forecast, and will hold steady or slightly fall throughout the day with rain overhead.

Forecast Update: A storm system is expected to affect the region on Thursday, likely spreading widespread precipitation across the region. Precipitation type remains uncertain, however, as similarly to the last few snow events, very cold temperatures will be present north of the low pressure but with a strong thermal gradient likely setting up. For today’s outlook I included an 80% of snow in northern areas and rain/snow in southern areas, which is subject to some changes over the next few days. Snow accumulations remain uncertain, but with latest indications supporting the potential for at least light-moderate accumulations.

2 thoughts on “Dec 29, 2013 Storm Updates

    • NYC Area Weather Post authorReply

      While there is still not enough confidence to forecast a foot of snow in NYC, it would not surprise me to see the models continue to trend towards a more significant system than currently modeled, in which case the possibility would be there for at least parts of the region to reach a foot of snow, with New England the favored spot for the highest totals at this time, although this is still subject to change.

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