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_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)
=== ===== === ==== ==== === === === ====
Sat 10/31 06Z 0.28 3326  91  24  -4 0.00
Sat 10/31 07Z 0.30 3327  91  14  -5 0.00
Sat 10/31 08Z 0.38 3225  93   8  -5 0.00
Sat 10/31 09Z 0.37 3224  92   8  -5 0.00
Sat 10/31 10Z 0.35 3223  89  16  -5 0.00
Sat 10/31 11Z 0.30 3222  84  21  -4 0.00
Sat 10/31 12Z 0.27 3222  79  24  -4 0.00
Sat 10/31 13Z 0.24 3222  74  27  -4 0.00
Sat 10/31 14Z 0.22 3222  69  30  -4 0.00
Sat 10/31 15Z 0.21 3221  68  32  -4 0.00
Sat 10/31 16Z 0.25 3219  69  27  -4 0.00
Sat 10/31 17Z 0.28 3219  71  19  -4 0.00
Sat 10/31 18Z 0.33 3217  73  13  -4 0.00
Sat 10/31 19Z 0.42 3117  78  11  -4 0.00
Sat 10/31 20Z 0.48 3017  82  15  -4 0.00
Sat 10/31 21Z 0.58 3017  86  21  -4 0.00
Sat 10/31 22Z 0.65 2918  87  23  -4 0.00
Sat 10/31 23Z 0.68 3019  87  36  -4 0.00
Sun 11/01 00Z 0.65 3020  86  44  -4 0.00
Sun 11/01 01Z 0.47 3120  83  37  -3 0.00
Sun 11/01 02Z 0.44 3120  82  24  -3 0.00
Sun 11/01 03Z 0.40 3020  80  14  -2 0.00
Sun 11/01 04Z 0.34 3019  76   6  -1 0.00
Sun 11/01 05Z 0.30 3018  71   6   0 0.00
Sun 11/01 06Z 0.28 3018  69   8   0 0.00
Sun 11/01 07Z 0.26 3119  63   9   0 0.00
Sun 11/01 08Z 0.25 3120  54  10   1 0.00
Sun 11/01 09Z 0.26 3121  48  13   1 0.00
Sun 11/01 10Z 0.28 3122  44  12   1 0.00
Sun 11/01 11Z 0.31 3123  45   6   1 0.00
Sun 11/01 12Z 0.33 3125  57   2   1 0.00
Sun 11/01 13Z 0.38 3126  73   7   1 0.00
Sun 11/01 14Z 0.42 3026  79   5   2 0.00
Sun 11/01 15Z 0.43 3026  70  11   2 0.00
Sun 11/01 16Z 0.43 3127  70  16   3 0.00
Sun 11/01 17Z 0.40 3127  74  18   3 0.00
Sun 11/01 18Z 0.45 3026  69  17   3 0.00
Sun 11/01 19Z 0.52 3027  68  20   3 0.00
Sun 11/01 20Z 0.63 2929  65  20   3 0.00
Sun 11/01 21Z 0.69 3030  65  20   4 0.00
Sun 11/01 22Z 0.74 2930  61  18   4 0.00
Sun 11/01 23Z 0.77 2930  61  22   4 0.00
Mon 11/02 00Z 0.79 2930  55  24   4 0.00
Mon 11/02 01Z 0.79 2929  55  27   4 0.00
Mon 11/02 02Z 0.84 2829  59  30   4 0.00
Mon 11/02 03Z 0.88 2829  63  45   4 0.00
Mon 11/02 04Z 0.92 2828  62  66   4 0.00
Mon 11/02 05Z 0.92 2829  57  74   5 0.00
Mon 11/02 06Z 0.94 2828  52  79   6 0.00
Mon 11/02 07Z 0.98 2729  48  82   6 0.00
Mon 11/02 08Z 0.93 2729  46  83   7 0.00
Mon 11/02 09Z 0.94 2729  44  85   7 0.00
Mon 11/02 10Z 0.91 2729  46  86   6 0.00
Mon 11/02 11Z 0.80 2829  53  86   7 0.00
Mon 11/02 12Z 0.71 2829  59  83   7 0.00
Mon 11/02 13Z 0.67 2827  61  75   7 0.00
Mon 11/02 14Z 0.66 2826  64  74   7 0.00
Mon 11/02 15Z 0.66 2825  66  85   7 0.00
Mon 11/02 16Z 0.61 2823  68  84   8 0.00
Mon 11/02 17Z 0.57 2821  70  78   8 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