Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261018_1200
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)
=== ===== === ==== ==== === === === ====
Sun 10/18 12Z 0.36 3016  73  62  -2 0.00
Sun 10/18 13Z 0.36 3016  78  56  -1 0.00
Sun 10/18 14Z 0.34 3014  80  46  -1 0.00
Sun 10/18 15Z 0.35 2912  81  42   0 0.00
Sun 10/18 16Z 0.37 2911  77  40   0 0.00
Sun 10/18 17Z 0.36 2810  71  38   0 0.00
Sun 10/18 18Z 0.34 2609  63  37   1 0.00
Sun 10/18 19Z 0.35 2510  56  35   1 0.00
Sun 10/18 20Z 0.33 2511  50  31   2 0.00
Sun 10/18 21Z 0.32 2512  44  22   4 0.00
Sun 10/18 22Z 0.32 2513  39  14   5 0.00
Sun 10/18 23Z 0.30 2613  38  13   6 0.00
Mon 10/19 00Z 0.26 2713  36  15   7 0.00
Mon 10/19 01Z 0.22 2711  29  18   8 0.00
Mon 10/19 02Z 0.19 2709  24  20   9 0.00
Mon 10/19 03Z 0.18 2709  21  21   9 0.00
Mon 10/19 04Z 0.18 2608  20  22   9 0.00
Mon 10/19 05Z 0.18 2608  20  22   9 0.00
Mon 10/19 06Z 0.18 2508  21  22   9 0.00
Mon 10/19 07Z 0.20 2509  21  21   9 0.00
Mon 10/19 08Z 0.22 2610  21  21   9 0.00
Mon 10/19 09Z 0.23 2611  19  21  10 0.00
Mon 10/19 10Z 0.22 2611  19  21  10 0.00
Mon 10/19 11Z 0.22 2710  18  22  10 0.00
Mon 10/19 12Z 0.21 2710  17  23  10 0.00
Mon 10/19 13Z 0.20 2709  16  24   9 0.00
Mon 10/19 14Z 0.20 2709  13  25   9 0.00
Mon 10/19 15Z 0.20 2709  11  26   9 0.00
Mon 10/19 16Z 0.20 2809  10  27  10 0.00
Mon 10/19 17Z 0.19 2708  10  28  10 0.00
Mon 10/19 18Z 0.19 2808   9  28  10 0.00
Mon 10/19 19Z 0.19 2909   9  29  10 0.00
Mon 10/19 20Z 0.20 3010   8  30  10 0.00
Mon 10/19 21Z 0.19 3011   9  30  10 0.00
Mon 10/19 22Z 0.18 3111  10  29  10 0.00
Mon 10/19 23Z 0.15 3211  12  29  10 0.00
Tue 10/20 00Z 0.12 3210  15  26  10 0.00
Tue 10/20 01Z 0.10 3210  19  25  10 0.00
Tue 10/20 02Z 0.08 3311  22  22  10 0.00
Tue 10/20 03Z 0.05 3310  25  22  10 0.00
Tue 10/20 04Z 0.03 3411  27  17  10 0.00
Tue 10/20 05Z 0.03 3411  30  11  10 0.00
Tue 10/20 06Z 0.02 3412  35   9  10 0.00
Tue 10/20 07Z 0.02 3514  42   8  10 0.00
Tue 10/20 08Z 0.04 3516  47   9   9 0.00
Tue 10/20 09Z 0.08 0016  48  10   9 0.00
Tue 10/20 10Z 0.11 0117  46  16   9 0.00
Tue 10/20 11Z 0.14 0118  40  21   9 0.00
Tue 10/20 12Z 0.18 0120  31  22   9 0.00
Tue 10/20 13Z 0.22 0222  25  20   9 0.00
Tue 10/20 14Z 0.25 0222  23  14   8 0.00
Tue 10/20 15Z 0.25 0221  25  10   8 0.00
Tue 10/20 16Z 0.24 0219  30   6   7 0.00
Tue 10/20 17Z 0.21 0218  30   2   7 0.00
Tue 10/20 18Z 0.18 0217  28   2   7 0.00
Tue 10/20 19Z 0.17 0117  29   2   7 0.00
Tue 10/20 20Z 0.18 0217  30   3   7 0.00
Tue 10/20 21Z 0.21 0218  36   4   7 0.00
Tue 10/20 22Z 0.25 0219  42   5   6 0.00
Tue 10/20 23Z 0.27 0319  46   5   6 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