NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261031_1200
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)
=== ===== === ==== ==== === === === ====
Sat 10/31 12Z 0.32 3222  89  22  -5 0.00
Sat 10/31 13Z 0.30 3224  88  24  -5 0.00
Sat 10/31 14Z 0.26 3223  87  23  -5 0.00
Sat 10/31 15Z 0.23 3220  82  22  -4 0.00
Sat 10/31 16Z 0.27 3218  79  21  -4 0.00
Sat 10/31 17Z 0.37 3218  78  19  -4 0.00
Sat 10/31 18Z 0.39 3117  78  16  -4 0.00
Sat 10/31 19Z 0.43 3117  78  14  -4 0.00
Sat 10/31 20Z 0.52 3017  81  14  -4 0.00
Sat 10/31 21Z 0.62 3018  82  13  -4 0.00
Sat 10/31 22Z 0.74 2920  81  14  -4 0.00
Sat 10/31 23Z 0.74 3022  78  41  -4 0.00
Sun 11/01 00Z 0.62 3024  75  56  -3 0.00
Sun 11/01 01Z 0.48 3124  74  26  -3 0.00
Sun 11/01 02Z 0.39 3223  74  12  -3 0.00
Sun 11/01 03Z 0.36 3222  77  10  -3 0.00
Sun 11/01 04Z 0.34 3121  78   7  -2 0.00
Sun 11/01 05Z 0.35 3121  77   7  -2 0.00
Sun 11/01 06Z 0.34 3122  74  10  -1 0.00
Sun 11/01 07Z 0.31 3122  69  11   0 0.00
Sun 11/01 08Z 0.31 3122  65  11   0 0.00
Sun 11/01 09Z 0.30 3122  60  11   0 0.00
Sun 11/01 10Z 0.30 3121  55  12   0 0.00
Sun 11/01 11Z 0.31 3122  50  13   1 0.00
Sun 11/01 12Z 0.35 3023  51  10   1 0.00
Sun 11/01 13Z 0.41 3025  62   5   1 0.00
Sun 11/01 14Z 0.45 3026  76   5   1 0.00
Sun 11/01 15Z 0.46 3025  77   8   2 0.00
Sun 11/01 16Z 0.45 3024  71   8   2 0.00
Sun 11/01 17Z 0.43 3125  72  12   3 0.00
Sun 11/01 18Z 0.47 3024  68  18   3 0.00
Sun 11/01 19Z 0.53 3025  71  25   3 0.00
Sun 11/01 20Z 0.59 2925  67  49   4 0.00
Sun 11/01 21Z 0.67 2926  66  59   4 0.00
Sun 11/01 22Z 0.74 2926  67  46   4 0.00
Sun 11/01 23Z 0.82 2829  65  40   4 0.00
Mon 11/02 00Z 0.89 2831  69  35   4 0.00
Mon 11/02 01Z 0.83 2930  70  32   4 0.00
Mon 11/02 02Z 0.78 2928  67  35   4 0.00
Mon 11/02 03Z 0.76 2927  63  39   5 0.00
Mon 11/02 04Z 0.77 2827  61  62   5 0.00
Mon 11/02 05Z 0.76 2826  61  74   5 0.00
Mon 11/02 06Z 0.77 2825  56  81   6 0.00
Mon 11/02 07Z 0.81 2726  53  83   6 0.00
Mon 11/02 08Z 0.86 2727  54  87   6 0.00
Mon 11/02 09Z 0.85 2726  52  88   6 0.00
Mon 11/02 10Z 0.85 2727  46  87   7 0.00
Mon 11/02 11Z 0.80 2727  46  83   7 0.00
Mon 11/02 12Z 0.76 2726  55  85   7 0.00
Mon 11/02 13Z 0.77 2726  63  86   7 0.00
Mon 11/02 14Z 0.80 2727  62  86   7 0.00
Mon 11/02 15Z 0.78 2728  71  80   7 0.00
Mon 11/02 16Z 0.72 2826  74  68   7 0.00
Mon 11/02 17Z 0.66 2825  79  70   7 0.00
Mon 11/02 18Z 0.61 2823  84  68   7 0.00
Mon 11/02 19Z 0.57 2922  86  65   7 0.00
Mon 11/02 20Z 0.55 2921  88  62   6 0.00
Mon 11/02 21Z 0.54 2919  90  59   6 0.00
Mon 11/02 22Z 0.50 2916  91  56   6 0.00
Mon 11/02 23Z 0.49 2816  92  58   6 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