NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260516_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)
=== ===== === ==== ==== === === === ====
Sat 05/16 00Z 0.21 2205  88  78   5 0.00
Sat 05/16 01Z 0.29 2307  87  66   5 0.00
Sat 05/16 02Z 0.45 2510  91  71   5 0.00
Sat 05/16 03Z 0.47 2612  89  69   6 0.00
Sat 05/16 04Z 0.43 2612  91  54   6 0.01
Sat 05/16 05Z 0.37 2712  91  42   6 0.01
Sat 05/16 06Z 0.36 2812  89  47   6 0.00
Sat 05/16 07Z 0.41 2713  93  55   5 0.00
Sat 05/16 08Z 0.53 2816  90  56   5 0.00
Sat 05/16 09Z 0.50 2815  83  24   5 0.00
Sat 05/16 10Z 0.57 2817  79  10   5 0.00
Sat 05/16 11Z 0.66 2718  77   6   4 0.00
Sat 05/16 12Z 0.71 2719  77  27   5 0.00
Sat 05/16 13Z 0.68 2618  69  73   5 0.00
Sat 05/16 14Z 0.69 2517  65  74   5 0.00
Sat 05/16 15Z 0.77 2516  53  64   6 0.00
Sat 05/16 16Z 1.47 2515  58  58   7 0.00
Sat 05/16 17Z 1.58 2414  59  62   7 0.00
Sat 05/16 18Z 2.49 2315  60  46   8 0.00
Sat 05/16 19Z 5.59 2217  65  20   8 0.00
Sat 05/16 20Z 6.78 2120  71   9   8 0.00
Sat 05/16 21Z 5.19 2122  71   5   9 0.00
Sat 05/16 22Z 2.17 2225  72  16   9 0.00
Sat 05/16 23Z 1.20 2227  72  37  10 0.00
Sun 05/17 00Z 1.21 2332  70  85  10 0.00
Sun 05/17 01Z 1.37 2335  71  78  10 0.00
Sun 05/17 02Z 1.74 2437  74  78  10 0.00
Sun 05/17 03Z 1.96 2537  83  84  10 0.01
Sun 05/17 04Z 1.42 2635  89  67  10 0.01
Sun 05/17 05Z 1.13 2733  89  22  10 0.01
Sun 05/17 06Z 0.93 2730  83   5  10 0.00
Sun 05/17 07Z 0.81 2831  66   5  10 0.00
Sun 05/17 08Z 0.71 3032  56   4  10 0.00
Sun 05/17 09Z 0.66 3032  56  13   9 0.00
Sun 05/17 10Z 0.72 2931  56  17   9 0.00
Sun 05/17 11Z 0.76 2930  58  21   9 0.00
Sun 05/17 12Z 0.81 2831  56  18   9 0.00
Sun 05/17 13Z 0.95 2831  66   6   9 0.00
Sun 05/17 14Z 1.38 2828  87  18   8 0.00
Sun 05/17 15Z 2.52 2825  89  18   7 0.00
Sun 05/17 16Z 4.30 2822  86  30   7 0.00
Sun 05/17 17Z 6.23 2820  85  30   7 0.00
Sun 05/17 18Z 5.96 2918  85  29   7 0.00
Sun 05/17 19Z 2.60 2917  85  29   7 0.00
Sun 05/17 20Z 1.10 2916  81  26   7 0.00
Sun 05/17 21Z 0.94 3017  82  24   7 0.00
Sun 05/17 22Z 0.61 3018  81  20   7 0.00
Sun 05/17 23Z 0.46 3119  78  17   7 0.00
Mon 05/18 00Z 0.43 3120  76  16   6 0.00
Mon 05/18 01Z 0.36 3120  76  15   6 0.00
Mon 05/18 02Z 0.29 3119  68  13   7 0.00
Mon 05/18 03Z 0.27 3118  63  12   7 0.00
Mon 05/18 04Z 0.22 3115  54  16   8 0.00
Mon 05/18 05Z 0.17 3113  46  28   9 0.00
Mon 05/18 06Z 0.19 3011  42  34   9 0.00
Mon 05/18 07Z 0.21 2911  39  44  10 0.00
Mon 05/18 08Z 0.22 2912  36  66  11 0.00
Mon 05/18 09Z 0.21 2912  35  72  11 0.00
Mon 05/18 10Z 0.21 2811  33  66  12 0.00
Mon 05/18 11Z 0.19 2709  31  81  13 0.00

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