NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261009_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)
=== ===== === ==== ==== === === === ====
Fri 10/09 06Z 0.78 2923  81  58   3 0.00
Fri 10/09 07Z 0.77 2823  83  46   2 0.00
Fri 10/09 08Z 0.73 2823  84  41   2 0.00
Fri 10/09 09Z 0.75 2824  85  50   2 0.00
Fri 10/09 10Z 0.84 2826  86  45   2 0.00
Fri 10/09 11Z 0.98 2829  88  51   2 0.00
Fri 10/09 12Z 1.06 2830  89  50   1 0.00
Fri 10/09 13Z 1.08 2731  86  53   1 0.00
Fri 10/09 14Z 1.17 2830  85  43   1 0.00
Fri 10/09 15Z 1.33 2827  86  36   1 0.00
Fri 10/09 16Z 1.90 2824  91  49   0 0.01
Fri 10/09 17Z 2.54 2822  89  55   0 0.00
Fri 10/09 18Z 3.07 2820  82  50   0 0.00
Fri 10/09 19Z 2.52 2719  75  41   1 0.00
Fri 10/09 20Z 3.46 2719  75  60   1 0.00
Fri 10/09 21Z 4.01 2520  77  68   2 0.00
Fri 10/09 22Z 2.79 2625  75  78   2 0.00
Fri 10/09 23Z 2.33 2727  71  59   2 0.00
Sat 10/10 00Z 1.62 2729  77  66   1 0.01
Sat 10/10 01Z 1.44 2831  86  49   1 0.01
Sat 10/10 02Z 1.30 2931  88  23   1 0.00
Sat 10/10 03Z 0.96 3029  91  10   0 0.01
Sat 10/10 04Z 0.61 3129  78   7   0 0.00
Sat 10/10 05Z 0.44 3127  77   6   0 0.00
Sat 10/10 06Z 0.39 3127  72   6   0 0.00
Sat 10/10 07Z 0.36 3126  64   9   0 0.00
Sat 10/10 08Z 0.33 3125  57  12   0 0.00
Sat 10/10 09Z 0.33 3126  55  17   0 0.00
Sat 10/10 10Z 0.31 3125  52  18   0 0.00
Sat 10/10 11Z 0.29 3125  48  23   0 0.00
Sat 10/10 12Z 0.27 3124  45  27   0 0.00
Sat 10/10 13Z 0.23 3223  42  29   0 0.00
Sat 10/10 14Z 0.23 3223  40  32   1 0.00
Sat 10/10 15Z 0.18 3221  38  40   1 0.00
Sat 10/10 16Z 0.14 3319  38  42   1 0.00
Sat 10/10 17Z 0.14 3317  40  42   2 0.00
Sat 10/10 18Z 0.11 3315  39  42   2 0.00
Sat 10/10 19Z 0.13 3315  37  42   3 0.00
Sat 10/10 20Z 0.12 3212  35  39   3 0.00
Sat 10/10 21Z 0.13 3213  33  42   3 0.00
Sat 10/10 22Z 0.13 3212  31  44   5 0.00
Sat 10/10 23Z 0.11 3210  28  42   6 0.00
Sun 10/11 00Z 0.11 3109  29  45   6 0.00
Sun 10/11 01Z 0.08 3106  29  47   6 0.00
Sun 10/11 02Z 0.10 2805  29  48   7 0.00
Sun 10/11 03Z 0.10 2704  26  46   7 0.00
Sun 10/11 04Z 0.12 2405  25  46   8 0.00
Sun 10/11 05Z 0.13 2207  23  47   8 0.00
Sun 10/11 06Z 0.15 2108  22  41   8 0.00
Sun 10/11 07Z 0.18 2110  21  37   9 0.00
Sun 10/11 08Z 0.20 2112  21  35   9 0.00
Sun 10/11 09Z 0.23 2114  20  32  10 0.00
Sun 10/11 10Z 0.26 2215  20  32  10 0.00
Sun 10/11 11Z 0.27 2216  19  32  10 0.00
Sun 10/11 12Z 0.30 2217  18  31  10 0.00
Sun 10/11 13Z 0.29 2218  20  30  10 0.00
Sun 10/11 14Z 0.27 2118  19  29  11 0.00
Sun 10/11 15Z 0.26 2117  18  34  11 0.00
Sun 10/11 16Z 0.26 2116  19  36  11 0.00
Sun 10/11 17Z 0.26 2116  20  35  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.04 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