Oct 25, 2013: Cold, Frost Tonight; Rain Returns Next Week

[notice]Blog News: Radar archives are now being added to selected storms in the storm archives, such as the February 2013 blizzard and Hurricane Sandy.[/notice]

Forecast Highlights:

temp17A trough remains in place over the region with below average temperatures, as the first widespread frost of the season affected the area with similar conditions again tonight. Temperatures will slowly moderate towards average, but with chilly lows continuing through the middle of next week. The next storm will approach late next week, but with uncertainty regarding rain totals, which will be closely watched given the current developing drought. (Image credit: PSU e-Wall)

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Thursday, October 24 Observations:

10.24.13As Wednesday’s low pressure exited the region, having failed to produce much rain in the area, a broad upper level trough moved into the region, resulting in westerly winds, more sunshine and high temperatures peaking in the low to mid 50s across the area. Cold temperatures were observed in the morning with widespread frost away from NYC and the immediate coast, falling as low as 26 degrees in Sussex, NJ and 29 degrees in Westhampton Beach, NY. The highest temperature was 57 degrees in multiple locations, and the lowest temperature was 50 degrees in Port Jervis, NY.




Tonight – Monday: Near To Slightly Cooler Than Average Temps

A relatively strong cool air mass remains in place over the region, with 850 millibar temperatures near -4C, the coolest so far this fall. With the high pressure approaching the region but remaining to the south, the coldest temperatures are expected tonight, with lows falling into the mid to upper 20s inland, upper 20s to low 30s in interior Long Island, low to mid 30s for the north/west suburbs of NYC and southern CT, and upper 30s in NYC and the immediate coast. With these temperatures, widespread frost is expected again away from NYC and the immediate coast. A weak low pressure will track through southern Canada on Saturday, resulting in the current trough lifting out with a southwest flow developing ahead of the next trough. Windy conditions are expected with a SW wind at 15-25 mph, gusting up to 30 mph, with high temperatures reaching the low to mid 50s inland and the mid to upper 50s for the rest of the area.

The low pressure will remain north of the region, keeping its associated rain and snow showers to the north as well on Saturday night, with overnight lows in the mid to upper 30s inland and the low-mid 40s elsewhere, which will be followed by partly sunny skies and warmer temperatures on Sunday in the mid 50s inland and the upper 50s elsewhere. The next trough will fail to dig deep into the region, and temperatures are expected to warm up slightly on Monday, reaching the mid 50s inland and upper 50s to low 60s for the rest of the area, which is close to average.


Tuesday – Next Weekend: Rain Returns, Temperatures Warm Up

Pattern Analysis: The pattern over the last week was dominated by strong ridging in the northeast Pacific, partly as a result of frequent recurving typhoons in the West Pacific basin, including typhoons Francisco and Lekima which are currently recurving northeast off the coast of Japan, and will help to enhance ridging in the northeast Pacific towards Sunday and Monday with 500mb heights reaching 588-594 decameters. With the highly amplified ridging in place, a trough will dive sharply to the south into the western US, which will result in ridging aloft building across the eastern and southern US. Surface temperatures in the region will fail to warm up much from this week initially, however, as a strong high pressure builds in from Canada into the northern US and shifts east, bringing colder temperatures at the surface into the region for the early-mid week, especially in New England.

A surface low pressure will organize in the central US with the strong trough shifting east, as moisture from the East Pacific and Gulf of Mexico is pulled north/NE into the developing system, resulting in heavy rain and severe weather in that region. Meanwhile, a frontal boundary will extend northeast into the region by Wednesday and Thursday, with rain spreading in as well. The main uncertainty at this time is regarding the exact setup of the trough and low pressure, as the model guidance is struggling to handle the specific details of the setup with consistency, as well as the setup of the frontal boundary over the region which will determine the temperatures, and how much rain falls in the area; the latest model guidance supports heavy rainfall with over 1/2 to 1 inch, although this is subject to change considering the time range.

If the system remains progressive, rain would affect the area on Halloween, 10/31, and into November 1st, with the frontal boundary likely settling near or perhaps slightly north of the area. At this time, most model guidance supports this scenario, although it is possible the upper level trough is slower to exit the western US, in which case the strong Canadian high pressure would be able to shift east, with ridging building into the eastern US and widespread highs in the 60s returning into the region ahead of the frontal passage in early November. At this time, I am leaning towards a somewhat more progressive scenario than the ECM but with the low still taking some time to organize in the Midwest, which would lead to a brief warm up in the late week with the cold front moving through around next Friday, 11/1, but with the timing of rain and temperatures especially subject to change over the next few days.


Forecast for NYC Area: As a strong high pressure builds in from Canada, temperatures are expected to remain similar to those of this week, in the mid to upper 50s for highs and 30s for lows away from NYC and the immediate NYC coast, perhaps in the upper 20s for interior northern areas. As a low pressure gradually develops in the central US, increased cloud cover is expected by the second half of the week, with scattered showers possible on Wednesday and Thursday. A brief warm up is possible into the low 60s on Thursday and/or Friday ahead of the next cold front, which is likely to produce widespread rainfall but with amounts uncertain at this time. There remains uncertainty regarding the exact pattern setup in this time frame, with temperatures and the timing of the frontal passage, currently forecast for next Friday, subject to change over the next few days.


Late October 2013 Review: Less Active, But Dry

Over the last few years, October 29 has been a date of highly anomalous weather events; last year at this time, hurricane Sandy made landfall in southern New Jersey, becoming one of the worst storms in recorded history to affect the area, just a year after a major snowstorm affected the area on October 29, 2011. A few years back, another early major snowstorm affected interior parts of the area on October 28-29, 2008. Other years have had their share of anomalous mid-late October weather, such as 2010 with an abnormally intense low pressure in the Midwest and 2009 with a mid-month snowstorm for Pennsylvania and northwest NJ. For the first time in a few years, the month of October 2013 looks to end on a much quieter note, with the main highlight of the week expected to be rain from a cold front on 10/31 or 11/1.

Relative to the current pattern, however, this has the potential to be the most significant rain event in nearly a month, as the region has been much drier than average this fall, with Central Park only recording 0.30 inch of rain so far this month. This would place October 2013 as the 3rd driest October and 9th driest month on record based on current conditions. The US Drought Monitor‘s latest update has placed NYC, Long Island and coastal Connecticut under a moderate drought, noting that rainfall in Central Park is 7.39 inches below average since July, while the rest of the area is covered with abnormally dry conditions. This situation will continue to be monitored, especially should the next cold front fail to produce as much rain as currently modeled.

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