Oct 20, 2010: Very Active Pattern To End October

Today was a mostly cloudy day due to a storm passing to the south of the area, bringing heavy rain to a narrow area from central VA into the Delmarva Peninsula and southern New Jersey. Low temperatures this morning were quite chilly, in the lower 30s inland and in the upper 30s to mid 40s in the immediate NYC area. High temperatures were in the upper 50s to lower 60s across most of the area.

Up to today, the pattern in October has generally been average, with no extremes as we have seen in previous October, such as lows well into the 30s and 20s, accumulating snow in the interior parts of the area as we’ve seen last year and in 2008, or high temperatures into the 80s or even 90s. The cold spell expected for Friday and Saturday will bring below average temperatures, but nothing unusual for this time of the year. Next week, however, a much more active pattern will set up, with two large storms and a potential cold spell to end October.

Tomorrow’s Outlook:

The area will see cloudy skies tomorrow morning and afternoon with some clearing in the late afternoon and evening hours, with a WSW turning WNW wind. High temperatures will be in the mid to upper 50s inland, lower to mid 60s for the immediate NYC area, and lower to mid 60s for Long Island/S CT.

The cold front moving through will bring scattered showers to the area, but thunderstorms may also be possible, potentially strong. There is expected to be a LI around -2, but bulk shear will be around 50 knots, which could lead to thunderstorms from NYC into Long Island and southern New England during the afternoon as the cold front moves through, with the main threat being small hail and gusty winds.

Tomorrow Night:

The trough will begin to move into the region tomorrow night, bringing much colder temperatures. Low temperatures will drop near or below the freezing mark in many places in the interior, which combined with scattered precipitation, could lead to widespread snow flurries mixing with the rain showers for a lot of places in the Northeast. Even accumulating snow may be possible in southern New York if some models verify.

Low temperatures will be chilly in the area, ranging from the mid 30s inland to the mid to upper 30s north and west of NYC and in S CT, upper 30s to lower 40s in Long Island, and lower to mid 40s in NYC.

Friday’s Outlook:

Friday will be the coldest day of this cold spell, with high temperatures ranging from the lower 50s inland to the lower to mid 50s in the immediate NYC area. That is when the air mass will be at its coldest, with 850 mb temperatures near -4 degrees celsius.

On Friday night, the trough will start to exit, but that is when the coldest temperatures will happen. The models have trended slower with the timing, which is more reasonable as they were too fast yesterday. Low temperatures are expected to be in the lower 30s inland, lower to upper 30s for the N/W suburbs of NYC, lower to mid 30s for S CT, mid to upper 30s for Long Island, and lower 40s for NYC. Even upper 20s may be possible for the interior in the colder case scenario. Accordingly, I issued frost alerts for most of the area, with a freeze watch for the interior.

Weekend Outlook: Warming Up

As the trough exits for Saturday, temperatures will be warmer but still chilly. High temperatures will reach the upper 50s inland and in the lower 60s for the immediate NYC area. Overnight lows will also be warmer, ranging from the lower to mid 40s inland to the mid 40s to lower 50s in the immediate NYC area, though cloud cover will increase ahead of a low pressure.

Sunday will bring mainly cloudy conditions and scatterd showers, mainly to the north of New York City, as a low pressure from the west approaches the region. This will also help to draw in a warmer air mass, with high temperatures in the lower 60s inland and in the mid 60s in the immediate NYC area.

Early To Mid Week Outlook: Active Pattern Begins

On Monday, as the low pressure continues to push northeast, the area will see scattered showers but even warmer temperatures, reaching the mid 60s inland, and the upper 60s in the immediate NYC area, where lower 70s may even be possible if the area is dry. The attention then turns to the Midwest, where a developing storm will set the pattern for the rest of the week.

A low pressure will enter the NW US/SW Canada between Saturday and Sunday, with the low pressure then moving into Canada, being in southern Canada by Monday. Between Monday night and Tuesday, the storm will merge with a rapidly developing area of low pressure to its south, forming an intense storm by Tuesday afternoon, which there is uncertainty on the location but it could be located near the NW Great Lakes. This storm will then expand, bringing heavy rain from the Great Lakes into the Ohio Valley, and while the timing is uncertain, the storm could bring rain and thunderstorms to the area between Tuesday afternoon and Wednesday afternoon.

This storm will draw in a warm air mass into the region while pulling down a trough into the north central US, and high temperatures could reach the lower 70s across parts of the area on Tuesday. This will leave a colder air mass in the area, but if the latest models verify, the trough may not move into the Mid Atlantic just yet.

Mid To Late Week: Potential Storm, Cold Spell

The models are now hinting of a low pressure forming in the Southeast and moving NE up the East Coast, affecting the area around Thursday. There is more uncertainty on this time frame, and this solution could change with the next few runs, but if the current solution was to verify, the storm could bring rain to the area on Thursday, and after it exits, the strong trough in the central US and Canada would drop into the region, bringing a cold end to the month and starting November on a cold note.

As I previously mentioned, this is still in the longer range, and can still change. Stay tuned for more details on this time frame.

Brief Tropics Update:

Invest 99L in the western Caribbean has gotten itself much more organized, and will become Tropical Depression 19 at 11 PM. If it is named, it will be named Richard, only the 3rd storm to have a name start with “R” since naming tropical cyclones started in 1950, and would be the 17th named storm of the season. There is uncertainty on where TD19 tracks, but it will likely affect the Gulf of Mexico. More updates will be posted on TD19 in the next few days if needed.

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