Sept 11, 2012: Warming Up This Week

Forecast Highlights:

- Following Morning Chilly Temps, Warming Up
- Highs Return To 85 Degrees Late Week
- Rain Likely Towards Late Weekend - Next Week
- Longer Range: Cooler Pattern Evolves

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Observations for September 8-11 are in the bottom of the post.


Tonight - Friday: Chilly, Then Warming Up

Following the chilly temperatures observed this morning, chilly temperatures are expected again for tonight but not as cold as those of last night, with temperatures dropping down into the mid 40s inland and the upper 40s to mid 50s for the rest of the area except for NYC, likely in the mid to upper 50s.

Mainly sunny skies are expected for Wednesday through Friday with highs warming up, reaching the upper 70s to low 80s across most of the area. Similar temperatures are expected through Thursday and Friday, with overnight lows gradually warming up with each night.


Next Weekend - Early Next Week: Some Rain



**Wednesday, 9/12 Noon Update: An unexpected change took place in the forecast which invalidates the previous outlook for Friday night through Tuesday. The original outlook called for a closed low to drift through the Northeast during the weekend with more clouds and scattered showers along with slightly cooler temperatures; this was supported by the entire model guidance with decent consistency. The trough dropping into the US was modeled to be more detached from the main flow, dropping into the north central US and then drifting east into the NE US. Instead, the entire 0z model guidance last night significantly altered that scenario, and instead, the trough is expected to remain progressive and quickly move out, which results in a dry and quick moving cold front on Friday night into Saturday with more cloud cover and perhaps a few sprinkles, followed by a short lasting surge of cooler temperatures on Sunday, slightly warming up early next week. More information will be posted on this with tonight's update.


Mid Next Week - Beyond: Cooler Pattern Develops

By the middle of next week, trends are pointing to a pattern change with increased amplification as stronger and more persistent ridging develops near Alaska and the western US. Having ridging in these areas is key to getting a colder pattern in the central/eastern US, and was almost entirely missing from last year's warm winter pattern. Teleconnection outlooks point to a positive PNA, a falling NAO although without a strong -NAO due to the absence of strong ridging near Greenland, and a negative EPO; during last year's season, the EPO was dominantly positive and was a contributing factor to the warm pattern. With the changes above, a pattern consisting of more troughs may develop for the central US with colder than average temperatures. Some of the cooler temperatures may occasionally spread into the eastern US, although the main trough axis appears to remain near the north central US, with temperatures potentially ending up near to slightly above average for the eastern US, below average at times, along with near-above average precipitation for the second half of the month; the time period around mid to possibly late next week has a stormier look for the eastern half of the US. Temperatures overall for September are still expected to end up at least slightly above average, continuing the unprecedented stretch of 18 months of consecutive warmer than average months for many places, but should end up not far from average as opposed to significantly warmer than average.


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Saturday, September 8

Detailed observations coming soon (updated 10/7/12)


Sunday, September 9

Detailed observations coming soon (updated 10/7/12)


Monday, September 10

Detailed observations coming soon (updated 10/7/12)


Tuesday, September 11

Detailed observations coming soon (updated 10/7/12)