Sept 27, 2013: Warmth Returns; Dry Pattern Continues

Forecast Highlights:

northeastA back door cold front moved through the region, keeping temperatures near to slightly below average while cloud cover today was more than forecast. Dry conditions will continue again for the next 9 days as the only storms nearby are a collapsing cold front and a coastal low offshore, while the chilly pattern that was in place for mid-September ends as temperatures gradually warm up into the mid-upper 70s into next week, possibly near 80 degrees.



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Thursday, September 26 Observations:

9.26.13Little changes were observed across the region with the air mass and overall setup with a high pressure still in control, with mostly to partly sunny skies and temperatures slightly below average, peaking in the upper 60s to low 70s across the area, which was slightly cooler than Wednesday. The highest temperature was 74 degrees in Somerset, NJ, and the coolest high temperature was 65 degrees in Montauk, NY.




Tonight – Monday – Slightly Warming Up; Few Showers Possible

Pattern Analysis: A highly amplified pattern remains in place across the US, with a strong trough in the western US, a strong ridge in the central US, and a broad upper level off the Atlantic coast. The strong trough in the central US will push northeast towards Canada, pushing the ridge northeast into southeastern Canada as well, where it will end up cutting north of the upper level low, which keeps the region under a stale cool air mass this weekend with 850mb temperatures near 6-8C as an anomalously warm air mass stays well to the north.

The westerns US trough will continue to lift north into Canada, which will result in the cold front collapsing as it reaches the region towards Monday while ridging begins to build behind it. As the ridging aloft and surface high pressure shift east of the western Atlantic upper level low, it will retrograde northwest towards New England while a stronger surface low pressure develops and tracks northwest as well, becoming vertically stacked east/SE of Massachusetts and then slowly lifting north/NE towards Canada. There are some differences between the models regarding the track of the low pressure; a few GFS runs earlier today were much more west with the low pressure, bringing widespread rain across the area, but otherwise the rest of the model guidance keeps the low far east enough to simply result in increased cloud cover on Monday and a few showers in eastern Long Island/CT. At this time, I am leaning towards the latter scenario, although slight westward adjustments to the forecast are possible.

Forecast for NYC area: After today’s unexpected widespread cloud cover, sunshine is expected to return for this weekend as a shortwave that moved through the area slides to the south, with temperatures reaching the upper 60s to low 70s for highs. Partly to mostly cloudy skies are expected on Monday, with more overcast cloud cover towards Long Island and Connecticut where isolated showers are possible, especially further east.


Tuesday – Saturday: Warmth Returns; 80 Degrees Possible

The upper level low will gradually depart the region as ridging gradually shifts east into the area. A strong trough currently over the northeast Pacific will quickly push east through the US/Canada border throughout next week; this will set up a zonal flow over the eastern half of the US with the jet stream to the north of the region, over southern Canada, while a trough begins to drop into the western US by the late week. This setup will place the region under widespread ridging, which along with 850mb temperatures up to 14-16C which is warmer than average for this time of the year, is likely to result in temperatures rising into the mid to upper 70s across the region with widespread low 80s likely south of the area; in the warmer case scenario, it is not out of the question that parts of the area reach the low 80s, with temperatures overall likely to end up.

The latest model guidance keeps the entire region with widespread warmth; the potential may be there for a back door cold front to affect New England and central-northern New York state, although at this time any potential back door cold front is likely to stay north of the area, with temperatures likely to end up at least 5 to 10 degrees above average. With the high pressure in place, mostly sunny skies and dry conditions will continue through the rest of next week as well; this may have to be watched more carefully should the next cold front fail to produce widespread precipitation, with the CPC Drought Monitor listing Long Island and parts of Connecticut under D0, or abnormally dry, conditions.


Next Sunday – Beyond: Rain Possible, Then Colder

While the previous pattern outlook from last weekend underestimated the magnitude of ridging expected to develop this week, largely due to the northeast Pacific troughing that quickly pushes east through southern Canada which prevents the originally anticipated western US ridging (+PNA) from developing, the potential cool down noted around the October 5-6 time frame remains a valid potential as troughing likely starts to approach the central US by next weekend. There is some uncertainty regarding the timing and setup of the trough, although at this time the next cold front may affect the area towards next Sunday, 10/6, which is when the next potential for rain is expected; by then, it will have been 15 days, exactly half a month, since the last widespread rain event affected the area on September 22. Temperatures are likely to cool down again towards the beginning of the following week with temperatures returning to near or slightly below average; the next pattern outlook will be posted on Saturday night, with more information regarding the upcoming 2-week outlook.

2 thoughts on “Sept 27, 2013: Warmth Returns; Dry Pattern Continues

    • NYC Area Weather Post authorReply

      No precipitation is expected this weekend as a high pressure stays in place. Monday will be dry for most, if not all of the area as well as the cold front currently in the central US collapses as it reaches the region and the coastal low pressure stays east.

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