NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260602_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)
=== ===== === ==== ==== === === === ====
Tue 06/02 06Z 0.22 3313  64  67   5 0.00
Tue 06/02 07Z 0.30 3314  65  68   6 0.00
Tue 06/02 08Z 0.33 3215  66  66   6 0.00
Tue 06/02 09Z 0.33 3216  64  65   6 0.00
Tue 06/02 10Z 0.31 3217  62  65   6 0.00
Tue 06/02 11Z 0.27 3317  58  62   6 0.00
Tue 06/02 12Z 0.28 3317  54  56   6 0.00
Tue 06/02 13Z 0.27 3318  48  47   6 0.00
Tue 06/02 14Z 0.26 3318  44  34   6 0.00
Tue 06/02 15Z 0.29 3318  44  27   6 0.00
Tue 06/02 16Z 1.16 3318  46  22   6 0.00
Tue 06/02 17Z 2.51 3318  46  17   6 0.00
Tue 06/02 18Z 3.84 3318  47  17   6 0.00
Tue 06/02 19Z 4.07 3318  48  26   6 0.00
Tue 06/02 20Z 3.76 3319  48  42   6 0.00
Tue 06/02 21Z 2.84 3420  50  54   6 0.00
Tue 06/02 22Z 1.60 3420  52  65   6 0.00
Tue 06/02 23Z 0.40 3521  53  68   6 0.00
Wed 06/03 00Z 0.18 3522  50  64   7 0.00
Wed 06/03 01Z 0.09 3523  48  58   7 0.00
Wed 06/03 02Z 0.17 0023  46  47   7 0.00
Wed 06/03 03Z 0.26 0121  44  37   7 0.00
Wed 06/03 04Z 0.27 0119  46  25   7 0.00
Wed 06/03 05Z 0.26 0017  47  15   7 0.00
Wed 06/03 06Z 0.19 0016  47  12   7 0.00
Wed 06/03 07Z 0.13 0015  47  22   7 0.00
Wed 06/03 08Z 0.13 0014  48  37   7 0.00
Wed 06/03 09Z 0.12 0013  48  54   8 0.00
Wed 06/03 10Z 0.07 0011  48  72   8 0.00
Wed 06/03 11Z 0.11 3510  48  83   8 0.00
Wed 06/03 12Z 0.22 3411  48  88   8 0.00
Wed 06/03 13Z 0.23 3311  48  88   8 0.00
Wed 06/03 14Z 0.33 3312  49  87   8 0.00
Wed 06/03 15Z 0.53 3212  50  84   8 0.00
Wed 06/03 16Z 0.66 3211  50  79   9 0.00
Wed 06/03 17Z 1.29 3110  52  72   9 0.00
Wed 06/03 18Z 1.64 3110  52  64   9 0.00
Wed 06/03 19Z 1.87 3010  53  60  10 0.00
Wed 06/03 20Z 1.64 3012  53  59  10 0.00
Wed 06/03 21Z 1.10 3012  54  59  11 0.00
Wed 06/03 22Z 0.68 3012  54  53  11 0.00
Wed 06/03 23Z 0.61 3012  54  47  11 0.00
Thu 06/04 00Z 0.66 2914  56  40  11 0.00
Thu 06/04 01Z 0.68 2913  56  38  11 0.00
Thu 06/04 02Z 0.71 2913  56  33  11 0.00
Thu 06/04 03Z 0.62 3013  57  33  11 0.00
Thu 06/04 04Z 0.48 3013  57  33  11 0.00
Thu 06/04 05Z 0.46 3012  54  33  11 0.00
Thu 06/04 06Z 0.47 2912  52  34  11 0.00
Thu 06/04 07Z 0.49 2912  50  37  11 0.00
Thu 06/04 08Z 0.52 2911  49  41  11 0.00
Thu 06/04 09Z 0.66 2912  52  40  11 0.00
Thu 06/04 10Z 0.68 2912  54  35  11 0.00
Thu 06/04 11Z 0.60 2912  53  31  11 0.00
Thu 06/04 12Z 0.53 2812  53  26  11 0.00
Thu 06/04 13Z 0.54 2713  55  21  11 0.00
Thu 06/04 14Z 0.66 2714  54  20  11 0.00
Thu 06/04 15Z 0.71 2715  43  20  11 0.00
Thu 06/04 16Z 0.82 2715  41  20  12 0.00
Thu 06/04 17Z 1.02 2716  51  23  11 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