Oct 23, 2011: Taste Of Winter Next Week, Weekend

NOTE: The winter outlook will not be posted tomorrow, as there are still parts of the outlook I need to complete. The outlook will be posted in the Long Range Outlooks page sometime around the middle or the end of this week.

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Last night, the potential was mentioned for frost to affect the interior parts of the area with cold temperatures across the rest of the area. Cloud cover unexpectedly increased across the area, however, and prevented temperatures from dropping across the area. Today brought slightly warmer temperatures, reaching the upper 50s to lower 60s inland, lower to mid 60s in the immediate NYC area, and the upper 50s to lower 60s in Long Island and southern Connecticut.
Temperatures will slightly warm up tomorrow, reaching the mid to upper 60s in the immediate NYC area, with similar, if not slightly cooler temperatures expected for Tuesday. Uncertainty returns into the forecast by Wednesday, however, as two waves of low pressure will affect the region, with the second wave around Thursday night bringing widespread rain into the region and the potential for snow in parts of the Northeast US, which will be followed by the coldest temperatures so far this fall.

Tomorrow’s Outlook:

As a low pressure in SE Canada pushes out the cold air mass, temperatures will warm up tomorrow, ending up slightly warmer than average. With a south wind and mostly cloudy skies expected, high temperatures will reach the lower to mid 60s inland, mid to upper 60s in the immediate NYC area, and the lower to mid 60s across Long Island and southern Connecticut. A few isolated showers may be possible west of NYC in the evening, but otherwise the area should stay dry.

Tuesday – Wednesday: Average Temperatures Persist

A low pressure in southeastern Canada will approach the northern Northeast on Monday, which will be responsible for tomorrow’s warmer temperatures. As the cold front moves through the area, isolated showers are possible on Monday night. Drier conditions will return for Tuesday with high temperatures peaking in the lower to mid 60s across the area.

On Tuesday night, a weak low pressure will move east through the southern Great Lakes, pushing a slightly warmer air mass into the region. There is some uncertainty with where this low pressure tracks, but at this time, I am expecting this low pressure to end up over southern NY on Wednesday, which will bring slightly warmer temperatures into the area, reaching the lower to mid 60s across most of the area, along with isolated showers towards the evening. Due to the uncertainty, high temperatures may end up slightly cooler than I am currently expecting.

Thursday – Friday: Storm Brings Uncertainty Into Forecast

Although no pattern change is expected to take place just yet, we will be seeing a type of set up which we haven’t seen so far this fall, giving the region its first taste of winter. A strong high pressure will push southwards into the central and southern US on Wednesday, at the same time that the weak low pressure moves over the region, which will keep the storm’s cold front stalled near the area for Wednesday night into Thursday as waves of light rain move ENE along the front. As a result, high temperatures on Thursday will be slightly cooler, likely reaching the upper 50s to lower 60s across most of the area, but as the frontal boundary should be near the area, any slight change in the location of the front could result in the high temperature forecast busting a few degrees too cold or warm.

The scenario will get more interesting for Thursday into Friday as a second wave of low pressure develops along the stalled front and moves ENE, towards the region. There is still uncertainty with this storm, but the models today came into better agreement than yesterday’s models, now agreeing on a weaker, more progressive and further south low pressure moving through the region on Thursday night instead of Friday night. The location of the low pressure, however, is still uncertain, and ranges from the CMC which takes the storm over the southern Mid Atlantic with a few showers in the, to the northern GFS which takes the low pressure over or just north of the area with a light snow event for parts of the interior Northeast. Except for the CMC, the rest of the model guidance mainly agrees with the snow potential for the interior Northeast; only the DGEX model shows any notable snow event for the NYC area, but is an outlier solution and will likely trend towards the model agreement tomorrow morning.

When looking at the overall picture, with a high pressure and a dropping cold air mass, the low pressure is not expected to track too far north of the area, but the initial surge of cold air before Thursday’s storm is not expected to be too strong, which likely won’t suppress the storm entirely to the south of the area. At this time, I am leaning towards the northern solutions, with the storm’s track potentially ending up near New Jersey, ranging between the Delmarva Peninsula and southern NY. Such a solution would bring widespread light to moderate rain across the area on Thursday into Thursday night, potentially between 1/2 and 1 inch, and as the storm ends, if there is still enough precipitation left when the cold air moves in, the potential may be there for flakes to fall in the interior parts of the area, towards NW NJ and Orange county, NY. This potential has a low confidence level at this time, however, and depends on the storm’s location, timing and intensity.

It should be noted that there is still a fair amount of uncertainty with this storm, and considering that the models are still having issues with handling this storm, changes are still likely with the scenario over the next few days, and it may not be until Tuesday when the models converge on a solid solution. While the original idea of a strong storm seems less likely than it was before, it cannot be ruled out yet, and it is possible that we may see a stronger storm further west with heavier rain for the area, or we may see a weaker and suppressed event, keeping most of the rain to the south of the area. Stay tuned for more information on this storm and its impact on the area.

Longer Range: Colder Pattern Begins To Develop

Regardless of the intensity of the late week storm, there is high confidence that a strong cold spell drops into the region between Friday and Sunday, bringing colder than average temperatures, with a chilly Halloween possible this year. Unless we see significant changes with the set up, high temperatures are likely to end up in the upper 40s to mid 50s range across the area, with more widespread low temperatures in the 30s possible. If there are mainly clear skies, widespread frost may be possible across the area. The coldest temperatures are likely for Friday and Saturday, with moderating temperatures for Sunday and Monday.

Looking beyond next weekend at the teleconnections, the NAO and AO are expected to rise towards positive, with a negative PNA persisting. This combination suggests that a moderation in temperatures is likely sometime around the start of November, and along with the fact that the current pattern doesn’t support sustained cold spells, another warm up may be possible to start November, though it does not appear at this time that a sustained warm pattern should continue through November. Stay tuned for more information on the longer range.

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