NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260705_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 07/05 06Z 0.05 0004  59   0  13 0.00
Sun 07/05 07Z 0.05 3503  59   0  13 0.00
Sun 07/05 08Z 0.06 3504  60   1  13 0.00
Sun 07/05 09Z 0.08 0103  61   1  13 0.00
Sun 07/05 10Z 0.11 0103  62   1  12 0.00
Sun 07/05 11Z 0.16 0303  63   2  12 0.00
Sun 07/05 12Z 0.10 0501  64   5  12 0.00
Sun 07/05 13Z 0.10 1700  64   8  12 0.00
Sun 07/05 14Z 0.28 2101  67   9  12 0.00
Sun 07/05 15Z 0.46 2002  68  11  12 0.00
Sun 07/05 16Z 0.56 2002  68  14  13 0.00
Sun 07/05 17Z 0.77 2202  68  18  13 0.00
Sun 07/05 18Z 0.65 2402  67  23  13 0.00
Sun 07/05 19Z 0.47 2602  67  27  13 0.00
Sun 07/05 20Z 0.23 2901  67  31  13 0.00
Sun 07/05 21Z 0.11 3301  67  31  14 0.00
Sun 07/05 22Z 0.13 3502  69  24  14 0.00
Sun 07/05 23Z 0.16 0103  71  18  13 0.00
Mon 07/06 00Z 0.24 0205  73  15  13 0.01
Mon 07/06 01Z 0.38 0406  75  11  13 0.00
Mon 07/06 02Z 0.46 0608  80  10  12 0.00
Mon 07/06 03Z 0.44 0809  85   8  12 0.00
Mon 07/06 04Z 0.34 1008  86  11  12 0.00
Mon 07/06 05Z 0.30 1107  83   7  12 0.00
Mon 07/06 06Z 0.29 1107  81   6  12 0.00
Mon 07/06 07Z 0.30 1108  80   8  12 0.00
Mon 07/06 08Z 0.27 1310  79  10  12 0.00
Mon 07/06 09Z 0.25 1412  77  11  12 0.00
Mon 07/06 10Z 0.24 1414  75  10  11 0.00
Mon 07/06 11Z 0.28 1316  69   9  11 0.00
Mon 07/06 12Z 0.26 1315  68  10  12 0.00
Mon 07/06 13Z 0.28 1215  67  12  12 0.00
Mon 07/06 14Z 0.31 1315  72  11  11 0.00
Mon 07/06 15Z 0.35 1313  80   9  11 0.00
Mon 07/06 16Z 0.46 1313  86   9  10 0.00
Mon 07/06 17Z 0.42 1313  86  14  10 0.00
Mon 07/06 18Z 0.51 1314  85  15  10 0.00
Mon 07/06 19Z 0.67 1315  83  16  10 0.00
Mon 07/06 20Z 1.04 1215  85  19  10 0.00
Mon 07/06 21Z 1.03 1217  83  23  10 0.00
Mon 07/06 22Z 0.81 1217  82  27  11 0.00
Mon 07/06 23Z 0.65 1219  84  32  10 0.00
Tue 07/07 00Z 0.60 1222  80  38  10 0.00
Tue 07/07 01Z 0.48 1222  72  41  11 0.00
Tue 07/07 02Z 0.41 1223  65  40  12 0.00
Tue 07/07 03Z 0.40 1223  63  47  12 0.00
Tue 07/07 04Z 0.39 1224  63  54  12 0.00
Tue 07/07 05Z 0.38 1223  64  60  12 0.00
Tue 07/07 06Z 0.38 1222  63  56  12 0.00
Tue 07/07 07Z 0.36 1222  62  54  13 0.00
Tue 07/07 08Z 0.37 1222  61  52  13 0.00
Tue 07/07 09Z 0.38 1222  62  52  13 0.00
Tue 07/07 10Z 0.39 1122  63  47  13 0.00
Tue 07/07 11Z 0.39 1122  67  51  12 0.00
Tue 07/07 12Z 0.38 1121  69  56  12 0.00
Tue 07/07 13Z 0.41 1122  73  57  12 0.00
Tue 07/07 14Z 0.43 1120  77  64  11 0.00
Tue 07/07 15Z 0.46 1118  78  67  11 0.00
Tue 07/07 16Z 0.48 1015  79  66  11 0.00
Tue 07/07 17Z 0.54 1012  80  68  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.01 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