Oct 4, 2012: Chilly Rain Expected Sunday

Forecast Highlights

– Sunshine briefly returns on Friday; highs in 70s
– Clouds, rain, colder temperatures this weekend
– Cold, warm, then chilly again next week



Tonight – Weekend: Briefly Warm, Then Cloudy, Chilly, Rainy

Mostly sunny skies will briefly make a return on Friday with above average temperatures expected, peaking in the mid 70s to lower 80s across most of the area, slightly cooler towards coastal areas with the warmest temperatures near NE NJ. The break from the persistent clouds and showers will only be brief, however, as a strong cold front approaches the region on Saturday with a stronger cold air mass behind it. Prior to the passage of the cold front towards Saturday evening, temperatures will climb into the mid to upper 70s for most of the area, slightly cooler in far western and eastern areas with highs in the low to possibly mid 70s. The cold front will move through the area during the afternoon to evening hours; while most of the shower activity is expected to dry up before reaching the area, at least a period of light to locally moderate showers is likely around the same time period. The cold front will be followed by a noticeable temperature drop into the 50s and low 60s, dropping overnight into the 40s away from NYC, perhaps the upper 30s in interior northern areas.

A coastal low pressure will develop along the cold front on Sunday, affecting the area with cloudy skies and showers. The model guidance has not settled on a single solution for this storm yet; extremes range from the 0z ECMWF, which showed a stronger low pressure producing moderate to heavy rain with high elevation snows in the Northeast, while the GFS has a weak low pressure with only light rain for the area. Regardless of the exact outcome, rain is expected to fall, although the intensity remains uncertain. Showers are expected throughout the day on Sunday, especially after the late morning hours, with high temperatures likely peaking in the morning hours in the low 50s inland, mid to possibly upper 50s in the immediate NYC area, and upper 50s to possibly low 60s in Long Island and southern Connecticut. Temperatures will then drop into at least the upper 40s to low 50s from NYC and further north/west as the showers develop, with the showers expected to end towards the early overnight hours as temperatures drop into the upper 30s inland and the 40s for the rest of the area. The storm will not be a significant rain producer, with at least 1/2 inch, perhaps a little lower/higher for some areas, likely.

While several models show temperatures at 850mb to end up near or below zero degrees Celsius, which during the winter time is typically used to determine the rain/snow line, there will not be any snow associated with this storm in the area. The low pressure is weak and there is not much heavy precipitation associated with the low, with a warm boundary layer expected which will prevent this from producing snow. Especially if the storm ends up further north/west closer to what the ECMWF shows, however, a few back end flakes would not be out of the question for the higher elevations of the Northeast.

Next Week: Cold, Warmer, Then Cold Again

Behind the wave of low pressure, the cold air mass will move into the region, with highs on Monday only in the mid to upper 50s inland and the upper 50s to low 60s across the rest of the area. Cold overnight lows are expected again with clear skies, likely dropping into the mid 30s inland and the upper 30s to mid 40s for the rest of the area except for NYC, in the upper 40s.

As the ridge off the coast of the western US amplifies, a frequent feature of this fall’s pattern, yet another trough will drop into the central US with a low pressure developing near the Great Lakes region. As a result, the cool air mass will move out of the region with a short warm up ahead of the next cold front on Wednesday. Highs are expected to warm back up into the 60s, with showers likely from the cold front on Wednesday. Behind the cold front, another cool air mass will enter the region, although the western US ridge will become less amplified as the strong -EPO and moderately positive PNA moderate. Cool temperatures are expected to stick around through late next week, perhaps next weekend, and although it does not appear that a persistently warm pattern should develop, a moderation in the current pattern is likely for the longer range. Stay tuned for more information on the longer range outlook.

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