Aug 23, 2013: Dry Weekend, Stormier Next Week

Forecast Highlights:

northeastAfter a cold front passed through the area last night, temperatures will be slightly cooler than average today and this weekend with mainly sunny skies and dry conditions. A strong ridge will set up over the central US next week, with the region under a northwest flow in between the ridging and troughing to the east, resulting in temperatures alternating between slightly above and slightly below average but with increased storminess likely as well.




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Thursday, August 22 Observations:

8.22.13The forecast for Thursday originally called for scattered showers and thunderstorms with highs in the mid to upper 80s; unlike the outlook, however, an area of heavy thunderstorms formed over the southern parts of the area, slowly shifting north towards the immediate NYC area and parts of Long Island/CT, with totals in central and northeast NJ especially near the I-78 corridor locally as high as 2-4 inches. The heavy rain mostly ended by the early afternoon, but with cloudy skies and scattered showers persisting through the rest of the day with cloud cover failing to clear as forecast, while locations to the north and south of the area cleared as expected with highs managing to reach the mid-upper 80s. This resulted in temperatures ending up nearly 10 degrees cooler than forecast, peaking in the low 80s in the western parts of the area, and the mid 70s to near 80 degrees elsewhere. The highest temperature was 83 degrees in Montgomery, NY, and the coolest high temperature was 76 degrees in multiple locations.



Today – Weekend: Drier, Slightly Cooler

As yesterday ended up cooler than forecast, today’s temperatures will be slightly warmer than those of yesterday, peaking in the low to mid 80s for most. Humidity will be lower, however, with dew points gradually dropping into the 50s. Partly sunny skies are expected today, with conditions generally dry across the area, although an isolated shower in the evening can’t be ruled out towards central NJ and Long Island.

A high pressure will build into the region on Saturday and Sunday, resulting in mainly clear skies, winds out of the north, and temperatures slightly cooler than average as 850mb temperatures fall to near 10C. High temperatures on both days are expected to reach the upper 70s to low 80s across the area, with Sunday a degree or two warmer than Saturday; overnight lows are forecast to fall into the low 50s inland, mid 50s to near 60 degrees in the north/west suburbs of NYC, southern CT and interior Long Island, and the low 60s near NYC and the immediate coast.

Next Week: Stormier Pattern Likely Develops

Towards the beginning of next week, a strong ridge will set up over the central US with widespread 90s and 100s for highs, with a trough pattern setting up over eastern Canada. The Northeast US region will be in between these two features with a northwest flow aloft, keeping the sustained heat west of the region but with occasional surges to the east with frequent shortwaves tracking around the ridge and into the region along the upper level flow, resulting in several thunderstorm potentials for next week and the possibility of severe thunderstorms and/or a MCS to affect the Great Lakes and the western Northeast regions. While there is overall high confidence on the large scale pattern, there is uncertainty regarding the smaller details within the pattern, such as exact location and timing of shortwaves and thus exactly when and where thunderstorms will set up next week.

As the high pressure from this weekend shifts south of the area, a southwest flow will set up with warmer temperatures for Monday, reaching the low to mid 80s across the area with partly sunny skies. The first shortwave appears to move through the region towards Monday night or Tuesday, with a risk of thunderstorms on Monday night and/or Tuesday especially north and NW of NYC, with warmer temperatures in the mid to possibly upper 80s likely on Tuesday. The model guidance indicates another potential low pressure on Wednesday or Thursday, with thunderstorms possible again especially west of NYC, which at this time is likely to be followed by a drier end to the week and weekend with temperatures slightly cooling down as models indicate highs may return into the upper 70s-low 80s. Uncertainty increases into the longer range depending on where the ridge shifts, although the possibility is there for another surge of warmth and/or heat into the region and more thunderstorms for the first week of September. More information will be posted on the outlook for next week as details become clearer.

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