Oct 19, 2010: Cold Friday, But Warmer Weather To Follow

Today started out mainly cloudy, with showers in parts of the area due to a wave of low pressure that brought up to 1 inch of rain in south-central PA and NJ, though skies cleared by the afternoon, with high temperatures rising into the upper 50s across most of the area other than a few lower 60s in the immediate NYC area.

Tomorrow’s Outlook:

Partly sunny skies are expected for the area tomorrow, with a SW wind. The air mass will remain similar to today, but slightly warmer, leading to slightly warmer temperatures. High temperatures will rise into the lower 60s inland, lower to mid 60s for the immediate NYC area, and lower 60s for Long Island/S CT.

Another wave of low pressure is expected to be active tomorrow morning, however it will be further south than today’s wave, with the low pressure expected to be off the Carolinas, producing locally moderate to heavy rain from Virginia into the Delmarva, where amounts locally up to 1 inch or slightly higher are expected. The rain will stay to the south of the NYC area.

Thursday – Saturday: Cold Spell, Widespread Frost Possible

On Thursday, a low pressure well to the north of the area will bring down a strong trough into the Mid Atlantic and Northeast, which will bring scattered showers to the area with highs in the mid to upper 50s inland and upper 50s to lower 60s in the immediate NYC area.

This air mass will be cold enough that it will be able to produce snow showers on Thursday night for a large part of New York State, and some flurries may even reach the interior parts of the area if it gets cold enough and there is precipitation. Low temperatures are expected to be in the lower to mid 30s inland, mid to upper 30s for S CT and the north/west suburbs of NYC, upper 30s to lower 40s for Long Island, and mid 40s for NYC.

Friday will be the coldest day of this cold spell. With the coldest 850 mb temperatures during Friday afternoon near -4c, this will lead to the coldest high temperatures yet for most of the area under dry conditions, with highs currently expected to be in the lower 50s inland and the mid 50s for the immediate NYC area as well as Long Island/S CT.

Friday night will have similar low temperatures to Thursday night, though the trough will start to exit around this time as another low pressure approaching the Great Lakes will push this trough quickly to the east while another trough develops behind the second low pressure. The second trough, however, won’t dig as far south as this one.

Saturday will bring a return of warmer temperatures as the trough exits the area and a low pressure is well to the north of the area. Partly sunny skies are expected with highs in the upper 50s to mid 60s across the area, but increasing clouds are expected on Saturday night, marking the start of a wet time frame from Sunday to Wednesday.

Sunday – Monday: Warmer, But Wetter

On Sunday, as the second trough settles in the Northeast, bringing dry conditions and cold temperatures for northern New England, the area will be south of the trough, with a low pressure near the Ohio Valley approaching the area. This will lead to occasional showers throughout the day, but with the warmer air mass, high temperatures will warm into the lower to mid 60s for most of the area.

On Monday, the trough will start to exit the Northeast as the low pressure pushes northeast, and the area will still see occasional showers but with warmer temperatures, near the upper 60s for the immediate NYC area.

Tuesday And Beyond: Storm Potential

For the middle of next week, the pattern will be dominated by an intense storm in the north central United States. Looking at the overall scenario, a low pressure entering the NW US on Saturday will be in south central Canada on Monday, and will likely merge with a rapidly developing low pressure to its south on Tuesday to form an intense low pressure located in the north central US. With a large ridge in the eastern US, a strong trough will start to drop into the Dakotas and Minnesota, which would interact with the storm. This will set the stage for Wednesday’s pattern.

Drier conditions are possible for the area on Tuesday, but a much warmer air mass will enter, with 850 mb temperatures above 10c, leading to highs potentially reaching the lower 70s if dry conditions take place. On Wednesday, as the low pressure reaches its peak intensity, a strong cold front approaching the area will push the ridge offshore, with a strong trough moving into the United States, which would later bring colder temperatures to the area. While there is uncertainty with the smaller details, given that this is a week away, the strong cold front would be able to produce heavy rain and thunderstorms for the area, and even severe weather cannot be ruled out.

This is my current understanding on the potential scenario for this time frame, and as this is in the longer range, could still change. Stay tuned for more details on this storm and how it may affect the area.

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