Thursday, December 8, 2016

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Steps Toward Winter Begin
A summary of what's ahead from our Long Range Team:

Image source: WGN TV Channel 9.
  • FIRST SIGNIFICANT COLD PERIOD OF SEASON ARRIVES IN MID-ATLANTIC THURSDAY  12/8 THROUGH THE WEEKEND.
  • JANUARY-LIKE CONDITIONS EXPECTED THROUGH FRIDAY 12/16, HIGHS BARELY CROSSING 40 F FOR MOST AREAS, OVERNIGHT LOWS IN 20S.
  • THIS WIDESPREAD COLD PERIOD RESEMBLES THE WEEK LEADING UP TO THE DECEMBER 19, 2009 MAJOR SNOW EVENT IN THE MID-ATLANTIC. 
  • WE HAVE TARGETED THE PERIOD FROM 12/12 TO 12/19 AS THE NEXT LIKELY PERIOD FOR ACCUMULATING SNOW EAST OF I-81 TO THE 95 CORRIDOR.

Does this mean a major storm is brewing?

Not exactly, at least not yet for the eastern Mid-Atlantic. It does however mean the essential ingredient needed to permit accumulating snowfall in the I-95 corridor and adjacent areas is falling into place: A solid week of serious cold in advance of any approaching storms, whether coastals or clippers. 

The difference between 2016 and 2009: This year, the influence of El Nino and it's associated moisture influx is absent from the indicators. Instead, U.S. weather is now being strongly influenced by a La Nina- driven pattern where the Pacific sea surface temperatures have cooled dramatically from last year at this time. The rapid cooling of surface waters induces ridge of High pressure over the western U.S., and in turn drives a Low pressure trough in the Eastern U.S. Learn more about La Nina's effect on U.S. weather patterns at this NOAA site.



Results of this La Nina so far? You are seeing it now:  
  • An Arctic front blasting through the Midwest heading east, dropping quick amounts of snow -- not crippling but happening fast enough to cause serious disruption.
  • For the metros & coast: Long periods of cold, dry, windy weather. Not much rain. But when it does rain, there are deluges-- but only for 1 day.
  • For areas bordering the Great Lakes:  Higher than normal rainfall and snowfall due to the warm waters being tapped by passing fronts.
  • For everyone east of the Rockies: Reduced snow cover until only just this week due to less moisture available to produce snow. 
What is next?

Once snowcover establishes in the northern and central U.S., and a period of cold controls the East, the stage will be set for any coastal or clipper storms to "over-perform" and be provided the conditions necessary to generate potentially significant snow in the next 2 weeks. We shall be watching as we are certain many Powderhounds will be also...


Latest snow cover from the NOAA National Ice Center


Sunday, November 20, 2016

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Pre-Season Insider's Peek 

This winter, we invite you to be among the first who receive our 
advance weather intel via updates by app, text and email. 
Consider joining the Powderhound Insiders!

Below: Sample screens from the Insider's app of the 2015-16 season.



Friday, October 14, 2016

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What About Winter? 

Part Two - October Indicators 



1) Arctic Sea ice: Slow to rebound from late September melt-off, and seasonal refreeze levels currently lagging behind levels seen before recent winters of 2014 and 2015. Researchers and bloggers alike have noted the unusual nature of this season's sea ice melt and rebound.

2) Snowcover in adjacent areas has rapidly expanded in western and central Siberia to northern & central Canada, relative to seasonal averages. Snowcover is clearly lagging in Alaska as compared to seasonal norms and observations from previous years at mid-October.

3) Polar temperatures: Seasonal readings above 80 North reported by the Danish Meteorological Institute are running several degrees above the seasonal range for this time of year. 

OUR EARLY ASSESSMENT OF WHAT IT MEANS: 
  • Early clues: Arctic/Polar conditions in October provide early indications of how climate factors may interact to influence the start of winter in the Northern Hemisphere, and North America,.
  • Strange days ahead: This season follows an above-normal temperature regime from last winter for the Arctic above 80 North. Now with sea ice lagging but snowcover rising in areas farther south than usual, these competing data point suggest a divergent and erratic start to winter.
  • Possible results:  This inconsistent alignment of ice & snow could lead to wildly fluctuating conditions in early winter. One option would be an early season sharp cold outbreak, then a rapid warm up, followed by equally strong cool downs and erratic snowfall events that briefly disrupt, then quickly disappear.


Part One - Clues from Summer


Finally, as the heat takes a break, we can get the winter forecast gears warmed up with this question: How many school closing curveballs and schedule shutouts could happen this winter? Science students and the FF team are on the case. 

The preliminary report begins below the bullet summary:

  • The above normal temperature pattern in East, connected to growing below normal pattern in West, may be early sign this winter could start like 2015-16: Mild first half, stormy and cold second half.
  • Seasonal melt-off of Arctic sea ice appears on level with readings of the past 3 years, not as low as the September 2012 record meltoff.
  • Rapid transition of El Nino to La Nina conditions sets stage for surprise ice events throughout the season ahead, especially in the Mid-Atlantic.
Orioles Opening Day in April 2003. Photo credit: The Baltimore Sun

ANALYZING SUMMER CLUES FOR THE PRE-WINTER PATTERN

Late summer in the Foot's Forecast team is the start of our seasonal process to identify how pre-winter indicators stand so as to detect developing trends. Large scale hemispheric trends known to influence how winter develops in the Mid-Atlantic include frequency and location of tropical systems, sea surface temperatures in the eastern Pacific and end-of-summer Arctic sea ice meltoff. 

In September 2016, this investigation will be conducted by science students at several high schools in the Baltimore metropolitan area, in collaboration with member of our team across the Mid-Atlantic. Initial findings released arround September 15, draft projections by October 1, full winter assessment by October 30.

Click below if ready for a sneak peek...