NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261101_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)
=== ===== === ==== ==== === === === ====
Sun 11/01 06Z 0.23 3114  82  14  -3 0.00
Sun 11/01 07Z 0.26 3115  79  12  -2 0.00
Sun 11/01 08Z 0.27 3115  74  12  -1 0.00
Sun 11/01 09Z 0.29 3116  70  13   0 0.00
Sun 11/01 10Z 0.28 3117  63  13   0 0.00
Sun 11/01 11Z 0.29 3117  60  14   0 0.00
Sun 11/01 12Z 0.30 3118  56  13   0 0.00
Sun 11/01 13Z 0.31 3119  52  10   1 0.00
Sun 11/01 14Z 0.33 3121  51   7   1 0.00
Sun 11/01 15Z 0.34 3122  56   8   2 0.00
Sun 11/01 16Z 0.37 3123  62   9   2 0.00
Sun 11/01 17Z 0.43 3023  64  15   2 0.00
Sun 11/01 18Z 0.48 3024  70  20   2 0.00
Sun 11/01 19Z 0.51 3024  71  24   3 0.00
Sun 11/01 20Z 0.55 3025  72  25   4 0.00
Sun 11/01 21Z 0.61 2926  72  23   4 0.00
Sun 11/01 22Z 0.67 2927  70  21   4 0.00
Sun 11/01 23Z 0.73 2928  70  20   4 0.00
Mon 11/02 00Z 0.75 2929  70  21   4 0.00
Mon 11/02 01Z 0.78 2930  68  20   4 0.00
Mon 11/02 02Z 0.82 2830  60  20   5 0.00
Mon 11/02 03Z 0.84 2829  58  18   5 0.00
Mon 11/02 04Z 0.86 2829  58  42   5 0.00
Mon 11/02 05Z 0.91 2830  57  70   6 0.00
Mon 11/02 06Z 0.90 2830  54  75   6 0.00
Mon 11/02 07Z 0.94 2830  53  83   6 0.00
Mon 11/02 08Z 0.97 2730  52  88   6 0.00
Mon 11/02 09Z 0.96 2729  52  92   6 0.00
Mon 11/02 10Z 0.89 2828  52  92   6 0.00
Mon 11/02 11Z 0.77 2826  52  87   7 0.00
Mon 11/02 12Z 0.71 2724  53  88   7 0.00
Mon 11/02 13Z 0.70 2724  55  85   8 0.00
Mon 11/02 14Z 0.74 2725  63  82   8 0.00
Mon 11/02 15Z 0.78 2726  65  79   8 0.00
Mon 11/02 16Z 0.78 2726  67  79   8 0.00
Mon 11/02 17Z 0.75 2725  64  80   8 0.00
Mon 11/02 18Z 0.71 2724  66  85   8 0.00
Mon 11/02 19Z 0.65 2723  70  90   8 0.00
Mon 11/02 20Z 0.63 2822  72  88   8 0.00
Mon 11/02 21Z 0.60 2822  75  87   8 0.00
Mon 11/02 22Z 0.60 2822  77  86   8 0.00
Mon 11/02 23Z 0.54 2820  76  83   9 0.00
Tue 11/03 00Z 0.53 2820  79  84   8 0.00
Tue 11/03 01Z 0.46 2818  79  82   8 0.00
Tue 11/03 02Z 0.42 2816  78  83   8 0.00
Tue 11/03 03Z 0.41 2716  77  82   8 0.00
Tue 11/03 04Z 0.44 2817  79  87   8 0.00
Tue 11/03 05Z 0.45 2817  81  90   8 0.00
Tue 11/03 06Z 0.41 2916  81  89   8 0.00
Tue 11/03 07Z 0.33 2914  80  87   8 0.00
Tue 11/03 08Z 0.32 2913  80  83   7 0.00
Tue 11/03 09Z 0.36 2913  81  83   7 0.00
Tue 11/03 10Z 0.36 2913  78  81   7 0.00
Tue 11/03 11Z 0.34 2912  76  82   7 0.00
Tue 11/03 12Z 0.33 2810  74  82   7 0.00
Tue 11/03 13Z 0.34 2709  73  84   7 0.00
Tue 11/03 14Z 0.32 2508  71  86   7 0.00
Tue 11/03 15Z 0.36 2310  71  90   7 0.00
Tue 11/03 16Z 0.38 2211  73  92   7 0.00
Tue 11/03 17Z 0.36 2112  75  93   7 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