Nov 22

Nov 22, 2014: Warmth Monday, Snow Wednesday?

Forecast Highlights:

gfs_namer_108_850_temp_mslp_precipThe cold pattern which has brought well below normal temperatures over the last week is finally breaking down, with a trend towards warmer temperatures peaking in the 50s on Sunday and the 60s to even 70 degrees on Monday. A cold front will slowly move through overnight but will later stall offshore, when a nor’easter may develop along the frontal boundary and potentially affect the region with rain and snow on Wednesday. Image from NCEP MAG.

Read the rest of this entry »

Nov 21

New 8-Day Forecast Available

As of November 21, 2014, the 8-Day Forecast page has been upgraded to a more visual and interactive format. As before, forecasts are still generated by county, with the exception of Passaic county which is split to west and east. This upgrade, however, adds several new features to the page, with more to come in the near future. The new features and enhancements to the page currently available are listed below:

 

1. Point-and-click format – In the top of this page, the “View Mode” section allows toggling between the standard city/zip code format and the point-and-click format, which displays the forecast for the selected county.

2. New Visual Format – When viewing the forecast for a location, the names of the city/town and county are now displayed in large font in the top of the forecast. The date the forecast is valid through is displayed as well.

3. Hazardous Weather Headline – Based on the forecast for each location, any potential hazards within the 5-day range, their timing and probability are displayed above the forecast.

4. 7-Day Forecast Graphic – In addition to plain text, a 7-day forecast graphic is now displayed for every location in the area above the forecast text.

5. Forecast Summary – The bottom of the page displays a broad overview of the forecast, including the warmest and coldest days of the week, as well as projected rain, snow and ice totals.

 

When opening the page, it should automatically refresh to load the latest available forecast, which will be indicated by an “/#updated” appearing at the end of the address bar. If this does not occur, a manual refresh of the page may be needed in order to view the latest forecast. Work on this page remains in progress, and additional features will be added in the short term. Any comments, suggestions, or error reports can be posted in the comments section below, or e-mailed to weatherinnyc@gmail.com. Included below is a preview of the latest forecast generated for Manhattan.

 

fcst_preview

Nov 19

Nov 19, 2014: Historic Lake Effect Snow in W NY

Notice

This post is an overview of the significant lake effect snow affecting western NY. For the latest NYC metro-centered forecast, please refer to yesterday’s forecast discussion.

Historic Lake Effect Snow Continues in West NY

While significant cold air continues to affect the region, with temperatures this morning in the 10s inland of NYC and even as cold as 22 degrees in Central Park, the main current highlight in the region is the excessive lake effect snow accompanying the strong cold blast, with snow totals over 5 feet over portions of western NY state.

 

les_setup

Graphic illustrating the typical development of lake-effect snow bands. Image URL from Pennsylvania State University, image credit to NWS Buffalo.

Posted above is a simple illustration of a typical lake effect snow setup; in this example, a shallow cold air mass advances over the warm Great Lakes into the northeast US, with moisture from the relatively warm lakes rising and condensing into clouds, which then advance over land and produce precipitation, in the form of snow if temperatures are cold enough. The setup and intensity of lake effect snow bands, among many other variables, also depend on the direction of the wind relative to the lake axis; if the wind in the lower atmosphere is nearly perpendicular to the lake axis, multiple narrow lake effect snow bands may develop, or simply no bands at all. If the lower level wind is parallel to the lake axis, however, development of a single, intense snow band is often favored, producing heavy snowfall rates just downwind of the lake.

 

nam_wind

3-hour 18z NAM forecast from yesterday, valid at 4 PM EST Tuesday (11/18), depicting surface dewpoints in colors and wind barbs in black. Wind barbs indicate the direction the wind is coming from; in this case, winds are coming from the southwest over Lakes Erie and Ontario, and from the west over the NYC area. Image from Tropical Tidbits.

Yesterday’s approximate surface temperatures and winds are illustrated above from the short term NAM forecast. Even though the map above shows dewpoints, the overall idea of cold temperatures over land and warmer lake temperatures can still be inferred from the map. Additionally, the wind direction was oriented nearly parallel to the axes of Lake Erie and Lake Ontario, conditions which are both indicative of the potential for significant lake effect snowfall. Ultimately, a single lake effect snow band developed just east of Lake Erie, remaining stationary over the same locations throughout the majority of the day while consistently producing heavy snow, resulting in excessive snow totals over western New York. Instability was also sufficient to result in thundersnow and snowfall rates over 4 inches per hour under this band earlier in the day yesterday.

 

11.18_1800

Regional radar imagery as of yesterday afternoon, depicting the heavy snow band south of Buffalo just east of Lake Erie, and another band over northwest NY east of Lake Ontario. This band was nearly stationary throughout most of the day, producing excessive snow totals. Image from PSU e-Wall.

Even though locations surrounding the Great Lakes frequently receive lake effect snowfall, especially early in the winter season before the lakes begin to freeze, snowfall of this magnitude is quite anomalous. According to the latest snowfall reports from the National Weather Service in Buffalo, as of 11 AM, many locations near Lake Erie recorded over 40 inches of snow, including a report of 63 inches in Lancaster, NY. Due to the persistence of the snow band over the same locations, however, these significant snow totals are also very localized; less than 10 miles to the north, Buffalo airport only recorded 6 inches of snow. While the lake effect snow will gradually decrease in intensity, snow continues to fall, and is approaching record values in some locations; according to the National Climatic Data Center (NCDC), the maximum 24-hour snowfall record in the US is 75.8 inches in Silver Lake, Colorado.

Nov 18

Nov 18, 2014: Significant Cold Outbreak Underway

Notice

Reminder: The 8-Day Forecast is NOT available this week, as improvements are under progress. The 8-Day Forecast page will be back up on or before Saturday, November 22, with a more visual and interactive format.

Forecast Highlights:

temp18A low pressure system affected the region yesterday with heavy rain and wind, as well as ice and snow well to the north of the area. The frontal passage last night ushered in an anomalously cold air mass for November for a second year in a row, with temperatures more typical of mid-January. The worst of the cold occurred today, with a gradual moderation in temperatures expected to follow, especially by the weekend as a much warmer but also stormier pattern evolves for late November. (Image credit: PSU e-Wall, NAM modeled lows for tonight)

Read the rest of this entry »

Nov 17

Nov 17, 2014 Storm Updates

Occasional updates will be posted below on the rain and wind event affecting the area today. Radar images are from the Pennsylvania State University e-Wall. The next forecast update will be posted tonight.

Links: Saturday’s Forecast | Twitter | Facebook


 

10:00 PM: Cold Blast Begins Tonight

11.18_0215As of 9m, the low pressure center is just north of NY state with a minimum pressure of 997 hPa, merging with a stronger low to its west. A secondary wave of low pressure is quickly tracking NE along the coast and is currently near coastal Maine with a minimum pressure of 997 hPa.

The cold front is currently progressing through the area from the west, with rain having moved out of the area as temperatures are beginning to slowly fall. Earlier this afternoon, a squall line progressed through the immediate NYC area into Long Island and coastal Connecticut, where heavy rainfall rates were observed; most stations in New York City, as well as Islip, NY, recorded over 1/2 inch of rain in just 1 hour. Along with this morning’s rain, the storm total rainfall is generally between 1 and 2 inches from northeast NJ/NYC into Long Island and coastal Connecticut. The heavy rain largely bypassed western NJ which also failed to significantly warm up as much, with totals generally around 1/2 to 1 inch. Strong wind gusts were observed with the squall line as well, including a wind gust of 37 mph at JFK airport.

 

18z NAM modeled high temperatures on Tuesday – while this model has a slight cool bias, this still easily indicates well below average temperatures. Image from Tropical Tidbits.

nam4km_T2m_neus_6Forecast Update: With the cold front off to the east, attention next turns to the significant cold air mass rushing into the region from the north central US, which will produce well below normal temperatures across the region through most of the week. Temperatures will steadily fall through the 30s and 20s tonight as the air mass filters into the region, with parts of Pennsylvania even falling below 10 degrees.

Even though mostly to partly sunny skies are expected on Tuesday, cold air will continue to advect into the region, leading to temperatures only peaking in the mid 20s to low 30s during the day, as shown to the left from the latest NAM forecast – putting this into perspective, Tuesday’s daytime highs will be several degrees below the average low temperatures for this time of the year. Along with a strong NW wind gusting up to 30-40 mph, wind chill values will remain in the 10s to low 20s throughout the day. Even colder temperatures are expected overnight, falling into the 10s across interior portions of the area and the low 20s elsewhere.

The next full forecast discussion will be posted on Tuesday evening, with more information on the upcoming cold, as well as a trend towards warmer but stormier weather around Thanksgiving.

Read the rest of this entry »

Nov 15

Nov 15, 2014: Rain Returns on Monday

Notice

Blog Notice: The 8-Day Forecast page will not be available this week as improvements are under progress. The page will be back online on or before November 22 with a more visual and interactive format.

Forecast Highlights:

gfsp_mslp_pcpn_frzn_us_7Following the first snow event of the season on Thursday night, temperatures have continued to trend cooler, peaking in the low to mid 40s today. A gradual warming trend will resume on Sunday and Monday leading up to a widespread rain event with over 1/2 to 1 inch of rain expected. The cold front will usher in a very cold air mass, with temperatures struggling into the mid 30s along with strong wind gusts resulting in wind chill values in the 10s and 20s. Image from Tropical Tidbits (0z parallel GFS).

Read the rest of this entry »

Nov 13

Nov 13, 2014 Storm Updates

Occasional updates will be posted below on the snow and rain event affecting the area tonight. Radar images are from the Pennsylvania State University e-Wall.

Links: Wednesday’s forecast | 8-Day Forecast | Twitter | Facebook
Estimated Snow Accumulation Map


 

9:40 AM: Storm Overview

nerad25As of 9am, the surface low pressure is positioned approximately south of eastern Maine and east of central NJ. Minimum pressure is near 1006 hPa, and the low pressure is continuing to track NE towards Nova Scotia while slowly deepening.

Since the previous update last night, precipitation continued to expand eastward through southern New England, although surface temperatures failed to cool down as much as forecast over New York City, Long Island, and the immediate coast of Connecticut including cities such as Bridgeport and New Haven, where precipitation type was predominantly rain with only a few snow showers towards the end in some sites. Farther inland, however, accumulations were recorded especially over higher elevations, with up to 1-2 inches of snow in Connecticut away from the coast and 1-3 inches of snow over the higher elevations of northern NJ and SE NY. Preliminary snow totals according to the National Weather Service storm reports peak at 4.0″ in Highland Lake, NJ (Sussex); 3.3″ in Lake Hoptacong, NJ (Morris); 3.2″ in Wolcott, CT (New Haven); and 2.2″ in West Milford, NJ (Passaic).

With the precipitation shield having progressed to the east, clearing skies are expected today with highs in the upper 30s to mid 40s. The next forecast update will be posted either late tonight or on Saturday, with an in-depth analysis on the next precipitation event on Monday, which based on the latest indications is likely to produce rain and warmer temperatures over the area.

 

Read the rest of this entry »

Nov 12

Nov 12, 2014: First Snow Expected Thursday Night

Forecast Highlights:

scenarioDespite the onset of meteorological winter still several weeks away, a winter-like pattern is already affecting much of the US with frigid temperatures in the central US. While the worst of this pattern will remain west of the area, some impacts will nonetheless spread eastward, with the first snow of the season expected on Thursday night especially north and west of NYC. Following a dry weekend, the next rain event is likely on Monday, followed by a second round of colder temperatures.

Read the rest of this entry »

Nov 10

Nov 10, 2014: Early Start To Winter

Forecast Highlights:

gfs_z500a_namer_23A brief warm up is expected over the region through Wednesday, with temperatures generally remaining above average, peaking in the low to mid 60s for highs. Following a strong but mostly dry frontal passage on Wednesday, the coldest temperatures of the winter season so far will spread into the region, with temperatures generally in the 40s for highs and the 20s for lows, along with a few precipitation potentials mainly in the longer range (Image credit: Tropical Tidbits).

Read the rest of this entry »

Nov 08

Nov 8, 2014: Brief Warmth Before Major Cool Down

Forecast Highlights:

f180Following the departure of another strong low pressure system which produced rain over the area on Thursday followed by cold temperatures through today, a high pressure will rebuild into the region with temperatures quickly rebounding into the 50s on Monday and the 60s on Tuesday. A strong cold front on Wednesday will usher in the coldest air mass of the season thus far, with temperatures falling into the 40s along with a few precipitation possibilities in the extended range.

Read the rest of this entry »

Older posts «