NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260710_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)
=== ===== === ==== ==== === === === ====
Fri 07/10 06Z 0.39 2710  85  82  15 0.00
Fri 07/10 07Z 0.52 2713  92  81  14 0.01
Fri 07/10 08Z 0.55 2816  94  81  14 0.04
Fri 07/10 09Z 0.51 3019  95  91  13 0.07
Fri 07/10 10Z 0.29 3218  94  87  13 0.01
Fri 07/10 11Z 0.23 3219  92  85  13 0.01
Fri 07/10 12Z 0.19 3318  92  73  13 0.01
Fri 07/10 13Z 0.12 3316  90  70  13 0.01
Fri 07/10 14Z 0.07 3414  87  66  13 0.00
Fri 07/10 15Z 0.07 3413  86  60  12 0.00
Fri 07/10 16Z 0.09 3513  86  46  12 0.00
Fri 07/10 17Z 0.18 3512  82  41  12 0.00
Fri 07/10 18Z 0.31 3511  77  33  12 0.00
Fri 07/10 19Z 0.23 3411  72  31  12 0.00
Fri 07/10 20Z 0.26 3411  68  34  12 0.00
Fri 07/10 21Z 0.15 3411  65  32  12 0.00
Fri 07/10 22Z 0.09 3411  65  32  12 0.00
Fri 07/10 23Z 0.07 3410  67  36  12 0.00
Sat 07/11 00Z 0.06 3411  68  33  12 0.00
Sat 07/11 01Z 0.07 3412  68  25  12 0.00
Sat 07/11 02Z 0.09 3413  71  34  12 0.00
Sat 07/11 03Z 0.08 3513  73  38  11 0.00
Sat 07/11 04Z 0.08 3413  75  45  11 0.00
Sat 07/11 05Z 0.05 3512  77  20  11 0.00
Sat 07/11 06Z 0.13 0011  76  12  10 0.00
Sat 07/11 07Z 0.16 0010  76  35  10 0.00
Sat 07/11 08Z 0.16 0009  74  29  10 0.00
Sat 07/11 09Z 0.19 0108  72  25  10 0.00
Sat 07/11 10Z 0.17 0108  70  21   9 0.00
Sat 07/11 11Z 0.08 3507  69  18   9 0.00
Sat 07/11 12Z 0.07 3507  67  19   9 0.00
Sat 07/11 13Z 0.11 3507  66  20   9 0.00
Sat 07/11 14Z 0.18 3406  65  20   9 0.00
Sat 07/11 15Z 0.47 3407  63  21   9 0.00
Sat 07/11 16Z 0.59 3306  61  19  10 0.00
Sat 07/11 17Z 0.72 3307  61  19  10 0.00
Sat 07/11 18Z 0.65 3307  60  19  10 0.00
Sat 07/11 19Z 0.29 3408  60  18  11 0.00
Sat 07/11 20Z 0.16 3409  62  17  11 0.00
Sat 07/11 21Z 0.25 3510  66  18  11 0.00
Sat 07/11 22Z 0.27 3510  70  22  11 0.00
Sat 07/11 23Z 0.28 3511  74  26  10 0.00
Sun 07/12 00Z 0.29 0012  75  28  10 0.00
Sun 07/12 01Z 0.35 0014  75  31  10 0.00
Sun 07/12 02Z 0.36 0115  73  29  10 0.00
Sun 07/12 03Z 0.43 0116  73  26   9 0.00
Sun 07/12 04Z 0.52 0217  74  21   9 0.00
Sun 07/12 05Z 0.51 0216  76  20   9 0.00
Sun 07/12 06Z 0.47 0215  77  20   9 0.00
Sun 07/12 07Z 0.42 0214  76  19   9 0.00
Sun 07/12 08Z 0.34 0212  73  18   9 0.00
Sun 07/12 09Z 0.28 0211  72  15   9 0.00
Sun 07/12 10Z 0.21 0209  72  14   9 0.00
Sun 07/12 11Z 0.19 0209  71  11   9 0.00
Sun 07/12 12Z 0.16 0109  71   9   9 0.00
Sun 07/12 13Z 0.12 0008  74  10   9 0.00
Sun 07/12 14Z 0.14 0007  76   9   9 0.00
Sun 07/12 15Z 0.26 0005  78   8   9 0.00
Sun 07/12 16Z 0.13 3503  79   6  10 0.00
Sun 07/12 17Z 0.23 3303  81   6  10 0.00

Run total areal avg QPF for the Central_Greens is: 0.16 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