Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20261018_0000
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 00Z 0.23 3216  70  40  -6 0.00
Sun 10/18 01Z 0.17 3318  64  43  -5 0.00
Sun 10/18 02Z 0.14 3317  62  57  -4 0.00
Sun 10/18 03Z 0.13 3317  61  58  -4 0.00
Sun 10/18 04Z 0.17 3217  62  59  -3 0.00
Sun 10/18 05Z 0.21 3216  61  61  -4 0.00
Sun 10/18 06Z 0.26 3115  58  60  -4 0.00
Sun 10/18 07Z 0.32 3115  54  57  -3 0.00
Sun 10/18 08Z 0.35 3014  49  57  -3 0.00
Sun 10/18 09Z 0.34 3014  47  58  -3 0.00
Sun 10/18 10Z 0.30 3013  51  59  -2 0.00
Sun 10/18 11Z 0.27 3013  59  62  -2 0.00
Sun 10/18 12Z 0.26 3012  69  64  -1 0.00
Sun 10/18 13Z 0.25 3011  74  64  -1 0.00
Sun 10/18 14Z 0.25 2910  75  57   0 0.00
Sun 10/18 15Z 0.25 2809  73  44   0 0.00
Sun 10/18 16Z 0.26 2809  73  42   0 0.00
Sun 10/18 17Z 0.30 2709  70  39   1 0.00
Sun 10/18 18Z 0.32 2610  62  37   2 0.00
Sun 10/18 19Z 0.31 2610  54  36   3 0.00
Sun 10/18 20Z 0.30 2611  47  32   4 0.00
Sun 10/18 21Z 0.29 2611  42  29   5 0.00
Sun 10/18 22Z 0.28 2612  37  23   6 0.00
Sun 10/18 23Z 0.25 2611  32  18   7 0.00
Mon 10/19 00Z 0.23 2611  29  14   7 0.00
Mon 10/19 01Z 0.22 2611  25  13   8 0.00
Mon 10/19 02Z 0.21 2610  21  16   8 0.00
Mon 10/19 03Z 0.20 2610  18  18   9 0.00
Mon 10/19 04Z 0.19 2609  17  19   9 0.00
Mon 10/19 05Z 0.17 2607  17  20   9 0.00
Mon 10/19 06Z 0.16 2607  17  20   9 0.00
Mon 10/19 07Z 0.15 2607  18  18   9 0.00
Mon 10/19 08Z 0.16 2707  18  17   9 0.00
Mon 10/19 09Z 0.15 2807  17  16   9 0.00
Mon 10/19 10Z 0.15 2807  17  17   9 0.00
Mon 10/19 11Z 0.14 2807  16  17   9 0.00
Mon 10/19 12Z 0.12 2906  15  18   9 0.00
Mon 10/19 13Z 0.11 2805  14  19   9 0.00
Mon 10/19 14Z 0.11 2704  13  19   9 0.00
Mon 10/19 15Z 0.12 2605  12  18   9 0.00
Mon 10/19 16Z 0.12 2705  12  18  10 0.00
Mon 10/19 17Z 0.12 2705  12  19  10 0.00
Mon 10/19 18Z 0.13 2906  12  18  10 0.00
Mon 10/19 19Z 0.11 3006  13  18  10 0.00
Mon 10/19 20Z 0.09 3105  13  18  10 0.00
Mon 10/19 21Z 0.08 3105  14  18  10 0.00
Mon 10/19 22Z 0.08 3205  15  19  10 0.00
Mon 10/19 23Z 0.06 3306  14  20  10 0.00
Tue 10/20 00Z 0.06 3307  13  23  10 0.00
Tue 10/20 01Z 0.07 3408  14  25  10 0.00
Tue 10/20 02Z 0.07 3409  15  26  10 0.00
Tue 10/20 03Z 0.05 3510  18  26  10 0.00
Tue 10/20 04Z 0.05 3511  20  25  10 0.00
Tue 10/20 05Z 0.06 0011  23  23  11 0.00
Tue 10/20 06Z 0.06 0011  26  19  11 0.00
Tue 10/20 07Z 0.07 0012  28  14  11 0.00
Tue 10/20 08Z 0.09 0014  31  11  10 0.00
Tue 10/20 09Z 0.12 0115  34  11  10 0.00
Tue 10/20 10Z 0.16 0216  40  10  10 0.00
Tue 10/20 11Z 0.21 0218  43  17   9 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