May 2, 2011: Warmth Returns Briefly Tomorrow

Note: The 5-Day Forecast was not updated tonight and will not be updated until Friday. A few brief updates will be posted this week, especially tomorrow concerning severe weather for parts of the region, though full updates will resume on Friday, 5/6. Regular daily discussions/updates will continue next week.


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As a cold front slowly approached the area today from the west, today brought mainly cloudy skies to the area, though the rain is still to the west of the area, and by the time it gets into the NYC area, it should be nothing more than an area of light to moderate rain and thunderstorms producing up to 1/4 inch or less. This storm, however, will help bring in much warmer temperatures for tomorrow, reaching the lower 80s in parts of the immediate NYC area, and resulting in an enhanced risk of severe weather in places such as Pennsylvania and West Virginia.


Tomorrow and Wednesday: Warm, Then Stormy

The cold front slowly moving towards the area is expected to stall, with a wave of low pressure then moving northeast. Today, there is a high confidence level in the forecast scenario, however it was difficult to forecast the storm over the last four days, with the models going through significant changes that were very difficult to predict in advance. Originally, the GFS model showed a coastal low with snow in parts of the region, which was almost immediately ruled out as an outlier with signs pointing towards a west trend, but the extent of this trend was unclear until it has actually taken place.

Almost all models showed the storm becoming a cut off low and stalling near the area for at least 2 days as a strong storm, bringing cold temperatures and heavy rain for the region, however the NAM was the only model that did not show this, siding with a storm tracking well west of the area and not stalling it as a strong storm. The NAM sometimes tends to be too strong and too far west in its longer range, however in this case, while not correct with its exact solution, it did perform better than the other models, which yesterday locked on a track west of the area, through Pennsylvania, and only showed the storm briefly stalling over the northernmost parts of the region.

Tomorrow’s Warmth/Storms:

Even after locking on the track, there continued to be adjustments with the front’s placement, which originally was supposed to stall near or at least just north of NYC. Yesterday’s models, however, trended much more north with the front than originally anticipated, with the area expected to be well into the warm sector, which will bring a much warmer air mass. The main limiting factor to how warm NYC and locations further east will get is a SSE/SE wind which will bring lower 70s at most to parts of northern Island and 60s for the rest of LI/southern Connecticut with the exception of the immediate coast, though northern NJ and interior SE NY are expected to reach the lower to upper 70s, and a few places in the immediate NYC area, especially near and just west of NYC, are capable of reaching the lower 80s.

With the storm tracking west of the area, severe weather is a risk for parts of the region. This risk was first introduced two days ago as it became apparent that the storm would track west of the area, and increased over the last two days. The models are showing decent CAPE and Lift Index amounts in the western parts of the region, along with supportive EHI and bulk shear values, which will result in an enhanced 15% risk, potentially a 30% risk of severe weather focusing on southern/SW Pennsylvania, NW Virginia, and northern West Virginia. As these storms move east, however, they are expected to weaken, with nothing more than light to moderate rain and non-severe thunderstorms affecting the area on Tuesday night, with up to at least 1/4 inch or less, and a few showers on Wednesday.


Longer Range: Dry conditions are expected for Thursday and Friday with partly to mostly cloudy skies, temperatures in the upper 50s to mid 60s, and a risk of isolated showers as the storm cuts off and stalls well north of the area. The next storm is expected to affect the area around the Sunday/Monday time frame. At this time, the models are once again showing a coastal storm, and while given the scenario, a coastal low would be more likely than an inland storm compared to tomorrow’s storm, I will continue to follow the models and the overall scenario for any changes, given that this is still in the longer range. More information will be posted as details become clearer.

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