July 24, 2013: Cooler Temps Expected Tonight

Forecast Highlights:

northeast2A cold front will move through the region today before stalling to the east, bringing in a cooler air mass into the region, with below average temperatures returning as well as much cooler overnight lows compared to the recent stretch of heat and humidity. The next storm is expected to affect the region with rain on Sunday and Monday, while heat looks to stay out of the forecast for the next 7-10 days.





Tuesday, July 23 Observations:

7.23.13 - CopyA developing wave of low pressure produced heavy rain across the interior Northeast in the early morning hours, while the area was in the northern end of a severe thunderstorm in central NJ, producing widespread heavy rain and thunder with 1/2 to 1 inch, locally higher, from NYC and further north/west. Drier conditions returned later in the morning, although additional scattered storms developed in the mid-late afternoon hours, producing locally heavy thunderstorms, especially in southern CT where totals locally as high as 1/2 to 1 inch were observed. Temperatures were warmer than those on Monday, peaking in the low to mid 80s in eastern coastal areas and the mid 80s to near 90 degrees for the rest of the area; the highest temperature was 91 degrees in LaGuardia.

Today – Saturday: Cooler Conditions, Some Showers Expected

As of this morning, the cold front was located over eastern Pennsylvania, and is gradually approaching the area. The front will move through the area during the day, but little to no rain is expected with the frontal passage. With a downsloping breezy NW wind, temperatures are expected to peak in the low to mid 80s inland and the mid to possibly upper 80s for the rest of the area along with partly sunny skies today. Partly cloudy skies are expected tonight with much cooler overnight lows, falling into the mid to upper 50s away from the immediate NYC area and Long Island, where lows are expected to reach the low to mid 60s; this will be the first time since July 13 that Central Park falls below 70 degrees.


With strong ridging stationary in the central Atlantic Ocean, the trough will be blocked from advancing further east, and the surface frontal boundary will stall off the coast on Thursday and Friday, keeping increased cloud cover and scattered showers along coastal regions, specifically in Long Island and southern CT. The latest model guidance keeps the boundary stalled closer to the area than earlier runs, with occasional showers and cloudy skies east of NYC on Thursday, with the ECM on the wetter end of the model guidance and the GFS on the drier end. A wave of low pressure will develop along this boundary on Thursday night, tracking up the coast while brushing eastern regions; to the left I posted the 6z run of the 4k NAM simulated reflectivity showing rain in Long Island and New England.

I am currently siding with a compromise of both solutions, with scattered showers on Thursday, mostly east of NYC, with up to 1/4 inch of rain, locally higher, and highs only peaking in the low to mid 70s. West of NYC, partly to mostly cloudy skies are expected with isolated showers and highs in the mid 70s to near 80 degrees. The wave of low pressure is then expected to brush eastern-central New England and parts of Long Island/SE CT with light-moderate rain overnight into Friday, clearing the region on Friday night with partly sunny skies returning for Saturday along with warmer high temperatures, peaking in the upper 70s to mid 80s.

Sunday – Next Week: Some Rain, Then Drier Mid Week

The next cold front will approach the area on Sunday as a slow moving upper level low tracks into southeastern Canada. A slightly warmer air mass will be pulled into the region, with increased cloud cover on Saturday night and overnight lows struggling to fall below the mid to upper 60s. Highs on Sunday are expected to reach the low to mid 80s along with occasional showers and thunderstorms, especially from NYC and north/west, which could be capable of producing heavy rainfall. The upper level low will then turn north in Canada, with the front slowly moving through the region, producing additional scattered showers and storms into Sunday night and Monday.

During the first half of next week, the trough will lift north of the region, allowing for heights aloft to rise and ridging attempting to rebuild into the region, but with heat likely failing to spread back in as temperatures remain generally seasonable, in the low to mid 80s for most of the area. With a weak surface high pressure building in, drier conditions are likely for the midweek period, with models showing the next potential rain event towards late next week but with uncertainty regarding the exact setup. More information will be posted on next week’s outlook over the next few days.

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