NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260425_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)
=== ===== === ==== ==== === === === ====
Sat 04/25 06Z 0.26 1008  72  21  -2 0.00
Sat 04/25 07Z 0.18 1309  73  21  -3 0.00
Sat 04/25 08Z 0.12 1409  75  21  -3 0.00
Sat 04/25 09Z 0.05 1608  75  21  -2 0.00
Sat 04/25 10Z 0.03 1607  73  21  -2 0.00
Sat 04/25 11Z 0.04 1506  73  20  -2 0.00
Sat 04/25 12Z 0.04 1506  73  19  -2 0.00
Sat 04/25 13Z 0.04 1605  74  19  -2 0.00
Sat 04/25 14Z 0.31 1405  73  18  -2 0.00
Sat 04/25 15Z 0.90 1405  73  18  -2 0.00
Sat 04/25 16Z 0.61 1505  71  18  -2 0.00
Sat 04/25 17Z 0.55 1503  69  19  -1 0.00
Sat 04/25 18Z 0.43 1503  69  19   0 0.00
Sat 04/25 19Z 0.80 1403  69  19   0 0.00
Sat 04/25 20Z 0.49 1302  70  19   0 0.00
Sat 04/25 21Z 0.54 1202  70  20   0 0.00
Sat 04/25 22Z 0.39 1002  70  23   0 0.00
Sat 04/25 23Z 0.42 0904  70  31   0 0.00
Sun 04/26 00Z 0.40 0906  67  42   0 0.00
Sun 04/26 01Z 0.38 1007  67  47   0 0.00
Sun 04/26 02Z 0.33 1106  69  49   0 0.00
Sun 04/26 03Z 0.26 1105  69  51   0 0.00
Sun 04/26 04Z 0.23 1105  68  51   0 0.00
Sun 04/26 05Z 0.22 1005  67  44   0 0.00
Sun 04/26 06Z 0.23 0905  67  38   0 0.00
Sun 04/26 07Z 0.23 0804  68  34   0 0.00
Sun 04/26 08Z 0.19 0604  69  31   0 0.00
Sun 04/26 09Z 0.25 0605  69  28   0 0.00
Sun 04/26 10Z 0.36 0607  68  28   0 0.00
Sun 04/26 11Z 0.46 0709  68  27   0 0.00
Sun 04/26 12Z 0.48 0709  67  22   0 0.00
Sun 04/26 13Z 0.95 0808  67  19   0 0.00
Sun 04/26 14Z 3.10 0907  69  16   0 0.00
Sun 04/26 15Z 3.58 0805  69  14   0 0.00
Sun 04/26 16Z 2.68 0504  68  12   0 0.00
Sun 04/26 17Z 2.10 0304  67  12   1 0.00
Sun 04/26 18Z 2.03 0305  65  11   1 0.00
Sun 04/26 19Z 1.84 0304  65  10   2 0.00
Sun 04/26 20Z 1.67 0304  65  11   2 0.00
Sun 04/26 21Z 1.73 0405  65  13   2 0.00
Sun 04/26 22Z 1.79 0506  66  27   3 0.00
Sun 04/26 23Z 1.00 0507  66  43   3 0.00
Mon 04/27 00Z 0.66 0608  65  50   2 0.00
Mon 04/27 01Z 0.56 0608  66  63   2 0.00
Mon 04/27 02Z 0.52 0608  67  68   2 0.00
Mon 04/27 03Z 0.46 0608  66  61   2 0.00
Mon 04/27 04Z 0.48 0609  66  55   2 0.00
Mon 04/27 05Z 0.54 0610  67  50   2 0.00
Mon 04/27 06Z 0.60 0711  68  48   2 0.00
Mon 04/27 07Z 0.65 0713  71  50   2 0.00
Mon 04/27 08Z 0.62 0714  70  56   2 0.00
Mon 04/27 09Z 0.59 0815  66  59   3 0.00
Mon 04/27 10Z 0.57 0816  61  58   3 0.00
Mon 04/27 11Z 0.56 0918  54  53   2 0.00
Mon 04/27 12Z 0.56 1018  59  48   2 0.00
Mon 04/27 13Z 0.50 1015  65  49   2 0.00
Mon 04/27 14Z 0.54 1012  65  50   2 0.00
Mon 04/27 15Z 1.21 1010  65  49   2 0.00
Mon 04/27 16Z 3.79 1007  64  47   2 0.00
Mon 04/27 17Z 4.31 0906  64  46   3 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