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_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)
=== ===== === ==== ==== === === === ====
Sat 04/25 00Z 0.35 0210  67  11  -1 0.00
Sat 04/25 01Z 0.41 0413  71  15  -2 0.00
Sat 04/25 02Z 0.38 0413  71  19  -2 0.00
Sat 04/25 03Z 0.44 0415  69  21  -2 0.00
Sat 04/25 04Z 0.48 0615  67  22  -2 0.00
Sat 04/25 05Z 0.43 0713  67  20  -2 0.00
Sat 04/25 06Z 0.39 1012  70  20  -3 0.00
Sat 04/25 07Z 0.26 1211  72  21  -3 0.00
Sat 04/25 08Z 0.16 1410  75  22  -3 0.00
Sat 04/25 09Z 0.11 1410  77  23  -2 0.00
Sat 04/25 10Z 0.08 1509  77  23  -2 0.00
Sat 04/25 11Z 0.06 1508  77  22  -2 0.00
Sat 04/25 12Z 0.04 1506  77  21  -2 0.00
Sat 04/25 13Z 0.05 1504  75  20  -2 0.00
Sat 04/25 14Z 0.11 1304  72  20  -2 0.00
Sat 04/25 15Z 0.39 1403  72  19  -2 0.00
Sat 04/25 16Z 0.85 1303  71  19  -2 0.00
Sat 04/25 18Z 0.82 1302  70  18   0 0.00
Sat 04/25 19Z 0.90 1302  70  18   0 0.00
Sat 04/25 20Z 0.94 1202  71  19   0 0.00
Sat 04/25 21Z 0.74 1203  71  19   0 0.00
Sat 04/25 22Z 0.46 1204  70  19   0 0.00
Sat 04/25 23Z 0.30 1104  69  19   0 0.00
Sun 04/26 00Z 0.21 1104  68  20   0 0.00
Sun 04/26 01Z 0.20 1004  66  22   0 0.00
Sun 04/26 02Z 0.29 0806  64  23   0 0.00
Sun 04/26 03Z 0.28 0706  62  23   0 0.00
Sun 04/26 04Z 0.33 0707  59  24   0 0.00
Sun 04/26 05Z 0.32 0807  59  24   0 0.00
Sun 04/26 06Z 0.32 0807  60  24   0 0.00
Sun 04/26 07Z 0.32 0807  60  26   0 0.00
Sun 04/26 08Z 0.37 0808  59  27   0 0.00
Sun 04/26 09Z 0.36 0908  59  19   0 0.00
Sun 04/26 10Z 0.39 0908  58  16   0 0.00
Sun 04/26 11Z 0.39 0908  58  13   0 0.00
Sun 04/26 12Z 0.46 1008  59  13   0 0.00
Sun 04/26 13Z 0.61 0907  61  12   0 0.00
Sun 04/26 14Z 1.89 0904  63  10   0 0.00
Sun 04/26 15Z 1.93 0603  63  10   0 0.00
Sun 04/26 16Z 1.74 0403  63  11   0 0.00
Sun 04/26 17Z 1.65 0303  61  13   1 0.00
Sun 04/26 18Z 1.47 0304  59  12   2 0.00
Sun 04/26 19Z 1.49 0204  58   8   2 0.00
Sun 04/26 20Z 1.29 0204  58   7   3 0.00
Sun 04/26 21Z 1.68 0405  58   7   3 0.00
Sun 04/26 22Z 1.50 0506  59  17   3 0.00
Sun 04/26 23Z 0.74 0507  61  29   3 0.00
Mon 04/27 00Z 0.63 0508  62  33   3 0.00
Mon 04/27 01Z 0.68 0610  63  35   3 0.00
Mon 04/27 02Z 0.62 0709  63  45   3 0.00
Mon 04/27 03Z 0.47 0807  65  50   3 0.00
Mon 04/27 04Z 0.43 0807  67  48   3 0.00
Mon 04/27 05Z 0.45 0809  69  51   3 0.00
Mon 04/27 06Z 0.44 0810  72  55   3 0.00
Mon 04/27 07Z 0.46 0812  73  56   3 0.00
Mon 04/27 08Z 0.47 0813  65  53   3 0.00
Mon 04/27 09Z 0.45 0914  60  54   3 0.00
Mon 04/27 10Z 0.42 0914  52  56   3 0.00
Mon 04/27 11Z 0.40 1013  46  54   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