Jan 13, 2013 Brief Update

Short Range: Rain on Tuesday, Cooling Down

Frequent temperature swings continued over the last 10 days; following last week’s highly anomalous cold blast as a piece of the polar vortex over Canada split and approached the US, with daytime highs only reaching the single digits and low 10s, the progressive pattern continued as the cold air mass lifted back north into northern Canada with highs returning into the 50s. A strong mid level shortwave trough is currently situated over the southern US, and will rapidly track northeast on Tuesday while consolidating as a weak surface low reflection forms near the coast. Given the lack of any nearby cold air mass and the initial warm temperatures, precipitation type will be rain, which will continue through Tuesday evening with up to 1/4 inch of rain expected. Highs are generally expected to peak in the 40s.

With persistent ridging expected to develop near the western US, a trough is expected to set up over the eastern US with a series of shortwaves diving southeast into and amplifying over the region, continuing the progressive pattern theme. The first will move through around Wednesday night into early Thursday, with highs in the upper 30s to low 40s and scattered rain showers as a low pressure develops near the coast and progresses northeast towards Atlantic Canada. Uncertainty increases by Friday into Saturday with typical model variations, as the ECM depicts a stronger coastal low developing near NYC, while the GFS remains weaker and more progressive with no precipitation. At this time, a setup closer to the ECM is favored with rain and/or snow showers possible mostly during Friday night, although both systems are currently unlikely to produce significant precipitation over the area. Highs are expected to reach the mid to upper 30s, cooling down into the low-mid 30s by Sunday before gradually warming up next week.

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