Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20261021_1200
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)
=== ===== === ==== ==== === === === ====
Wed 10/21 12Z 0.06 0603  47   2   5 0.00
Wed 10/21 13Z 0.06 0403  45   2   6 0.00
Wed 10/21 14Z 0.05 0304  43   2   6 0.00
Wed 10/21 15Z 0.06 0305  43   2   6 0.00
Wed 10/21 16Z 0.10 0406  44   2   6 0.00
Wed 10/21 17Z 0.11 0506  44   2   6 0.00
Wed 10/21 18Z 0.13 0805  45   2   6 0.00
Wed 10/21 19Z 0.12 0805  44   2   6 0.00
Wed 10/21 20Z 0.09 0803  43   2   7 0.00
Wed 10/21 21Z 0.07 0603  41   2   7 0.00
Wed 10/21 22Z 0.08 0703  37   2   7 0.00
Wed 10/21 23Z 0.07 0703  35   2   7 0.00
Thu 10/22 00Z 0.06 0503  35   2   7 0.00
Thu 10/22 01Z 0.04 0203  35   2   7 0.00
Thu 10/22 02Z 0.03 3505  34   2   7 0.00
Thu 10/22 03Z 0.02 3508  32   3   8 0.00
Thu 10/22 04Z 0.03 0010  29   3   8 0.00
Thu 10/22 05Z 0.05 0111  27   3   7 0.00
Thu 10/22 06Z 0.07 0112  25   5   7 0.00
Thu 10/22 07Z 0.08 0112  24   8   7 0.00
Thu 10/22 08Z 0.07 0114  24  10   7 0.00
Thu 10/22 09Z 0.07 0116  24  14   6 0.00
Thu 10/22 10Z 0.06 0019  23  16   6 0.00
Thu 10/22 11Z 0.07 0020  22  18   6 0.00
Thu 10/22 12Z 0.06 0021  24  20   7 0.00
Thu 10/22 13Z 0.06 0021  32  19   6 0.00
Thu 10/22 14Z 0.05 0021  43  18   6 0.00
Thu 10/22 15Z 0.03 0021  56  24   5 0.00
Thu 10/22 16Z 0.02 3522  69  24   4 0.00
Thu 10/22 17Z 0.05 3523  79  24   4 0.00
Thu 10/22 18Z 0.05 3523  85  29   3 0.00
Thu 10/22 19Z 0.05 3524  88  30   2 0.00
Thu 10/22 20Z 0.08 3525  87  29   2 0.00
Thu 10/22 21Z 0.06 3526  79  24   2 0.00
Thu 10/22 22Z 0.04 3527  68  21   2 0.00
Thu 10/22 23Z 0.05 0028  59  30   2 0.00
Fri 10/23 00Z 0.08 0028  57  34   1 0.00
Fri 10/23 01Z 0.16 0127  58  33   1 0.00
Fri 10/23 02Z 0.25 0227  57  22   0 0.00
Fri 10/23 03Z 0.30 0227  46  14   0 0.00
Fri 10/23 04Z 0.29 0227  46   6   0 0.00
Fri 10/23 05Z 0.24 0225  46   4  -1 0.00
Fri 10/23 06Z 0.21 0125  47   3  -1 0.00
Fri 10/23 07Z 0.20 0124  47   3  -1 0.00
Fri 10/23 08Z 0.17 0124  46   3  -1 0.00
Fri 10/23 09Z 0.18 0124  44   2   0 0.00
Fri 10/23 10Z 0.20 0225  42   2   0 0.00
Fri 10/23 11Z 0.22 0224  43   2   0 0.00
Fri 10/23 12Z 0.23 0223  40   3   0 0.00
Fri 10/23 13Z 0.24 0223  38   4   0 0.00
Fri 10/23 14Z 0.23 0322  37   4   0 0.00
Fri 10/23 15Z 0.22 0320  36   3   0 0.00
Fri 10/23 16Z 0.20 0318  35   2   0 0.00
Fri 10/23 17Z 0.18 0316  34   2   0 0.00
Fri 10/23 18Z 0.16 0214  31   2   1 0.00
Fri 10/23 19Z 0.13 0212  28   2   2 0.00
Fri 10/23 20Z 0.12 0212  25   2   3 0.00
Fri 10/23 21Z 0.11 0212  21   2   4 0.00
Fri 10/23 22Z 0.10 0211  19   2   4 0.00
Fri 10/23 23Z 0.10 0210  16   2   4 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