NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260705_0600
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)
=== ===== === ==== ==== === === === ====
Sun 07/05 06Z 0.09 3405  62   1  13 0.00
Sun 07/05 07Z 0.09 3304  62   1  13 0.00
Sun 07/05 08Z 0.09 3404  63   2  13 0.00
Sun 07/05 09Z 0.09 3503  63   2  13 0.00
Sun 07/05 10Z 0.11 3503  63   2  12 0.00
Sun 07/05 11Z 0.13 0102  63   3  12 0.00
Sun 07/05 12Z 0.11 3301  64   4  12 0.00
Sun 07/05 13Z 0.13 2601  64   6  12 0.00
Sun 07/05 14Z 0.27 2602  66   7  12 0.00
Sun 07/05 15Z 0.37 2502  67   8  12 0.00
Sun 07/05 16Z 0.45 2402  67  10  12 0.00
Sun 07/05 17Z 0.75 2502  67  13  13 0.00
Sun 07/05 18Z 0.94 2603  67  16  13 0.00
Sun 07/05 19Z 0.89 2802  67  18  13 0.00
Sun 07/05 20Z 0.56 3002  67  21  13 0.00
Sun 07/05 21Z 0.28 3302  68  23  13 0.00
Sun 07/05 22Z 0.12 3503  70  19  13 0.00
Sun 07/05 23Z 0.11 0104  72  13  13 0.00
Mon 07/06 00Z 0.23 0305  75  11  13 0.00
Mon 07/06 01Z 0.39 0507  76   9  12 0.00
Mon 07/06 02Z 0.53 0609  79   8  12 0.00
Mon 07/06 03Z 0.54 0810  83   7  12 0.00
Mon 07/06 04Z 0.49 0909  83   9  12 0.00
Mon 07/06 05Z 0.40 1008  81   7  12 0.00
Mon 07/06 06Z 0.37 1008  80   7  12 0.00
Mon 07/06 07Z 0.36 1109  78   7  12 0.00
Mon 07/06 08Z 0.35 1210  77   9  12 0.00
Mon 07/06 09Z 0.33 1311  76   9  12 0.00
Mon 07/06 10Z 0.30 1413  77   9  11 0.00
Mon 07/06 11Z 0.32 1415  75   8  11 0.00
Mon 07/06 12Z 0.28 1414  75   9  12 0.00
Mon 07/06 13Z 0.27 1312  74  10  12 0.00
Mon 07/06 14Z 0.30 1312  78   9  11 0.00
Mon 07/06 15Z 0.34 1311  83   8  11 0.00
Mon 07/06 16Z 0.44 1311  87   8  10 0.00
Mon 07/06 17Z 0.43 1312  87  13  10 0.01
Mon 07/06 18Z 0.55 1313  85  12  11 0.00
Mon 07/06 19Z 0.64 1313  83  14  11 0.00
Mon 07/06 20Z 1.01 1313  84  16  11 0.00
Mon 07/06 21Z 1.01 1315  83  18  11 0.00
Mon 07/06 22Z 0.81 1315  82  22  11 0.00
Mon 07/06 23Z 0.65 1317  82  28  11 0.00
Tue 07/07 00Z 0.60 1319  80  32  11 0.00
Tue 07/07 01Z 0.49 1320  74  34  11 0.00
Tue 07/07 02Z 0.43 1320  69  32  12 0.00
Tue 07/07 03Z 0.40 1320  66  38  12 0.00
Tue 07/07 04Z 0.41 1321  64  43  12 0.00
Tue 07/07 05Z 0.40 1321  63  48  12 0.00
Tue 07/07 06Z 0.40 1220  62  44  12 0.00
Tue 07/07 07Z 0.39 1220  61  43  12 0.00
Tue 07/07 08Z 0.39 1220  59  41  12 0.00
Tue 07/07 09Z 0.40 1220  60  40  12 0.00
Tue 07/07 10Z 0.40 1219  61  37  12 0.00
Tue 07/07 11Z 0.39 1218  65  40  12 0.00
Tue 07/07 12Z 0.38 1218  67  45  12 0.00
Tue 07/07 13Z 0.40 1118  70  45  12 0.00
Tue 07/07 14Z 0.40 1116  73  50  11 0.00
Tue 07/07 15Z 0.42 1114  75  53  11 0.00
Tue 07/07 16Z 0.48 1011  77  54  11 0.00
Tue 07/07 17Z 0.67 1009  79  57  11 0.00

Run total areal avg QPF for the 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