** Winter Weather Options **

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** DEFINITIONS **

[CPR]  = Combined probability (Prob_Field_1 x Prob_Field_2 x ... x
Prob_Field_N)
[MAX]  = Maximum from any member at each grid point
[MD]   = Median
[MDXN] = Median value contoured.  The dashed red line is the union of
all members at the lowest contour value plotted (i.e., where
at least one of the 16 members exceeds the value of the first
median contour).  The dashed blue line is the intersection of
all members at the lowest contour value plotted (i.e., where
all 16 members exceed the value value of the first median
contour).
[MIN]  = Minimum from any member at each grid point
[MN]   = Mean
[MNSD] = Mean and Standard Deviation
[PM]   = Probability Matched Mean Value
[PR]   = Probability (percentage of members meeting/exceeding some
condition)
[SP]   = Spaghetti

** SPECIFIC INFORMATION ON AVAILABLE FIELDS **

[PR]:Prob_Ptype_Snow_or_Ice ->Probability NCEP precipitation type
algorithm indicates snow OR freezing
rain OR ice pellets
[PR]:SnowRate_>=_1"/Hour ->Probability snowfall rate exceeds 1"/hour
for a 3h period.  Conversion of liquid
amount to snowfall uses a snow density
(kg/m^3) = 109 + 6*(TMP - 273.15)
[from J. Hydromet, Aug 2001, pg 377] where
TMP is the maximum temperature of the surface
or from the saturated layer up to 300 mb AGL
[MN]:Snowfall_(3hrs) ->SREF mean snowfall over the previous 3h period.
Conversion of total precip to snow uses a snow
density (kg/m^3) = 109 + 6*(TMP - 273.15)
[from J. Hydromet, Aug 2001, pg 377] where
TMP is the maximum temperature of the surface
or from the saturated layer up to 300 mb AGL
[MAX]:Snowfall_(3hrs) ->As above, except the maximum from any SREF
member
[PR]:Blizzard_Conditions ->Probability of snow or ice pellets AND
wind >= 30 kts AND visibility <= 1/4 mile
[PR]:1000-500MB_Thck<=528 ->Probability 1000 to 500 mb thickness
<= 5280 meters
[PR]:1000-500MB_Thck<=534 ->As above but for thickness <= 5340 meters
[PR]:1000-500MB_Thck<=540 ->As above but for thickness <= 5400 meters
[PR]:Dendritic_Depth>=50mb ->Probability dendritic growth conditions
occur over a 50 mb depth.  Dendritic
growth conditions are defined here as:
omega < 0; dew point depression <= 3 degC
in the layer; -11 degC <= temp <= -17
degC.
[SP]:1000-500MB_Thck_5400m ->Spaghetti plot of 5400 meters 1000 to
500 mb thickness
[SP]:850MB_Temp_0C ->Spaghetti of 850 mb temperature at 0 degC

All SREF information presented herein is for guidance purposes
only and should not be confused with official SPC operational
forecasts.  Links to official SPC operational products are found
at the bottom of every menu.

Many of the SREF products were developed for testing the utility
of SREF analysis in the prediction of SPC mission critical items,
including: thunderstorms and severe thunderstorms, large scale
critical fire weather conditions, and mesoscale areas of hazardous
winter weather. In order to accomplish this goal and test new and
unqiue methods of SREF application in an operational environment,
many fields not produced in the NCEP postprocessor were calculated
locally for SPC purposes.

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