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_1800
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 18Z 0.34 1500  66  30   0 0.00
Sat 04/25 19Z 0.49 1300  65  30   0 0.00
Sat 04/25 20Z 0.47 1401  66  29   1 0.00
Sat 04/25 21Z 0.36 1301  68  28   1 0.00
Sat 04/25 22Z 0.29 0901  70  27   1 0.00
Sat 04/25 23Z 0.26 0902  71  28   0 0.00
Sun 04/26 00Z 0.17 1102  71  30   0 0.00
Sun 04/26 01Z 0.07 1402  71  32   0 0.00
Sun 04/26 02Z 0.06 1100  71  32   0 0.00
Sun 04/26 03Z 0.06 0600  71  31   0 0.00
Sun 04/26 04Z 0.07 0601  71  32   0 0.00
Sun 04/26 05Z 0.05 0400  71  36   0 0.00
Sun 04/26 06Z 0.05 0001  71  39   0 0.00
Sun 04/26 07Z 0.03 3502  71  40   0 0.00
Sun 04/26 08Z 0.10 0203  69  38   0 0.00
Sun 04/26 09Z 0.25 0405  66  34   0 0.00
Sun 04/26 10Z 0.21 0305  66  33   0 0.00
Sun 04/26 11Z 0.21 0305  66  32   0 0.00
Sun 04/26 12Z 0.21 0305  66  33   0 0.00
Sun 04/26 13Z 0.44 0305  67  32   0 0.00
Sun 04/26 14Z 1.55 0405  69  27   0 0.00
Sun 04/26 15Z 2.25 0404  70  24   0 0.00
Sun 04/26 16Z 1.23 0204  71  24   1 0.00
Sun 04/26 17Z 1.11 0104  71  21   1 0.00
Sun 04/26 18Z 0.81 0004  72  19   1 0.00
Sun 04/26 19Z 0.73 0004  73  16   2 0.00
Sun 04/26 20Z 0.92 0105  73  12   2 0.00
Sun 04/26 21Z 1.03 0205  73  11   2 0.00
Sun 04/26 22Z 0.78 0205  73  11   2 0.00
Sun 04/26 23Z 0.69 0305  73  10   2 0.00
Mon 04/27 00Z 0.52 0306  72  10   2 0.00
Mon 04/27 01Z 0.66 0406  71  10   2 0.00
Mon 04/27 02Z 0.74 0406  72  10   2 0.00
Mon 04/27 03Z 0.71 0507  72   9   2 0.00
Mon 04/27 04Z 0.64 0607  72   8   2 0.00
Mon 04/27 05Z 0.51 0607  72   9   2 0.00
Mon 04/27 06Z 0.41 0606  70   9   2 0.00
Mon 04/27 07Z 0.32 0605  69  11   2 0.00
Mon 04/27 08Z 0.25 0504  69  18   2 0.00
Mon 04/27 09Z 0.22 0404  70  29   2 0.00
Mon 04/27 10Z 0.31 0505  70  30   2 0.00
Mon 04/27 11Z 0.44 0607  69  31   2 0.00
Mon 04/27 12Z 0.43 0707  69  36   2 0.00
Mon 04/27 13Z 0.57 0707  69  37   2 0.00
Mon 04/27 14Z 1.45 0704  71  39   2 0.00
Mon 04/27 15Z 2.74 0905  70  37   2 0.00
Mon 04/27 16Z 2.28 1004  67  39   3 0.00
Mon 04/27 17Z 2.12 1103  65  38   4 0.00
Mon 04/27 18Z 3.22 1105  62  33   4 0.00
Mon 04/27 19Z 2.46 1305  60  32   5 0.00
Mon 04/27 20Z 2.02 1405  59  30   5 0.00
Mon 04/27 21Z 1.08 1505  61  29   5 0.00
Mon 04/27 22Z 0.31 1605  64  30   5 0.00
Mon 04/27 23Z 0.15 1607  64  27   5 0.00
Tue 04/28 00Z 0.11 1709  63  25   5 0.00
Tue 04/28 01Z 0.25 1811  62  23   5 0.00
Tue 04/28 02Z 0.20 1810  62  17   5 0.00
Tue 04/28 03Z 0.11 1709  60  12   5 0.00
Tue 04/28 04Z 0.07 1709  58  11   5 0.00
Tue 04/28 05Z 0.13 1512  54   9   5 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