NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260601_1200
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)
=== ===== === ==== ==== === === === ====
Mon 06/01 12Z 0.24 0307  92  43   1 0.00
Mon 06/01 13Z 0.26 0406  94  39   1 0.00
Mon 06/01 14Z 0.25 0306  95  34   1 0.00
Mon 06/01 15Z 0.24 0206  94  35   1 0.01
Mon 06/01 16Z 0.30 0206  91  39   1 0.01
Mon 06/01 17Z 0.71 0106  87  36   2 0.01
Mon 06/01 18Z 1.35 0206  83  35   3 0.00
Mon 06/01 19Z 1.25 0305  83  40   3 0.00
Mon 06/01 20Z 0.59 0304  85  39   3 0.02
Mon 06/01 21Z 0.32 0103  84  34   3 0.01
Mon 06/01 22Z 0.13 0003  84  37   4 0.00
Mon 06/01 23Z 0.11 0103  83  42   4 0.00
Tue 06/02 00Z 0.06 0004  81  45   4 0.00
Tue 06/02 01Z 0.04 3505  79  43   4 0.00
Tue 06/02 02Z 0.04 3507  74  42   4 0.00
Tue 06/02 03Z 0.04 3509  70  42   4 0.00
Tue 06/02 04Z 0.05 3510  67  44   4 0.00
Tue 06/02 05Z 0.04 3509  67  43   4 0.00
Tue 06/02 06Z 0.07 3410  66  39   4 0.00
Tue 06/02 07Z 0.11 3310  65  44   4 0.00
Tue 06/02 08Z 0.16 3312  65  51   4 0.00
Tue 06/02 09Z 0.22 3213  68  48   5 0.00
Tue 06/02 10Z 0.25 3214  67  46   5 0.00
Tue 06/02 11Z 0.29 3216  66  37   5 0.00
Tue 06/02 12Z 0.28 3216  64  26   5 0.00
Tue 06/02 13Z 0.25 3317  56  16   5 0.00
Tue 06/02 14Z 0.32 3317  49  13   5 0.00
Tue 06/02 15Z 1.44 3318  46  16   5 0.00
Tue 06/02 16Z 2.07 3319  47  17   5 0.00
Tue 06/02 17Z 2.38 3319  46  16   5 0.00
Tue 06/02 18Z 2.68 3319  45  17   5 0.00
Tue 06/02 19Z 2.61 3318  46  36   5 0.00
Tue 06/02 20Z 2.11 3318  48  52   6 0.00
Tue 06/02 21Z 1.10 3319  48  69   6 0.00
Tue 06/02 22Z 0.51 3419  49  71   6 0.00
Tue 06/02 23Z 0.12 3420  48  78   6 0.00
Wed 06/03 00Z 0.08 3522  46  65   6 0.00
Wed 06/03 01Z 0.18 3523  47  59   7 0.00
Wed 06/03 02Z 0.25 3522  46  52   7 0.00
Wed 06/03 03Z 0.29 0020  46  41   7 0.00
Wed 06/03 04Z 0.37 0019  46  31   7 0.00
Wed 06/03 05Z 0.41 0117  46  23   7 0.00
Wed 06/03 06Z 0.39 0115  46  15   7 0.00
Wed 06/03 07Z 0.33 0014  46   9   7 0.00
Wed 06/03 08Z 0.38 0013  47   9   7 0.00
Wed 06/03 09Z 0.23 0013  48  17   7 0.00
Wed 06/03 10Z 0.07 3512  49  22   7 0.00
Wed 06/03 11Z 0.02 3413  49  22   7 0.00
Wed 06/03 12Z 0.03 3512  50  16   7 0.00
Wed 06/03 13Z 0.08 3411  51  10   7 0.00
Wed 06/03 14Z 0.32 3311  53  14   7 0.00
Wed 06/03 15Z 0.66 3311  54  33   8 0.00
Wed 06/03 16Z 1.13 3311  54  54   8 0.00
Wed 06/03 17Z 1.92 3212  54  76   8 0.00
Wed 06/03 18Z 1.89 3212  52  83   9 0.00
Wed 06/03 19Z 1.83 3211  51  80   9 0.00
Wed 06/03 20Z 1.72 3111  51  75  10 0.00
Wed 06/03 21Z 1.30 3011  53  70  10 0.00
Wed 06/03 22Z 0.72 3012  56  63  10 0.00
Wed 06/03 23Z 0.52 3012  57  50  11 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