NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260426_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)
=== ===== === ==== ==== === === === ====
Sun 04/26 06Z 0.04 0003  65  35   0 0.00
Sun 04/26 07Z 0.09 0204  64  34   0 0.00
Sun 04/26 08Z 0.17 0305  63  32   0 0.00
Sun 04/26 09Z 0.22 0406  64  32   0 0.00
Sun 04/26 10Z 0.22 0406  65  31   0 0.00
Sun 04/26 11Z 0.25 0406  66  30   0 0.00
Sun 04/26 12Z 0.26 0506  67  29   0 0.00
Sun 04/26 13Z 0.32 0505  67  28   0 0.00
Sun 04/26 14Z 1.19 0604  67  24   0 0.00
Sun 04/26 15Z 1.87 0604  66  18   0 0.00
Sun 04/26 16Z 1.67 0403  66  12   1 0.00
Sun 04/26 17Z 1.67 0304  65   7   1 0.00
Sun 04/26 18Z 1.75 0304  64   5   2 0.00
Sun 04/26 19Z 1.19 0203  65   5   2 0.00
Sun 04/26 20Z 1.15 0105  66   6   2 0.00
Sun 04/26 21Z 1.07 0105  68   5   2 0.00
Sun 04/26 22Z 0.91 0205  69   4   2 0.00
Sun 04/26 23Z 0.64 0306  69   3   2 0.00
Mon 04/27 00Z 0.55 0307  68   3   2 0.00
Mon 04/27 01Z 0.68 0408  68   4   2 0.00
Mon 04/27 02Z 0.77 0409  69   5   2 0.00
Mon 04/27 03Z 0.72 0508  70  10   2 0.00
Mon 04/27 04Z 0.59 0508  70  15   2 0.00
Mon 04/27 05Z 0.51 0507  71  25   2 0.00
Mon 04/27 06Z 0.42 0407  73  34   2 0.00
Mon 04/27 07Z 0.42 0508  73  33   2 0.00
Mon 04/27 08Z 0.43 0508  73  35   2 0.00
Mon 04/27 09Z 0.44 0608  73  38   2 0.00
Mon 04/27 10Z 0.46 0709  75  39   2 0.00
Mon 04/27 11Z 0.48 0810  76  38   2 0.00
Mon 04/27 12Z 0.40 0808  75  38   1 0.00
Mon 04/27 13Z 0.36 0907  74  38   2 0.00
Mon 04/27 14Z 0.41 0905  73  37   2 0.00
Mon 04/27 15Z 0.59 1003  71  39   2 0.00
Mon 04/27 16Z 0.93 0902  69  39   2 0.00
Mon 04/27 17Z 1.10 0902  67  38   3 0.00
Mon 04/27 18Z 1.53 1003  63  34   4 0.00
Mon 04/27 19Z 1.89 1103  59  30   4 0.00
Mon 04/27 20Z 1.51 1203  58  30   5 0.00
Mon 04/27 21Z 1.02 1303  58  28   5 0.00
Mon 04/27 22Z 0.41 1402  60  30   5 0.00
Mon 04/27 23Z 0.06 1602  62  30   5 0.00
Tue 04/28 00Z 0.08 1503  62  23   5 0.00
Tue 04/28 01Z 0.07 1606  61  19   5 0.00
Tue 04/28 02Z 0.04 1706  62  18   5 0.00
Tue 04/28 03Z 0.05 1704  63  14   5 0.00
Tue 04/28 04Z 0.05 1704  63  12   5 0.00
Tue 04/28 05Z 0.06 1803  63  11   4 0.00
Tue 04/28 06Z 0.12 1204  62   8   4 0.00
Tue 04/28 07Z 0.19 1206  61   6   4 0.00
Tue 04/28 08Z 0.14 1306  63   7   4 0.00
Tue 04/28 09Z 0.25 1210  64   7   4 0.00
Tue 04/28 10Z 0.07 1508  67   7   4 0.00
Tue 04/28 11Z 0.08 1510  69   7   3 0.00
Tue 04/28 12Z 0.16 1413  68   8   3 0.00
Tue 04/28 13Z 0.23 1416  67   9   4 0.00
Tue 04/28 14Z 0.27 1417  69   9   4 0.00
Tue 04/28 15Z 0.30 1316  70   8   4 0.00
Tue 04/28 16Z 0.31 1416  65   7   4 0.00
Tue 04/28 17Z 0.41 1416  60   6   4 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