Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261024_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 10/24 12Z 0.14 3008  22   1   5 0.00
Sat 10/24 13Z 0.17 3010  20   1   5 0.00
Sat 10/24 14Z 0.15 3111  22   1   5 0.00
Sat 10/24 15Z 0.12 3110  24   1   5 0.00
Sat 10/24 16Z 0.11 3108  26   1   5 0.00
Sat 10/24 17Z 0.10 3107  28   1   5 0.00
Sat 10/24 18Z 0.11 3006  30   1   5 0.00
Sat 10/24 19Z 0.11 3006  30   2   6 0.00
Sat 10/24 20Z 0.13 2906  28   2   6 0.00
Sat 10/24 21Z 0.15 2907  25   3   6 0.00
Sat 10/24 22Z 0.16 3008  22   4   6 0.00
Sat 10/24 23Z 0.14 3008  22   7   6 0.00
Sun 10/25 00Z 0.13 3109  26   9   6 0.00
Sun 10/25 01Z 0.10 3108  27  12   7 0.00
Sun 10/25 02Z 0.10 3107  27  12   7 0.00
Sun 10/25 03Z 0.10 3106  25  13   7 0.00
Sun 10/25 04Z 0.09 3106  20  14   7 0.00
Sun 10/25 05Z 0.09 3005  17  16   8 0.00
Sun 10/25 06Z 0.08 2904  14  19   8 0.00
Sun 10/25 07Z 0.09 2704  13  24   8 0.00
Sun 10/25 08Z 0.13 2706  14  28   8 0.00
Sun 10/25 09Z 0.16 2607  14  32   8 0.00
Sun 10/25 10Z 0.19 2609  15  34   8 0.00
Sun 10/25 11Z 0.20 2709  14  34   8 0.00
Sun 10/25 12Z 0.19 2709  13  33   8 0.00
Sun 10/25 13Z 0.18 2809  10  32   8 0.00
Sun 10/25 14Z 0.18 2708   7  29   9 0.00
Sun 10/25 15Z 0.18 2708   7  26   9 0.00
Sun 10/25 16Z 0.19 2609   8  24   9 0.00
Sun 10/25 17Z 0.21 2609  10  24   9 0.00
Sun 10/25 18Z 0.21 2609   9  25  10 0.00
Sun 10/25 19Z 0.23 2510   9  25  10 0.00
Sun 10/25 20Z 0.25 2511   9  27  10 0.00
Sun 10/25 21Z 0.27 2612   9  25   9 0.00
Sun 10/25 22Z 0.28 2612  10  25  10 0.00
Sun 10/25 23Z 0.28 2612  10  24  10 0.00
Mon 10/26 00Z 0.29 2613  11  21  11 0.00
Mon 10/26 01Z 0.30 2614  12  19  11 0.00
Mon 10/26 02Z 0.32 2616  13  17  11 0.00
Mon 10/26 03Z 0.33 2616   9  16  11 0.00
Mon 10/26 04Z 0.33 2616   8  15  11 0.00
Mon 10/26 05Z 0.35 2617  10  14  11 0.00
Mon 10/26 06Z 0.35 2718   9  12  11 0.00
Mon 10/26 07Z 0.34 2717   9  12  11 0.00
Mon 10/26 08Z 0.35 2817  10  13  10 0.00
Mon 10/26 09Z 0.35 2918  13  12  10 0.00
Mon 10/26 10Z 0.34 2918  20  39  10 0.00
Mon 10/26 11Z 0.36 2918  28  22   9 0.00
Mon 10/26 12Z 0.38 2919  34  36   9 0.00
Mon 10/26 13Z 0.41 2921  46  48   9 0.00
Mon 10/26 14Z 0.44 2922  55  55   9 0.00
Mon 10/26 15Z 0.47 2923  71  75   8 0.00
Mon 10/26 16Z 0.46 2923  89  84   8 0.00
Mon 10/26 17Z 0.46 2923  94  92   7 0.01
Mon 10/26 18Z 0.44 3023  95  91   7 0.01
Mon 10/26 19Z 0.43 3022  89  92   6 0.00
Mon 10/26 20Z 0.44 3022  88  87   5 0.00
Mon 10/26 21Z 0.44 3021  86  70   4 0.01
Mon 10/26 22Z 0.40 3122  81  60   4 0.01
Mon 10/26 23Z 0.33 3224  81  65   3 0.01

Run total areal avg QPF for the Central_Greens is: 0.05 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