Sept 22, 2013: Colder Again; Frost Possible Mon Night

Forecast Highlights:

nam_namer_024_850_temp_mslp_precipA strong cold front moved through the area last night, with a much cooler air mass returning into the region expected to bring temperatures back to below average levels for the first half of the week with frost possible for interior locations on Monday night. A gradual warm up will take place for the rest of the week into next weekend, with mostly sunny skies and generally seasonable temperatures.

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Saturday, September 21 Observations:

9.21.13A strong cold front moved through the region, with a line of heavy rain and storms slowly approaching the area throughout the day. Partly cloudy skies were observed for most locations, with a localized heavy shower affecting Nassau and Fairfield counties in the early afternoon with 1/3 inch of rain. Cloud cover increased again in the evening as the line of storms approached, with heavy rain starting west of NYC around 9-10 PM, and east of NYC between 11 PM and 2 AM. Rain continued to fall through the early-mid overnight hours, with rain totals of at least 1/2 to 1 inch across most of the area. The highest temperature was 80 degrees in Teterboro and Newark, NJ, and the coolest high temperature was 72 degrees in Danbury, CT.



Today – Wednesday: Colder Temps Return, Frost Possible Inland

The cold front that moved through last night is currently near Maine, and is slowly moving to the east. The front will become negatively tilted, with a cutoff low pressure forming near Nova Scotia and persisting through Wednesday. This will keep the region under a trough with a northwest flow, bringing another round of chilly temperatures through Tuesday before slowly starting to moderate.

High temperatures are expected to reach the upper 60s inland and the low-mid 70s across the rest of the area today along with partly sunny skies and a breezy NW wind at 10-15 mph, gusting up to 20-30 mph at times. Mostly clear skies are expected tonight with lows in the 40s for most, with NYC near or slightly under 50 degrees. Monday will be the coolest day of the week, with sunny skies and highs peaking in the mid 60s across most of the area, likely struggling to rise above 65 degrees in NYC and northeast NJ.

The coolest temperatures are expected on Monday night, with clear skies and lows falling into the mid-upper 30s inland, upper 30s-low 40s in the high elevations of CT and the Long Island Pine Barrens, low-mid 40s in the north/west suburbs of NYC, mid-upper 40s in Long Island and coastal CT, and upper 40s-low 50s in NYC and the immediate coast. Temperatures will then begin to slowly rise, with sunny skies again on Tuesday with highs in the upper 60s to low 70s. An increase in cloud cover is expected on Wednesday as a shortwave trough moves through but without producing any precipitation, with highs in the low 70s for most of the area.


Late Week – Weekend: Gradually Warming Up

Behind the Wednesday shortwave trough, ridging will amplify over the central US in response to a strong trough digging into the western US, which will likely result in the shortwave diving southeast east of the region, keeping the NE US under a northwest flow aloft as another high pressure builds in from eastern Canada. This will keep the region under seasonable temperatures for Thursday and Friday, with highs in the low to mid 70s for most of the area, reaching near/a bit above 75 degrees in NYC and northeast NJ. By the weekend, the high pressure is forecast to slide over/east of the region, allowing for some of the warmer air mass from the west to enter; while temperatures are not expected to end up much above average, widespread highs in the mid 70s are likely with upper 70s possible near and southwest of NYC in the warmer case scenario.

By the weekend, a strong trough will likely be positioned over the northeast Pacific, resulting in ridging in the western US. The next cold front will approach the Great Lakes by Sunday, but there is uncertainty regarding the flow aloft in the western US and central Canada, with the possibility that the trough lifts north into Canada instead of continuing east into the region, which would result in a slower frontal passage sometime around early-mid next week and a delay in the next round of cooler temperatures. More information will be posted with the next pattern outlook to be posted tonight.

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