Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20261023_1200
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 10/23 12Z 0.09 0116  66   1  -1 0.00
Fri 10/23 13Z 0.08 0116  64   1   0 0.00
Fri 10/23 14Z 0.10 0116  61   1   0 0.00
Fri 10/23 15Z 0.13 0115  56   2   0 0.00
Fri 10/23 16Z 0.14 0214  53   3   0 0.00
Fri 10/23 17Z 0.13 0212  49   4   0 0.00
Fri 10/23 18Z 0.13 0211  46   3   1 0.00
Fri 10/23 19Z 0.13 0210  43   2   2 0.00
Fri 10/23 20Z 0.11 0209  39   2   2 0.00
Fri 10/23 21Z 0.11 0309  34   2   3 0.00
Fri 10/23 22Z 0.09 0308  29   2   4 0.00
Fri 10/23 23Z 0.07 0207  25   2   4 0.00
Sat 10/24 00Z 0.07 0306  22   2   4 0.00
Sat 10/24 01Z 0.05 0304  20   2   5 0.00
Sat 10/24 02Z 0.04 0203  19   2   5 0.00
Sat 10/24 03Z 0.03 3402  18   2   5 0.00
Sat 10/24 04Z 0.05 3103  17   2   5 0.00
Sat 10/24 05Z 0.08 3004  16   2   4 0.00
Sat 10/24 06Z 0.10 3005  14   2   4 0.00
Sat 10/24 07Z 0.14 3007  13   2   4 0.00
Sat 10/24 08Z 0.16 3009  12   1   4 0.00
Sat 10/24 09Z 0.18 3110  12   1   4 0.00
Sat 10/24 10Z 0.18 3111  13   1   4 0.00
Sat 10/24 11Z 0.15 3211  15   1   4 0.00
Sat 10/24 12Z 0.13 3211  17   1   4 0.00
Sat 10/24 13Z 0.12 3310  16   1   4 0.00
Sat 10/24 14Z 0.10 3310  15   1   4 0.00
Sat 10/24 15Z 0.11 3209  15   3   5 0.00
Sat 10/24 16Z 0.12 3208  16   5   5 0.00
Sat 10/24 17Z 0.13 3108  15   5   5 0.00
Sat 10/24 18Z 0.15 3109  16   7   5 0.00
Sat 10/24 19Z 0.17 3110  15  10   5 0.00
Sat 10/24 20Z 0.17 3111  12  19   5 0.00
Sat 10/24 21Z 0.15 3211  11  28   5 0.00
Sat 10/24 22Z 0.14 3211  12  34   5 0.00
Sat 10/24 23Z 0.12 3311  15  40   5 0.00
Sun 10/25 00Z 0.10 3310  15  45   6 0.00
Sun 10/25 01Z 0.08 3308  14  47   6 0.00
Sun 10/25 02Z 0.07 3306  13  50   7 0.00
Sun 10/25 03Z 0.07 3205  12  52   7 0.00
Sun 10/25 04Z 0.08 3004  12  52   7 0.00
Sun 10/25 05Z 0.10 2905  12  48   7 0.00
Sun 10/25 06Z 0.11 2805  12  45   7 0.00
Sun 10/25 07Z 0.16 2707  13  48   7 0.00
Sun 10/25 08Z 0.17 2708  13  45   8 0.00
Sun 10/25 09Z 0.16 2807  12  42   8 0.00
Sun 10/25 10Z 0.15 2807  10  34   9 0.00
Sun 10/25 11Z 0.13 2806  10  31   9 0.00
Sun 10/25 12Z 0.13 2706  10  30   9 0.00
Sun 10/25 13Z 0.15 2707  10  30   9 0.00
Sun 10/25 14Z 0.17 2608  10  28   9 0.00
Sun 10/25 15Z 0.17 2508   9  27   9 0.00
Sun 10/25 16Z 0.18 2509  10  27   9 0.00
Sun 10/25 17Z 0.22 2510  11  28   9 0.00
Sun 10/25 18Z 0.23 2511   9  29   9 0.00
Sun 10/25 19Z 0.24 2511   7  28  10 0.00
Sun 10/25 20Z 0.26 2512   6  26  10 0.00
Sun 10/25 21Z 0.29 2513   5  22  10 0.00
Sun 10/25 22Z 0.34 2515   7  24  10 0.00
Sun 10/25 23Z 0.36 2516  10  27  10 0.00

Run total areal avg QPF for the 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