Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260628_0000
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 06/28 00Z 0.03 3406  86  65  12 0.00
Sun 06/28 01Z 0.02 3405  85  63  12 0.00
Sun 06/28 02Z 0.07 0005  82  66  12 0.00
Sun 06/28 03Z 0.10 0105  79  68  12 0.00
Sun 06/28 04Z 0.10 0205  77  72  12 0.00
Sun 06/28 05Z 0.09 0105  76  76  12 0.00
Sun 06/28 06Z 0.06 0004  74  76  12 0.00
Sun 06/28 07Z 0.10 0106  71  63  12 0.00
Sun 06/28 08Z 0.09 0107  67  48  12 0.00
Sun 06/28 09Z 0.09 0008  64  41  12 0.00
Sun 06/28 10Z 0.11 0009  62  35  12 0.00
Sun 06/28 11Z 0.14 0110  64  30  11 0.00
Sun 06/28 12Z 0.19 0110  67  28  11 0.00
Sun 06/28 13Z 0.28 0209  72  29  11 0.00
Sun 06/28 14Z 0.41 0108  76  33  11 0.00
Sun 06/28 15Z 0.94 0106  78  31  11 0.00
Sun 06/28 16Z 1.16 0105  78  34  11 0.00
Sun 06/28 17Z 0.77 0003  76  43  12 0.03
Sun 06/28 18Z 0.33 3403  74  40  12 0.03
Sun 06/28 19Z 0.37 3304  75  39  12 0.01
Sun 06/28 20Z 0.47 3305  75  32  12 0.01
Sun 06/28 21Z 0.28 3306  73  23  13 0.01
Sun 06/28 22Z 0.21 3307  68  28  13 0.00
Sun 06/28 23Z 0.09 3307  61  26  13 0.00
Mon 06/29 00Z 0.03 3408  55  26  13 0.00
Mon 06/29 01Z 0.09 0008  54  20  13 0.00
Mon 06/29 02Z 0.13 0008  55  18  13 0.00
Mon 06/29 03Z 0.12 0008  53  19  13 0.00
Mon 06/29 04Z 0.08 0008  53  22  13 0.00
Mon 06/29 05Z 0.13 0008  53  22  12 0.00
Mon 06/29 06Z 0.16 0108  56  20  12 0.00
Mon 06/29 07Z 0.14 0108  58  20  12 0.00
Mon 06/29 08Z 0.13 0008  60  18  12 0.00
Mon 06/29 09Z 0.11 0008  63  14  12 0.00
Mon 06/29 10Z 0.09 3508  66  14  11 0.00
Mon 06/29 11Z 0.11 0008  68  11  11 0.00
Mon 06/29 12Z 0.08 3507  70  10  11 0.00
Mon 06/29 13Z 0.11 3506  72   9  11 0.00
Mon 06/29 14Z 0.30 3505  72   5  11 0.00
Mon 06/29 15Z 0.23 3403  73   5  12 0.00
Mon 06/29 16Z 0.31 3303  74  11  12 0.00
Mon 06/29 17Z 0.62 3103  73  13  12 0.00
Mon 06/29 18Z 0.86 3104  69   9  13 0.00
Mon 06/29 19Z 0.89 3004  65   6  13 0.00
Mon 06/29 20Z 0.98 3004  61   4  13 0.00
Mon 06/29 21Z 0.98 3006  58   5  13 0.00
Mon 06/29 22Z 0.42 3005  59   8  13 0.00
Mon 06/29 23Z 0.23 3004  62  11  13 0.00
Tue 06/30 00Z 0.23 2903  65  10  13 0.00
Tue 06/30 01Z 0.29 2704  69  15  13 0.00
Tue 06/30 02Z 0.38 2605  71  18  13 0.00
Tue 06/30 03Z 0.49 2507  73  21  13 0.00
Tue 06/30 04Z 0.62 2508  74  20  13 0.00
Tue 06/30 05Z 0.71 2509  76  21  13 0.00
Tue 06/30 06Z 0.74 2610  75  22  13 0.00
Tue 06/30 07Z 0.75 2511  77  20  13 0.00
Tue 06/30 08Z 0.72 2611  75  22  13 0.00
Tue 06/30 09Z 0.61 2611  74  27  13 0.00
Tue 06/30 10Z 0.55 2610  74  30  13 0.00
Tue 06/30 11Z 0.57 2611  74  32  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.09 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