Oct 3, 2011: Frost Possible Late This Week

The cutoff low remained stationary over the region once again today, producing mostly cloudy skies, chilly temperatures, and scattered showers across the region once again. Temperatures across the NYC area were slightly cooler than yesterday, reaching the mid to upper 50s inland, upper 50s to lower 60s in the immediate NYC area, and the upper 50s to mid 60s in Long Island and southern Connecticut. Temperatures aloft warmed above the freezing point across the Mid Atlantic today, ending the mountain snows observed over the last 2 days, which have dumped as much as 8-9 inches of snow in the higher elevations of West Virginia and brought flakes as far north as Pennsylvania. Although snow can happen in the Mid Atlantic mountains in October, this much snow this early in the fall is uncommon.

The upper level low will slowly drift away from the area, with showers ending by Tuesday night across the area. As the cutoff low phases with a Canadian trough, a strong cold air mass will drop into the Northeast between Wednesday and Friday, keeping chilly temperatures in place while bringing the potential for frost in parts of the immediate NYC area, where temperatures will drop into the 30s away from NYC. As the trough exits by Friday, however, it will quickly be replaced by a significant surge of warmth, which will bring temperatures well into the 70s across the area for the weekend into early next week, and if the warmer case scenario verifies, we may not have seen the last 80+ degree days just yet.

Tonight’s Rain: With the upper level low drifting towards New England, the cutoff low pressure will drift towards New England tonight as well while intensifying. The cutoff low will bring a round of moderate rain across Long Island and southern Connecticut, which will amount to at least 1/2 inch, locally higher in some areas. From NYC and further west, lighter amounts are expected, with a few showers bringing less than 1/4 inch of rain. The rain will end by tomorrow afternoon across the area as the widespread rain reaches New England.

Tomorrow’s Outlook:

As mentioned above, the cutoff low will drift towards New England, ending the rain by the afternoon while bringing slightly warmer temperatures. With a NW wind expected, temperatures will warm up into the lower 60s inland and the lower to mid 60s across the rest of the area. Mostly cloudy skies are expected once again.

Wednesday – Friday: Cold Spell Brings Frost Potential

With the cutoff low phasing back into the main flow, the low pressure will quickly intensify while moving into Nova Scotia. Combined with a strong Canadian high pressure, this will pull down a strong cold air mass into the region. Due to the position of the storm, the cold outbreak will focus on New England, but the NYC area will be affected by the cold temperatures as well.

Ahead of the cold air mass, a brief surge of warmth is expected for Wednesday, with temperatures reaching the mid 60s to lower 70s across the area, which is near to slightly above the average for this time of the year. By Wednesday night, however, with a cold NW wind expected, low temperatures will drop into the lower to upper 40s across the area, with a few upper 30s possible inland. With the high pressure moving into the region on Thursday, sunny skies are expected with colder high temperatures, reaching the lower 60s inland, lower to mid 60s in the immediate NYC area, and the upper 50s to lower 60s in Long Island and southern Connecticut.

Thursday night will be the coldest night in the area. Due to the strong high pressure, clear skies and light winds are expected. With 850 mb temperatures likely near 2-4 degrees celsius, temperatures will quickly drop across the area, and are expected to reach the mid to upper 30s inland, upper 30s in southern Connecticut, upper 30s to lower 40s in Long Island, lower 40s in the north/west suburbs of NYC, and the mid to upper 40s in NYC. These conditions may be capable of producing the first frost of the season for the interior parts of the area.

As the cold air mass begins to exit the area on Friday, warmer temperatures will begin to return. The return of warmth will be slow at first, with Friday only slightly warming up, bringing high temperatures into the lower to mid 60s inland and the mid 60s across the rest of the area.

Next Weekend – Next Week: 80+ Degrees Return?

With the last cutoff system across the region, cold air was pulled into the region as it merged with a Canadian storm, and with the current cutoff low, another cold spell will be pulled into the region as it phases back into the main flow. With the low pressure late next week located over Newfoundland along with a strong high pressure over the region, however, there will not be any feature to pull in additional cold. With a strong trough moving into the west coast, the existing warmth in the western US will be forced eastwards, bringing widespread above average temperatures for the eastern US from next weekend through next week.

The warmth will start to move in on Saturday, with high temperatures likely reaching the upper 60s to mid 70s across the area. The warmest day will be on Sunday, with 850 mb temperatures expected to end up near 14 degrees celsius along with a west wind. These conditions will bring temperatures into the upper 70s across much of the area, and a few lower 80s are expected in the immediate NYC area. Similar temperatures are expected for Monday, possibly a degree or two lower.

By Monday and Tuesday, another weak trough will likely affect the Northeast, but it should stay further north, in northern New England, with temperatures staying in the 70s across the area. As the high pressure weakens, rain may gradually return into the forecast by the second half of next week. Stay tuned for more information on the longer range.

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