NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260603_1800
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)
=== ===== === ==== ==== === === === ====
Wed 06/03 18Z 2.84 3209  46  27  11 0.00
Wed 06/03 19Z 2.68 3110  47  30  12 0.00
Wed 06/03 20Z 1.97 3209  47  32  12 0.00
Wed 06/03 21Z 1.17 3208  48  35  12 0.00
Wed 06/03 22Z 0.58 3207  48  37  12 0.00
Wed 06/03 23Z 0.39 3107  47  39  12 0.00
Thu 06/04 00Z 0.49 3008  48  42  12 0.00
Thu 06/04 01Z 0.62 2909  51  44  12 0.00
Thu 06/04 02Z 0.71 2710  55  45  12 0.00
Thu 06/04 03Z 0.74 2710  57  44  12 0.00
Thu 06/04 04Z 0.65 2710  58  42  12 0.00
Thu 06/04 05Z 0.43 2809  60  41  12 0.00
Thu 06/04 06Z 0.40 2809  57  40  12 0.00
Thu 06/04 07Z 0.40 2708  55  37  12 0.00
Thu 06/04 08Z 0.41 2708  55  34  12 0.00
Thu 06/04 09Z 0.44 2608  55  32  12 0.00
Thu 06/04 10Z 0.50 2610  53  27  12 0.00
Thu 06/04 11Z 0.58 2612  53  26  12 0.00
Thu 06/04 12Z 0.64 2713  54  25  11 0.00
Thu 06/04 13Z 0.66 2715  57  23  12 0.00
Thu 06/04 14Z 0.78 2814  58  22  12 0.00
Thu 06/04 15Z 1.72 2815  58  21  12 0.00
Thu 06/04 16Z 2.58 2613  56  20  12 0.00
Thu 06/04 17Z 3.76 2613  56  16  12 0.00
Thu 06/04 18Z 7.41 2612  56  19  12 0.00
Thu 06/04 19Z 8.73 2614  51  19  13 0.00
Thu 06/04 20Z 7.98 2614  51  21  13 0.00
Thu 06/04 21Z 6.09 2615  53  23  13 0.00
Thu 06/04 22Z 3.13 2716  51  23  13 0.00
Thu 06/04 23Z 1.82 2817  53  21  13 0.00
Fri 06/05 00Z 1.77 2819  55  18  12 0.00
Fri 06/05 01Z 1.59 2821  58  17  12 0.00
Fri 06/05 02Z 1.39 2823  57  12  12 0.00
Fri 06/05 03Z 1.14 2923  60   8  12 0.00
Fri 06/05 04Z 1.01 2924  64   5  11 0.00
Fri 06/05 05Z 0.92 3023  68   4  11 0.00
Fri 06/05 06Z 0.91 3022  70   6  11 0.00
Fri 06/05 07Z 0.83 3022  65   7  11 0.00
Fri 06/05 08Z 0.74 3021  63   7  11 0.00
Fri 06/05 09Z 0.66 3020  64   8  11 0.00
Fri 06/05 10Z 0.61 3018  63   9  11 0.00
Fri 06/05 11Z 0.54 3016  61  10  11 0.00
Fri 06/05 12Z 0.47 3014  57  12  11 0.00
Fri 06/05 13Z 0.42 2912  56  15  11 0.00
Fri 06/05 14Z 0.50 2910  56  16  11 0.00
Fri 06/05 15Z 0.51 2909  55  18  11 0.00
Fri 06/05 16Z 1.13 2909  57  18  11 0.00
Fri 06/05 17Z 2.41 2810  59  17  12 0.00
Fri 06/05 18Z 3.65 2809  61  14  12 0.00
Fri 06/05 19Z 4.11 2708  64   9  12 0.00
Fri 06/05 20Z 4.08 2708  66   9  13 0.00
Fri 06/05 21Z 3.62 2708  68  21  13 0.00
Fri 06/05 22Z 1.70 2609  72  40  13 0.00
Fri 06/05 23Z 0.87 2610  73  42  12 0.00
Sat 06/06 00Z 0.95 2611  74  43  12 0.00
Sat 06/06 01Z 0.98 2613  72  45  13 0.00
Sat 06/06 02Z 1.20 2614  72  46  12 0.00
Sat 06/06 03Z 1.97 2617  75  46  12 0.00
Sat 06/06 04Z 1.30 2517  79  36  12 0.00
Sat 06/06 05Z 0.98 2518  81  38  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