NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260723_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)
=== ===== === ==== ==== === === === ====
Thu 07/23 06Z 0.60 3123  90  41   6 0.00
Thu 07/23 07Z 0.55 3123  85  37   6 0.00
Thu 07/23 08Z 0.47 3121  83  38   6 0.00
Thu 07/23 09Z 0.41 3122  77  53   6 0.00
Thu 07/23 10Z 0.40 3122  75  58   6 0.00
Thu 07/23 11Z 0.37 3119  73  38   7 0.00
Thu 07/23 12Z 0.31 3116  69  21   7 0.00
Thu 07/23 13Z 0.33 3014  67  28   7 0.00
Thu 07/23 14Z 0.39 2912  67  32   7 0.00
Thu 07/23 15Z 0.54 2811  66  31   7 0.00
Thu 07/23 16Z 1.24 2712  66  36   8 0.00
Thu 07/23 17Z 3.45 2613  71  43   8 0.00
Thu 07/23 18Z 8.11 2614  73  40   8 0.00
Thu 07/23 19Z 9.61 2714  70  40   9 0.00
Thu 07/23 20Z 8.41 2714  66  28   9 0.00
Thu 07/23 21Z 8.19 2713  66  22   9 0.00
Thu 07/23 22Z 4.57 2712  64  18   9 0.00
Thu 07/23 23Z 1.71 2714  63  21  10 0.00
Fri 07/24 00Z 1.94 2715  64  31  10 0.00
Fri 07/24 01Z 1.30 2714  63  28  10 0.00
Fri 07/24 02Z 1.01 2714  60  25  10 0.00
Fri 07/24 03Z 1.05 2714  60  24   9 0.00
Fri 07/24 04Z 0.94 2715  57  31   9 0.00
Fri 07/24 05Z 0.76 2814  55  31   9 0.00
Fri 07/24 06Z 0.68 2813  54  26   9 0.00
Fri 07/24 07Z 0.65 2812  55  21   9 0.00
Fri 07/24 08Z 0.60 2911  58  18   9 0.00
Fri 07/24 09Z 0.54 2910  61  17   9 0.00
Fri 07/24 10Z 0.41 3008  64  17   9 0.00
Fri 07/24 11Z 0.30 2906  65  18   9 0.00
Fri 07/24 12Z 0.30 2805  66  19   9 0.00
Fri 07/24 13Z 0.27 2603  67  20   9 0.00
Fri 07/24 14Z 0.45 2302  68  20   9 0.00
Fri 07/24 15Z 0.76 2103  67  21   9 0.00
Fri 07/24 16Z 0.92 2003  66  21  10 0.00
Fri 07/24 17Z 1.30 2103  63  21  10 0.00
Fri 07/24 18Z 1.14 2203  60  21  11 0.00
Fri 07/24 19Z 0.86 2202  59  21  11 0.00
Fri 07/24 20Z 0.34 2001  58  20  12 0.00
Fri 07/24 21Z 0.15 1801  59  20  12 0.00
Fri 07/24 22Z 0.13 1502  60  19  12 0.00
Fri 07/24 23Z 0.10 1503  62  18  12 0.00
Sat 07/25 00Z 0.04 1605  63  18  12 0.00
Sat 07/25 01Z 0.05 1606  62  17  12 0.00
Sat 07/25 02Z 0.04 1707  62  17  12 0.00
Sat 07/25 03Z 0.05 1707  61  17  12 0.00
Sat 07/25 04Z 0.03 1708  61  18  11 0.00
Sat 07/25 05Z 0.09 1708  61  18  11 0.00
Sat 07/25 06Z 0.05 1706  59  18  11 0.00
Sat 07/25 07Z 0.05 1705  58  17  11 0.00
Sat 07/25 08Z 0.06 1504  58  17  11 0.00
Sat 07/25 09Z 0.15 1306  58  16  11 0.00
Sat 07/25 10Z 0.19 1409  58  15  11 0.00
Sat 07/25 11Z 0.19 1409  61  14  11 0.00
Sat 07/25 12Z 0.21 1410  64  14  11 0.00
Sat 07/25 13Z 0.22 1410  69  13  10 0.00
Sat 07/25 14Z 0.45 1409  71  13  10 0.00
Sat 07/25 15Z 0.71 1309  67  12  11 0.00
Sat 07/25 16Z 0.84 1308  62  10  11 0.00
Sat 07/25 17Z 1.44 1208  61   9  11 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