Temperatures will continue to gradually warm up today and on Friday, returning into the mid 50s for highs, along with scattered showers on Friday-Saturday but with minimal rain totals. A strong cold surge will enter the region on Sunday and Monday, bringing the coldest temperatures of this fall with winter-like temperatures, barely reaching 32 degrees for highs and falling into the mid 10s-low 20s away from NYC and the coast. This cold will be transient, however, with moderating temperatures by the mid week followed by a possibility of rain by the middle of next week.
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Wednesday, November 20 Observations:
With the cold air mass in place following Tuesday’s midnight high temperatures, colder maximum temperatures were recorded on Wednesday, in the low to mid 40s across the area, at least 6-10 degrees below average. Mostly sunny skies were generally observed with a strong high pressure nearby, with a decreasing northerly wind. The highest temperature was 47 degrees in Somerville, NJ, and the coolest high temperature was 41 degrees in Montgomery, NY and Sussex, NJ.
Today – Saturday: Warmer Temps, Some Showers
With a strong high pressure moving through last night, cold temperatures were observed this morning away from NYC and the coast, with lows near 16 degrees in Sussex, NJ and Montgomery, NY. With strong radiational cooling due to clear skies and light winds, Long Island was able to significantly cool down as well, with a low of 19 degrees in Westhampton Beach, NY. Temperatures have quickly rebounded afterwards, however, with light southerly winds expected today along with partly sunny skies and highs reaching the upper 40s to low 50s. Cloud cover will increase overnight into Friday, however, as a fast moving cold front associated with a weak wave of low pressure near northern Maine passes through the region.
12z run of the high resolution 4k NAM, for 12z Friday (7 AM), depicting an area of light rain focused mostly north of NYC (image credit: NCEP MAG).
The timing of the front has slightly changed from the previous forecasts, however, with occasional showers now expected on Thursday night into Friday morning ahead of the front, followed by another round on Friday night associated with the actual front. Rain amounts are generally expected to be minimal, less than 0.1 to 0.2 inch, with the highest totals north of NYC. In between the two rounds of light rain showers, temperatures are expected to rise into the low to mid 50s across the area, perhaps above 55 degrees near and/or southwest of NYC. Saturday is now expected to be dry, with partly sunny skies, a breezy NW wind at 10-15 mph, and highs reaching the low-mid 40s inland and mid-upper 40s for the rest of the area.
Sunday – Tuesday: Very Cold, Windy, Possible Snow Showers
While temperatures will cool down on Saturday, the strongest cold won’t arrive until Sunday, however, behind a second cold front moving through on Saturday night. A strong cold air mass has been building up over western Canada over the last few days, and along with ridging building over the western US, this air mass will be able to spill southeast into the eastern US behind Saturday night’s cold front, bringing the coldest temperatures of this fall. Widespread unseasonably cold 850 millibar temperatures of -14C to -18C are expected across the region, typical of an average wintertime cold surge, which along with a tight pressure gradient on Sunday setting up for strong cold air advection and windy conditions, will make Sunday feel more like January than late November. With the trough axis moving through the area on Sunday, partly cloudy skies are expected with the possibility of isolated snow showers across the area.
12z NAM for Sunday, showing the tight pressure gradient, strong NW winds, and cold high temperatures; this run may be 1-2 degrees too cold for some (image credit: PSU e-Wall).
The 24-hour high temperatures on Sunday are expected to occur at midnight, peaking in the mid-upper 20s inland and the low-mid 30s from NYC and further east/south. This will be as warm as temperatures get, however, as with the aforementioned strong cold air advection, partly sunny skies and a strong NW wind at 20-30 mph, gusting up to 40-45 mph, very cold temperatures are expected with unseasonably cold afternoon high temperatures, peaking in the mid to upper 20s inland and upper 20s to low 30s for the rest of the area; based on latest indications, it is possible the entire area may fail to rise above 32 degrees during the day. Along with the strong winds, wind chill values during the day are expected to end up in the 15-25 degree range. These temperatures are approximately 20 degrees below average, and are even colder than the average high temperatures in January.
The coldest temperatures are expected overnight, with the high pressure moving overhead resulting in clearing cloud cover along with very cold temperatures aloft. A continued NW wind will somewhat limit how cold temperatures will end up, especially for interior locations, but with the immediate NYC area likely approaching record lows. Temperatures at this time are likely to fall into the low to mid 10s in interior NW NJ/SE NY and interior CT, mid 10s to low 20s in the north/west suburbs of NYC, southern CT and Long Island, and the mid 20s in NYC and the immediate coast. While winds won’t be as strong as during the day, wind chill values in the single digits to low 10s are likely inland. Temperatures will slightly warm up on Monday into the low-mid 30s inland and mid-upper 30s for the rest of the area with mostly sunny skies as the cold air mass begins to moderate.