NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260706_0000
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Mon 07/06 00Z 0.08 0004  62  27  14 0.00
Mon 07/06 01Z 0.24 0305  63  18  14 0.00
Mon 07/06 02Z 0.30 0406  64  11  13 0.00
Mon 07/06 03Z 0.37 0608  66   8  13 0.00
Mon 07/06 04Z 0.43 0809  66   7  13 0.00
Mon 07/06 05Z 0.47 0910  66   7  13 0.00
Mon 07/06 06Z 0.47 1011  69   8  13 0.00
Mon 07/06 07Z 0.43 1110  70  10  13 0.00
Mon 07/06 08Z 0.40 1312  72  13  13 0.00
Mon 07/06 09Z 0.34 1312  75  15  13 0.00
Mon 07/06 10Z 0.30 1413  76  18  13 0.00
Mon 07/06 11Z 0.28 1414  77  23  13 0.00
Mon 07/06 12Z 0.31 1415  74  22  13 0.00
Mon 07/06 13Z 0.31 1415  74  28  13 0.00
Mon 07/06 14Z 0.32 1414  73  32  12 0.00
Mon 07/06 15Z 0.39 1314  76  36  12 0.00
Mon 07/06 16Z 0.63 1214  80  41  12 0.00
Mon 07/06 17Z 1.09 1213  78  44  12 0.00
Mon 07/06 18Z 1.28 1213  74  47  12 0.00
Mon 07/06 19Z 1.06 1214  73  52  12 0.00
Mon 07/06 20Z 1.68 1214  71  51  12 0.00
Mon 07/06 21Z 1.47 1314  71  46  12 0.00
Mon 07/06 22Z 0.81 1314  71  39  12 0.00
Mon 07/06 23Z 0.63 1316  71  31  12 0.00
Tue 07/07 00Z 0.56 1318  69  26  12 0.00
Tue 07/07 01Z 0.52 1320  65  25  12 0.00
Tue 07/07 02Z 0.47 1322  61  30  12 0.00
Tue 07/07 03Z 0.48 1223  59  35  13 0.00
Tue 07/07 04Z 0.49 1224  56  39  13 0.00
Tue 07/07 05Z 0.50 1225  57  38  13 0.00
Tue 07/07 06Z 0.50 1225  60  40  12 0.00
Tue 07/07 07Z 0.46 1224  62  43  12 0.00
Tue 07/07 08Z 0.44 1223  63  42  12 0.00
Tue 07/07 09Z 0.43 1222  66  40  12 0.00
Tue 07/07 10Z 0.41 1220  66  41  12 0.00
Tue 07/07 11Z 0.39 1219  66  41  12 0.00
Tue 07/07 12Z 0.39 1118  65  40  12 0.00
Tue 07/07 13Z 0.41 1118  65  35  12 0.00
Tue 07/07 14Z 0.44 1016  65  36  12 0.00
Tue 07/07 15Z 0.48 1014  65  32  12 0.00
Tue 07/07 16Z 0.66 1013  67  32  11 0.00
Tue 07/07 17Z 1.47 1011  68  32  11 0.00
Tue 07/07 18Z 2.46 0909  69  33  11 0.00
Tue 07/07 19Z 2.96 0909  69  33  12 0.00
Tue 07/07 20Z 2.02 1008  67  33  12 0.00
Tue 07/07 21Z 1.02 1007  67  30  12 0.00
Tue 07/07 22Z 0.52 1006  68  28  12 0.00
Tue 07/07 23Z 0.31 1005  70  26  12 0.00
Wed 07/08 00Z 0.25 1005  71  25  12 0.00
Wed 07/08 01Z 0.20 1005  72  23  12 0.00
Wed 07/08 02Z 0.15 0904  72  20  12 0.00
Wed 07/08 03Z 0.13 0802  71  19  12 0.00
Wed 07/08 04Z 0.11 0602  70  16  13 0.00
Wed 07/08 05Z 0.10 0302  71  13  13 0.00
Wed 07/08 06Z 0.10 0102  72  10  13 0.00
Wed 07/08 07Z 0.06 0102  72   9  13 0.00
Wed 07/08 08Z 0.04 3503  72   9  13 0.00
Wed 07/08 09Z 0.06 3404  73  11  12 0.00
Wed 07/08 10Z 0.05 3404  74  12  12 0.00
Wed 07/08 11Z 0.05 0004  73  10  12 0.00

Run total areal avg QPF for the greens is: 0.00 inches.

Froude Number (Frd#): 
Frd# < 0.5 Flow is subcritical and blocked.
         Upslope clouds/precip backed farther upwind of and up to mtn crest.
         W Upslope snow favors eastern Champlain Valley, BTV, and Western slopes.
         Gap winds possible.
Frd# 0.5-1 Flow is subcritical/slow moving/blocked.
         Upslope clouds/precip falls immediately upwind of mtn crest.
         W Upslope snow favors western slopes to the Green Mt. spine including:
         Montgomery,Underhill,Jericho,Bolton,Richmond,Huntington,Lincoln.
         Gap winds possible.
Frd# 1-2 Flow is critical.
         With strong winds, Mountain waves/downslope winds possible.
         Precip falls close to mountain ridge crests and on lee side.
         W Upslope snow favors Green Mt Spine,Jay,Stowe,Waterbury,NE Kingdom.
Froude > 2 Flow is supercritical/unblocked(rapid flow).
         Air flows freely over terrain.
         Persistent upslope snow not favored. Scattered snow showers and flurries.

Relative Humidity (RH): 
         925-850 mb RH > 90% needed for upslope precipitation.
         with 700mb RH > 70% favors upslope snow.
         with 700mb RH > 90% greater amounts of W upslope snow possible.

850mb Temperature (T degC) Westerly Upslope Snow Ratios: (Avg=28:1)
        T > -11       10-15:1
        T -11 to -15  25-35:1
        T < -15       15-20:1