Tag Archives: noreasters

NYC Weekend Weather – Mar 16, 2018

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An uneventful, though kind of cold weekend is in store for the NYC area. Great news for those of you going out for St. Patrick’s Day festivities. Looking ahead into mid-week next week, we have the potential for yet another nor’easter impacting the region with, you guessed it, the possibility for more snow.

Rest of today – partly sunny to mostly cloudy skies with a high near 40°F.

Saturday (St. Patrick’s Day) – warmer, sunny, with a high in the mid-40s, pretty much ideal conditions for the parade.

Sunday – sunny, high in the low-40s. High pressure will be in control of the area.

Monday – mostly sunny with highs in the mid-40s.

Why Seemingly Unending Conveyor Belt of Nor’easters?

The simple answer: The Greenland Block. You may have heard the term “blocking high” mentioned in regards to the anomalously active and cold weather pattern over the Northeast this month. In essence, what’s happened is that a strong ridge of persistent high pressure has formed over Greenland this month. Very cold air over snow-covered landmasses like Greenland is often quite stable. Colder, denser air, also increases surface pressures.

Cyclonic flow around such an area of strong high pressure can wreak havoc with the polar jet stream – diverting its normal flow around the high. This can (and has in our case) lead to the polar jet diving far to the south, allowing large intrusions of Arctic air into the Eastern US. Jet streams can also enhance storms via upper level divergence, lowering surface pressures. Lastly, the blocking high can slow the normal eastward progression of storm systems, causing storms to linger over areas and extended periods of precipitation and coastal impacts in the case of nor’easters.

The Greenland Block is correlated with an index called the North Atlantic Oscillation. When values of this index are negative, it’s more likely that such a blocking pattern arises. Lucky for us, it appears that we may finally get a break in this pattern towards the end of the month.

 

 

NYC Weekend Weather – Nor’easter Inbound – Jan 21, 2016

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All eyes turn towards this weekend’s Nor’easter which will bring us the most snow we’ve seen since last winter. Confidence is growing that NYC and points south could receive over a foot of snow by Sunday. In addition, forecasters anticipate that this storm will bring sustained winds of 30mph to coastal areas with gusts as high as 40-60mph leading to whiteout blizzard conditions. However, it is important to not, even at this point, 48 hours from the start of this event, that a good deal of uncertainty remains about these forecast snow totals.

Rest of today – mostly clear with high temperatures reaching into the mid-30s but a northwest wind in the 15mph range making it feel colder.

Friday – slightly cooler with highs in the low-mid 30s, clouds I increasing through the day as the headline storm for the weekend approaches.

Saturday – snow should begin falling from southwest to northeast overnight Friday and continue throughout the day Saturday. Sustained northeast winds 25mph-30mph could lead to drifting and blowing snow, making for hazardous teavel conditions. Some potential exists that enough warmer air wraps into the storm off the Atlantic that some areas see a changeover to a rain/sleet/snow mix in the afternoon before transitioning back to all snow Saturday night. Total daytime accumulations are currently forecast between 3-7″. Overnight accumulations could be in the 4-8″ range.

MinSnowWeb
Minimum snowfall for this Nor’easter
StormTotalSnowWeb1
Most likely snowfall totals
MaxSnowWeb
Maximum snowfall possible with this storm


Sunday – some lingering snow showers are possible Sunday morning but conditions should improve rapidly as cloud cover decreases with the storm exiting to our east. High temperatures are expected to be in the mid-30s.

Monday – warmer with high temperatures in the mid-30s and sunny skies.

Complicating Factors for Forecasting the Nor’easter

  • Model divergence – European models favor a solution that has the storm moving quicker and further south than US based models. This scenario would result in minimal snow for NYC, hence why the minimum snow forecast is only 2″.
  • Unpredictable snow bands – as we are all too aware from last year’s fiasco of subway shutdowns in anticipation for a blizzard that didn’t materialize, when it comes to Nor’easter type storms, where, when, and for how long deformation banding features (heavy bands of snow) set up will make or break a snowfall total forecast in either direction. However, these types of mesoscale banding features are not easy to predict with confidence before they actually start forming. Should parts of our region fall under one of these banding features where snow could be falling at rates of 1″+ per hour, you could easily see total snowfall forecasts be shattered.
  • Intrusion of warm air – if enough warm air works its way into this storm off the warm waters of the Atlantic (where above normal temperatures thus far this winter have kept the sea surface temperatures abnormally warm), then some areas could see a rain/sleet mix for periods of time. Forecasters are overall confident the window for this mixing is small enough that overall totals won’t be dented too much, though.
lowtrack_ensembles
The closer this storm center tracks to the 40ºN 70ºW benchmark, the better the chances become for our are to get a lot of snow. Climatologically, Nor’easters that track closest to this benchmark have been the biggest snowmakers for the NYC region.

 

NYC Weather Update – Jan 18, 2016

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Weather to start this week will be rather uneventful, predominantly featuring windy, cold days, but little in the way of precipitation. We did get our first dusting of snow so far this winter in the city last night, and the potential for significantly more exists with a possible Nor’easter coming this weekend. As always, even though we’re within a week of this event, our local forecast office is only forecasting with 30% confidence due to the large changes in impact that even small fluctuations in storm track and intensity could bring.

Rest of today – we’ve already hit high temperatures for the day around 30ºF. A tight pressure gradient is causing breezy west winds near 20mph translating to wind chill values in the 10-15ºF range.

Tuesday – basically a repeat of today, but with slightly stronger winds. High temperatures will be in the upper-20s to around 30ºF with west winds in the 20-25mph leading to wind chills in the single digits to low teens under mostly sunny skies.

Wednesday – warmer, with high temperatures closer to normal in the mid-30s, calmer winds and sunny skies. There could be some flurries Wednesday night with a passing clipper system, but no accumulation is expected in the city.

Thursday – mostly sunny again with high temperatures in the mid-30s.

 

Possible Nor’easter This Friday – Saturday

Looking ahead towards the end of the week, there is a possibility for the first significant snowfall event in the NYC region thus far this winter. Forecasters are keeping close tabs on the possible formation of a classic Nor’easter towards the end of this week. It is important to stress that even at this point in time, there’s still considerable uncertainty about how this scenario will unfold. A deviation in the track of this coastal low too far north would result in a mainly rain event along the coast, while a deviation too far south would mean significantly less precipitation. If this scenario plays out under optimal conditions, our region would be in the northwest quadrant of this low, an area that favors the development of heavy snow. Even then, as was the case a couple winters ago, slight changes to the track and position of the heaviest snow bands could mean the difference between 5″ of snow or over a foot. Stay tuned for updates.

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NYC Weekend Weather – Nov 14, 2014

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You can feel the chill in the air now. This cold will continue Saturday, but we’ll get a slight warmup Sunday and Monday ahead of a low pressure system moving in from the southwest. Behind that low pressure system, we get a reinforcing blast of arctic air that will be entrenched through the rest of next week. I’m also monitoring the potential for a Nor’easter just in time for the busy travel day Wednesday and through Thanksgiving.

Saturday – a cold day on tap despite ample sunshine. High temperatures will be generally in the lower 40s. There’ll be a noticeable northwest wind making it feel like it’s in the 30s.

Sunday – a milder day with warm air flowing in ahead of a low pressure system, but by warm, I mean highs only around 50. Clouds will increase throughout the day and there could be some rain Sunday night.

Monday – rain will be falling for the majority of the day, with highs in the city in the mid-40s. Monday night gets interesting with the potential for a rain/snow mix in the city, and all snow in interior regions north and west. Depending on the timing of the main slug of precipitation with this system, we could actually get some accumulating snow in the city also (the later in the night the main body of precipitation falls, the colder it will be, and the better the conditions for snow).gfs_namer_075_1000_850_thickTuesday – cold air rushes back in behind this storm on Monday and we drop back into high temperatures hovering in the low 40s.

Potential Thanksgiving Nor’easter?

In looking ahead at the long-term GFS model output, I’m noting the possibility for a possible high-impact Nor’easter that would be timed to coincide with the busiest travel day right before and then during Thanksgiving. Of course, this far out, there’s still considerable uncertainty to the forecast, so this scenario could not pan out, or the storm track could be nowhere close to where it needs to be to produce a high-impact Nor’easter. Still, it’s worth watching, as it could be a major headache for folks if it does materialize.gfs_namer_276_1000_850_thick (1)