NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260609_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)
=== ===== === ==== ==== === === === ====
Tue 06/09 00Z 0.33 2506  66   3  12 0.00
Tue 06/09 01Z 0.32 2507  55   3  12 0.00
Tue 06/09 02Z 0.29 2607  48   3  12 0.00
Tue 06/09 03Z 0.31 2606  49   3  12 0.00
Tue 06/09 04Z 0.43 2709  57   2  12 0.00
Tue 06/09 05Z 0.58 2611  61   2  11 0.00
Tue 06/09 06Z 0.65 2613  62   2  11 0.00
Tue 06/09 07Z 0.65 2615  64   3  11 0.00
Tue 06/09 08Z 0.64 2615  66   3  11 0.00
Tue 06/09 09Z 0.61 2716  74   3  11 0.00
Tue 06/09 10Z 0.56 2717  86   3  11 0.00
Tue 06/09 11Z 0.47 2715  84   3  11 0.00
Tue 06/09 12Z 0.38 2712  83   3  11 0.00
Tue 06/09 13Z 0.32 2610  82   3  11 0.00
Tue 06/09 14Z 0.32 2509  81   3  11 0.00
Tue 06/09 15Z 0.41 2408  79   2  11 0.00
Tue 06/09 16Z 0.66 2406  74   2  11 0.00
Tue 06/09 17Z 1.33 2507  68   2  12 0.00
Tue 06/09 18Z 1.26 2607  65   1  12 0.00
Tue 06/09 19Z 0.98 2608  69   1  13 0.00
Tue 06/09 20Z 1.35 2610  77   1  13 0.00
Tue 06/09 21Z 1.15 2611  79   1  13 0.00
Tue 06/09 22Z 0.94 2513  85   1  13 0.00
Tue 06/09 23Z 0.76 2516  88   1  13 0.00
Wed 06/10 00Z 0.74 2618  89   1  14 0.00
Wed 06/10 01Z 0.75 2719  88   1  14 0.00
Wed 06/10 02Z 0.64 2818  82   0  14 0.00
Wed 06/10 03Z 0.58 2816  80   0  14 0.00
Wed 06/10 04Z 0.48 2814  80   0  14 0.00
Wed 06/10 05Z 0.44 2813  79   0  14 0.00
Wed 06/10 06Z 0.40 2712  78   0  14 0.00
Wed 06/10 07Z 0.37 2611  81   3  14 0.00
Wed 06/10 08Z 0.35 2511  86  48  14 0.01
Wed 06/10 09Z 0.36 2412  90  75  14 0.01
Wed 06/10 10Z 0.36 2313  90  76  14 0.00
Wed 06/10 11Z 0.35 2313  86  78  15 0.00
Wed 06/10 12Z 0.33 2212  85  81  15 0.00
Wed 06/10 13Z 0.28 2211  84  72  15 0.00
Wed 06/10 14Z 0.34 2111  83  78  15 0.00
Wed 06/10 15Z 0.37 2010  84  82  15 0.00
Wed 06/10 16Z 0.52 2010  84  81  15 0.00
Wed 06/10 17Z 0.37 1910  83  85  15 0.00
Wed 06/10 18Z 0.42 1911  83  90  16 0.00
Wed 06/10 19Z 0.37 1911  84  83  16 0.00
Wed 06/10 20Z 0.42 1912  83  78  16 0.00
Wed 06/10 21Z 0.36 1911  82  79  16 0.00
Wed 06/10 22Z 0.49 2013  86  88  16 0.00
Wed 06/10 23Z 0.39 2013  90  83  16 0.00
Thu 06/11 00Z 0.38 2113  96  90  16 0.01
Thu 06/11 01Z 0.41 2117  98  90  16 0.03
Thu 06/11 02Z 0.48 2219  96  79  16 0.23
Thu 06/11 03Z 0.54 2319  96  70  16 0.11
Thu 06/11 04Z 0.57 2418  97  81  15 0.02
Thu 06/11 05Z 0.62 2419  96  72  15 0.03
Thu 06/11 06Z 0.55 2517  96  65  15 0.03
Thu 06/11 07Z 0.45 2714  97  67  15 0.02
Thu 06/11 08Z 0.39 2914  96  77  15 0.01
Thu 06/11 09Z 0.45 2815  97  75  15 0.01
Thu 06/11 10Z 0.47 2816  96  72  15 0.01
Thu 06/11 11Z 0.46 2816  97  72  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.53 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