Dec 9, 2013: Snow Likely Tomorrow

Forecast Highlights:

cld36After relatively poor short range forecasts and model guidance verification for the last two storms, including much less snow than expected on Friday in PA/NY and a surprise 10-14 inches of snow in Maryland/south NJ on Sunday, another event appears to be on the way as a light-moderate snow event is expected for Tuesday, with the possibility of 1 to 4 inches of snow in parts of the area. Behind this storm, colder than average temperatures will return with highs in the mid 20s-low 30s and lows in the 10s (Image credit: PSU e-Wall).




Today – Tomorrow: Light Rain Today, Snow Tomorrow

Since last night’s previous storm update, the steady moderate to heavy precipitation remained to the south, towards central NJ into the Mid Atlantic, but as surface temperatures remained near to slightly below freezing, most of the area observed steady light freezing drizzle/showers overnight into the early morning, only recently changing to plain rain in the north/west suburbs of NYC. No reports of ice have been published yet by the National Weather Service, although airport observations show at least 0.05 to 0.10 inch of precipitation having fallen as freezing rain north/west of NYC. As temperatures continue to slowly warm up, the area will change over to rain extending further inland from 7-10am, with scattered showers expected through the late morning to early afternoon as high temperatures reach the upper 30s to low 40s for most. For locations that observed accumulating freezing rain, hazardous road conditions are expected this morning.

The biggest change in the forecast comes for Tuesday, however, as the model guidance has unexpectedly trended towards a weak wave of low pressure developing along the front close enough to produce widespread light to moderate snow across the I-95 corriodor and further east on Tuesday, mainly in the morning and afternoon hours. The NAM, which has a long history of incorrectly handling storms even in the short range, has been surprisingly consistent with showing this potential, along with the GFS which yesterday increasingly trended towards this solution while the ECM, CMC and UKMET models did not begin to show more than scattered snow showers until last night’s 0z runs. The main uncertainty is the accumulations, as the exact axis of moderate snow is uncertain, with the potential for 3-6 inch accumulations along this axis. At this time, I included 1-3 inches north/west of NYC and 2-4 inches near and south/east of NYC, although this outlook is subject to some changes. A brief update will be posted later today if necessary, otherwise the next update will be posted on Tuesday morning.


Wednesday – Friday: Cold Returns; Highs In 20s For Thursday

Behind tomorrow’s storm, the next round of frigid temperatures will dive south from central Canada associated with the continuation of strong blocking near Alaska, and will approach the region by the mid week. With a flattening ridge in the western US, the core of the air mass will remain well to the north, but with enough cold sliding into the region to support a return to below average temperatures. Partly cloudy skies are expected on Wednesday with highs in the upper 20s-low 30s inland and low-mid 30s for the rest of the area. Cold temperatures are expected overnight, falling into the 10s for most locations north/west of NYC and in southern CT. The coldest temperatures are expected on Thursday, with partly sunny skies, a westerly wind at 5-10 mph, and highs in the mid-upper 20s inland and the upper 20s to near 30 degrees for the rest of the area. Temperatures overnight are forecast to fall into the low 20s in NYC and 10s for the rest of the area, with the possibility of sub-10 degree lows towards NW NJ and interior SE NY. A slight moderation in temperatures is then expected for Friday with mostly sunny skies and highs in the upper 20s to low 30s.


Weekend – Next Week: Rain/Snow Possible, Then Colder Again

The next area of uncertainty exists towards next weekend, when the next storm may affect the region. There remains a significant spread in the model guidance regarding the setup, although there is more confidence regarding some sort of a storm system affecting parts of the region. At this time, I included a chance of light rain/snow in the forecast, although this is a very preliminary outlook and subject to change. Behind the storm, the next feature to watch is the polar vortex over southern Canada, as currently the forecast is for temperatures to return closer to average, although the possibility is there for the frigid air mass to briefly dip south into parts of the region. More information will be posted on the weekend storm potential and the cold possibility as details become clearer over the next few days.



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Sunday, December 8 Observations:

12.8.13Read more: December 8 Storm Updates

As another system entered the region, widespread snow developed across the region; the heaviest snow fell in Maryland into Philadelphia and southern NJ, where unexpected heavy snow accumulated up to 8-12 inches. The area was in the north end of the snow, with up to 1 inch of snow recorded, locally higher in some locations. Temperatures slowly warmed up overnight as coastal locations changed to light rain and interior locations changed to light freezing rain with highs generally in the upper 20s to low 30s. The highest temperature was 35 degrees in Montauk, NY, and the coolest high temperature was 29 degrees in Port Jervis, NY and Andover, NJ.

Saturday, December 7 Observations:

12.7.13Behind Friday night’s wave of low pressure, colder temperatures gradually entered the region as an arctic air mass in the north central US continued to spread towards the region. After an unseasonably warm first 6 days of the month, temperatures cooled back down to near to slightly below average, in the mid to upper 30s inland and the low 40s for the rest of the area. The highest temperature was 43 degrees in JFK airport, and the coolest high temperature was 37 degrees in Sussex, NJ and Andover, NJ.

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