Winter Weather Spotter Course

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Winter Weather Spotter Course

• National Weather Service Northern Indiana

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Course Outline

• Introduction to NWS Winter Weather
  Advisories/Watches/Warnings
• Snow Spotters our network today
• Reporting real time information what do we need
  to know about?
• What to report after the storm is over
• How to measure snow
• How to report your information

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Definitions

• Freezing Rain Rain falls as liquid and then
  freezes on contact
• Sleet Rain drops freeze into ice pellets prior
  to reaching ground.
• Snow An aggregation of many ice crystals
• Graupel Snowflakes which have been heavily
  rimed. Also called snow pellets, soft hail, and
  hominy snow. Looks like uncooked white grits.

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Definitions (cont.)

• Snowfall Amount of new snow which has fallen.
  Measured to the nearest tenth of an inch.
• Snow Depth Total amount of snow on the ground
  (old and new). Measured to the nearest inch.

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Precipitation Type Diagram
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Dec 5, 2002 Raleigh, NC
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Jan 30, 2002 North Webster, IN
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NWS Winter Weather Products
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Watches/Warnings/Advisories

• Hazardous Weather Outlook
• Winter Storm Watch
• Winter Storm Warning
• Lake Effect Snow Warning
• Blizzard Warning
• Winter Weather Advisory

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Hazardous Weather Outlook

• Issued each day between 5am and 6am
• Outlines potential weather hazards expected over
  the next 7 days
• The potential for major storms beyond 2 days will
  be discussed in the HWO

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Winter Storm Watch

• Typically issued 24 to 36 hours in advance of the
  storm
• Issued when potential exists for
• 6 inches or more of snow in 12 hours
• 8 inches or more of snow in 24 hours
• Significant mixed precipitation

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Winter Storm Warning

• Typically issued 6 to 12 hours in advance of the
  storm
• Issued when the following are likely
• 6 inches or more of snow in 12 hours
• 8 inches or more of snow in 24 hours
• 0.25 inches or more of freezing rain

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Lake Effect Snow Warning

• Same criteria as a Winter Storm Warning
• 6 inches in 12 hours
• 8 inches in 24 hours
• Lake effect snow warning implies the localized
  nature of the heavy snow in most cases not
  everyone in a county will receive warning
  criteria snowfall

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Blizzard Warning

• Wind speeds of 35 mph or greater AND
• Visibility of ¼ mile or less in blowing snow
• Conditions must persist for at least 3 hours
• Blizzards may or may not be accompanied by
  falling snow (Ground Blizzard)

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Winter Weather Advisory

• Typically issued 6 to 12 hours in advance of
  storm
• Issued when the following are likely
• 4 to 5 inches of snow in 12 hours
• Light accumulation of freezing rain
• (less than 0.25 inches)

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Where We are Today

• Existing Snow Spotter Network
• At
• NWS Northern Indiana

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Existing Coop Spotters
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2002 Snow Spotters
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Need for More Spotters

• Existing COOP network is evenly spread over our
  County Warning Area (CWA)
• We need to fill in the gaps between COOP and
  official NWS observing sites as you well know,
  snowfall can vary widely within the same county,
  especially in areas which receive lake effect
  snow
• This is where YOU come in!

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Reporting Real time Information

• What type of Information can be useful to us?

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Real Time Information

• Heavy Snow for example, snow falling at the
  rate of 1 inch per hour
• Precipitation type change snow to rain, rain to
  snow, freezing rain, etc.
• Is the precipitation causing problems on roads?
• Significant Blowing and Drifting Snow Is
  drifting making travel difficult (or impossible)?

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Freezing Rain

• Is there a glaze accumulation on roads and
  sidewalks or only on elevated surfaces, such as
  trees and power lines?
• How much ice has accumulated on surfaces. This
  can be difficult to measure directly, but can be
  easily estimated.
• Measuring trick Crack a piece of ice off a
  railing and measure the thickness.

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What to Report After the Storm
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When the Snow Lets Up

• Get a final measurement.
• Report your total snowfall for the event, and how
  long it was snowing.
• For example 7 inches in 10 hours.
• In the case of freezing rain, also report the
  total amount of glaze on surfaces.

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What Do We Use Your Reports For?

• Update forecasts, warnings, and advisories to
  better match conditions being reported
• Our updated forecasts and warnings in turn allow
  local officials to make better decisions
• We use storm total snowfall and ice accumulation
  data to verify forecasts and warnings

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How to Measure Snow

• Yes, that says 54 inches!

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Before the Snow Flies

• Place a snowboard outside. Choose a location away
  from trees, shadows, and known drifting areas.
• A snowboard can be any light colored board, about
  2 feet by 2 feet. A piece of plywood painted
  white works great!
• Mark the snowboard location with a stake so you
  can find it easily in the snow.

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Typical Snow Board
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Measuring the Snow

• If it is windy, it can be more accurate to take
  several measurements on the board and take an
  average.
• After you measure, sweep the snow board clean.
• You can clean the snow board off up to 4 times in
  24 hours, but no more than once in 6 hours.

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Take a Measurement
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Sweep the Snow Board
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Special Cases

• If snow falls and accumulates, then melts, the
  total snowfall will be the maximum measured
  before the snow melts
• If snow falls and melts on contact, never
  reaching 0.1 inch depth, a trace of snow is
  recorded.
• Sleet counts towards the snowfall total, but
  freezing rain does not.

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Let the Snow Fly!