NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260914_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 09/14 12Z 0.52 3125  92  24   4 0.00
Mon 09/14 13Z 0.40 3228  91  16   5 0.00
Mon 09/14 14Z 0.30 3226  85  15   5 0.00
Mon 09/14 15Z 0.32 3225  82  13   5 0.00
Mon 09/14 16Z 0.41 3223  76   8   4 0.00
Mon 09/14 17Z 1.10 3221  72   6   4 0.00
Mon 09/14 18Z 3.11 3219  73   9   4 0.00
Mon 09/14 19Z 3.97 3219  74  15   4 0.00
Mon 09/14 20Z 3.96 3219  77  18   4 0.00
Mon 09/14 21Z 2.63 3219  81  17   4 0.00
Mon 09/14 22Z 1.04 3219  82  16   3 0.00
Mon 09/14 23Z 0.54 3220  83  15   3 0.00
Tue 09/15 00Z 0.52 3222  83  16   3 0.00
Tue 09/15 01Z 0.25 3321  81  14   4 0.00
Tue 09/15 02Z 0.11 3319  76  11   5 0.00
Tue 09/15 03Z 0.06 3418  69   9   6 0.00
Tue 09/15 04Z 0.03 3515  61   7   6 0.00
Tue 09/15 05Z 0.08 0013  58   7   7 0.00
Tue 09/15 06Z 0.08 0109  55   7   7 0.00
Tue 09/15 07Z 0.04 0006  51   8   8 0.00
Tue 09/15 08Z 0.01 3404  50   8   8 0.00
Tue 09/15 09Z 0.02 0301  48   9   8 0.00
Tue 09/15 10Z 0.02 1201  46  10   8 0.00
Tue 09/15 11Z 0.03 2002  47  10   7 0.00
Tue 09/15 12Z 0.02 1604  46  11   7 0.00
Tue 09/15 13Z 0.06 1905  48  12   7 0.00
Tue 09/15 14Z 0.08 2005  48  13   8 0.00
Tue 09/15 15Z 0.09 2105  50  14   8 0.00
Tue 09/15 16Z 0.09 2006  49  15   9 0.00
Tue 09/15 17Z 0.06 1907  47  16  10 0.00
Tue 09/15 18Z 0.08 1810  47  15  11 0.00
Tue 09/15 19Z 0.12 1911  51  28  11 0.00
Tue 09/15 20Z 0.15 1912  48  42  11 0.00
Tue 09/15 21Z 0.18 2014  43  22  12 0.00
Tue 09/15 22Z 0.20 2016  37  22  13 0.00
Tue 09/15 23Z 0.22 2018  31  67  14 0.00
Wed 09/16 00Z 0.24 2020  25  88  15 0.00
Wed 09/16 01Z 0.26 2022  23  84  16 0.00
Wed 09/16 02Z 0.31 2123  26  84  16 0.00
Wed 09/16 03Z 0.34 2224  29  84  16 0.00
Wed 09/16 04Z 0.40 2224  33  86  16 0.00
Wed 09/16 05Z 0.40 2323  37  84  16 0.00
Wed 09/16 06Z 0.42 2423  37  84  16 0.00
Wed 09/16 07Z 0.50 2425  38  85  15 0.00
Wed 09/16 08Z 0.52 2525  47  87  15 0.00
Wed 09/16 09Z 0.50 2524  57  91  15 0.00
Wed 09/16 10Z 0.45 2621  63  92  15 0.00
Wed 09/16 11Z 0.43 2720  73  87  15 0.00
Wed 09/16 12Z 0.41 2718  83  85  15 0.00
Wed 09/16 13Z 0.38 2717  89  70  14 0.00
Wed 09/16 14Z 0.33 2815  92  57  14 0.00
Wed 09/16 15Z 0.28 2813  94  52  14 0.00
Wed 09/16 16Z 0.25 2811  95  42  14 0.00
Wed 09/16 17Z 0.25 2911  96  46  14 0.00
Wed 09/16 18Z 0.23 2910  92  24  13 0.00
Wed 09/16 19Z 0.21 3009  92  11  13 0.00
Wed 09/16 20Z 0.19 3008  91  10  13 0.00
Wed 09/16 21Z 0.16 3109  88  11  13 0.00
Wed 09/16 22Z 0.12 3108  85  13  13 0.00
Wed 09/16 23Z 0.10 3207  84  12  13 0.00

Run total areal avg QPF for the Central_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