April 12, 2013: Seasonable Weekend Ahead

Reminder: The blog will remain in a limited updating schedule through Friday, April 19. Until then, updates will be posted every 2 days.

Forecast Highlights:

Following the clearing of today's storm, mostly to partly sunny skies are expected for the weekend with seasonable temperatures, peaking in the 50s to low 60s. Warmer temperatures are expected for next week, back into the 60s and 70s, but with a cold front possible towards the mid week with another late week storm expected.

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This Weekend: Partly-Mostly Sunny, Seasonable

Today's storm ended up colder than expected, with temperatures generally in the 40s across the area, while a widespread sleet storm took place further north towards central-northern New England. Following the clearing of the storm, a trough will drop into the region, but with the storm out of the region along with clear skies and a WSW wind as opposed to today's and yesterday's north and east winds, temperatures will actually warm up, reaching the upper 50s to low 60s across most of the area along with partly sunny skies. Mostly sunny skies are expected for Sunday with WNW winds and slightly cooler temperatures compared to those of Saturday.


Next Week: Warmer Temperatures, Another Late Week Storm

The pattern next week, while not nearly as active as this week with significant warmth in the south/east US, a major severe weather outbreak in the south and a snowstorm and cold outbreak in the north/west, will again consist of a warm up across the eastern US, a cold front approaching by the mid week, and a potentially significant late week storm but with differences compared to this week.

Regarding the large scale pattern, the biggest difference will be the lack of blocking over Canada. With this week's pattern, blocking persisted over northern Canada with an upper level low near southern Canada, signaling the frontal boundary was likely to be mainly south of New England and the Great Lakes region but with uncertainty regarding how far south it would end up. Solutions on the model guidance ranged from a frontal boundary over northern New England with the entire region warming up into the 70s and 80s, to a frontal boundary almost entirely over the central Mid Atlantic, in which case aside from 2 days of 65-70 degree weather, chilly temperatures would have been persistent this week in NYC. Each of these outlooks was wrong, as while the area did warm up significantly on Tuesday and Wednesday as the GFS indicated and the ECM initially failed to show correctly, the frontal boundary did shift south on Thursday and Friday which the GFS did not show; the ECM did show this happening, but originally significantly exaggerated the southward extent of the boundary. My outlook last week sided too close to the models keeping the frontal boundary north of the area; while I noted ECM was originally an outlier with the southern extent of the boundary, the GFS and CMC were ultimately northern outliers as well, with the end result somewhat of a compromise.

In this case, as previously noted, the difference is the anticipated lack of blocking in Canada; assuming that this scenario does play out as currently expected, this would result in more of a W-SW flow aloft over the Northeast US/SE Canada as opposed to a WNW flow observed this week, leading to more northward expansion of eastern US ridging with the absence of a strong upper level low in SE Canada, which also allows for a further north track of the expected late week storm compared to the current storm which tracked through the Ohio Valley and into the Northeast region. After an initial warm up on Monday and Tuesday, a cold front will approach the region on Wednesday; unlike last week, however, in this case the GFS brings the cold front south of the area for the late week with cooler temperatures, while the ECM keeps temperatures in the upper 60s and 70s from Tuesday through Friday. At this time, I am siding with a compromise of these two scenarios with the Wednesday cold front, slightly dropping to the south but not staying persistently to the south, eventually lifting back north. Confidence is not very high on this outlook at this time and is still subject to change, although the aforementioned differences in the pattern at this time favor a further north frontal boundary for late next week compared to yesterday and today, as well as a further north storm track. Stay tuned for more information on next week's pattern outlook.


Forecast for NYC Area: Temperatures will begin to warm up on Monday, reaching the mid to upper 50s east of NYC and the low to mid 60s from NYC and further west with partly cloudy skies. As the cold front slowly approaches on Tuesday, mostly cloudy skies are expected with highs likely in the mid to upper 60s away from the coast, and near the mid 50s to low 60s east of NYC.

Towards Wednesday, with the cold front likely to make its closest approach to the area, partly to mostly cloudy skies are expected with a risk of scattered showers with temperatures at this time likely to reach the 60s for coastal areas and the mid to upper 60s, possibly low 70s from NYC and further north/west. While the possibility is there for temperatures on Wednesday to end up warmer than currently expected, a scenario like this week where temperatures significantly exceeded the forecast and reached the 80s is unlikely with this air mass not nearly as warm as that of this recent week. Thursday and Friday's outlook is more uncertain at this time and is subject to change, although the latest expectation is for high temperatures in the 60s for both days, especially away from the coast where cooler temperatures are expected, with widespread rain expected next Friday as the next cold front moves through.