Mar 5, 2011: Moderate Rain Tomorrow

Evening Brief Updates:

- The 5-Day Forecast page was updated for the Immediate NYC Area and the Interior. The 5-Day Forecast covers the time frame through Thursday evening, when another heavy rain potential exists.

- Storm updates will be posted throughout the day tomorrow regarding the storm and any potential changes to the forecast. With the latest data coming in, it appears that even though rain will fall from the afternoon to early Monday morning, the heaviest rain could come in the form of a line of heavy rain, and even a rumble of thunder cannot be ruled out especially for the eastern parts of the area.


Afternoon Update: Discussion For Tomorrow, Thursday Storms


Storm Track: This afternoon's model runs shifted slightly east of the morning runs, especially the GGEM, now taking the low pressure over NYC, and the NAM, which has continued to adjust eastward with each run today. I made some slight changes to the map from this morning with the new one posted to the left, moving the track slightly further east in central VA and slightly west in Maine and shifting it slightly east near the area. The new model consensus is similar to that which I mentioned this morning and my forecast track from last night, taking the low pressure near or just west of New York City.

Rain Totals: The 12z NAM, which brought barely 1/2 inch of rain to New York City and less than that further south, was the driest run of the day, and is likely a dry outlier. For precipitation, I sided with an outcome closer to the GFS and the 18z NAM, bringing at least 1 to 2 inches of rain for the immediate NYC area with the highest rain totals in the area towards northwestern New Jersey and Orange County in NY. The 12z GGEM is much wetter, bringing as much as 3 inches of rain to New York City, however there is no support for such a solution, and while it is not expected to verify at this time, it will be watched.

Storm Timing: Most models bring in the steady rain into the area by the early to mid afternoon hours. The NAM is slower, only showing a short duration rain event with the rain not starting until the overnight hours, though with the NAM being slower than every single model, and one of its biases being too slow in some cases, I went with the faster solutions, bringing in the rain into the area by the early afternoon hours. The heaviest rain will fall in the evening to the early overnight hours, starting to end after 2 AM.


Overall, the storm is expected to bring moderate to heavy rain across the area, however there will not be as much rain as originally expected, expected to range between 3/4 and 1.5 inch in Long Island, 1 to 2 inches in the immediate NYC area, and 1.5 to 2.5 inches in the western parts of the area. As the storm ends, sleet/freezing rain may fall especially towards Orange and Sussex counties, however any frozen precipitation will be light and should not last long. Tonight's update will discuss any additional changes to the expected set up and storm scenario, and updates will be posted on this storm tomorrow.


Next Week: Comfortable Start, Wet Ending

The time frame from Monday afternoon through Wednesday will be a dry one, with temperatures expected to be in the 40s across the area with no major weather event expected. By Thursday, however, stormy conditions will return to the region. A storm will track towards the Great Lakes on Wednesday night, with a cold front moving east, however unlike the original scenario shown on the models, the cold front is not expected to simply keep moving east with nothing more than a cold front moving through. A secondary low is expected to form further south, but where this happens and the timing and intensity of the storm are still uncertain. When looking at the overall set up, however, there is a threat for heavy rain to affect the area between Thursday evening and Friday morning, which may cause additional flooding. Stay tuned for more information on this storm.


Morning Update: Today's Outlook And Brief Storm Update


Today's Outlook:

Originally, temperatures were expected to peak in the lower to upper 50s in the immediate NYC area and upper 40s to lower 50s for the rest of the area. Temperatures this morning, however, unexpectedly surged as much as 10 degrees in an hour in the immediate NYC area, and are already in the lower 60s.

As a result, I raised the forecast temperatures to cover this change, now expecting temperatures to peak in the lower to upper 50s in the western parts of the area, mid 50s to lower 60s north of NYC and in the mid 60s for NYC and further south, and lower to upper 50s for the eastern parts of the area. A south wind is expected.


Sunday - Monday Storm: How Much Rain?

As I mentioned last night, the models have once again taken a wide split in the potential outcomes for this storm. I sided last night with a track in between, closer to the GFS/ECMWF, taking the storm over the area, keeping the heavy rain west of NYC but still bringing a widespread 1 to 2 inches. This morning, the models began converging on a track that would take the storm somewhere near central/western Virginia into western New Jersey/eastern Pennsylvania and towards downeast Maine. This track would bring the heaviest precipitation from central Pennsylvania into New York State and Maine, with a portion of that falling as frozen precipitation, but the question is now how much rain falls in the eastern side of the storm.

This change will lead to at least 1 to 2 inches in the western parts of the area, and 3/4 to 1.5 inch in the eastern parts of the area. As a result, I removed the Heavy Rain Watch and downgraded the warning to a watch in Long Island. Stay tuned for more updates in the afternoon.