Winter Summary 2017-2018

After a warmer than normal winter of 2016-2017, the outlook for the winter of 2017-2018 was also for above normal temperatures and precipitation.  The ENSO (El Nino/Southern Oscillation) cycle for the winter was that of a weak La Nina where a cooler than average sea surface temperature is present near the Eastern Equatorial Pacific Ocean.  This pattern of a weak La Nina usually supports cooler than normal temperatures for Western New York.  More on the larger scale weather patterns can be found below in the Hemispheric Pattern section. 

Thanks in part to a very warm February, the winter turned out to be near normal with temperatures slightly cooler than average in Buffalo and Watertown, and just above average in Rochester.  Other than February, every month at each of the three climate locations were at or below normal for temperatures, except one, January in Rochester, which was 0.3 degrees above normal.  Precipitation for the winter was above normal at both Rochester and Buffalo, but well below normal at Watertown.  Snowfall for both the Rochester and Buffalo Airports were near twenty percent above normal from October through April.  The Buffalo Airport received 112.3” of snow, which is 17.9” above the normal of 94.4”.  The Rochester Airport received 120.5” of snow, which is 21.4” above the normal of 99.1”. 

Lake effect snow didn’t really ramp up until December, as there was just one lake effect event in November with areas east of Lake Ontario picking up the most snow on November 19-20^th.  During the month of November, Buffalo received just 0.1” of snow and Rochester received 2.6” of snow.  Starting in December, every month through April for Rochester and Buffalo experienced above normal snowfall except for February in Rochester.  For Cooperative Observer snowfall amounts from the winter, December and March were the months with the most locations reporting above normal snowfall amounts.  In all, there were 12 lake effect events that affected the Buffalo County Warning Area during the winter of 2017-2018.  This is two more lake effect events than the normal of ten for an average winter. 

Snowfall

The winter started off slow for most of Western and North Central New York with only one lake effect snow event through the end of November, and most locations receiving below normal snowfall for the month.  Snowfall in December was well above normal for almost all of Western and North Central New York.  There were six lake effect events for the month of December that dropped several rounds of lake effect snow on different areas of Western and North Central New York.  Two cooperative observer locations received very high snowfall totals for December 2017, they are Perrysburg, NY with 126.4” and 8N Redfield, NY with 160.3”; both of these amounts are greater than amounts received for the entire winter for some other areas.  The month of January saw near normal snowfall amounts across much of the area, with some areas having slightly above or below normal snowfall.  The Buffalo and Rochester Airports were above normal by 5.9” and 4.7” respectively.  January 2018 brought three lake effect events across Western and North Central New York.  Snow in February was near normal.  The last two lake effect events of the season occurred in February, both of which impacted areas east of Lake Ontario the greatest. 

Widespread synoptic snow events were certainly present during the winter of 2017-2018.  The first event occurred on December 11-13^th, when a synoptic system moved through the area and a transition to lake enhancement occurred as the storm passed.  Another synoptic system moved through and transitioned to lake effect snow from December 24-26^th, with this event bringing significant snowfall to the more favored lake effect areas.  Other synoptic events were fairly well spread out throughout the winter with the exception of January where no major synoptic event impacted the Western and North central New York area.  The largest synoptic snowfall for the Buffalo Airport occurred with the snowfall on March 1-2^nd, when a storm total of 12.1” of snow accumulated.  Rochester also received its greatest storm total snowfall for the winter from this storm with a total of 13.3”.  One last large synoptic storm affected Western and North Central New York from March 13-15^th.  With this storm, the Rochester Airport received 9.5” of snowfall, and the Buffalo Airport received 6.0” of snowfall. 

Temperatures

Temperatures this winter were near normal for most areas, especially after a very warm February.  Temperatures through January across the Northeastern United States were running below normal, with Western and North Central New York no different.  A persistent trough was present over the Eastern U.S. through January, until a weak ridge resulting in warmer temperatures setup for the month of February.  Up until the month of February, the winter was well on its way to below normal temperatures.  February was warm enough not only to bring Rochester to above normal for the season, but it also ranked as the warmest February on record for Rochester (33.6F).  February 2018 also ranked 6^th warmest for Buffalo (31.9F) and 4^th warmest for Watertown (29.2F) for monthly February temperatures.  Another cool stretch, due to a persistent trough, extended from March through April. 

Winter Statistics for Buffalo, Rochester and Watertown

Buffalo

Average Temperature, November – March: 30.5F (0.7F below normal)

Snowfall: 112.2” (20^th snowiest)

Days with 1.0” or more of snowfall accumulation: 37 (tied 7^th greatest number of days)

Days with 1” or more on ground: 83

Rochester 

Average Temperature, November – March: 31.5F (0.3F above normal)

Snowfall: 120.5” (19^th snowiest)

Days with 1.0” or more of snowfall accumulation: 31

Days with 1” or more on ground: 83

Watertown

Average Temperature, November – March: 26.7F (0.4F below normal)

Below are tables for temperature records set at the three climate locations for the winter of 2017-2018.

Buffalo

Rochester

Watertown

Hemispheric Pattern

The winter of 2017-18 was relatively cold across Western and North Central New York, as temperatures averaged below normal during four of the five winter months (Nov-March).  This came as a subtle surprise to many, as most long range forecasts were suggesting that temperatures would average closer to normal.  A large part of these predictions hinged on the expected impacts from a weak La Nina, which interestingly enough has been shown by local studies to support relatively cold winters across the Lower Great Lakes. 

La Nina events are defined by lower than normal ocean water temperatures across the Equatorial Pacific.  The cooler water deters convection over the far western Pacific, which in turn allows the overlying jet stream winds to be uninterrupted.  In the case of an El Nino event, enhanced convection in the same area disrupts the upper level winds over the Pacific.  These upper level winds ultimately determine the large scale weather patterns downstream across North America.  During a typical La Nina event, a highly amplified jet stream pattern will be found over the mid latitudes where a large ridge will be favored near the Gulf of Alaska, while a deep downstream trough will be found over the eastern half of North America.  This amplified pattern can be further exaggerated and locked in place by a second hemispheric teleconnection, the North Atlantic Oscillation (NAO).

The NAO is part of the larger scale Arctic oscillation, which as one would expect, relates to the pattern of the arctic jet circling the Pole.  In most cases, this circulation pattern includes troughiness over the northern Atlantic and is directly responsible for supporting a surface feature known as an Icelandic Low.  A low amplitude, Pacific based flow over the east coast of the United States typically feeds into this large storm system.  This fast, near zonal flow will essentially block the southward push of true arctic air into the Great Lakes region, keeping temperatures on the warm side of normal.  There are times though where a Greenland block will set up over the north Atlantic.  Strong ridging in this area will lead to a closed low becoming established over Quebec and often encourages the notorious polar vortex to drift south towards the Lower 48.  This scenario occurs during the negative phase of the NAO which has a high correlation to colder than normal weather over our region.  When this pattern coincides with an amplified flow from a weak La Nina the correlation is even stronger for cold weather in our region.  Such was the case this past winter.

As we opened the season in November, weak troughing became established over eastern Canada as a result of a teleconnection to ridging over the Aleutians.  This led to colder than normal weather over much of Canada, which in turn allowed early season snows to accumulate and persist over Manitoba and Ontario.  The building of this snowpack helped to set the stage for the colder than normal winter which was to follow for the Great Lakes region.

Keep in mind that during four of the five winter months, the hemispheric pattern was dominated by ridging over the northern Pacific and extensive troughing over the eastern half of Canada.  This flow was exaggerated December into early January when the polar vortex drifted some 500 miles further to the south than usual, averaging in a location near James Bay.  Not only did this promote frequent cross polar flows, but it also directed cold air that was manufactured over the abnormally extensive snowpack over Manitoba and Ontario towards our region.  Temperatures over our area plummeted to nearly 5 degrees below normal during this period with even greater departures found just to our north. 

While this general pattern remained in place for the first half of January, the amplitude started to relax as we pushed deeper into the month.  By February, a trough had become established over the western states.  This allowed a broad, flat ridge to develop over the eastern states with a strong southerly jet favoring significant warming over the Great Lakes region.  After several months of colder than normal weather, the mercury in February soared to more than five degrees above normal.  This brought hope for an end to the cold weather, but Mother Nature had a different idea. 

A renewed Greenland block in March enabled a closed low to once again set up shop over eastern Canada.  Temperatures over our region returned to below normal levels where they stayed in place through the spring month of April.  In fact…only 11 of the 61 days (<20%) of March and April had mercury readings above normal.  This cold pattern finally broke down in May as the polar jet retreated to the north while the general amplitude flattened. 

Monthly Highlights

November

There was below normal snowfall for November as a constant flow of Pacific air bottled colder air well to the north for the month, with the one true, brief surge of arctic air mid-month, this on the 10-11^th.  Along with this surge of arctic air, came the first measurable snowfall of the season for many areas including Rochester and Buffalo.  The month finished with several days of above normal temperatures, but the monthly temperature averaged near normal to around one degree below normal across Western and North Central New York.  The first lake effect snow event occurred on Sunday the 19^th through Monday the 20^th. Behind a cold front, lake effect snow began during the morning hours Sunday east of Lake Erie.  Off Lake Ontario, the lake effect snow became heaviest Monday morning with up to a foot of snow falling over the southern Tug Hill region.  Snowfall for the month was lacking, but rainy conditions ended up bringing the monthly precipitation to above normal for many areas, especially in Western New York. 

December

December featured plenty of impactful winter weather events for Western and North Central New York with active lake effect snows and multiple surges of arctic air masses.  After a slow start to the winter season, winters fury rapidly increased with many lake effect snow events, leading to an above normal snowfall month.  In all, there were six lake effect events that occurred across Western and North Central New York.  Snowfall for the month finished between 25-50 percent above normal for most locations.  Major snow events were lacking at both the Buffalo and Rochester Airports, with the heaviest lake effect snow falling south of Buffalo and east of Rochester.  A large portion of the snow that fell in December for both airports was primarily due to several days of snowfall where only a few inches of snow accumulated. 

Two arctic surges brought the temperature for the month to below normal.  All three climate locations were between four and seven degrees below normal for the monthly temperature average.  For some areas, it was the coldest December since the year 2000.  The month can be broken down into four distinct patterns.  The first week to ten days averaged above normal, including a few days in the Lower 50s.  The first arctic surge of the month then lasted through mid-month, dropping overnight temperatures below freezing each night, and subzero for a few nights in the North Country.  A brief thawing spell occurred from the 18^th through the 23^rd, including a few days in the 40s.  Thereafter, arctic air poured over the great lakes region, progressively lowering daytime highs from the lower 30s to the single digits by month’s end.  

January

January started out the same way that December ended, cold.  Temperatures the first week of January were up to 34 degrees below normal for some locations across Western and North Central New York.  Temperatures began warming to much above normal after the first week of January, which helped to contribute to ice jam flooding that occurred in portions of Western and North Central New York. Following the warm spell, an arctic airmass and widespread snowfall affected the area for the middle of the month. This second cold stretch that spanned the middle of the month was then followed by another longer stretch of mostly above normal temperatures to end the month.  January ended up being close to normal with Buffalo and Watertown around one degree below normal for the month, and Rochester 0.3 degrees above normal. 

On January 2^nd lake effect snow combined with high winds caused blizzard conditions in Northern Erie, Oswego and Jefferson counties.  Snowfall during this event was limited, but the combination of snow on the ground and high winds were enough to create the blizzard conditions.  Large lake effect and synoptic snow events were limited for the month of January with only three lake effect events for the month.  Snow for the month was pretty evenly dispersed with most locations getting a few inches of accumulating snow on several days of the month.  Rochester and Buffalo each had a day where a little over six inches of snow accumulated for their maximum daily snowfall in January.  These days were January 17^th at Buffalo and January 30^th at Rochester, with each day there was a weak synoptic system that affected the area.  Snowfall at both the Buffalo and Rochester Airports were above normal, but most location in Western and North Central New York were near or slightly below normal for the month. 

February

February started off with mostly below normal temperatures for the first two weeks, especially across Western New York. On February 14th, a warming trend propelled temperatures above normal for all but one day for the rest of the month.  A persistent trough that was anchored over the Eastern United States through early February started to de-amplify and a low amplitude ridge became the dominant pattern for the rest of February.  During this stretch, daily average temperatures soared to well above average, with some days reaching more than 30 degrees above average.  With the above normal temperatures in February, the average temperature for the winter was significantly increased, helping the winter overall achieve closer to normal temperatures. 

Snowfall for the month finished near normal with some locations receiving below normal snowfall and others getting above normal snowfall.  Buffalo was almost an inch above normal for snowfall, while Rochester experienced its largest monthly deficit of the winter with 5.8 inches below normal.  The majority of the snow in Rochester and Buffalo for February fell on four separate days from weak synoptic systems that transitioned to lake effect.  These days were February 6^th - 7^th and February 9^th - 10^th, and accounted for around two thirds of the snowfall at Buffalo and Rochester for February.

March

For a second year in a row, March 2018 finished cooler than the previous February as a persistent track of storms went mainly to our south and east. Most of March saw an abnormally high number of days with maximum temperatures in the 30s across Western and North Central New York; this resulted in below normal.  Extreme cold wasn’t present for Western New York with temperatures at night for most locations dipping down only into the teens a few nights.  However, some nighttime single digits to near zero temperatures were present in the usual cold spots of North Central New York.  Temperatures finished off warmer than normal for most of the last week of the month. 

The largest snowstorm of the season occurred the first 2 days of the month, when 12.1 inches and 13.3 inches accumulated at the Buffalo and Rochester Airports respectively.  Another storm occurred from March 13^th-15^th, resulting in 6.0 inches and 9.5 inches of accumulating snow at the Buffalo and Rochester Airports respectively.  In total, there were four nor`easters that affected the Northeast in March.  Other than the two mentioned above, the rest of these storms tracked to the south and east of the region leaving Western and North Central New York in a persistent cool pattern. Snowfall, almost all of which fell within the first half of the month, finished well above normal for March. 

April

Temperatures in April were well below normal with monthly temperature records set in Watertown for coldest on record, 10^th coldest on record in Rochester, and Buffalo tied its 11^th coldest April on record. Temperatures in April were below normal for all but seven days in Rochester, three days in Buffalo, and two days in Watertown. Snowfall for the month of April was above normal for most locations including at the Buffalo Airport, where there was 6.9 inches of snow, which is 4.2 inches above normal for April, and Rochester received 5.2 inches, which is 1.3 inches above normal. 

Most of the snowfall for the month fell during two events.  One was a weak synoptic system that brought 2-3 inches of snow; the other was a mixed precipitation event that affected different parts of the area from April 14^th – 16^th.  With the event that affected the area from April 14^th – 16^th, a strong temperature gradient due to a stationary front over the area was in place.  As waves of low pressure moved along this zone, areas to the north in the colder air received snow and areas to the south in the warmer air received rain.  Areas along this boundary received a wintery mixture of rain, freezing rain, sleet and snow as above freezing air.  Some areas during this event received heavy ice accumulations, such as 1.00” in Lowville, 0.65” in Watertown, and 0.50” in Alden.  The hardest hit area for ice accumulation occurred in the North Country during this event. 

Overall it was a snowy winter with near normal temperatures, thanks to a warm February.