Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261022_0600
Using the MB925 to MB850 layer.
Assumes Central_Greens are orthogonal to 260 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Central_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Thu 10/22 06Z 0.08 0110  38   7   7 0.00
Thu 10/22 07Z 0.07 0013  35   8   7 0.00
Thu 10/22 08Z 0.08 0016  31  10   7 0.00
Thu 10/22 09Z 0.10 0019  30  11   7 0.00
Thu 10/22 10Z 0.15 0021  28  14   6 0.00
Thu 10/22 11Z 0.18 0123  28  18   6 0.00
Thu 10/22 12Z 0.22 0122  30  21   6 0.00
Thu 10/22 13Z 0.20 0122  34  21   6 0.00
Thu 10/22 14Z 0.17 0122  37  19   6 0.00
Thu 10/22 15Z 0.15 0021  42  16   6 0.00
Thu 10/22 16Z 0.13 0022  51  22   5 0.00
Thu 10/22 17Z 0.11 3522  63  35   4 0.00
Thu 10/22 18Z 0.08 3523  75  45   4 0.00
Thu 10/22 19Z 0.05 3524  83  37   4 0.00
Thu 10/22 20Z 0.04 3525  85  21   3 0.00
Thu 10/22 21Z 0.06 3528  83  16   2 0.00
Thu 10/22 22Z 0.10 3530  74  22   3 0.00
Thu 10/22 23Z 0.14 0031  68  16   3 0.00
Fri 10/23 00Z 0.17 0031  65  14   3 0.00
Fri 10/23 01Z 0.20 0030  61  16   2 0.00
Fri 10/23 02Z 0.25 0129  58  14   1 0.00
Fri 10/23 03Z 0.30 0129  57   5   0 0.00
Fri 10/23 04Z 0.35 0230  49   1   0 0.00
Fri 10/23 05Z 0.41 0229  40   1   0 0.00
Fri 10/23 06Z 0.44 0227  35   1   0 0.00
Fri 10/23 07Z 0.42 0326  38   2  -1 0.00
Fri 10/23 08Z 0.39 0226  39   3  -1 0.00
Fri 10/23 09Z 0.39 0226  37   3  -1 0.00
Fri 10/23 10Z 0.37 0227  37   2   0 0.00
Fri 10/23 11Z 0.36 0227  33   1   0 0.00
Fri 10/23 12Z 0.36 0226  29   1   0 0.00
Fri 10/23 13Z 0.36 0324  29   2   0 0.00
Fri 10/23 14Z 0.33 0322  37   3   0 0.00
Fri 10/23 15Z 0.29 0220  40   4   0 0.00
Fri 10/23 16Z 0.27 0218  38   3   0 0.00
Fri 10/23 17Z 0.23 0217  40   2   0 0.00
Fri 10/23 18Z 0.20 0116  39   2   0 0.00
Fri 10/23 19Z 0.21 0217  35   2   1 0.00
Fri 10/23 20Z 0.20 0217  33   2   2 0.00
Fri 10/23 21Z 0.20 0217  29   2   3 0.00
Fri 10/23 22Z 0.21 0218  24   2   3 0.00
Fri 10/23 23Z 0.21 0217  20   2   4 0.00
Sat 10/24 00Z 0.20 0316  18   2   4 0.00
Sat 10/24 01Z 0.19 0315  15   2   4 0.00
Sat 10/24 02Z 0.19 0314  13   3   5 0.00
Sat 10/24 03Z 0.17 0312  11   2   5 0.00
Sat 10/24 04Z 0.13 0309   9   2   5 0.00
Sat 10/24 05Z 0.09 0208   8   2   5 0.00
Sat 10/24 06Z 0.06 0107   8   2   5 0.00
Sat 10/24 07Z 0.02 3507   7   2   5 0.00
Sat 10/24 08Z 0.02 3408   6   1   5 0.00
Sat 10/24 09Z 0.03 3408   6   1   5 0.00
Sat 10/24 10Z 0.05 3309   6   1   5 0.00
Sat 10/24 11Z 0.07 3311   6   1   5 0.00
Sat 10/24 12Z 0.07 3312   5   1   5 0.00
Sat 10/24 13Z 0.06 3313   5   1   5 0.00
Sat 10/24 14Z 0.04 3414   6   2   5 0.00
Sat 10/24 15Z 0.04 3413   8   2   5 0.00
Sat 10/24 16Z 0.05 3311  10   2   5 0.00
Sat 10/24 17Z 0.06 3311  12   2   5 0.00

Run total areal avg QPF for the Central_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