All posts by Lei Zhao

NYC Weather Update – Mar 29, 2021

A cool and breezy start to the week with temperatures warming into the 50s and low-60s by midweek. A storm system arrives Wednesday bringing a round of soaking rain. An even colder air mass sweeps in behind this storm with below average highs in the upper-40s. Overnight lows going into Friday may dip into the upper-20s.

Rest of today – breezy with with northwesterly winds 20-25 mph and gusts up to 45 mph. A wind advisory is in effect as a result. Mostly sunny with high temperatures in the mid-50s, but feeling like the mid-40s with the wind chill. Overnight lows in the low-40s.

Weather Prediction Center surface forecast for 8AM Tuesday. High pressure will be more directly overhead and ease winds in the region. Warmer flow from the southwest should help temperatures up into low-60s.

Tuesday – sunny with high temperatures in the low-60s. Much less windy with high pressure more directly overhead. Overnight lows in the mid-40s.

Wednesday – slightly warmer with high temperatures in the low-60s but with mostly cloudy skies. Rain moves in later in the day, and will be moderate and steady. Overnight lows drop considerably to around 40ºF with robust cold air advection behind the cold front bringing this rain.

GFS model 850 mb temperature, height, and winds for 8PM Thursday. Much colder temperatures at this height are forecast. 850 mb temperatures are often a decent proxy for surface temperatures.

Thursday wraparound moisture with this storm may bring about more showers Thursday morning with high temperatures in the upper-40s. Overnight lows dropping to around 30ºF as skies clear.

NYC Weekend Weather – Mar 26, 2021

Possibly record-breaking warmth in the low-70s to start the weekend along with strong winds accompanying the passage of a cold front. This frontal boundary brought an outbreak of violent tornadoes to the South yesterday, but luckily will be rather tame in comparison for our region. Cooler weather will occur behind this cold front but especially behind a second storm system Sunday bringing rain. Temps will drop to the low-50s by the end of the weekend.

Rest of today – cloudy with high temperatures in the low-70s. Southwesterly winds 15-20 mph picking up later in the afternoon with gusts up to 40 mph. Overnight lows in the upper-50s as skies clear out.

GFS model 2 meter above ground temperatures and 10 meter above ground winds. Very warm temperatures in the low to maybe even mid-70s by about 3PM this afternoon.

Saturday – sunny with high temperatures in the mid-60s. Overnight lows again in the upper-40s.

Sunday – mostly cloudy with rain developing in the morning and continuing in periods throughout the day. High temperatures around 60ºF. Overnight lows in the low-40s with rain ending and skies gradually clearing.

Weather Prediction Center surface forecast for 8AM Sunday. Low pressure traversing the Great Lakes will bring the potential for a good, soaking rain.

Monday cooler with high temperatures in the low-50s under sunny skies. Overnight lows in the upper-30s.

NYC Weekend Weather – Mar 19, 2021

The rainy day yesterday yields a weekend of largely unbroken sunshine and above average warmth. Strong high pressure will dominate our sensible weather bringing stable, dry conditions. Temperatures will be in the mid-50s generally and this mild trend continues into next week. In fact, this mild weather could carry on for the balance of the month. No major chances for rain to speak of in the upcoming days into mid-week next week.

Rest of today – windy with sunny skies and highs in the low-40s. Overnight lows in the low-30s.

Weather Prediction Center surface forecast for 8AM Saturday. Strong high pressure will be nearly directly overhead.

Saturday – sunny with high temperatures in the mid-50s. Overnight lows again in the upper-30s.

Sunday – very similar to Saturday, sunny with highs in the mid-50s. Overnight lows in the upper-40s.

Monday another great day with high temperatures in the mid-50s and perhaps a few more clouds. Overnight lows in the mid-40s.

NYC Weather Update – Mar 9, 2021

A surge of warmth is coming today and late this week, with highs near or in the 60s. This will be punctuated briefly by a cooler day Wed in the mid-50s, which is still almost 10ºF above normal this time of year. Enjoy the warmth while it lasts because there will be a colder pattern next couple of weeks, starting as soon as this weekend.

Rest of today – warm and sunny with high temperatures around 60ºF. Overnight lows drop to around 40ºF with a backdoor cold front moving through overnight.

Weather Prediction Center surface forecast for 7PM Tuesday. A backdoor cold front is forecast to move through, leading to a slightly cooler day tomorrow before temperatures rebound again late in the week.

Wednesday – the backdoor cold front’s primary impact will be to make Wednesday cooler, in the mid-50s, with a good amount of sun. Overnight lows will be in the mid-60s.

Thursday – this is when the warmth really surges with the backdoor cold front returning northeast as a warm front. Behind this, south winds will lead to temperatures rising well into the mid-60s. The only cap on temperatures will be possible partly sunny cloud cover. Overnight lows in the mid-50s.

Friday a cold front approaches the region from the west. Ahead of this, temperatures remain warm in the mid-60s. A chance of rain will accompany the passage of the front. Otherwise, expect mostly cloudy skies. Overnight lows dropping into the mid-40s. Temperatures will continue to drop through weekend.

NYC Weekend Weather – Mar 5, 2021

We have a cool start to most of the weekend with gradual warming trend taking place as high temperatures move up through the upper-30s into the low-40s. High pressure will be dominating sensible weather with lots of sun and calm conditions. This high remains in control until late next week, when we have our next chance at rain. The center of the high will gradually shift east during this time, inducing warm, southerly/southwesterly return flow next week, continuing the warm up to the point that temperatures could reach near 60ºF by mid-week.

Rest of today – windy with sunny skies and highs in the mid-30s. Overnight lows in the upper-20s.

Weather Prediction Center surface forecast for 7PM Saturday. High pressure is set to build to our west and move in.

Saturday – partly sunny with high temperatures reaching the upper-30s. Overnight lows again in the upper-20s.

Sunday – very similar to Saturday but with sunnier skies and high temperatures in the upper-30s and overnight lows in the upper-20s.

GFS model 850 mb temperature, height and winds for 10PM next Thursday. This shows a remarkable warming trend underway at this level of the atmosphere, which serves as a good proxy for surface temperatures.

Monday warmer with high temperatures in the low-mid 40s under sunny skies. Overnight lows in the low-30s.

NYC Weather Update – Mar 1, 2021

March brings in week of great contrasts, typical of a transition into spring. Periods of rain off and on today before a plunge in temperatures going into Tuesday. Strong northwesterly winds will accompany the cold as the pressure gradient tightens around the departing low bringing rain today. Temps rebound into the upper-40s midweek but drop back towards end of week into the upper-30s.

Rest of today – periods of rain mostly before noon. Breezy with northwest winds increasing into the 15-20 mph by later in the day. Temperatures start dropping with these winds kicking in after noon bringing on strong cold air advection. Clouds clear towards the overnight when lows are expected to drop into low-20s.

GFS model 2-meter above ground level temperatures, and 10-meter above ground level winds at 7AM Tuedsay.

Tuesday – mostly sunny with high temperatures in the mid-30s. Strong northwest winds in the 20-30 mph range with gusts above 45 mph possible. Overnight lows in the low-30s.

Wednesday – high temperatures rebound quickly to near 50ºF with winds subsiding and mostly sunny skies. Overnight temperatures dropping into the mid-30s.

GFS model surface precipitation, and 1000-500 mb thickness for Thursday at 11AM. The blue thickness lines over much of the northeast indicate a return to below normal temperatures on the way.

Thursday temperatures cooling a touch back into the mid-40s with mostly sunny skies. Overnight lows dropping back into the upper-20s.

NYC February 18-19 Snowstorm Forecast – Feb 17, 2021

Synopsis

A very active weather pattern this month brings yet another chance for decent accumulations of snow in NYC. This storm will be on the weaker side, and will slow down as it tracks offshore of the region. The result should be a long duration but likely a generally light to moderate snowfall event. Snowfall totals around NYC will probably be in the range of 4-6″, though with every storm this season, some potential exists for both higher and lower totals. If colder scenarios and better lift are realized, we could see > 8″. A warmer scenario would see more mixing and totals below 4″. Light snow should spread over NYC during the afternoon hours with periods of moderate and potentially heavy snow in the early evening. Mixing with sleet and rain even is possible during the early overnight hours. Snow and sleet could continue into the early afternoon hours Friday.

Forecast Details

At the Surface

Deep arctic air precedes this storm, which will form along a frontal boundary stretching from the Gulf Coast to offshore of the Mid-Atlantic. This low will be on the weak side, only hitting around 1012-1000 mb. For reference, the last couple storms that hit us were about 10-15 mb deeper. Over the course of the week, models have trended colder with the storm, pushing its trajectory further offshore, close to or outside of the 40ºN 70ºW benchmark that signals the best snowmaking potential for NYC during coastal winter storms. It is important to note that even with the track trending colder, mixing is still likely at some point during the storm, and significant mixing would lower overall totals. If we have an overall colder scenario, we may see closer to 8″ by this time Friday.

850 mb Level

There isn’t a strong sign of a robust 850 mb low-level jet with this storm. That’s in line with the profile of a weaker storm with less intense precipitation. However, most models do show the 850 mb warm nose setting up just south of the city, which would favor the strongest precipitation occurring as mostly snow over the city during the Thursday afternoon-early evening time frame.

500 mb Level

A longwave trough that reflects the very cold air over the central part of the US will be in place upstream of this low. There will not be any negatively tilted trough at this level providing enhanced lift for this low, thus explaining the weaker profile of this storm.

300 mb Level

Similarly, the best support for strong lift at this level of the atmosphere won’t come until late in this storm’s evolution. There are no clear entrance or exit regions co-located with the storm early on, signifying an absence of enhanced lift from divergence at this level.

NYC Weekend Snowstorm Update – Feb 5, 2021

Synopsis

Another accumulating snow event is possible during the day Sunday this weekend, with accumulations somewhere in the 2-4″ range currently most likely. If this storm tracks a bit closer to shore, we could see totals more in the 4-6″ range. The timing of this storm is much faster than the previous one, with onset of snow early in the day Sunday, lasting potentially through the early afternoon hours. As a weaker system, without as strong a high pressure system downstream, winds should also not be as robust as with the Monday storm.

Forecast Details

At the Surface

Low pressure developing over the Southern Plains will emerge offshore of the Carolinas later tonight. This surface low will strengthen modestly as it tracks quickly northeast. Current thinking is that the storm track takes it outside of the classic 40ºN/70ºW benchmark that leads to maximized snowfall for nor’easter type systems in this area.

850 mb Level

At this level of the atmosphere, it’s apparent that this storm is much less of a headline maker than Monday’s snowstorm. It’s evident from various models that while there should be enough moisture to sustain precipitation, the winds at this level are not forecast to be anywhere near as strong as on Monday. The lack of a truly robust low-level jet will make for an overall slightly drier scenario.

500 mb Level

Unlike the last storm, the 500 mb level flow for this upcoming storm is more progressive. This will lead to the storm moving faster through the area. One notable factor contributing to the potential for a decent storm this time is that there will be a negatively tilted trough at this level, indicative of a maturing and deepening low. This feature will serve to enhance divergence at this level and induce surface lift in response.

300 mb Level

As was the case with Monday’s storm, a curved jet streak should set up just north and east of this storm’s surface low. The entrance region of this jet streak should allow stronger divergence and enhanced lift as a result.

NYC Nor’easter Snowstorm Update – Jan 31, 2021

Synopsis

A significant snowstorm in store for NYC Monday into early Tuesday morning. Current trends point to 8-12″ likely for most of the city. There is uncertainty with possible mixing late Monday that could cut into this over Long Island, and if the mixing line pushes further northwest, which The European model portrays, this could lower totals in the city to more of the 6-10″ range. It is worth noting that the 850 mb set up suggests the possibility for much bigger totals closer to 18″ if the colder scenarios play out. The timing of this storm is such that the most intense snowfall should occur during the day. A narrow, intense deformation band could remain nearly stationary over some parts of the region during the daytime hours Monday. Strong northeasterly winds will accompany this storm despite relatively modest pressure falls, due to the presence of a 1034 mb high pressure center over eastern Canada creating a tight pressure gradient.

Forecast Details

At the Surface

A low pressure center that tracked through the Midwest this weekend will transfer its energy as it hits the Appalachians to a secondary low offshore of Virginia tonight. The low will then slowly track to the northeast as it deepens somewhat. This isn’t a particularly strong low, and it will elongate, translating eastwards overnight into Tuesday morning (see the last image in the gallery below). The North American models (GFS, NAM) suggest a colder scenario that would see higher snow totals (2nd, 3rd imges below), while the European model (1st image) shows potential for mixing Monday evening. Strong northeasterly winds will accompany the storm.

The presence of very cold air this weekend should help lead to better chances for big totals, however, the cold air will be retreating ahead of this storm, and cold air damming will be modest.

850 mb Level

At this level, a strong easterly low-level jet will bring plenty of moisture into the cold conveyor belt of the storm. The advancement of the warm nose of the low will be key to where the greatest potential for deformation banding and the heaviest snowfall rates set up during the day Monday. The GFS and NAM models (2nd, 3rd images below) depict this warm nose staying just offshore. This would favor the best potential for a mesoscale band setting up right over NYC and slightly north as these bands are typically situated just on the cold side warm nose of a low.

500 mb Level

Part of the reason the surface low of this storm will progress so slowly, bounce around, and elongate is due to the presence of a closed 500 mb low accompanying it. This isn’t really a “classic” set up for a big nor’easter blizzard here, however, the closed low does help keep cold air aloft and help enhance lift via increasing the lapse rate between the surface and this level.

300 mb Level

A curved jet streak should set up just north and east of the developing low during the day Monday. The entrance region of this jet streak should allow stronger divergence and enhanced lift for this low.

NYC Weekend Weather – Jan 29, 2021

An arctic chill with bitterly cold winds kicks off the weekend as strong high pressure moves in. Overnight lows in the teens and high temperatures in the 20s will range 10-15ºF below normal for this time of year. This cold air could set the stage for a nor’easter bringing significant snowfall to the region, with totals > 6″ possible Monday into Tuesday. As usual, track details on this storm will be pivotal, and are not clear at this time.

Rest of today – mostly clear, cold, and windy with high temperatures in the low-20s. A strong arctic high and a departing low will create a tight pressure gradient that ushers in stiff northwesterly winds 20-25 mph. Wind chills will hover around 0ºF. Overnight temperatures drop into the mid-teens with wind chills likewise dropping below zero.

Weather Prediction Center surface forecast for 7AM Saturday. A strong area of high pressure is parked over much of the Eastern US.

Saturday – winds abate with high pressure moving more directly overhead. Sunny, but still cold with high temperatures around 30ºF. Overnight lows will be in the upper-teens under increasing cloud cover.

Sunday – mostly cloudy as the next storm system starts to work in. High temperatures around 30ºF. Overnight lows in the upper-20s with the possibility of snow developing overnight into Monday morning.

Monday stiff northeasterly winds developing along with snow. High temperatures in the low-30s. The storm possibly bringing us significant snow came ashore over the west coast yesterday and will be transiting the country the next couple days. It is eventually forecast to spawn a coastal low, bringing a nor’easter into our region. Even though cold air will precede this storm, offshore waters are still mild, in the low 40s-50s, and with the storm likely to bring southerly/northeasterly flow at the outset, we could see enough warming to mix to rain at the coast. Storm track and strength will be vital to the eventual snowfall totals. Models seem to signal a very tight banding feature bringing heavy snow – you’ve heard this before but these bands are notoriously difficult to pinpoint even a day ahead of the event. If the optimal scenario plays out, we could see a storm with similar or possibly bigger totals than the one in December. Overnight lows Monday shouldn’t budge much, in the low-30s, with some warm advection associated with portions of the storm.