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Winter Weather Pattern
Recognition
Ice Storm (500mb)• Trough or upper level low to the west
o Source for upper level divergence (rising motion) and southerly winds which bring moisture and low-level warmer air northward
• Short wave trough or long wave trough generally to the northeasto Source of near surface cold air
• Cold front associated with the upper level trough • Typically shallow arctic air
Ice Storm (500mb)
Ice Storm (500mb)
Ice Storm (850mb)• Southerly component to the wind
o Warm air advection
• Warm (above freezing) temperatures o Must melt the falling snow
Ice Storm (850mb)
Ice Storm (Surface)• Surface temperatures obviously must be below
freezing• Low pressure to the west• High pressure in the northern plains or upper
Midwest• Northerly component to the winds
o Cold air advection
Ice Storm (Surface)
Typical Sounding
Blizzard/Snow Storm (500mb)
• Long wave trough with embedded short wave trough or upper-level closed lowo Upper-level low tends to track over northern Texas
Blizzard/Snow Storm (500mb)
Blizzard/Snow Storm (850mb)
• Low pressure to the east• Cold air (below freezing)• Northerly winds
o Cold air advectiono Frequently strong
• Blizzard
• Gulf moisture to the east or southeasto Advected around the cyclone
Blizzard/Snow Storm (850mb)
Blizzard/Snow Storm (850mb)
Blizzard/Snow Storm (Surface)
• Surface low to the east• Sustained winds (or frequent gusts) of 35+ mph
and visibility of less than ¼ mileo Must be present for at least 3 consecutive hours for a blizzard
• Dense packing of isobars (blizzard)o “Tight” pressure gradient
• Strong winds
• Northerly component to wind
Blizzard/Snow Storm (Surface)
Typical Sounding
500mb Vorticity Average Tracks
From Vanyo 2010
Ice Storm, Blizzard, or Snow
Storm?
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