A statistical relationship between fall temperatures and winter snowfall

Warmer than normal average temperatures were recorded across Upstate New York during October and November 2015.  The month of November for Glens Falls was the 2nd warmest November on record and for Albany it was the 5th warmest November.

The NWS Albany, NY shows a comparison of monthly average temperatures over the past five years.

The Case Study for GFL

Onto the study: The study was modeled after one done for Boston by R.J. Panuto a former NWS meteorologist, I used the temperature and snowfall data for Glens Falls (GFL), NY The point of the study is to see if there is any correlation between the departure of average monthly temperatures for the month's of October and November and the upcoming winter's (December-April) snowfall departure. The hypothesis is: Warmer than normal fall temperatures lead to below normal snowfall. Colder than normal fall temperatures lead to above normal snowfall.

First the average monthly temperature for October (47.8°)  and November (37.5°) for GFL was computed. Next the average snowfall for December through April was computed. (Note that since October and November temperature data was used in this study the average monthly snowfall for these month's were removed from the total snowfall data for the winter season. These amounts were minimal and would not have any impact on the goal of the study). The average December through April snowfall for GFL is 64.6". (Note that the standard deviation for GFL's snowfall is around 18").

The graphs below are the average October and November temperatures and December through April for GFL for the period of record ( which is 1949-2015 for temperature data and 1949-2001 for snowfall. [Snowfall measurements ceased at the airport with the implementation of Automated Surface Observation Systems or ASOS].

Now a statistical analysis was done to see if there was a correlation between a warmer or colder than normal October or a warmer or colder than normal November and whether or not the following December through April snowfall was above or below normal. A third analysis was done comparing BOTH October and November temperature departures and the upcoming winter snowfall.

The image below shows the number of occurrences of BELOW or ABOVE normal temperatures for October and above or below normal snowfall.


The correlation for October is rather poor at best. Now let's move onto November's temperature departures and snowfall as shown in the next image:



As the graph above shows when temperatures are ABOVE normal for November there were a greater number of cases of BELOW normal snow (histogram on the left side) and when temperatures are BELOW observed snowfall seasons was ABOVE normal in a greater number of cases..

Lastly a comparison between BOTH months having the SAME temperature departure compared to the snowfall departure:



Once again a strong correlation shows up when BOTH months are ABOVE normal then snowfall is BELOW norma l(histograms on the left side of above image) . A similar inverse relationship exists for BELOW normal temperatures for both months and having ABOVE normal snowfall (histogram on the right side of above). However, this last analysis should be used with caution due to the small sample size.

Even though both the two months temperature departure compared to snowfall departure is with a limited number of cases, as well as the November temperature departure used by itself, there is strong significance of a correlation.

All in all the analysis I performed is similar to the results of the Panuto's work and I think that the correlation would probably hold true for other locations in Eastern NY State and New England as well. Also note that this study just gives a simple yes/no "forecast" as to whether or not snowfall will be above or below normal. It doesn't give a quantitative snowfall amount.

This years expected snowfall for Glens Falls (and Albany)?

Based on a very warm November 2015 and my study I would tend to go with BELOW normal snowfall for Glens Falls (and Albany) for the Dec 2015-Apr 2016 period.  Sorry snow lovers but then again there were some seasons that had above normal snowfall with a warmer than normal October, November, and both months together (not many though!)

Harsh Winter Weather Heading Our Way this Weekend

As I mentioned in my most recent blog post very cold air will plunge down across the Northeast States during Sunday and last into Monday. Prior to the arrival of the arctic blast a strong "Clipper" system will move to New York State, spreading snow our way. This system is expected to redevelop off the Delaware/South Jersey Coast. This new low is forecast to intensify at a very rapid pace. This coastal storm will cause additional snow to fall over Eastern NY State into Central and Southern New England during Saturday through Saturday night. Snow accumulations are likely and they could be on the heavy side across the region, especially over New England.

As a matter of Fact BLIZZARD conditions are possible for Southern and Eastern New England and perhaps across Long Island during Saturday

I'll have more on this system later today after new data comes in. Please stay tuned to all the latest forecasts.

Expect More Snow and Frigid Weather

4 Feb 2015 11 AM Surface Map & Radar 

Expect a bit of thaw across the region for today but it will be short-lived as yet another arctic cold front currently extending from the Eastern Great Lakes to Missouri late this morning, blasts through the region by early Thursday AM. This front will be preceded and accompanied by some light snow or snow showers. The most persistent snow fall will occur during early Thursday morning. While the snowfall will be mostly light in intensity there will be a few pockets or briefly moderate and this will occur during the Thursday morning commute so count on some travel impacts.

Snowcast for Thurs 5 Feb 2015

The combination of colder air coming in behind the front on a WNW wind along with a weak wave of low pressure riding up along the front may allow from a few more inches of accumulation for folks across the Taconics and the higher spots in the Greens of Vermont and the Berkshires. But again it looks like a light snowfall not a big storm at all. The snow should taper off by around noon most places (early afternoon to the southeast of Albany). During the afternoon it will turn windy and colder along with falling temperatures. During Thursday morning, temperatures will range from the teens to some mid 20s to the southeast of Albany but by afternoon everyone will see them fall through the teens (into the digits to the northwest of Albany) along with moderate NW winds causing wind chill values between -10° and -20°. The winds will abate some Thursday night and with clear skies it looks like plenty of sub-Zero temperatures. Once again some locations across the Adirondacks to Glens Falls could drop to -20° to -25° by Friday morning. Friday will be sunny but cold throughout with temperatures generally in the teens.

During Saturday, yet another arctic cold front moves through accompanied by clouds and some snow showers. This front looks to have less moisture with it then the one on Thursday, so any snow accumulations that might occur will be even less. Unfortunately this front is expected to stall on Sunday to our south with low pressure riding along it through Monday. As shown on the maps below from the Weather Prediction Center. With arctic air to the north of the front and low "overrunning" is expected to develop, resulting in snow once again returning to the region by Sunday evening or night and continuing through Monday.

Forecast surface maps for 7 AM EST Sunday 8 Feb on left Monday 9 Feb on right

Various data sources including the GFS, GFS ensembles and CIPS Winter weather analog system are indicating the potential for a widespread moderate to marginally heavy snow accumulation across the region by Monday February 9, 2015, especially along and north of an approximate Buffalo to Albany to Boston line.

Percentage of COOP snowfall > 4 inches

Right now the potential for a widespread snowfall of  4 inches is high based on the CIPS analog map as shown to the left.

Percentage of COOP snowfall > 8 inches

Percentage of COOP snowfall > 12 inches

With a moderate chance for 8 inches or more of snow exists especially to the north of Interstate 90, as indicated on the map to the right

Meanwhile the potential for a very heavy snow appears to be very low, <30% from this storm, as shown by the CIPS analog map below.

So once again we'll have another end of the weekend/start of the work week snow threat to deal with. Then following this snow threat expect more of the same - BELOW normal temperatures for much of the remainder of next week.

Major Winter Storm Heading Our Way

A complex , significant, slow moving and muti-hazard winter storm will affect the region from Tuesday through (at least) Thursday night. Even though the start time of the storm is now less than 18 hours from starting, weather data regarding the actual evolution and track of the storm is still uncertain.

The uncertainty in the storm's track will be VERY CRUCIAL in determining precipitation type. If the low tracks right along the coast towards New York City and western Long Islnad then precipitation, while initially starting as snow could mix with or change to sleet and rain in the Hudson Valley and points east late Tuesday and Wednesday; a slightly more east or offshore track to the storm will allow for colder air to remain in place and a mostly all snow will then fall.

One thing is certain about this storm it will have a lot of moisture associated with it thus precipitation amounts will be heavy. Where this precip falls as ALL snow, snowfall totals will be very high likely exceeding a foot with perhaps some areas near 2 feet possible. Right now the central and northern Catskills and the southern Adirondacks as well as the higher terrain to the west of Lake George appear to be mostly snow.

Elsewhere, snowfall amounts will range from a few inches across the lower Hudson Valley and northwest Connecticut to as much as 6-12 inches from about Hudson north (including the Capital District) to Glens Falls. Expect similar amounts to the east across Southern Vermont and the Berkshires. Its over these latter two locations where a better chance for snow changing to or mixing with rain or sleet could occur as temperatures here will be warmer.

The Hudson Valley region may be subjected to the snow mixing with or changing to sleet, freezing rain or rain. In addition "downslope" easterly winds may cause a “precipitation” shadow to develop here. If this were to happen then the air would dry and warm lessening the amount of preciptation. However if the shadow is NOT strong and warmer air doesn't allow for the snow to mix or change to rain or sleet then snowfall amounts here will be much higher.

The above map shows most of Western New England, Eastern and Central New York State under a Winter Storm Watch (WSW). In addition the Lower Hudson Valley and Connecticut while NOT under a WSW ARE under a FLOOD WATCH

STORM HAZARDS:

Heavy precipitation: 

Heavy snow: across the Catskills and Hilltowns and Southern Adirondacks where accumulations will exceed 12 inches.

Heavy Rain: Lower Hudson Valley and NW Connecticut after a period of accumulating snow. Potential small stream and urban flooding

Wind:

Periods of gusty East winds with gusts to 40-50 mph possible across the higher terrain of the Catskills, Taconics, Berkshire and Green Mountains during Tuesday could cause blowing snow and perhaps some sporadic power outages.

START TIME: Daybreak Tuesday over the Lower and Mid-Hudson Valley, Capital District between 9AM and Noon with areas north of the CD between Noon and 3 PM

END TIME:  When its finished...seriously very Late Thursday night.

I'll have more on the storm this evening as well as maps including a snowfall forecast, too.