11:15 AM | *Cold is getting old, but it just won't fold*

Discussion

While we are entering a noticeably milder stretch of weather in the Mid-Atlantic region for the second half of this week, there are signs for a return to a very cold weather pattern across the central and eastern U.S. by the middle and latter parts of next week. In fact, upcoming changes to the upper level atmosphere in the northern hemisphere resemble the overall pattern seen during the “polar vortex” cold air outbreak experienced earlier this winter.

The polar vortex is an area of cold low pressure that typically circulates and strengthens around the Arctic region in the wintertime and then weakens in the summer. During winter, pieces of the polar vortex can break off and be sent southward with the jet stream to either the Europe/Asia side of the North Pole or to North America. Meteorologists try to track the positioning of the polar vortex as a way of predicting Arctic air outbreaks that potentially could drop southward into the mid-latitudes. Computer forecast models can show the position of the polar vortex through their forecasts of heights of different atmospheric pressure levels. Last night’s European computer model 10-day forecast of the 500 millibar height field (~18,000 feet up in the atmosphere) clearly shows yet another example of the polar vortex being distributed to mid-latitudes – in this case to both sides of the pole (see forecast map above). This particular upper-level scenario is forecasted to occur in 10 days and it will likely be accompanied by much colder-than-normal air in the central and eastern US.

Not to be outdone, the main U.S. (NOAA) forecast model called the Global Forecast System (GFS) confirms this idea of future cold as it also has a very cold-looking overall weather pattern in the 7-10 time period that coincides with the European model forecast. Last night’s GFS Ensemble 500 millibar forecast map (below) for the 7-10 day time period features a deep trough of low pressure in the northeastern part of the U.S. (blue) and a strong ridge of high pressure (red/orange) extending northward along the west coast of the U.S. and Canada. The combination of the trough in the east and the ridge in the west will likely force numerous Arctic air masses to drop southward from central Canada into the central and eastern U.S. as we close out February and begin the new month of March – just as it did earlier this winter. In addition, the high pressure ridging that virtually surrounds the eastern trough is indicative of a “blocking” pattern in the upper atmosphere that promises to keep the cold air in place for awhile in the central and eastern U.S well into the month of March.

One final note...this winter has had a habit of generating snow at the front-end of a warm-up (e.g., this morning) and at the back-end of a warm-up (e.g. the snowstorm on the day after Super Bowl Sunday). If this pattern holds true, look out for possible significant snow in the early or middle part of next week as we transition back to a much colder-than-normal weather pattern.

[map courtesy Penn State eWALL]

10:20 AM | Two large and active sunspot regions rotating out of the "line of fire"

[Image from Saturday, February 8th]

Discussion

The sun continues to go through a relatively weak solar maximum phase during solar cycle 24; however, in recent days there were two active and large sunspot regions (AR1967 and AR1968) which were being closely monitored for possible major eruptions. Fortunately, these two sunspot regions have now crossed much of the visible side of the sun without producing a single X-class solar flare (most severe type). The latest image of the sun (above) shows these two sunspot regions just about to move onto the back side of the sun and completely out of the “line of fire” with respect to the Earth. NOAA forecasters are still estimating chances of an M-class solar flare at about 60% from these regions and X-class flares at about 20%, but these chances are diminishing and any eruption at this time would likely produce only a glancing blow to the Earth’s upper atmosphere. A minor coronal mass ejection did hit the Earth’s magnetic field on Friday, February 7th, producing northern lights across much of the high latitudes.

12:15 PM | February Outlook: stormy and still cold for the Mid-Atlantic region with above-normal snowfall

Discussion

A look back at January January has featured well below-normal temperatures in the Mid-Atlantic region along with above-normal snowfall in most areas; especially, north of the PA/MD border. Specifically, temperatures through Tuesday, January 28th were 4.2 degrees below-normal at Philly Intl Airport, 3.4 below-normal in Central Park, New York City, and 3.2 degrees below-normal at Reagan National Airport in Washington, DC. Snow-wise it has been a banner month in much of the Mid-Atlantic region north of the PA/MD border. Philadelphia, for example, has received 24.9 inches of snow which ranks as the 4th snowiest January since 1872. Central Park, NY is also well above-normal for January with 18.9 inches of snow accumulation.

A look ahead to February February looks like it’ll be a stormy and colder-than-normal month for the Mid-Atlantic region, but temperature departures from normal will likely not be as significant as they were in January. Snowfall should be above-normal for February as an active and stormy pattern will likely produce multiple snow threats in the region beginning as early as next week – the first full week of the new month. The core of the coldest air in terms of temperature departures from normal has been centered over the Upper Midwest/Great Lakes and that pattern should continue in February. As a consequence, the December-February time period could very well end up being in the “top ten coldest” for places like Chicago, Illinois by the time February is over.

Upper level differences and an "atmospheric battle zone" One difference in the overall upper level pattern in February will likely be the re-establishment of the southeastern ridge of high pressure that was largely absent in January. This will probably result in warmer-than-normal temperatures in the Southeast US for the month and, given the expected continuing cold air across the northern US, it should set up quite an “atmospheric battle zone” with a large temperature gradient across the south-central US and an active southern branch of the jet stream. This "battle zone" between the increasingly warm air in the Southeast US and the lingering cold across the northern tier of states should fuel some pretty strong storms during the month and lead to above-normal snowfall in the Mid-Atlantic region. An important aspect of the increasingly strong southeastern upper level ridge is that it will tend to "open the door" for Gulf of Mexico moisture to flow into the Mid-Atlantic region from the southwest.

NOAA temperature anomaly forecast map for February Finally, one of NOAA’s longer-range computer forecast models (Climate Forecast System) is predicting a cold month for much of the nation (above) where “blues” represent below-normal temperature regions and “red/oranges” warmer-than-normal areas. This model has had a pretty good track record when close to event time and its forecast map represents quite well my thinking for the month of February with respect to nationwide temperature anomalies.

10:00 AM | ***Siberian connection to next week's cold as this incredible long-lasting frigid pattern continues into early February***

[GFS forecast of 2-meter temperature anomalies; courtesy WeatherBEll Analytics]

[GFS forecast of 2-meter temperature anomalies; courtesy WeatherBEll Analytics]

Discussion

Overview In my many years of weather forecasting, I have seldom seen an overall pattern with the type of sustained bitter cold that will likely be experienced in much of the eastern half of the nation this week right into February. To find such brutal cold one has to go back to January 1994 or January 1985 and for sustained cold perhaps to the winters of the middle 1970's (76-77, 77-78). The current air mass in the eastern US rivals the “polar vortex” cold air outbreak of earlier this month, but that was a rather short-lived, albeit very painful, period compared to what we’ll likely experience from today into early February. It is certainly time to take notice when the main US computer forecast model (GFS) predicts temperatures anomalies of 30 to 50 degrees below normal - in back-to-back weeks - during the climatologically coldest time of the year [purple regions of the GFS 2-meter temperature anomaly forecast maps; courtesy WeatherBell Analytics at weatherbell.com]. Heating systems will be sorely tested during this period and, needless to say, the bills will be as high as they have been in a long time.

Next couple of days Tuesday's Mid-Atlantic snowstorm ushered in the first Arctic air mass that began this long-lasting cold weather pattern. Temperatures bottomed out around zero in many of the suburbs of the big cities during the past couple of nights and will no doubt drop to the low single digits late tonight with a fresh influx of Arctic air. Flirting with the 0 degree mark in the I-95 suburban locations for three nights in a row is indeed a rarity in this part of the country. It is not just the Mid-Atlantic region that is in the deep freeze. Temperatures dropped to the freezing mark in many parts of Florida and there is a winter storm warning for the southeastern coastal region of Texas as Houston and Galveston may receive some frozen precipitation in the near term.

Siberian connection to next week's cold Yet another Arctic air outbreak is destined to move into the Mid-Atlantic region on Sunday and then, after a less harsh Monday, an absolute brutal air mass will invade the central and eastern US on Tuesday and Wednesday. That particular Arctic blast has its origins in Siberia and it promises to feature some incredible cold (more details below in the video discussion). Siberian air masses are often quite noteworthy as they have in the past produced some record-breaking cold in this part of the world. Siberia is an extensive land mass and air masses that spend some time in that region this time of year can get amazingly cold as there is no nearby water body to help modify its temperatures. The “cross polar” air mass that is expected to arrive in the eastern US on Tuesday and Wednesday may not be the last as the overall weather pattern could certainly bring another into the US.

Snow threats As far as snow is concerned, with these multiple Arctic air outbreaks there will be numerous snow threats. Snow showers are possible late Thursday in the I-95 corridor before the arrival of the next Arctic blast, but this should not amount to much in terms of accumulations. The next Arctic front on Saturday will contain more moisture and there can be a couple inches of snow as a result in the I-95 corridor before more frigid air moves in for Sunday. Yet another Arctic front will approach the Mid-Atlantic region on Sunday night and Monday and there is the potential for a storm to form along the frontal boundary zone. In fact, the upper air pattern for this frontal system resembles somewhat the pattern associated with Tuesday's snowstorm as there is an impressive short wave of energy rounding the base of a long wave trough. No matter if a storm does actually materialize on Monday near the Mid-Atlantic coast, there will no doubt be some painfully cold air invading the central and eastern US on Tuesday and Wednesday with the arrival of the "Siberian" air mass. Temperatures next week could drop to 25 degrees below zero in Chicago, near zero around the big cities along the I-95 corridor, and a deep freeze is likely way down in the Deep South.

Video

httpv://youtu.be/Ev_17fNbjWo

12:15 PM | **The polar vortex will once again get distributed to the mid-latitudes**

Discussion

The polar vortex is an area of cold low pressure that typically circulates and strengthens around the Arctic region in the wintertime and then weakens in the summer. During winter, pieces of the polar vortex can break off and be sent southward with the jet stream to either the Europe/Asia side of the North Pole or to North America. Meteorologists try to track the positioning of the polar vortex as a way of predicting Arctic air outbreaks that potentially could drop southward into the mid-latitudes. Computer forecast models can show the position of the polar vortex through their forecasts of heights of different atmospheric pressure levels. Last night’s European computer model 10-day forecast of the 500 millibar height field (~18,000 feet up in the atmosphere) clearly shows another rather typical example of the polar vortex being distributed to mid-latitudes – in this case to both sides of the pole (see forecast map). This particular upper-level setup is forecasted to occur in 10 days and it will continue the bitter cold weather pattern that begins early next week in the central and eastern US. One major Arctic air outbreak arrives in the Mid-Atlantic region this coming Tuesday and, given the expectation for the polar vortex to be distributed southward by later this month, another major Arctic air outbreak can be anticipated here in the mid-latitudes as we close out the month of January. This upcoming deep freeze will rival the outbreak earlier this month with sub-zero readings in many areas across the central and eastern US and it will last for a considerably longer period of time.

9:30 AM | A downward trend in global temperature anomalies and the role of the Pacific Ocean

Discussion

Overview Solar and oceanic cycles are the most important drivers of all weather and climate on our planet and the most important ocean of all is the Pacific. This large body of water covers about a third of the planet’s surface and is bigger than all of the Earth’s land masses combined. Both the Pacific and Atlantic Oceans go through sea surface temperature phases that are characterized as cool (negative) and warm (positive). While there are other important factors that impact global temperatures (e.g., solar cycles, volcanic eruptions), the given temperature phase of the Pacific Ocean has historically been found to be a major factor in global temperature anomaly trends. Indeed, the Pacific Ocean seemingly flipped into a long-term cool phase during the previous decade and global temperature anomalies have generally been trending downward since that period of time.

Pacific Decadal Oscillation (PDO) The Pacific Decadal Oscillation (PDO) is a climate index based upon long-term patterns of variation in sea surface temperature of the north Pacific. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of about 20°N. During a warm (positive) phase, the west Pacific becomes cool and part of the eastern ocean warms; during a cool (negative) phase, the opposite occurs. These phases result from the direction of winter winds in the northern Pacific: winter winds blowing chiefly from the southwest result in warmer conditions in the northern California Current (CC); conversely, when winds blow primarily from the north, upwelling occurs both in the open ocean and at the coast, leading to cooler conditions in the northern CC.

The PDO temperature phase in the north Pacific tends to have an impact on the shorter-term sea surface temperature cycles of the tropical Pacific in the equatorial region. Specifically, warm phases of the PDO are generally associated with stronger and more numerous El Nino (warmer-than-normal) events in the tropical Pacific and weaker and fewer La Nina (colder-than-normal) episodes. During cold phases of the PDO, La Nina tends to dominate El Nino in the tropical Pacific. In the past several years, during the current cool phase of the PDO, La Nina conditions have indeed dominated the scene in the tropical Pacific region.

Warm and cool phases of the PDO can persist for decades, usually about 20 to 30 years. A warm phase occurred from 1925 to 1946, a cool phase from 1947 to 1976, and then another warm phase from 1977 to 1998 [PDO Index plot below]. Global temperature anomalies have tended to track these phases quite well with, for example, the very warm decade of the 1930’s having occurred during a warm phase, the colder-than-normal period of the 1950’s, 1960’s and first part of the 1970’s corresponding with a cool phase, and the warmer-than-normal decades of the 1980’s and 1990’s having occurred during a warm phase of the PDO. While the PDO trend has been somewhat jagged after the turn of the 21st century, it now appears that it slipped into a long-term cool (negative) phase during the middle part of last decade and that same sea surface temperature pattern continues today.

PDO Index Plot courtesy NOAA: Time series of shifts in sign of the Pacific Decadal Oscillation (PDO), 1925 to present. Values are averaged over the months of May through September. Red bars indicate warm (positive) years; blue bars cool (negative) years. Note that 2008 and 2012 were the most negative PDO Index values recorded since 1956. For more info: http://www.nwfsc.noaa.gov/research/divisions/fe/estuarine/oeip/ca-pdo.cfm

A downward trend in global temperature anomalies Global temperature anomalies have tended to trend downward, albeit in a jagged fashion, since around the time of the latest flip in the PDO from a warm-to-cool phase. The 2-meter global temperature anomaly plot (below) produced by WeatherBELL Analytics utilizes data from NOAA/NCEP’s Climate Forecast System (CFS). This dataset is an appropriate choice for historical global temperature comparisons and it is described in detail below.

[2-meter global temperature anomaly plot since 2005; courtesy WeatherBELL Analytics at weatherbell.com]

NOAA/NCEP Climate Forecast System “reanalysis” NOAA/NCEP’s Climate Forecast System is a model representing the global interaction between the oceans, land and atmosphere. This model offers hourly data with a horizontal resolution down to one-half degree (about 56km) on a global basis for a number of weather parameters. The CFS model uses the latest scientific approaches for taking-in, or assimilating, observations from many data sources: surface observations, upper air balloon observations, aircraft observations, and satellite observations. This approach has advantages over using “thermometer-based” surface data alone as that type of data is more limited in spatial resolution and often requires “adjustments” in order to reduce or eliminate the known problem of the “urban heat island” effect which impacts many official weather stations around the world. Indeed, the NOAA/NCEP “reanalysis” effort has produced a uniform, continuous, and best-estimate record of the state of the ocean-atmosphere for use in climate monitoring and diagnostics. The NOAA/NCEP method keeps the model’s software constant and runs the model retrospectively from 1979 (beginning of the satellite observation record-keeping era) to the present. [For more info on the NOAA/NCEP CFSR data: http://www.ncdc.noaa.gov/data-access/model-data/model-datasets/climate-forecast-system-reanalysis-and-reforecast-cfsrr].

11:45 AM | January looks to be colder than normal in the central/eastern US - perhaps even significantly - thanks in part to a stratospheric warming event

Discussion

There are reasons to believe that January will be a colder-than-normal month in the eastern and central US - perhaps even much colder-than-normal and the coldest in many years - and part of the reason for this outlook is a stratospheric warming event that is now underway over the northern latitudes. In addition to the stratospheric warming event that is forecasted to continue by the GFS computer forecast model (5-day polar stratospheric temperature forecast map shown above), supporting evidence for a colder-than-normal January comes from the very latest NOAA/NCEP Coupled Forecast System model temperature anomaly forecast for January which is significantly colder-than-normal in the central and eastern US.

The phenomenon of stratospheric warming was first discovered in 1952 and there have been about 30 events registered since then or about one every two winters. Research suggests that stratospheric warming events are a consequence of the interaction between the North Atlantic, the troposphere and the stratosphere, and there tends to be an increased number with a warm North Atlantic Ocean as currently exists. During the winter months in the lower polar stratosphere, temperatures on average are below minus 70 degrees Celsius. The cold temperatures are combined with strong westerly winds that form the southern boundary of the stratospheric polar vortex. The polar vortex plays a major role in determining how much Arctic air spills southward toward the mid-latitudes. This dominant structure is sometimes disrupted in some winters or even reversed. Under these circumstances, the temperatures in the lower stratosphere can rise by more than 50 degrees in just a few days. This sets off a reversal in the west-to-east winds and the partial or even complete collapse of the polar vortex.

In response to the stratospheric warming at the high latitudes, the troposphere in turn cools down dramatically and this cold air displacement is then transported from the tropospheric high latitudes to the tropospheric middle latitudes. The entire process from the initial warming of the stratospheric at high latitudes to the cooling in the troposphere at middle latitudes can take weeks to unfold and ultimately can lead to numerous Arctic air outbreaks in the central and eastern US. An in-depth video discussion on the stratospheric warming phenomenon can be found at http://thesiweather.com/meteorology-101/. A detailed video on the current situation is available (below). We’ll continue to monitor all of this in the days and weeks to come here at "thesiweather.com".

Video

httpv://youtu.be/RchIBfSIhmU

10:15 AM | Weakest solar cycle in a century

[current solar image courtesy NASA]

Discussion

Overview We are now about halfway through the solar maximum phase of the current solar cycle, 24, but it is remarkably weak relative to previous cycles. In fact, solar cycle 24 is on a pace that would make it the weakest cycle in one hundred years. Not since solar cycle 14 which peaked in 1906 have we experienced such a weak solar cycle. Solar cycle 24 began after an unusually deep solar minimum that lasted from 2007 to 2009. In fact, in 2008 and 2009, there were almost NO sunspots, a very unusual situation that had not happened for almost a century.

Consequences of a weak solar cycle First, the weak solar cycle has resulted in rather benign “space weather” in recent times with generally weaker-than-normal geomagnetic storms. Research suggests that this is likely due to reduced magnetic field strength inside the coronal mass ejections that shoot off the sun’s surface. The milder space weather reduces drag on satellites which makes it easier to keep them in orbit; however, it also allows space junk to last longer which can pose problems for operational satellites.

Second, it is pretty well understood that solar activity has a direct impact on temperatures at very high altitudes in a part of the Earth’s atmosphere called the thermosphere. This is the biggest layer of the Earth’s atmosphere which lies directly above the mesosphere and below the exosphere. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation and are highly dependent on solar activity.

Finally, if history is a guide, it is safe to say that weak solar activity for a prolonged period of time can have a negative impact on global temperatures in the troposphere which is the bottom-most layer of Earth’s atmosphere - and where we all live. There have been two notable historical periods with decades-long episodes of low solar activity. The first period is known as the “Maunder Minimum”, named after the solar astronomer Edward Maunder, and it lasted from around 1645 to 1715. The second one is referred to as the “Dalton Minimum”, named for the English meteorologist John Dalton, and it lasted from about 1790 to 1830. Both of these historical periods coincided with below-normal global temperatures in an era now referred to by many as the “Little Ice Age”. In addition, research studies in just the past couple of decades have found a complicated relationship between solar activity, cosmic rays, and clouds on Earth. This research suggests that in times of low solar activity where solar winds are typically weak; more cosmic rays reach the Earth’s atmosphere which, in turn, has been found to lead to an increase in certain types of clouds that can act to cool the Earth.

Outlook The increasingly likely outcome for a weak solar cycle continues the recent downward trend in sunspot cycle strength that began over twenty years ago with solar cycle 22. If this trend continues for the next couple of cycles, then there would likely be more talk of another “grand minimum” for the sun. Some solar scientists are already predicting that the next solar cycle, 25, will be even weaker than this current one. However, it may be just a bit too early for high confidence in these predictions since some solar scientists believe that the best predictor of future solar cycle strength involves activity at the sun’s poles during a solar minimum and the next solar minimum is still likely several years away.

Video

httpv://youtu.be/QN_iIyqy9G0

12:15 PM | Global sea ice areal extent at highest level since 1994; southern hemisphere continues on an amazing run

Discussion

The southern hemisphere sea ice areal extent continues its recent impressive run at daily record high levels when compared to all prior years in the satellite record-keeping era which began in 1979. This stretch of daily record high sea ice areal extent in the southern hemisphere has actually been occurring for the past several weeks. In fact, the southern hemisphere sea ice areal extent has had quite an amazing run during the past few years from below normal levels to the current well above normal values (above map courtesy University of Illinois "cryosphere"). On a global basis, sea ice areal extent is currently above normal and, in fact, has now reached levels not seen since around 1994 - thanks in large part to the happenings in the southern hemisphere.

The northern hemisphere sea ice areal extent is still below normal for this time of year although it has gained significantly compared to one year ago. In general, the northern hemisphere sea ice areal extent has been at below normal levels since the mid 1990’s. Two distinct trend lines can be seen in the northern hemisphere sea ice areal extent dating back to 1979. First, the northern hemisphere sea ice areal extent featured an “above normal” and general “sideways” trend until the mid 1990’s and then, following that point in time, there has been an overall downward trend to the current below normal values. This directional change in trend during the mid 1990’s correlates quite well with a northern Atlantic Ocean sea surface temperature cycle that is tracked by meteorologists through an index called the Atlantic Multidecadal Oscillation (AMO). Indeed, the Atlantic Ocean has a significant impact on northern hemisphere sea ice and the AMO index flipped in phase during the mid 1990’s from negative (cold) to positive (warm), and the northern hemisphere sea ice areal extent has been in a general downward trend ever since. Once the northern Atlantic Ocean sea surface temperatures flip back to cooler-than-normal values – perhaps 5 or 10 years from now - the northern hemisphere sea ice areal extent should return to the normal or above normal levels seen prior to the mid 1990’s.

Video

httpv://youtu.be/wSV_VPvbj_g

12:00 PM | 2013-2014 Winter Outlook for the Mid-Atlantic Region

Video

httpv://youtu.be/KMh5WcZwBCo

Discussion

Looks like the Mid-Atlantic region is leaning towards the colder and snowier side of normal for the upcoming winter of 2013-2014…

Recap of last winter Last winter featured warmer-than-normal conditions in the Mid-Atlantic region during December and January, but then temperatures slid to slightly below normal during February and well below normal in March. Perhaps the most memorable feature from last winter is that there, in fact, were no memorable snowstorms. While several small snow accumulation events did occur in the region, there were no significant storms last winter with anything above 4 inches or so. This winter, however, should feature some episodes in which the timing will be just right between cold air outbreaks, an active southern jet, and storminess to produce significant snow events.

There are three major factors that will play an important role in the winter weather around here:

1) Lack of a strong El Nino/Southern Oscillation (ENSO) signal in the tropical Pacific Ocean 2) Low solar activity that frequently leads to high latitude blocking and, in turn, Arctic air outbreaks for the central and eastern US 3) Above normal snowpack across the Northern Hemisphere

Neutral ENSO signal in the tropical Pacific Ocean All indications are that the sea surface temperature (SST) anomalies in the tropical Pacific Ocean will stay rather close to neutral during the upcoming winter season. It is very likely that there will be not be a strong El Nino (warmer-than-normal SSTs) or La Nina (colder-than-normal SSTs) any time soon in the tropical Pacific Ocean and that tends to open the door for a bigger influence around here from another part of the world such as in the northern latitudes and the North Atlantic Ocean. A strong signal from the tropical Pacific Ocean would typically become the dominating factor with respect to Mid-Atlantic winter weather no matter what takes place elsewhere around the world; however, with a neutral signal expected this winter, it is time to look elsewhere.

Low solar activity and high latitude blocking Research has shown that low solar activity tends to lead to the formation of a blocking pattern in the high latitudes (e.g., Greenland) during winter months which, in turn, leads to numerous Arctic air outbreaks into the central and eastern US from central Canada. While we are actually in a period of solar maximum for the current solar cycle, #24, it happens to be one of the weakest solar cycles in many decades and low solar activity is expected to continue this winter. Indeed, a look at numerous analog years with low solar activity reveals an unmistakable signal for high latitude blocking during winter months. This type of blocking pattern can be tracked through an index called the North Atlantic Oscillation (NAO) which would typically turn negative in times of high latitude blocking, and I expect that to happen frequently during this upcoming winter season as this may turn out to be the most important factor of all.

Above-normal snowpack in the Northern Hemisphere An important source region for cold air in this part of the US during the winter season is Eurasia - on the other side of the North Pole - and studies have shown that when snowpack increases in that part of the world during the month of October, and is above normal at the end of the month, then Arctic cold air outbreaks are sure to follow during the subsequent winter months in the central and eastern US. Indeed, snow cover in Eurasia increased dramatically during October reaching above normal levels by the end of the month. In fact, the Eurasian snowpack reached the 4th highest level in the past 46 years and the entire Northern Hemisphere snow cover reached the 7th highest level in that same 46 year period.

Summary of Winter Outlook for the Mid-Atlantic Region: The Mid-Atlantic region will lean towards the colder and snowier side of normal with temperatures some 0.5 to 1.0 degrees below normal for the winter season (November through March) and snowfall at 100-140% of normal. Normal snowfall amounts (which should be the minimal amounts this winter) are as follows: 15” at DCA, 21” at BWI, 21” at PHL, 29” at Central Park, NY