Sept 24: Rain, Storms On Tuesday

Notes:

– A Rain Watch remains in effect for the area. It is possible that with tomorrow’s update, this watch is upgraded to a warning, and a Severe Thunderstorm Alert may also be issued. In addition, the poll for how much rain could fall during this time frame is still open, please vote your thoughts in the poll.

– The 5-Day Forecast page was updated tonight.

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This morning brought foggy conditions to a lot of the area, however the fog took much longer to burn off than expected, leading to the high temperatures being much lower than the forecast, only reaching the lower to mid 80s in the immediate NYC area. The Mid Atlantic, however, was able to quickly warm up, and a lot of places reached the upper 90s. Tomorrow will be mild again as the cold front moves through, with a much cooler Sunday, but afterwards the next potential for rain returns on Tuesday, and severe thunderstorms may return again.

Tomorrow’s Outlook:

Tomorrow will be a partly cloudy day with a SW wind expected. High temperatures will reach the lower 80s inland, mid to potentially upper 80s in the immediate NYC area, and lower 80s for Long Island/S CT. The cold front will move through, however it will be a dry frontal passage, with no rain expected.

Sunday And Monday: Much Cooler

As the cold front moves through, Sunday will bring much cooler temperatures. There is a split between the models at this time, the NAM is expecting highs in the upper 50s-lower 60s, the GFS in the mid 60s-lower 70s, and the GGEM is slightly warmer than the GFS. At this time, I am thinking that the NAM is too cold for both Sunday and Monday, but despite this, for now I am leaning a little closer to the NAM than the GFS, with highs in the mid 60s inland and mid-upper 60s for NYC, though this is still subject to change.

Monday will be slightly warmer but still chilly, with highs in the mid 60s to lower 70s across the area, but cloud cover will increase ahead of the next storm.

Tuesday Storm: Heavy Rain, Severe Weather?

Rain will likely start falling across the area on Monday night, and the low pressure slowly moves north to NNE from the Southeast into Pennsylvania and towards southern Canada, its cold front will approach, bringing a line of heavy rain and thunderstorms for Tuesday. This is a very moist air mass, with precipitable water values near 2 inches, which will support locally heavy rainfall, bringing the storm total likely into the range of 1-3 inches, though it could end up higher. I am currently considering upgrading the Rain Watch to a warning, however I will wait until tomorrow before deciding whether to do so or not.

With the cold front, however, comes the potential for severe weather. The GFS is showing shear up to 50 knots, with supportive CAPE/LI, and if the timing and the low position work out, severe thunderstorms could be possible along this storm line on Tuesday, with the main threat being gusty winds. While this only recently started showing up, I am waiting to see tomorrow’s runs before deciding whether this is still likely to happen or not, I mentioned gusty winds and heavy rainfall for Tuesday in my 5-Day Forecast. Stay tuned for more details on this potential.

Longer Range: Significant Cool Spell Possible Starting Friday

As I mentioned yesterday, a strong trough could approach the East Coast by Friday, affecting the area on Saturday and Sunday. If a tropical cyclone was to not affect the area and the trough would move into the area, as the latest GFS/ECMWF/DGEX runs show, this would bring well below average temperatures, with highs in the 50s and lows in the 30s, however it is also possible that the trough isn’t as strong as the models are showing, or a hurricane could move up the East Coast and interact with the trough to form a strong storm (more on that below in the Tropics section). Stay tuned for more details on this time frame and what it may bring to the area.

Tropics: Matthew To Weaken, But Another Storm To Form?

Tropical Storm Matthew made landfall over Nicaragua earlier today as a 50 mph tropical storm, and while it will likely continue to weaken from this point, and will eventually become a tropical depression over land, the models are now hinting that the storm to affect the United States will be a separate storm forming close to Matthew.

The models are currently showing a tropical cyclone forming near Jamaica, intensifying while moving through Cuba, then affecting Florida. Afterwards, solutions vary, ranging from a Gulf of Mexico solution, to an out to sea solution, or moving up the East Coast, directly affecting the NYC area.

It should be noted, however, that if it does move up the East Coast, following the model solutions earlier today that showed this, it would be an extra-tropical cyclone interacting with a strong trough, leading to a strong extra-tropical storm with cold, heavy rain possible for NYC and even snow for parts of the Northeast. There is a lot of uncertainty on this time frame at this time, stay tuned for more details on this over the next few days and how this may affect the area.

Elsewhere in the tropics: Julia’s remnants are no longer labeled for redevelopment by the National Hurricane Center, and are not expected to redevelop. Lisa, like several other storms this season, gave a quick round of unexpected rapid intensification, and is now a hurricane, the 7th one this season so far. Lisa could intensify some more, but will then likely start to weaken. Lisa is currently not a threat to land.

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