NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260531_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 05/31 00Z 0.17 0014  82  45   1 0.00
Sun 05/31 01Z 0.21 0016  75  36   2 0.00
Sun 05/31 02Z 0.23 0017  63  26   3 0.00
Sun 05/31 03Z 0.31 0118  53  17   4 0.00
Sun 05/31 04Z 0.31 0117  50  17   4 0.00
Sun 05/31 05Z 0.24 0116  49  21   5 0.00
Sun 05/31 06Z 0.12 0013  52  31   5 0.00
Sun 05/31 07Z 0.06 3512  55  58   5 0.00
Sun 05/31 08Z 0.11 3311  58  78   5 0.00
Sun 05/31 09Z 0.25 3111  66  88   5 0.00
Sun 05/31 10Z 0.37 2914  67  88   5 0.00
Sun 05/31 11Z 0.42 2915  72  75   5 0.00
Sun 05/31 12Z 0.43 3018  69  85   6 0.00
Sun 05/31 13Z 0.34 3118  64  82   6 0.00
Sun 05/31 14Z 0.36 3217  63  85   6 0.00
Sun 05/31 15Z 0.77 3217  66  81   5 0.00
Sun 05/31 16Z 1.92 3217  70  85   5 0.00
Sun 05/31 17Z 1.74 3215  78  92   5 0.00
Sun 05/31 18Z 0.89 3115  85  91   4 0.01
Sun 05/31 19Z 0.68 3217  87  93   4 0.02
Sun 05/31 20Z 0.84 3118  83  92   4 0.03
Sun 05/31 21Z 1.02 3019  83  94   4 0.00
Sun 05/31 22Z 0.93 3022  84  90   4 0.00
Sun 05/31 23Z 1.01 3021  83  83   4 0.01
Mon 06/01 00Z 0.95 3020  87  70   4 0.00
Mon 06/01 01Z 0.98 3120  88  60   3 0.00
Mon 06/01 02Z 0.70 3220  84  48   3 0.00
Mon 06/01 03Z 0.48 3219  82  52   3 0.00
Mon 06/01 04Z 0.37 3219  80  62   3 0.00
Mon 06/01 05Z 0.31 3218  83  69   3 0.00
Mon 06/01 06Z 0.22 3217  82  72   3 0.00
Mon 06/01 07Z 0.16 3316  83  66   3 0.00
Mon 06/01 08Z 0.10 3316  86  65   2 0.00
Mon 06/01 09Z 0.03 3415  88  69   2 0.00
Mon 06/01 10Z 0.05 3512  91  71   2 0.00
Mon 06/01 11Z 0.11 0010  93  72   2 0.00
Mon 06/01 12Z 0.20 0210  96  74   1 0.00
Mon 06/01 13Z 0.28 0409  98  77   1 0.00
Mon 06/01 14Z 0.34 0608  99  80   1 0.01
Mon 06/01 15Z 0.34 0808  99  78   1 0.01
Mon 06/01 16Z 0.29 0807  99  71   1 0.01
Mon 06/01 17Z 0.25 0707  94  58   1 0.00
Mon 06/01 18Z 0.29 0507  88  50   1 0.00
Mon 06/01 19Z 0.39 0205  83  37   2 0.00
Mon 06/01 20Z 0.40 0005  80  26   2 0.00
Mon 06/01 21Z 0.54 0006  80  22   3 0.00
Mon 06/01 22Z 0.39 0006  82  24   3 0.00
Mon 06/01 23Z 0.19 0007  83  30   3 0.00
Tue 06/02 00Z 0.22 0108  80  31   3 0.00
Tue 06/02 01Z 0.22 0108  76  41   3 0.00
Tue 06/02 02Z 0.22 0108  72  52   3 0.00
Tue 06/02 03Z 0.21 0109  68  57   4 0.00
Tue 06/02 04Z 0.18 0009  65  52   4 0.00
Tue 06/02 05Z 0.11 0009  64  46   4 0.00
Tue 06/02 06Z 0.05 3508  64  42   4 0.00
Tue 06/02 07Z 0.06 3409  64  45   4 0.00
Tue 06/02 08Z 0.09 3409  64  51   4 0.00
Tue 06/02 09Z 0.12 3310  65  52   4 0.00
Tue 06/02 10Z 0.16 3310  65  52   4 0.00
Tue 06/02 11Z 0.19 3211  67  52   4 0.00

Run total areal avg QPF for the Central_Greens is: 0.10 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