Nov 17, 2012: Pattern Lasts Through This Week

Forecast Highlights:

The drier pattern that has been in place since Wednesday will fail to break apart through the medium range, with a high pressure keeping dry conditions and little variation in temperatures sticking around through Sunday and the rest of the upcoming week as a coastal low pressure remains suppressed to the south and east. Beyond Friday, however, changes will begin to take place in the pattern leading up to December, starting with a likely cold spell around next weekend.

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Sunday - Friday: Pattern Continues

Since a cold front moved through the region on Tuesday, a high pressure stayed in place with dry conditions and high temperatures generally reaching the 40s, which is colder than average. The current pattern is still in place and expected to stick around through at least the next 7 days, with a high pressure on top of the region while a coastal low remains suppressed offshore, to the southeast of the area.

As the high pressure will be located to the north of the area, a persistent NE flow will continue, gradually turning more north by Wednesday. Little variation in temperatures is expected, with highs generally in the upper 40s to low 50s, slowly trending slightly warmer into the low to mid 50s by mid week, along with lows in the 30s for most of the area with mid to upper 20s for interior parts of the area. Mostly to partly sunny skies are expected through most of this time frame with increased cloud cover on Tuesday and Wednesday. By late in the week, the high pressure will shift south as a cold front approaches with winds switching to the west, resulting in additional warming in temperatures. Partly sunny skies are expected for Thanksgiving day with temperatures reaching the mid to upper 50s for highs, possibly reaching the low 60s in NE NJ.


Next Weekend - Beyond: Colder Pattern Develops

While uncertainty increases regarding the specific details in the forecast by this time frame considering this is 7+ days out, changes are expected in the pattern starting during this time period. A trough will approach the region by Saturday as 500mb heights slightly rise over the northwestern US, breaking the current zonal flow with little amplification. The model guidance is still having difficulty with this time frame, although the overall consensus is for colder temperatures for next weekend, likely below average again.

This will be the beginning of a pattern change going into early December, although should the pattern transition to a colder one, changes at least in the late November time frame are more likely to be gradual rather than abrupt and significant, especially with the eastern Pacific pattern not as supportive of persistent eastern US cold as the PNA remains close to neutral. The main focus is in the Atlantic side, however, where signals point to the potential for a -NAO to return late in the month or in early December. While the model guidance varies from run to run with this potential, including the timing and magnitude of the -NAO, the potential exists for a cold pattern going forward into December. More information on this will be posted with Tuesday's pattern outlook, which will also feature a preview of this year's winter outlook.