NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260408_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 04/08 06Z 0.37 3220  81  39 -12 0.00
Wed 04/08 07Z 0.44 3221  73  37 -12 0.00
Wed 04/08 08Z 0.36 3220  66  27 -11 0.00
Wed 04/08 09Z 0.30 3219  60  26 -10 0.00
Wed 04/08 10Z 0.24 3217  56  16 -10 0.00
Wed 04/08 11Z 0.20 3215  54  15  -9 0.00
Wed 04/08 12Z 0.17 3112  53  12  -9 0.00
Wed 04/08 13Z 0.16 3110  52  10  -8 0.00
Wed 04/08 14Z 0.18 2908  50   7  -8 0.00
Wed 04/08 15Z 0.18 2907  46   5  -7 0.00
Wed 04/08 16Z 0.17 2905  40   4  -7 0.00
Wed 04/08 17Z 0.22 2703  36   3  -6 0.00
Wed 04/08 18Z 0.48 2603  34   3  -6 0.00
Wed 04/08 19Z 0.50 2403  32   4  -5 0.00
Wed 04/08 20Z 0.55 2304  30   4  -4 0.00
Wed 04/08 21Z 0.35 2306  28   5  -4 0.00
Wed 04/08 22Z 0.26 2407  26   5  -3 0.00
Wed 04/08 23Z 0.25 2308  25   5  -2 0.00
Thu 04/09 00Z 0.27 2210  25   6  -2 0.00
Thu 04/09 01Z 0.29 2113  21   7  -1 0.00
Thu 04/09 02Z 0.34 2215  18   8  -1 0.00
Thu 04/09 03Z 0.38 2217  17  12   0 0.00
Thu 04/09 04Z 0.38 2318  21  19   0 0.00
Thu 04/09 05Z 0.36 2219  22  23   1 0.00
Thu 04/09 06Z 0.32 2218  21  29   2 0.00
Thu 04/09 07Z 0.30 2119  20  35   2 0.00
Thu 04/09 08Z 0.30 2120  19  42   2 0.00
Thu 04/09 09Z 0.31 2121  19  45   2 0.00
Thu 04/09 10Z 0.32 2122  17  43   2 0.00
Thu 04/09 11Z 0.34 2122  15  40   3 0.00
Thu 04/09 12Z 0.35 2222  12  41   3 0.00
Thu 04/09 13Z 0.36 2222  10  46   3 0.00
Thu 04/09 14Z 0.34 2123  10  61   3 0.00
Thu 04/09 15Z 0.34 2124  10  67   3 0.00
Thu 04/09 16Z 0.36 2024  11  71   3 0.00
Thu 04/09 17Z 0.38 2024  14  67   3 0.00
Thu 04/09 18Z 0.44 2023  18  57   3 0.00
Thu 04/09 19Z 0.51 2024  20  47   3 0.00
Thu 04/09 20Z 0.48 2025  22  44   3 0.00
Thu 04/09 21Z 0.47 2026  22  49   4 0.00
Thu 04/09 22Z 0.44 2027  21  41   5 0.00
Thu 04/09 23Z 0.42 2028  25  37   6 0.00
Fri 04/10 00Z 0.41 2129  32  42   6 0.00
Fri 04/10 01Z 0.48 2131  42  47   6 0.00
Fri 04/10 02Z 0.53 2231  52  45   6 0.00
Fri 04/10 03Z 0.61 2333  59  41   6 0.00
Fri 04/10 04Z 0.65 2333  62  50   6 0.00
Fri 04/10 05Z 0.70 2434  65  66   5 0.00
Fri 04/10 06Z 0.68 2532  68  65   5 0.00
Fri 04/10 07Z 0.67 2531  73  77   5 0.00
Fri 04/10 08Z 0.62 2528  74  56   4 0.00
Fri 04/10 09Z 0.56 2625  77  61   4 0.00
Fri 04/10 10Z 0.51 2624  77  79   4 0.00
Fri 04/10 11Z 0.46 2620  75  29   4 0.00
Fri 04/10 12Z 0.44 2619  74  11   3 0.00
Fri 04/10 13Z 0.43 2618  74  10   3 0.00
Fri 04/10 14Z 0.46 2618  76  18   3 0.00
Fri 04/10 15Z 0.54 2619  78  45   2 0.00
Fri 04/10 16Z 0.63 2618  74  44   2 0.00
Fri 04/10 17Z 0.59 2615  72  93   2 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