Dec 5, 2012: Rain Returns Weekend, Next Week

Forecast Highlights:

Following another unseasonably warm day on Tuesday, slightly colder but still above normal temperatures returned today (Wednesday) behind a cold front, with chilly temperatures sticking around through Thursday night. The cool temperatures will only be short lasting, however, as a warmer air mass returns for the weekend into early next week with persistent cloud cover and occasional showers, peaking on Monday into Monday night as another cold front moves through the region.

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Tonight - Friday: Chilly Temperatures Continue

The coolest temperatures of the current cold air mass are expected tonight, with lows dropping into the low to mid 20s inland and the mid to upper 20s for the rest of the area except for NYC and the immediate coast, which should be slightly warmer. Chilly temperatures are expected for Thursday, only peaking in the upper 30s to low 40s across the area, a significant change from the widespread 60s observed 1-2 days ago. This will be the peak of the cool spell, however, with slightly warmer lows on Thursday night in the mid 20s inland and upper 20s to mid 30s for the rest of the area, although Friday's temperatures will only be slightly warmer, in the low to mid 40s from NYC and further north/west and in the mid to possibly upper 40s further east due to increasing cloud cover.


Saturday - Tuesday: Warmer, Rainy

A more active pattern will develop for this time frame, with mainly cloudy skies and occasional showers from Friday night through Tuesday. The first part of this time frame through Sunday will contain generally scattered showers as opposed to widespread showers, with the steadier showers mostly north of NYC. Highs for the weekend are likely to be in the upper 40s inland and in the low to mid 50s for the rest of the area.

The models continue to show differences with the exact scenario for the stronger low pressure in the early week, but with ridging in the southeastern US along with the trough axis near the central US, the low pressure is expected to track north and west of the area, with a mild rain expected. Due to this north and west track, most of the rain will stay to the north and west as well, with a cold front moving through on Monday night and/or Tuesday resulting in additional rain. Temperatures ahead of the front on Monday are expected to surge well into the 50s across the area and into the low 60s for some, especially southwest of NYC. Stay tuned for more information on this time frame.


Longer Range: Trending Colder, But No Persistent Cold Pattern

The model guidance is still in disagreement with the specifics regarding the pattern towards the medium to long range, but there are signs that the pattern overall should gradually trend cooler for the area behind the early week storm, but still not quite changing to a persistent cold pattern with frequent snows for the region. The Pacific pattern remains unfavorable for a persistent cold and snow pattern in the region, especially with a neutral to slightly positive EPO persisting along with a solid negative PNA, as there is ridging near the northeast Pacific, but the ridging is offshore with troughs likely to drop into the western and central US. Despite this Pacific pattern, the medium range model guidance is suggesting that a stronger, more central or potentially west based -NAO block develops. Some of the models, especially the GFS and GEFS, may be overdoing these changes or bringing them too quickly, but even with the potential blocking near Greenland, with the current Pacific pattern in place this is still unlikely to result in a persistent cold and snowy type pattern as observed during the winter of 2010-11, for example. Instead, the storm track is likely to remain to the west of the area, with a few snow events possible towards the middle of the month but with the best chance of more sustained cold and frequent snow events more likely towards the central US and perhaps including the Northeast. More information on the longer range will be posted with the next medium range pattern outlook on Sunday.