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Decoding FWC

Decoding FWC Numeric Guidance

Decoding MAV, and NGM, and NGM Guidance
The NGM-Based MOS FWC guidance is generated from 0000 UTC and 1200 UTC model output from the NGM run of NCEP's Global Spectral Model. Forecast elements are valid from 6 to 72 hours in advance.

Sample FWC Message 

FOUS14 KWBC 060357                                                   
DCA  ESC  NGM MOS GUIDANCE   3/06/91  0000 UTC                      
DAY /MAR   6             /MAR   7                /MAR   8           
HOUR   06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12      
MX/MN                    59          39          54          24      
TEMP   37 34 33 38 45 53 52 49 46 43 40 42 47 51 42 39 35 30 24      
DEWPT  27 28 28 30 32 36 40 38 41 41 37 33 28 27 25 21 20 19 19      
CLDS   OV OV OV OV OV OV OV OV OV OV BK BK BK SC SC SC CL CL CL      
WDIR   26 18 08 12 14 14 15 18 24 27 28 29 29 29 29 33 01 02 00      
WSPD   01 04 06 10 11 12 16 18 13 15 12 20 24 22 14 12 14 08 00      
POP06         4     9    46    85    62     3     7    12     8      
POP12                    49          91           8          19
QPF         0/    0/    1/1   3/    2/4   0/    0/0   0/    0/0      
TSV06      2/ 0  3/ 0  4/ 1  5/ 1  6/ 2 16/ 3 11/ 1  8/ 0  0/ 0      
TSV12            4/ 0        8/ 1       21/ 4        9/ 1            
PTYPE   S  S  S  S  S  R  R  R  R  R  R     R     R     S     Z      
POZP    8 10 12  6  0  0  0  0  0  1  3     0     2    24    35      
POSN   65 67 70 48 41 14 11 13 15 16 20     9    16    50    42      
SNOW        0/    0/    0/1   0/    0/0   0/    0/0   0/    0/0
CIG     4  5  4  4  5  6  7  6  3  2  1     5     6                  
VIS     3  4  3  5  5  5  5  4  2  2  1     3     4                  
OBVIS   H  H  H  N  N  N  N  F  F  F  F     H     N
  • HOUR = Forecast hour, i.e. how many hours from the model run time.
  • MX/MN = daytime maximum/nightime minimum surface temperatures.
  • TEMP = surface temperature valid at that hour.
  • DEWPT = surface dewpoint valid at that hour.
  • CLDS = forecast categories of total sky cover valid at that hour.
  • WDIR = forecasts of the 10-meter wind direction at the hour, given in tens of degrees.
  • WSPD = forecasts of the 10-meter wind speed at the hour, given in knots.
  • TYP = conditional precipitation type at the hour.
  • POP06 = probablity of precipitation (0.01 or more) during a 6-h period ending at that time.
  • POP12 = probablity of precipitation (0.01 or more) during a 12-h period ending at that time.
  • QPF = QPF category for liquid equivalent precipitation amount during a 12-h period ending at the indicated time.
  • TSV06 = probablity of severe thunderstorms during a 6-h period ending at that time.
  • TSV12 = probablity of severe thunderstorms during a 12-h period ending at that time.
  • POZP = conditional probability of freezing pcp occurring at the hour.
  • POSN = conditional probability of snow occurring at the hour.
  • SNOW = snow fall categorical forecasts during a 24-h period ending at the indicated time.
  • CIG = ceiling height categorical forecasts at the hour.
  • VIS = visibility categorical forecasts at the hour.
  • OBVIS = obstruction to vision categorical forecasts at the hour.
Definitions of Categorical Elements
FWC Ceiling Height Categories
1 < 200 feet
2 200 - 400 feet
3 500 - 900 feet
4 1000 - 3000 feet
5 3100 - 6500 feet
6 6600 - 12,000 feet
7 > 12,000 feet or unlimited ceiling
FWC Visibility Categories
1 1/2 mile or less
2 more than 1/2 - or less than 1 mile
3 1 mile - less than 3
4 3 - 5 miles
5 Greater than 5 miles
FWC QPF Categories
6-Hour Period
0 no precipitation
1 0.01 to 0.09 inches
2 0.10 to 0.24 inches
3 0.25 to 0.49 inches
4 0.50 to 0.99 inches
5 1.00 inches or greater
FWC QPF Categories
12-Hour Period
0 no precipitation
1 0.01 to 0.09 inches
2 0.10 to 0.24 inches
3 0.25 to 0.49 inches
4 0.50 to 0.99 inches
5 1.00 to 1.99 inches
6 2.00 inches or greater
FWC Snow Fall Amount Categories (6 hour)
0 no snow expected
1 Trace to < 2 inches
2 More than 2 inches

FWC Snow Fall Amount Categories (12 hour)
0 no snow expected
1 Trace to < 2 inches
2 2 to < 4 inches
4 4 to < 6 inches
6 6 inches or more

FWC Obstruction to Vision Categories
N none of the following
H haze, smoke, dust
B mist (fog with visibility >= 5/8 mile)
FWC Precipitation Type Categories
S pure snow or snow grains
Z freezing rain/drizzle, ice pellets, or sleet.
R Liquid Precipitation