Sept 14, 2012 Brief Update

Note: The next full update and discussion will be posted on Saturday.

Tonight - Monday: As of 1 AM Saturday, a line of light to locally moderate showers is moving east through NE PA. Isolated showers are expected into early Saturday with clearing skies later into the day. Highs will reach the low to mid 70s across the area.

Mainly clear skies will continue through Monday with a trough in place along with a high pressure. Chilly temperatures will briefly return, with lows dropping into the upper 40s to mid 50s away from NYC for Saturday and Sunday nights with mid 40s for interior areas and mid to upper 50s in NYC. Highs will meanwhile reach the lower to mid 70s on Sunday, perhaps slightly below 70 degrees inland, warming up with more widespread mid 70s on Monday.


Tuesday - Early Wednesday: Rain, Strong/Severe Storms

A developing low pressure will move from the Ohio Valley into Canada, bringing a widespread moderate-heavy rain event for the East Coast along with a potential for strong to severe storms. Most of the rain and thunderstorms are expected to take place towards the second half of Tuesday into the overnight hours; mainly cloudy skies and occasional storms could be a limiting factor for severe weather chances, although shear is modeled to be favorable for severe weather, with high precipitable water values near 2 inches resulting in the potential for heavy rain with the storms. Saturday's update will discuss the thunderstorm potential in more detail.


Beyond: Colder Central US, Transient Cold Eastern US

A pattern change is expected for the medium range as the pattern becomes noticeably more amplified, with the development of stronger and more persistent ridging into the western US and Alaska along with some ridging near Greenland while a strong trough drops into the central US. The main trough axis will remain over the central US where the coldest temperatures are expected; the cool temperatures will be more transient over the eastern US including the area, resulting in additional storm chances and a higher probability of near-above average precipitation for the medium range. Temperatures are likely to end up generally close to average as a whole, accounting for transient cool spells and warmth surges, with above average temperatures towards New England and below average temperatures into the central US.