Sept 26, 2012: Rain, Chilly Temperatures Return

Forecast Highlights:

- Mostly cloudy skies to persist through Monday
- Chilly rain expected on Friday; sub-60 highs possible inland
- Showers possible Saturday through Monday
- Warm up expected by middle of next week

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Tonight - Thursday: Scattered Showers, Cooling Down

The latest radar shows scattered showers across parts of New York and Pennsylvania. Scattered showers are possible throughout tonight and Thursday at times with mostly cloudy skies persisting; originally, Thursday was expected to clear out, although the front will fail to progress as far south as originally expected, instead slowing down and stalling over the region rather than dropping south and then retreating north. Temperatures on Thursday will reach the upper 60s to low 70s inland and the low to mid 70s across the rest of the area.


Friday - Monday: Cloudy, Chilly, Rainy

A weak wave of low pressure is expected to move through the region, producing a round of rain on Thursday night into the first half of Friday. There is still some uncertainty regarding exactly where the heavier rain axis sets up and how much rain falls, which will also influence the temperatures, although at this time there is a high probability of at least a steady moderate to locally heavy rain to focus from NYC and further north/west especially in the first half of Friday. If the currently modeled scenario verifies, high would end up in the mid to upper 50s north/west of NYC and in the low to mid 60s from NYC and further east. Some of the latest models are further north, however, with the latest NAM run taking almost all of the rain north of the area with highs in the upper 60s to low 70s. For tonight's forecast, I am siding with a scenario north of the model consensus, with highs potentially in the mid 60s inland and the upper 60s across the rest of the area. With the aforementioned uncertainty, the forecast is still subject to some changes. Stay tuned for more information on Friday's forecast with updates on Thursday.

It does not appear that a stronger organized area of low pressure will develop, although showers and clouds will persist across the region throughout the weekend, mostly focusing over New England but with scattered showers across the area, mainly east of NYC but extending west of NYC occasionally as well. Temperatures will be slightly warmer, in the mid to upper 60s on Saturday with more widespread upper 60s on Sunday, perhaps getting into the low 70s in the immediate NYC area. Additional showers are expected for Monday with highs similar to those of Sunday. More information will be posted on this time frame as details become clearer.

With the additional chilly temperatures expected, the possibility may be there that parts of the area could end up slightly below average for the month of September; since early 2011, the majority of the area failed to have any cooler than average months. More on this possibility will be posted over the next few days.


Longer Range: Warming Up

The persistent trough pattern that has been in place since 9/15 is expected to break down early next week, with a less amplified pattern returning as ridging temporarily rebuilds into the East. A surge of warmth is expected to move into the region with temperatures reaching the 70s across parts of the region, including NYC on Tuesday, and a larger part of the region on Wednesday. Afterwards, model differences emerge again, with the GFS quickly bringing a cold front followed by a strong cold air mass, while the ECM and CMC keep a warm pattern in place through next weekend. At this time, I am considering the 18z GFS scenario a likely outlier, with a strong cold pattern unlikely to return in the medium range. Stay tuned for more information on the longer range outlook.