Tag Archives: downslope winds

NYC Weather Update – Jan 25, 2021

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A long duration but light impact winter weather event is forecast to hit Tuesday and Wednesday. Since last week, the track of this storm has shifted north, resulting in warmer air present near the coast. This will result in wintry mix and little to now accumulating snow. We miss out on a more potent storm later in the week which will move well offshore of the area. Temperatures throughout the period remain below normal in the mid-30s at best, with a reinforcing blast of cold air late in the week.

Rest of today – mostly sunny with high temperatures in the upper-30s. Clouds increasing overnight with low temperatures around 30ºF.

  • ECMWF forecast total accumulated snowfall valid 7AM Wednesday
  • GFS forecast total accumulated snowfall valid 7AM Wednesday

Tuesday – mostly cloudy with high temperatures in the mid-30s. Periods of light wintry mix/snow during the day as a couple of modest low pressure centers impact the area. Light accumulations expected, probably around half an inch. Overnight lows steady in the mid-30s with rain/snow mixing possible.

Wednesday – rain/snow mix possibly extending into Wednesday morning. High temperatures in the upper-30s. Any accumulated wintry precipitation should melt rather quickly. Overnight temperatures dropping into the low-30s.

GFS model surface precipitation and 1000-500 mb thickness for 7AM Thursday. A potent storm is seen exiting east well offshore from NYC.

Thursday – another low pressure, center, much stronger than the ones associated with the early week develops and tracks well south of us. High temperatures in the mid-30s. The main impact of this storm for us will be the stiff winds it produces as it continues to deepen and the pressure gradient around it tightens. These winds will also be from the northwest, bringing in a colder air mass. Overnight lows in the low-20s as a result.

NYC Weather Update – Jan 11, 2021

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It’s been two weeks now without any appreciable precipitation in NYC and this dry stretch continues this week. A mostly zonal flow regime aloft should provide for generally calm conditions, esp. given a lack of any meaningful supply of moisture. Temperatures should trend into mid-40s with warming westerly downsloping flow modifying the air mass, eventually transitioning to a mild southwest flow later in the week.

Rest of today – mostly cloud with highs in the low-40s. Overnight lows in the low-30s.

Weather Prediction Center surface forecast for 7AM Tuesday. High pressure to our southwest should help drive westerly winds our way.

Tuesday – mostly sunny with high temperatures in the low-40s. Overnight lows in the low-30s.

Wednesday – still mostly sunny with high pressure remaining in control. High temperatures in the mid-40s. Overnight temperatures dropping into the mid-30s.

GFS model 500 mb height and vorticity for 7AM Thursday. Generally flat, zonal flow is seen over our area. However, signs of a big change are visible to the west, over the Northern Plains.

Thursday – High temperatures in the mid-40s again with mostly sunny skies. Overnight lows in the mid-30s.

NYC Weather Update – Dec 29, 2020

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Messy weather ahead going into the New Years holiday for NYC. We start with high pressure moving overhead. This then gives way to a frontal system tomorrow night. After a brief lull, another storm, similar in some ways to the Christmas storm comes in Friday. Both these precipitation will be rain in the city. Temperatures during this period will generally be above normal in the 40s, warming into the mid-upper 40s.

Rest of today – partly cloudy with high temperatures around 40ºF. Clouds will be streaming in from the northwest, originating from the Great Lakes as lake effect snow showers. These clouds will tend to thin out as northwest flow downslopes dries out across the higher terrain north and west of the city. This northwest flow could also result in some strong wind gusts. With strong high pressure forecast to move nearly directly overhead tonight, winds should calm with skies becoming mostly clear. This will favor good radiational cooling, leading to cold overnight lows in the mid-20s.

GOES Geostationary Satellite visible imagery this morning showing clouds streaming off the surface of the Great Lakes towards the East Coast.

Wednesday – partly cloudy with high temperatures again around 40ºF. Overnight, a warm front passes, followed by a cold front. This will result in an increase in temperatures overnight from the mid-30s as well as rain.

Thursday – a mild day despite the passage of the cold front mentioned above, with forecasters noting the air mass behind the front being of milder Pacific origin. High temperatures around 50ºF. Rain chances should diminish quickly after the morning passage of the cold front. The respite will not last too long as the next storm system follows up quickly. Overnight temperatures dropping into the low-30s.

  • ECMWF “Euro” model 24 hour quantitative precipitation forecast ending 7AM Saturday, about .70″.
  • GFS model 24 hour quantitative precipitation forecast ending 7AM Saturday, close to 1″.

Friday – high temperatures in the mid-40s with another storm system approaching. Rain chances increase going into the overnight hours. This storm, like the Christmas storm, is expected to deliver some moderate to heavy rain. However, since it’s forecast to be weaker overall, the winds and precipitation totals shouldn’t be nearly as robust as the last storm. Overnight should shape up to be similar to Wednesday, where temperatures may actually increase into the upper-40s with the passage of a warm front and corresponding warm air advection.