[notice]Due to technical difficulties, no update was posted yesterday, 8/2/13.[/notice]
A cold front moved through the region on Thursday, having produced moderate showers and thunderstorms with unseasonably cool temperatures during the day. Behind the front, more seasonable conditions returned for Saturday, although a strong trough is currently digging into the region, which will result in another round of colder than average temperatures through early next week. Although brief warm ups are expected, as with late next week, the pattern continues to favor generally near-below average temperatures through the next 2 weeks.
Today – Tuesday: Chilly Temperatures Return
As of early this morning, the large scale setup consists of a broad trough over southern Canada diving into the Northeast region, with a weak cold front approaching at the surface, forecast to move through the area tonight. This front will fail to produce widespread thunderstorm activity, although mostly cloudy skies and isolated showers/thunderstorms are expected today, especially this afternoon and evening as the front moves through. With the increased cloud cover, high temperatures are expected to reach the upper 70s to low 80s across the area.
As the trough continues to push into the region, a surface high pressure will gradually build in with a NW flow aloft bringing in an unseasonably cool air mass, with 850mb temperatures as low as 6C; this overall setup supports below average temperatures from Sunday through the middle of next week. Sunday is forecast to be partly sunny with highs in the mid-upper 70s inland and the upper 70s-low 80s for the rest of the area. The coolest overnight lows are forecast for Sunday night, with temperatures falling into the upper 50s to low 60s in NYC and the immediate coast, low to mid 50s for the north/west suburbs and southern CT, and upper 40s to low 50s for northwest NJ, interior SE NY and interior CT. Sunny skies are forecast for Monday with highs in the low-mid 70s inland and the mid-upper 70s for the rest of the area, with overnight temperatures slightly higher than those of Sunday night.
As a low pressure develops near the Great Lakes and southern Canada region, a frontal boundary will gradually lift north towards the region, slowly bringing increased cloud cover from the southwest. The models differ with the timing of the warm front slowly lifting north towards the region, although Tuesday should have at least partly sunny skies and highs in the mid 70s inland and upper 70s for the rest of the area. Cool overnight lows are expected again overnight, in the low-mid 50s inland, but with increasing cloud cover also likely.
Wednesday – Next Weekend: Rain/Storms, Then Chilly Again
The current pattern consisting of near-below average temperatures will remain generally stable through the rest of next week and into the weekend, with high latitude ridging continuing across northern Canada keeping a strong upper level low stationed over south central Canada. With the ULL in this position, a southwest flow will be in place over the region through the mid-late week, which will gradually push a warm front northeast through the area, followed by a frontal passage towards Friday as the ULL tracks east, sending the unseasonably cool air mass from the Midwest into the Great Lakes and the Northeast.
The warm front is currently modeled to move through towards Wednesday night; the timing will determine the exact outlook for Wednesday, although given the current forecast conditions, mainly cloudy skies and occasional showers are forecast with the area to the north of the front, which along with a southeast wind would result in unseasonably cool high temperatures, in the upper 60s to mid 70s across the area. This outlook is subject to some changes due to the uncertainty in the exact timing and location of the front, however, and it is possible the warm front is slower to move through, which would allow temperatures to climb into the upper 70s early in the day. The area is expected to briefly be located in the warm sector on Thursday as the front lifts to the northeast and the cold front slowly approaches, with widespread showers and thunderstorms likely. At this time, there is uncertainty regarding any risk of severe weather, although with high precipitable water values, storms will be capable of producing heavy rainfall. High temperatures are slightly uncertain depending on the exact placement of the system and the warm/cold fronts, although based on current indications may rise into the low-possibly mid 80s. Storms are likely to continue until the frontal passage, which based on the latest model guidance is likely to be around Friday but is subject to some changes.
Behind the cold front, another unseasonably cool air mass will drop southeast into the region, resulting in another round of cooler temperatures for the weekend into early next week as the ULL tracks back north into Canada. Temperatures are not expected to be as cool as this weekend as the core of the cool air mass is pulled back into Canada, but are still expected to remain below average, likely in the mid-upper 70s for highs and the 50s for lows away from the coast. Temperatures are expected to warm up towards early-mid next week, but are likely to remain generally near to slightly below average. While additional brief periods of heat/humidity are still likely this year, especially towards the last 10-15 days of August and possibly September, the current pattern does not support sustained periods of heat, and the strongest heat of the summer appears to have passed with mid July.