NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260710_1200
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 07/10 12Z 0.13 3415  96  83  12 0.00
Fri 07/10 13Z 0.08 3514  94  79  12 0.00
Fri 07/10 14Z 0.07 3513  91  76  12 0.00
Fri 07/10 15Z 0.08 3512  88  68  12 0.00
Fri 07/10 16Z 0.11 3511  85  59  12 0.00
Fri 07/10 17Z 0.32 3510  82  54  12 0.00
Fri 07/10 18Z 0.51 3410  79  45  12 0.00
Fri 07/10 19Z 0.61 3410  75  37  13 0.00
Fri 07/10 20Z 0.60 3410  71  34  13 0.00
Fri 07/10 21Z 0.47 3410  68  30  13 0.00
Fri 07/10 22Z 0.29 3509  67  24  13 0.00
Fri 07/10 23Z 0.28 3509  67  22  12 0.00
Sat 07/11 00Z 0.19 3410  66  23  12 0.00
Sat 07/11 01Z 0.13 3510  65  25  12 0.00
Sat 07/11 02Z 0.15 3410  65  26  12 0.00
Sat 07/11 03Z 0.21 3411  67  25  12 0.00
Sat 07/11 04Z 0.16 3510  69  20  11 0.00
Sat 07/11 05Z 0.11 3510  69  17  11 0.00
Sat 07/11 06Z 0.07 0009  68  25  11 0.00
Sat 07/11 07Z 0.06 3508  66  28  11 0.00
Sat 07/11 08Z 0.04 3507  65  42  11 0.00
Sat 07/11 09Z 0.05 0007  64  54  11 0.00
Sat 07/11 10Z 0.09 0107  65  65  10 0.00
Sat 07/11 11Z 0.09 0006  65  70  10 0.00
Sat 07/11 12Z 0.08 0005  64  62  10 0.00
Sat 07/11 13Z 0.12 3505  65  54  10 0.00
Sat 07/11 14Z 0.34 3404  67  57  10 0.00
Sat 07/11 15Z 0.70 3305  68  46  10 0.00
Sat 07/11 16Z 1.08 3306  69  41  10 0.00
Sat 07/11 17Z 0.90 3407  70  27  10 0.00
Sat 07/11 18Z 0.48 3507  70  27  10 0.00
Sat 07/11 19Z 0.34 3508  70  22  10 0.00
Sat 07/11 20Z 0.29 3508  71  15  11 0.00
Sat 07/11 21Z 0.25 3508  72  14  11 0.00
Sat 07/11 22Z 0.21 0009  72  12  11 0.00
Sat 07/11 23Z 0.20 0010  71  10  10 0.00
Sun 07/12 00Z 0.18 0112  71  12  10 0.00
Sun 07/12 01Z 0.28 0114  70  14  10 0.00
Sun 07/12 02Z 0.42 0215  70  16  10 0.00
Sun 07/12 03Z 0.54 0216  70  18  10 0.00
Sun 07/12 04Z 0.62 0316  71  18   9 0.00
Sun 07/12 05Z 0.57 0315  72  17   9 0.00
Sun 07/12 06Z 0.52 0314  73  17   9 0.00
Sun 07/12 07Z 0.47 0312  74  17   9 0.00
Sun 07/12 08Z 0.37 0311  74  14   9 0.00
Sun 07/12 09Z 0.28 0309  74  11   9 0.00
Sun 07/12 10Z 0.18 0208  74  10   9 0.00
Sun 07/12 11Z 0.14 0108  74   9   9 0.00
Sun 07/12 12Z 0.13 3508  75   9   9 0.00
Sun 07/12 13Z 0.13 3508  75   7   9 0.00
Sun 07/12 14Z 0.14 3507  76   7   9 0.00
Sun 07/12 15Z 0.16 3505  76   7   9 0.00
Sun 07/12 16Z 0.32 3404  76   7  10 0.00
Sun 07/12 17Z 0.57 3304  77   7  10 0.00
Sun 07/12 18Z 0.65 3204  77   7  10 0.00
Sun 07/12 19Z 0.76 3104  75   8  11 0.00
Sun 07/12 20Z 0.71 2903  71   8  11 0.00
Sun 07/12 21Z 0.63 2904  64   7  12 0.00
Sun 07/12 22Z 0.41 2905  56   7  12 0.00
Sun 07/12 23Z 0.32 2906  54   5  12 0.00

Run total areal avg QPF for the 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