NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20251119_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)
=== ===== === ==== ==== === === === ====
Wed 11/19 06Z 0.16 2707  80  15  -5 0.00
Wed 11/19 07Z 0.21 2708  78   7  -5 0.00
Wed 11/19 08Z 0.29 2712  76   3  -5 0.00
Wed 11/19 09Z 0.31 2814  71   1  -5 0.00
Wed 11/19 10Z 0.29 2914  68   0  -6 0.00
Wed 11/19 11Z 0.27 3014  68   0  -6 0.00
Wed 11/19 12Z 0.25 3013  71   0  -7 0.00
Wed 11/19 13Z 0.23 3113  71   0  -7 0.00
Wed 11/19 14Z 0.21 3112  68   1  -7 0.00
Wed 11/19 15Z 0.19 3111  64   3  -7 0.00
Wed 11/19 16Z 0.19 3111  59   5  -6 0.00
Wed 11/19 17Z 0.17 3111  54   7  -6 0.00
Wed 11/19 18Z 0.13 3210  48   8  -5 0.00
Wed 11/19 19Z 0.13 3210  44   9  -5 0.00
Wed 11/19 20Z 0.09 3311  42  10  -5 0.00
Wed 11/19 21Z 0.09 3311  41  11  -4 0.00
Wed 11/19 22Z 0.09 3312  43  12  -4 0.00
Wed 11/19 23Z 0.08 3311  45  14  -3 0.00
Thu 11/20 00Z 0.05 3310  46  16  -3 0.00
Thu 11/20 01Z 0.06 3309  47  17  -3 0.00
Thu 11/20 02Z 0.02 3407  45  19  -3 0.00
Thu 11/20 03Z 0.01 3406  45  19  -2 0.00
Thu 11/20 04Z 0.01 3405  45  21  -2 0.00
Thu 11/20 05Z 0.01 3404  44  27  -2 0.00
Thu 11/20 06Z 0.04 3204  45  18  -2 0.00
Thu 11/20 07Z 0.07 3005  45  23  -2 0.00
Thu 11/20 08Z 0.06 3104  44  43  -2 0.00
Thu 11/20 09Z 0.06 3004  45  56  -2 0.00
Thu 11/20 10Z 0.04 3204  42  59  -2 0.00
Thu 11/20 11Z 0.03 3203  40  71  -1 0.00
Thu 11/20 12Z 0.04 3103  37  68  -1 0.00
Thu 11/20 13Z 0.03 3102  35  68   0 0.00
Thu 11/20 14Z 0.03 3002  34  61   0 0.00
Thu 11/20 15Z 0.04 2902  33  63   0 0.00
Thu 11/20 16Z 0.03 2901  33  57   0 0.00
Thu 11/20 17Z 0.02 2700  33  48   0 0.00
Thu 11/20 18Z 0.03 2201  35  48   0 0.00
Thu 11/20 19Z 0.03 2102  34  56   0 0.00
Thu 11/20 20Z 0.03 2102  33  63   0 0.00
Thu 11/20 21Z 0.03 2002  32  66   1 0.00
Thu 11/20 22Z 0.06 2203  32  67   1 0.00
Thu 11/20 23Z 0.07 2104  30  67   1 0.00
Fri 11/21 00Z 0.05 2004  28  63   2 0.00
Fri 11/21 01Z 0.07 2105  27  55   2 0.00
Fri 11/21 02Z 0.06 2005  25  47   2 0.00
Fri 11/21 03Z 0.12 2108  26  57   2 0.00
Fri 11/21 04Z 0.16 2211  26  48   2 0.00
Fri 11/21 05Z 0.11 2109  23  44   3 0.00
Fri 11/21 06Z 0.13 2110  23  44   2 0.00
Fri 11/21 07Z 0.16 2112  22  45   2 0.00
Fri 11/21 08Z 0.19 2114  22  32   3 0.00
Fri 11/21 09Z 0.23 2216  25  27   3 0.00
Fri 11/21 10Z 0.26 2217  30  29   2 0.00
Fri 11/21 11Z 0.25 2216  32  38   2 0.00
Fri 11/21 12Z 0.27 2217  34  53   2 0.00
Fri 11/21 13Z 0.32 2320  38  53   2 0.00
Fri 11/21 14Z 0.35 2320  44  64   2 0.00
Fri 11/21 15Z 0.35 2319  50  82   1 0.00
Fri 11/21 16Z 0.35 2317  51  68   1 0.00
Fri 11/21 17Z 0.42 2418  69  56   0 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