NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260712_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 07/12 06Z 0.29 0310  75  26  11 0.00
Sun 07/12 07Z 0.31 0210  77  25  11 0.00
Sun 07/12 08Z 0.28 0308  77  29  11 0.00
Sun 07/12 09Z 0.24 0207  77  39  11 0.01
Sun 07/12 10Z 0.21 0207  78  48  11 0.01
Sun 07/12 11Z 0.19 0207  77  39  11 0.00
Sun 07/12 12Z 0.17 0206  76  31  11 0.00
Sun 07/12 13Z 0.16 0205  76  25  11 0.00
Sun 07/12 14Z 0.20 0203  78  18  11 0.00
Sun 07/12 15Z 0.39 0301  81  14  11 0.00
Sun 07/12 16Z 0.31 0001  82  14  11 0.00
Sun 07/12 17Z 0.24 3202  82  23  11 0.02
Sun 07/12 18Z 0.25 3202  78  25  12 0.02
Sun 07/12 19Z 0.30 3102  76  20  12 0.00
Sun 07/12 20Z 0.52 3002  72  15  12 0.00
Sun 07/12 21Z 0.46 2904  70  17  12 0.00
Sun 07/12 22Z 0.29 2904  67  36  13 0.00
Sun 07/12 23Z 0.21 2803  66  34  13 0.00
Mon 07/13 00Z 0.22 2703  68  31  12 0.00
Mon 07/13 01Z 0.27 2504  71  13  12 0.00
Mon 07/13 02Z 0.35 2305  74  14  12 0.00
Mon 07/13 03Z 0.52 2307  74  13  12 0.00
Mon 07/13 04Z 0.68 2310  77  14  12 0.00
Mon 07/13 05Z 0.91 2413  78  17  12 0.00
Mon 07/13 06Z 0.92 2415  82  21  12 0.00
Mon 07/13 07Z 0.84 2516  82  19  12 0.00
Mon 07/13 08Z 0.88 2617  80  24  12 0.00
Mon 07/13 09Z 0.82 2616  76  32  12 0.00
Mon 07/13 10Z 0.75 2616  71  42  12 0.00
Mon 07/13 11Z 0.65 2616  66  57  12 0.00
Mon 07/13 12Z 0.54 2714  65  70  13 0.00
Mon 07/13 13Z 0.44 2712  64  72  13 0.00
Mon 07/13 14Z 0.37 2710  62  71  14 0.00
Mon 07/13 15Z 0.37 2709  60  69  14 0.00
Mon 07/13 16Z 0.65 2608  63  66  14 0.00
Mon 07/13 17Z 0.97 2507  62  65  14 0.00
Mon 07/13 18Z 1.19 2408  61  66  15 0.00
Mon 07/13 19Z 1.48 2409  63  69  15 0.00
Mon 07/13 20Z 1.77 2310  72  69  15 0.00
Mon 07/13 21Z 1.06 2413  82  68  15 0.00
Mon 07/13 22Z 0.87 2415  86  69  15 0.00
Mon 07/13 23Z 0.93 2518  86  73  15 0.00
Tue 07/14 00Z 0.76 2618  86  76  15 0.00
Tue 07/14 01Z 0.77 2620  85  70  15 0.00
Tue 07/14 02Z 0.74 2620  83  67  16 0.00
Tue 07/14 03Z 0.59 2619  74  60  16 0.00
Tue 07/14 04Z 0.53 2619  67  55  17 0.00
Tue 07/14 05Z 0.57 2720  60  61  16 0.00
Tue 07/14 06Z 0.66 2823  62  62  16 0.00
Tue 07/14 07Z 0.61 2822  66  51  16 0.00
Tue 07/14 08Z 0.59 2822  70  37  16 0.00
Tue 07/14 09Z 0.59 2821  77  32  16 0.00
Tue 07/14 10Z 0.56 2820  79  22  16 0.00
Tue 07/14 11Z 0.59 2721  79  23  16 0.00
Tue 07/14 12Z 0.74 2726  78  27  16 0.00
Tue 07/14 13Z 0.71 2726  73  28  17 0.00
Tue 07/14 14Z 0.66 2726  71  31  18 0.00
Tue 07/14 15Z 0.65 2726  70  37  19 0.00
Tue 07/14 16Z 0.64 2725  70  41  19 0.00
Tue 07/14 17Z 0.68 2625  73  38  20 0.00

Run total areal avg QPF for the Central_Greens is: 0.06 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