GEMPAK-SNMAP>restore $GEMPAKHOME/defaults/snmap.nts
 GEMPAK-SNMAP>display
 AREA      Data area                         
 GAREA     Graphics area                     
 SNPARM    Sounding parameter list           skyc;tmpf;wsym;rmsl;ptnd;dwpf;p03i;brbk:.7:2
 DATTIM    Date/time                         
 LEVELS    Vertical levels                   
 VCOORD    Vertical coordinate type          
 SNFILE    Sounding data file                
 COLORS    Color list                        1;2;3;25;5;6;7;9
 MAP       Map color/dash/width              3/1/1
 LATLON    Line color/dash/width/label/inc   0
 MARKER    Marker color/type/size/width/hw   0
 TITLE     Title color/line/title            1/-2
 CLEAR     Clear screen flag                 YES
 PANEL     Panel location/color/dash/width   0
 DEVICE    Graphics device                   xw
 PROJ      Map projection/angles/margins     nps
 FILTER    Filter data factor                no
 TEXT      Text size/font/width/hw flag      1.3/23//HW
 GEMPAK-SNMAP>

 GEMPAK-SNMAP>area=us
 GEMPAK-SNMAP>garea=usnps

Note: This graphics area was not just pulled out of thin air. It's listed with all others in the $GEMPAKHOME/tables/geog.tbl. Here's a peek at where you can find it in the table:

DC      DISTRICT OF COLUMB   38.85  -77.0     5.50    8.00
US      UNITED STATES        37.5   -95.0    12.5    30.00
USNPS   UNITED STATES NPS    34.5   -90.0     16.5   28.00
USLCC   UNITED STATES LCC    35.5   -90.0     15.5   28.00
MX      MEXICO               23.50 -100.0    10.5    17.0

Okay, back to the rest of the answer. Look for the parameter names in the on-line help for SFPARM, or in your Users Manual. You're looking for temperature in C, dew point depression in C, a wind barb in knots and the height in decameters (first three digits in meters = decameters!).

 GEMPAK-SNMAP>snparm=brbk;tmpc;;hgtd;;dwpc
 GEMPAK-SNMAP>levels=500
 GEMPAK-SNMAP>vcoord=pres
 GEMPAK-SNMAP>snfile=$GEMPAKHOME/data/hrcbob.snd
 GEMPAK-SNMAP>dattim=18/12

As we showed previously, filter=yes or 1 can sometimes yield sparce data, so let's set it to filter=0.7:

 GEMPAK_SFMAP>filter=0.7
 GEMPAK-SNMAP>d
 AREA      Data area                         us
 GAREA     Graphics area                     usnps
 SNPARM    Sounding parameter list           brbk;tmpc;;hgtd;;dwpc
 DATTIM    Date/time                         18/12
 LEVELS    Vertical levels                   500
 VCOORD    Vertical coordinate type          pres
 SNFILE    Sounding data file                $GEMPAKHOME/data/hrcbob.snd
 COLORS    Color list                        1;2;3;25;5;6;7;9
 MAP       Map color/dash/width              3/1/1
 LATLON    Line color/dash/width/label/inc   0
 MARKER    Marker color/type/size/width/hw   0
 TITLE     Title color/line/title            1/-2
 CLEAR     Clear screen flag                 YES
 PANEL     Panel location/color/dash/width   0
 DEVICE    Graphics device                   xw
 PROJ      Map projection/angles/margins     nps
 FILTER    Filter data factor                0.7
 TEXT      Text size/font/width/hw flag      1.3/23//HW
 GEMPAK-SNMAP>r
  vparm is PRES
 SNMAP PARAMETERS:
 
 Data area:          us                                              
 Graphics area name: usnps                                           
 Valid parameters:    BRBK TMPC BLNK HGTD BLNK DWPC
 Parameter colors:     1    2    0    3    0   25 
 Time:              910818/1200         
 Level:                500
 Vert coord:          PRES
 File:              $GEMPAKHOME/data/hrcbob.snd                                 
 Map:               3/1/1                   
 Marker:            0                       
 Title:             1/-2                                            
 Device:            xw                      
 Projection:        nps                             
 Clear screen:      YES
 Filter:            YES
 Filter factor: 0.70
 Panel:             0                                               
Enter <cr> to accept parameters or type EXIT: