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 northeast o Source of near surface cold air Cold front associated with the upper level trough Typically shallow arctic air

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 low o 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 advection o Frequently strong Blizzard Gulf moisture to the east or southeast o Advected around the cyclone

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 mile o 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? 1

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