Nov 19, 2013: Gradually Warming Up; Weekend Rain

Forecast Highlights:

temp24After Monday morning’s frontal passage, bringing 1/4 to 1/2 inch in what was the most significant rain event since September and wind gusts up to/locally over 40 mph, unseasonable warmth was quickly pushed out last night as a much colder air mass returns for today and Wednesday, keeping high temperatures mostly in the 40s. The progressive pattern continues as highs return into the 50s by the late week, with some rain next weekend followed by an even stronger cool down. (Image credit: PSU e-Wall)




Today – Friday: Cold, Then Warming Up

A transient but strong cold air mass is currently located over the region, with 850 millibar temperatures near -6C to -8C. A breezy NW wind is expected today up to 15-20 mph, with gusts locally up to 30-35 mph. Although the 24-hour high temperatures peaked at midnight, daytime high temperatures are expected to reach the low-mid 40s inland and mid-upper 40s elsewhere. As a strong high pressure moves overhead, clearing skies and decreasing winds are expected tonight, with lows falling into the upper 10s-low 20s inland, low-mid 20s in southern CT and interior Long Island, mid to upper 20s in the immediate suburbs of NYC, and upper 20s-low 30s in NYC and the immediate coast. Clear to mostly clear skies are expected tonight into Wednesday, with highs expected to reach the low to mid 40s inland and mid to upper 40s elsewhere.

The progressive pattern continues this week as the cold air mass quickly moves out of the region by Wednesday night, with warmer temperatures for Thursday and Friday as another trough digs into the north central US with ridging returning to the eastern US. Partly sunny skies are expected on Thursday with highs in the upper 40s-low 50s, with a continued warm up into the low to mid 50s on Friday but with mostly cloudy skies ahead of the next approaching storm.


Friday Night – Monday: Some Rain, Then Much Colder

Storm Analysis: Towards the second half of next week, a cutoff low is expected to end up stalled over southern California, with a ridge placed to its north. Ridging will continue through late next week over the eastern US into eastern Canada, squeezed in between the trough dropping into the north central US and a closed upper level low near Atlantic Canada, partly associated with the soon-to-be remnants of subtropical storm Melissa, the latest addition to this year’s unusually inactive Atlantic hurricane season. Given the setup, the trough entering the northern US will amplify with a surface low pressure expected to form near the north central US. From there, the model guidance significantly diverges with the track, ranging from the GFS with a strong 980mb low pressure tracking through the Great Lakes and Canada, to the ECM bringing a fast moving, weak wave of low pressure through the Northeast.

While the general storm track so far this fall has been similar to that of the GFS, cutting through the Great Lakes, in this case it is likely too amplified, strong and too far north, especially when considering all of the GFS ensemble members are less amplified than the operational run. Given the setup with ridging and a lack of cold air ahead of the storm, and the overall progressive pattern, precipitation type is expected to be rain for the majority of the region, with any snow likely limited to northern-perhaps central New England. At this time, I am siding towards a somewhat stronger low pressure than the ECM tracking through the central-northern Northeast region, producing light to moderate rain across the region with the highest rain totals once again north of the area, although the exact scenario is subject to some changes over the next few days.

Despite differences with the storm track, however, there is much higher confidence for what is expected to be the strongest cold surge this fall reaching the region by Sunday. The storm and cold front moving through will allow a strong cold air mass that has been building up over Canada to spill into the region, with 850mb temperatures likely in the -12C to -16C range. While the exact intensity of the cold partially depends on the setup of the weekend storm, widespread below average temperatures are expected, along with windy conditions on Sunday due to the tight pressure gradient behind the cold front.

Forecast for NYC Area: While there is some uncertainty with next weekend’s outlook, a likely scenario at this time is for occasional light to moderate rain showers to affect the area on Friday night into Saturday, with the highest rain totals north of the area. Temperatures are likely to stay mild, in the 40s for lows and low-mid 50s for highs, with any snow remaining well to the north of the area. Behind the low pressure/cold front, the strongest cold surge of this fall is likely, with strong NW winds on Sunday at 15-30 mph, gusting up to 30-40 mph, along with high temperatures likely struggling to rise above the mid 30s, perhaps even struggling to reach 30 degrees inland in the colder case scenario. The coldest temperatures are likely overnight, with widespread lows in the 20s for most and 10s inland.


Thanksgiving Preview: Fluctuating Temperatures, Storm Potential

As Thanksgiving enters the 10-day range, there are some hints regarding the potential setup towards the second half of next week. Given the continued progressive mid-upper level flow and the strong weekend trough lifting north into Canada following the transient ridging near Greenland (east based -NAO) likely moving out, a moderation in temperatures is expected towards next Tuesday and/or Wednesday, returning back into the 40s for highs. The longer range models have hinted at a storm potential towards late next week, however, as the upper level low stuck under the western North America ridging is able to move east through the southern US by early-mid next week, but with uncertainty regarding its track and how it interacts with the jet stream to the north. As should be expected in the 10-day range, there is a wide variety of solutions showing up on the models, ranging from a suppressed rain storm on the GFS, to a rain/snow mix on the ECM/CMC, or no storm on some of the previous runs. At this time, it is too early to determine the specifics of the setup in this time frame, although the potential for a storm in the late week time frame will continue to be monitored as this time frame enters the 7-day range.



<< November 16 | Nov 17 | Nov 18 | November 19 >>

Monday, November 18 Observations:

11.18.13A weakening cold front associated with Sunday’s severe weather outbreak in the Ohio Valley spread into the area early on Monday morning, producing a short round of locally heavy showers and strong wind gusts, up to and locally over 40 mph with the heavier showers. Rain totals were generally near 1/4 inch, with a storm total of 0.25″ in Central Park, making it the 3rd biggest rainstorm this fall. Temperatures reached the low to mid 60s early in the morning just ahead of the frontal passage, slightly falling in the morning before rising again into the mid 60s during the afternoon. The highest temperature was 67 degrees in multiple locations, and the coolest high temperature was 61 degrees in New Haven, CT.

Sunday, November 17 Observations:

11.17.13Mainly cloudy skies were observed across the area along with areas of fog as clouds and isolated showers spread in from the west ahead of a major severe weather outbreak in the Ohio Valley. Little to no rain fell, with amounts generally below 0.05 inch. Temperatures remained mild, however, generally peaking in the low to mid 60s for most. The highest temperature was 64 degrees in Newark, NJ, and the coolest high temperature was 59 degrees in Danbury, CT and White Plains, NY.

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