Nov 12, 2013: Cold Tonight, Tomorrow; Rain Next Week

Forecast Highlights:

temp18Behind this morning’s light snow event, which produced totals locally up to 1-2 inches northeast of NYC, a strong cold air mass entered the region with the coldest temperatures so far this fall with widespread low temperatures below 30 degrees and localized lows below 20 degrees inland. Chilly temperatures will continue into Wednesday, but with a quick late week warming trend as high temperatures return into the 50s and 60s by the weekend and early next week ahead of the next rain event (Image credit: PSU e-Wall).




Tonight – Saturday: Cold Start, Then Warming Up

A cold front moved through the area late last night, but with most of the precipitation falling behind the surface cold front. With a much colder air mass entering the region, temperatures were cold enough to support a changeover to snow across the area this morning, resulting in the first widespread snow event of the winter. Most of the snow was focused over Long Island and Connecticut where minor accumulations up to 1/2 inch were generally reported, locally higher in parts of southern CT with a report of 2.0 inches in Ridgefield, CT (Fairfield county).

The core of the cold air mass is currently centered over the region, with 850 millibar temperatures near the -10C to -14C range. A steady northwest wind at 4-8 mph is expected to continue tonight with a pressure gradient in place and continued cold air advection, although mostly clear skies are expected which should allow for cold temperatures, with temperatures falling into the upper 20s-low 30s in NYC, low-mid 20s in the north/west suburbs, southern CT and Long Island, and the upper 10s for interior NE NJ/SE NY and higher elevations of CT. Locations that have yet to experience sub-freezing temperatures are expected to reach and fall below 32 degrees tonight. Mostly sunny skies are expected on Wednesday with highs struggling to warm above the mid to upper 30s.

The cold air mass will be quickly removed from the region, however, as ridging aloft builds into the region as more persistent lower heights set up over the western half of the US, along with the strong surface high pressure extending south of the area, setting up for a west-SW flow which will quickly bring a much warmer air mass into the region with 850mb temperatures reaching the 6-8C range. After another cold night with widespread lows in the 20s, temperatures on Thursday will warm into the mid to upper 40s with mostly sunny skies, and the low to mid 50s on Friday, returning closer to average. An increase in cloud cover is likely starting on Saturday with highs reaching the mid to upper 50s range, perhaps near 60 degrees in NYC and northeast NJ.


Sunday – Next Week: Warming Up, Rainy, Then Cold Again

Pattern Overview: As previous updates have mentioned, an anomalously strong ridge is currently stationed over the north central Pacific, with 500 millibar heights up to 588 decameters nearly as far north as the Aleutian islands, which is over 48 dm higher than average. Meanwhile, a strong upper level low is located to its east, off the western US coast. The upper level low will continue to slide west underneath the ridging, allowing the ridge to expand further east towards the northeastern Pacific around the same time that a strong shortwave trough tracks around the ridging, over Alaska before diving sharply south towards the western US. By early next week, a strong low pressure is likely to develop near Alaska, which is likely to continue the progressive theme of this pattern, with the northeast Pacific ridging expanding east into the west-central US as the aforementioned trough progressively moves east through the eastern half of the US, bringing a strong cold front and a transient but strong cold air mass before temperatures likely moderate again towards the end of next week.

Forecast for NYC Area: The region is expected to remain under a warm air mass until the frontal passage, with scattered showers spreading in on Sunday and Monday. Most of the model guidance keeps these showers north of the area, which appears reasonable given the overall setup and the trend of underperforming rainfall events in the area this fall, although a risk of rain is still possible during these days. Temperatures are likely to stay in the 50s on Sunday, but are likely to climb into the low to possibly mid 60s on Monday, with overnight lows struggling to fall below the upper 40s-mid 50s with the cloud cover and warm air advection.

A strong cold front is then likely to move through around the middle of next week; exact timing is uncertain, although at this time a Tuesday frontal passage is likely. While moderate to locally heavy rain can’t be ruled out, the amount of rain that falls is somewhat uncertain, especially given previous strong frontal passages this fall where the model guidance overestimated the rain totals. At this time, a reasonable call is for near 1/2 inch of rain, possibly higher with the highest amounts staying north and west of the area, although rain totals could be enhanced if the cold front slows down over the region and/or a wave of low pressure forms along the front. Behind the cold front, colder and windy conditions are expected to return for mid-late next week with widespread lows in the 20s and highs likely in the 30s-lower 40s range. At this time it does not appear this cold air mass will become sustained, with a warm up likely again towards the end of next week and/or next weekend, although a sustained warm pattern also appears unlikely for the last 10 days of November with the continued progressive pattern. Stay tuned for more information on next week’s outlook.

2 thoughts on “Nov 12, 2013: Cold Tonight, Tomorrow; Rain Next Week

    • NYC Area Weather Post authorReply

      I’ve been too busy to update them recently; I plan to add the November 1-14 daily observations in their respective posts by this Saturday.

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