NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260715_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)
=== ===== === ==== ==== === === === ====
Wed 07/15 12Z 0.46 3022  92  73  16 0.00
Wed 07/15 13Z 0.52 3023  86  64  15 0.00
Wed 07/15 14Z 0.53 3122  81  48  15 0.00
Wed 07/15 15Z 0.63 3022  77  48  15 0.00
Wed 07/15 16Z 3.67 3021  81  76  14 0.00
Wed 07/15 17Z 12.01 3025  62  84  14 0.00
Wed 07/15 18Z 10.93 3025  56  85  14 0.00
Wed 07/15 19Z 9.36 3026  53  85  14 0.00
Wed 07/15 20Z 10.90 2926  55  77  13 0.00
Wed 07/15 21Z 8.84 2925  55  53  13 0.00
Wed 07/15 22Z 5.16 2925  55  32  13 0.00
Wed 07/15 23Z 2.27 3026  57  32  13 0.00
Thu 07/16 00Z 1.76 3026  61  32  13 0.00
Thu 07/16 01Z 1.58 3028  64  26  12 0.00
Thu 07/16 02Z 1.40 3029  66  31  12 0.00
Thu 07/16 03Z 0.97 3130  63  34  13 0.00
Thu 07/16 04Z 0.82 3127  64  33  13 0.00
Thu 07/16 05Z 0.70 3127  62  35  13 0.00
Thu 07/16 06Z 0.65 3127  61  38  12 0.00
Thu 07/16 07Z 0.63 3125  63  36  12 0.00
Thu 07/16 08Z 0.51 3224  64  37  12 0.00
Thu 07/16 09Z 0.46 3122  67  36  12 0.00
Thu 07/16 10Z 0.46 3120  68  37  12 0.00
Thu 07/16 11Z 0.49 3019  67  28  12 0.00
Thu 07/16 12Z 0.52 2918  68  35  12 0.00
Thu 07/16 13Z 0.67 2819  69  43  12 0.00
Thu 07/16 14Z 0.94 2722  68  55  12 0.00
Thu 07/16 15Z 1.67 2723  68  52  12 0.00
Thu 07/16 16Z 11.34 2723  75  49  12 0.00
Thu 07/16 17Z 5.62 2725  76  36  12 0.01
Thu 07/16 18Z 13.08 2726  69  38  13 0.00
Thu 07/16 19Z 16.33 2727  64  51  13 0.00
Thu 07/16 20Z 10.75 2928  63  49  13 0.00
Thu 07/16 21Z 2.80 3026  76  63  12 0.02
Thu 07/16 22Z 0.52 3124  87  59  11 0.01
Thu 07/16 23Z 0.59 3124  88  29  10 0.01
Fri 07/17 00Z 0.66 3124  89  18   9 0.01
Fri 07/17 01Z 0.58 3126  75   7   9 0.00
Fri 07/17 02Z 0.64 3228  63   5   8 0.00
Fri 07/17 03Z 0.62 3229  62   4   7 0.00
Fri 07/17 04Z 0.60 3229  62  10   7 0.00
Fri 07/17 05Z 0.54 3228  65  19   7 0.00
Fri 07/17 06Z 0.54 3228  65  26   7 0.00
Fri 07/17 07Z 0.45 3227  65  27   7 0.00
Fri 07/17 08Z 0.41 3227  64  25   7 0.00
Fri 07/17 09Z 0.30 3227  56  22   8 0.00
Fri 07/17 10Z 0.26 3226  47  21   8 0.00
Fri 07/17 11Z 0.25 3226  44  20   8 0.00
Fri 07/17 12Z 0.23 3225  44  19   8 0.00
Fri 07/17 13Z 0.23 3223  44  19   9 0.00
Fri 07/17 14Z 0.25 3222  45  19   9 0.00
Fri 07/17 15Z 0.25 3220  47  19   9 0.00
Fri 07/17 16Z 0.25 3218  53  19   9 0.00
Fri 07/17 17Z 0.30 3215  58  18   8 0.00
Fri 07/17 18Z 0.68 3113  61  16   8 0.00
Fri 07/17 19Z 1.58 3012  60  14   8 0.00
Fri 07/17 20Z 1.88 3011  60  13   9 0.00
Fri 07/17 21Z 1.46 2809  63  13   9 0.00
Fri 07/17 22Z 0.84 2709  64  13  10 0.00
Fri 07/17 23Z 0.55 2709  62  12  10 0.00

Run total areal avg QPF for the Central_Greens is: 0.06 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