NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260615_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 06/15 12Z 0.41 3218  99  68   7 0.00
Mon 06/15 13Z 0.50 3117  97  53   7 0.01
Mon 06/15 14Z 0.75 3018  97  43   7 0.01
Mon 06/15 15Z 0.69 3017  97  37   7 0.01
Mon 06/15 16Z 0.92 3015  95  40   7 0.01
Mon 06/15 17Z 0.82 3016  96  29   8 0.02
Mon 06/15 18Z 2.30 3116  91   9   7 0.01
Mon 06/15 19Z 3.24 3014  89   5   7 0.00
Mon 06/15 20Z 3.51 3013  87   8   7 0.00
Mon 06/15 21Z 3.05 3013  85  11   7 0.00
Mon 06/15 22Z 1.69 3013  87  13   7 0.00
Mon 06/15 23Z 0.74 3016  93  15   6 0.00
Tue 06/16 00Z 0.69 3018  94  13   6 0.01
Tue 06/16 01Z 0.68 3019  92  11   6 0.00
Tue 06/16 02Z 0.62 3020  92  11   5 0.00
Tue 06/16 03Z 0.53 3021  93  12   5 0.00
Tue 06/16 04Z 0.49 3122  95  10   5 0.00
Tue 06/16 05Z 0.44 3122  95   3   5 0.01
Tue 06/16 06Z 0.42 3122  96   1   4 0.01
Tue 06/16 07Z 0.40 3223  94   2   4 0.00
Tue 06/16 08Z 0.33 3222  88   5   4 0.00
Tue 06/16 09Z 0.25 3221  83   7   5 0.00
Tue 06/16 10Z 0.18 3319  79   8   5 0.00
Tue 06/16 11Z 0.16 3216  76   9   6 0.00
Tue 06/16 12Z 0.18 3214  73  10   6 0.00
Tue 06/16 13Z 0.23 3113  70  11   6 0.00
Tue 06/16 14Z 0.33 3112  67  17   6 0.00
Tue 06/16 15Z 1.26 3011  65  26   6 0.00
Tue 06/16 16Z 3.04 2910  62  33   7 0.00
Tue 06/16 17Z 4.41 2809  63  42   7 0.00
Tue 06/16 18Z 5.51 2709  66  46   8 0.00
Tue 06/16 19Z 6.19 2609  69  44   8 0.00
Tue 06/16 20Z 6.24 2509  72  39   9 0.00
Tue 06/16 21Z 5.35 2410  73  35   9 0.00
Tue 06/16 22Z 2.87 2409  70  27   9 0.00
Tue 06/16 23Z 0.80 2309  63  22   9 0.00
Wed 06/17 00Z 0.65 2311  58  12   9 0.00
Wed 06/17 01Z 0.69 2314  58   6   9 0.00
Wed 06/17 02Z 0.78 2315  62  11   9 0.00
Wed 06/17 03Z 0.76 2416  65  22   9 0.00
Wed 06/17 04Z 0.76 2416  68  23   9 0.00
Wed 06/17 05Z 0.67 2414  71  22   9 0.00
Wed 06/17 06Z 0.63 2313  72  24   8 0.00
Wed 06/17 07Z 0.56 2312  74  19   8 0.00
Wed 06/17 08Z 0.50 2311  75  20   8 0.00
Wed 06/17 09Z 0.44 2210  78  17   8 0.00
Wed 06/17 10Z 0.42 2110  80  14   8 0.00
Wed 06/17 11Z 0.42 2111  82  13   8 0.00
Wed 06/17 12Z 0.48 2011  84  11   7 0.00
Wed 06/17 13Z 1.60 1910  85   7   7 0.00
Wed 06/17 14Z 1.87 1910  85   3   8 0.00
Wed 06/17 15Z 2.08 1910  83   4   8 0.00
Wed 06/17 16Z 1.63 1910  76   8   8 0.00
Wed 06/17 17Z 1.50 1812  75  50   9 0.00
Wed 06/17 18Z 0.66 1812  73  87   9 0.00
Wed 06/17 19Z 0.37 1713  74  93   9 0.00
Wed 06/17 20Z 0.27 1714  79  94   9 0.00
Wed 06/17 21Z 0.21 1714  83  81  10 0.00
Wed 06/17 22Z 0.33 1816  82  53  10 0.00
Wed 06/17 23Z 0.43 1816  87  42  10 0.01

Run total areal avg QPF for the Central_Greens is: 0.11 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