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_1800
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 18Z 0.80 3011  84  17  -4 0.00
Sat 10/31 19Z 0.92 2914  86  12  -4 0.00
Sat 10/31 20Z 0.83 2914  87  14  -4 0.00
Sat 10/31 21Z 0.83 2914  90  20  -3 0.00
Sat 10/31 22Z 0.88 2916  91  21  -4 0.00
Sat 10/31 23Z 0.94 2919  90  20  -4 0.00
Sun 11/01 00Z 0.84 3021  88  32  -4 0.00
Sun 11/01 01Z 0.75 3123  89  36  -4 0.00
Sun 11/01 02Z 0.58 3122  90  33  -4 0.00
Sun 11/01 03Z 0.47 3121  88  23  -4 0.00
Sun 11/01 04Z 0.41 3120  85  12  -3 0.00
Sun 11/01 05Z 0.40 3120  84   9  -2 0.00
Sun 11/01 06Z 0.33 3120  80  11  -1 0.00
Sun 11/01 07Z 0.30 3120  75  12   0 0.00
Sun 11/01 08Z 0.28 3120  70  13   0 0.00
Sun 11/01 09Z 0.28 3121  67  13   0 0.00
Sun 11/01 10Z 0.28 3121  62  12   1 0.00
Sun 11/01 11Z 0.27 3122  54  12   1 0.00
Sun 11/01 12Z 0.28 3123  46  13   1 0.00
Sun 11/01 13Z 0.32 3125  44  12   1 0.00
Sun 11/01 14Z 0.38 3127  57  10   1 0.00
Sun 11/01 15Z 0.43 3128  72   7   1 0.00
Sun 11/01 16Z 0.42 3127  74   8   2 0.00
Sun 11/01 17Z 0.42 3124  70  10   2 0.00
Sun 11/01 18Z 0.44 3024  69  14   3 0.00
Sun 11/01 19Z 0.49 3024  65  18   3 0.00
Sun 11/01 20Z 0.54 2924  63  19   3 0.00
Sun 11/01 21Z 0.59 2925  59  19   4 0.00
Sun 11/01 22Z 0.63 2926  57  20   4 0.00
Sun 11/01 23Z 0.64 2926  55  20   4 0.00
Mon 11/02 00Z 0.66 2926  53  23   5 0.00
Mon 11/02 01Z 0.69 2926  48  27   5 0.00
Mon 11/02 02Z 0.72 2827  46  23   5 0.00
Mon 11/02 03Z 0.75 2826  52  45   5 0.00
Mon 11/02 04Z 0.81 2827  59  73   5 0.00
Mon 11/02 05Z 0.86 2827  60  76   5 0.00
Mon 11/02 06Z 0.89 2828  53  77   6 0.00
Mon 11/02 07Z 0.91 2828  50  79   6 0.00
Mon 11/02 08Z 0.92 2828  49  80   6 0.00
Mon 11/02 09Z 0.91 2828  48  80   7 0.00
Mon 11/02 10Z 0.89 2828  44  80   7 0.00
Mon 11/02 11Z 0.85 2827  43  79   7 0.00
Mon 11/02 12Z 0.79 2826  43  83   7 0.00
Mon 11/02 13Z 0.73 2724  42  86   7 0.00
Mon 11/02 14Z 0.68 2723  45  77   7 0.00
Mon 11/02 15Z 0.68 2723  48  78   7 0.00
Mon 11/02 16Z 0.69 2724  57  81   7 0.00
Mon 11/02 17Z 0.66 2723  67  81   7 0.00
Mon 11/02 18Z 0.58 2820  70  77   7 0.00
Mon 11/02 19Z 0.51 2818  70  73   7 0.00
Mon 11/02 20Z 0.53 2819  72  77   7 0.00
Mon 11/02 21Z 0.56 2820  76  75   7 0.00
Mon 11/02 22Z 0.58 2819  79  78   7 0.00
Mon 11/02 23Z 0.59 2820  80  82   8 0.00
Tue 11/03 00Z 0.55 2820  77  74   8 0.00
Tue 11/03 01Z 0.53 2820  74  69   9 0.00
Tue 11/03 02Z 0.55 2821  72  68   9 0.00
Tue 11/03 03Z 0.52 2821  71  70   9 0.00
Tue 11/03 04Z 0.50 2820  67  76   9 0.00
Tue 11/03 05Z 0.49 2819  66  88   9 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