NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260521_0000
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 05/21 00Z 0.42 3116  71  44  10 0.00
Thu 05/21 01Z 0.44 3218  75  26   8 0.00
Thu 05/21 02Z 0.46 3220  77  16   7 0.00
Thu 05/21 03Z 0.50 3223  76  15   6 0.00
Thu 05/21 04Z 0.39 3324  73  15   5 0.00
Thu 05/21 05Z 0.23 3324  68  15   4 0.00
Thu 05/21 06Z 0.09 3422  65  19   4 0.00
Thu 05/21 07Z 0.05 3421  64  19   3 0.00
Thu 05/21 08Z 0.04 3421  64  17   2 0.00
Thu 05/21 09Z 0.04 3421  65  13   1 0.00
Thu 05/21 10Z 0.03 3420  66   8   1 0.00
Thu 05/21 11Z 0.03 3419  65   5   1 0.00
Thu 05/21 12Z 0.04 3416  58   3   0 0.00
Thu 05/21 13Z 0.06 3413  51   3   1 0.00
Thu 05/21 14Z 0.08 3312  46   3   1 0.00
Thu 05/21 15Z 0.09 3312  42   3   0 0.00
Thu 05/21 16Z 0.12 3312  42   3   0 0.00
Thu 05/21 17Z 0.22 3313  41   4   0 0.00
Thu 05/21 18Z 0.37 3314  38   4   1 0.00
Thu 05/21 19Z 0.38 3314  35   4   1 0.00
Thu 05/21 20Z 0.33 3315  33   5   1 0.00
Thu 05/21 21Z 0.26 3316  34   5   1 0.00
Thu 05/21 22Z 0.15 3316  35   5   1 0.00
Thu 05/21 23Z 0.13 3316  35   5   1 0.00
Fri 05/22 00Z 0.08 3418  35   5   1 0.00
Fri 05/22 01Z 0.03 3418  35   5   1 0.00
Fri 05/22 02Z 0.05 3517  35   3   1 0.00
Fri 05/22 03Z 0.07 3516  38   2   1 0.00
Fri 05/22 04Z 0.08 3515  43   1   1 0.00
Fri 05/22 05Z 0.12 0014  46   1   0 0.00
Fri 05/22 06Z 0.16 0113  47   2   0 0.00
Fri 05/22 07Z 0.18 0112  46   2   0 0.00
Fri 05/22 08Z 0.18 0112  43   2   0 0.00
Fri 05/22 09Z 0.21 0212  39   2   1 0.00
Fri 05/22 10Z 0.25 0313  33   3   1 0.00
Fri 05/22 11Z 0.25 0312  30   3   1 0.00
Fri 05/22 12Z 0.26 0411  28   4   1 0.00
Fri 05/22 13Z 0.23 0409  27   5   1 0.00
Fri 05/22 14Z 0.25 0408  28   5   1 0.00
Fri 05/22 15Z 0.45 0405  33   6   1 0.00
Fri 05/22 16Z 0.94 0404  37   7   1 0.00
Fri 05/22 17Z 0.79 0202  40   9   2 0.00
Fri 05/22 18Z 0.96 0302  42  10   3 0.00
Fri 05/22 19Z 0.68 0202  45  11   3 0.00
Fri 05/22 20Z 0.25 0001  47  12   4 0.00
Fri 05/22 21Z 0.17 0101  50  12   4 0.00
Fri 05/22 22Z 0.10 3201  52  12   4 0.00
Fri 05/22 23Z 0.07 0201  53  14   4 0.00
Sat 05/23 00Z 0.13 0302  52  15   4 0.00
Sat 05/23 01Z 0.15 0402  50  15   4 0.00
Sat 05/23 02Z 0.23 0604  48  18   4 0.00
Sat 05/23 03Z 0.30 0605  47  22   4 0.00
Sat 05/23 04Z 0.38 0608  44  24   4 0.00
Sat 05/23 05Z 0.44 0808  45  26   4 0.00
Sat 05/23 06Z 0.51 0810  47  27   4 0.00
Sat 05/23 07Z 0.54 0811  46  24   4 0.00
Sat 05/23 08Z 0.60 0912  44  21   4 0.00
Sat 05/23 09Z 0.63 1014  42  17   4 0.00
Sat 05/23 10Z 0.63 1015  41  11   4 0.00
Sat 05/23 11Z 0.62 1117  42   7   4 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