NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260327_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)
=== ===== === ==== ==== === === === ====
Fri 03/27 12Z 0.19 3322  91   5  -9 0.00
Fri 03/27 13Z 0.20 3324  84   3 -11 0.00
Fri 03/27 14Z 0.17 3324  77   5 -11 0.00
Fri 03/27 15Z 0.15 3322  68   5 -12 0.00
Fri 03/27 16Z 0.16 3320  58   4 -12 0.00
Fri 03/27 17Z 0.35 3319  53   2 -12 0.00
Fri 03/27 18Z 0.79 3317  52   2 -13 0.00
Fri 03/27 19Z 0.96 3314  48   3 -13 0.00
Fri 03/27 20Z 0.68 3314  42   4 -13 0.00
Fri 03/27 21Z 0.29 3315  36   6 -12 0.00
Fri 03/27 22Z 0.16 3314  37   7 -12 0.00
Fri 03/27 23Z 0.16 3212  41   8 -12 0.00
Sat 03/28 00Z 0.20 3212  48   9 -12 0.00
Sat 03/28 01Z 0.22 3111  55  10 -12 0.00
Sat 03/28 02Z 0.20 3111  60  11 -12 0.00
Sat 03/28 03Z 0.19 3213  61  12 -13 0.00
Sat 03/28 04Z 0.19 3214  61  14 -13 0.00
Sat 03/28 05Z 0.18 3214  59  17 -14 0.00
Sat 03/28 06Z 0.18 3213  58  20 -14 0.00
Sat 03/28 07Z 0.19 3214  57  36 -15 0.00
Sat 03/28 08Z 0.21 3214  57  49 -16 0.00
Sat 03/28 09Z 0.22 3215  61  66 -16 0.00
Sat 03/28 10Z 0.21 3214  65  82 -17 0.00
Sat 03/28 11Z 0.29 3215  70  81 -17 0.00
Sat 03/28 12Z 0.35 3215  72  76 -18 0.00
Sat 03/28 13Z 0.73 3114  74  70 -18 0.00
Sat 03/28 14Z 1.27 3113  71  60 -18 0.00
Sat 03/28 15Z 1.65 3112  64  64 -17 0.00
Sat 03/28 16Z 1.62 3110  56  69 -16 0.00
Sat 03/28 17Z 2.25 3009  50  75 -15 0.00
Sat 03/28 18Z 4.27 2908  50  72 -15 0.00
Sat 03/28 19Z 5.97 2709  55  66 -14 0.00
Sat 03/28 20Z 6.32 2610  61  67 -14 0.00
Sat 03/28 21Z 6.38 2713  70  63 -13 0.00
Sat 03/28 22Z 7.31 2917  67  40 -14 0.00
Sat 03/28 23Z 3.93 2818  76  34 -14 0.00
Sun 03/29 00Z 3.72 2821  83  44 -14 0.00
Sun 03/29 01Z 4.18 2923  79  29 -15 0.00
Sun 03/29 02Z 4.61 2822  75  22 -15 0.00
Sun 03/29 03Z 4.13 2822  76  13 -15 0.00
Sun 03/29 04Z 1.84 2821  73  16 -15 0.00
Sun 03/29 05Z 1.20 2921  65  46 -15 0.00
Sun 03/29 06Z 1.09 2823  62  77 -14 0.00
Sun 03/29 07Z 0.81 2923  69  71 -14 0.00
Sun 03/29 08Z 0.85 2821  80  68 -14 0.00
Sun 03/29 09Z 0.83 2719  84  69 -14 0.00
Sun 03/29 10Z 0.71 2719  87  81 -13 0.00
Sun 03/29 11Z 0.54 2716  86  83 -12 0.00
Sun 03/29 12Z 0.54 2617  85  68 -12 0.00
Sun 03/29 13Z 0.54 2518  81  60 -11 0.00
Sun 03/29 14Z 0.54 2517  78  43 -10 0.00
Sun 03/29 15Z 0.58 2418  69  28  -9 0.00
Sun 03/29 16Z 0.62 2319  57  37  -8 0.00
Sun 03/29 17Z 0.84 2321  50  74  -8 0.00
Sun 03/29 18Z 1.50 2220  53  78  -7 0.00
Sun 03/29 19Z 4.72 2220  50  78  -7 0.00
Sun 03/29 20Z 3.85 2221  50  53  -6 0.00
Sun 03/29 21Z 1.26 2223  52  24  -5 0.00
Sun 03/29 22Z 1.03 2225  54  15  -4 0.00
Sun 03/29 23Z 1.03 2326  54  21  -4 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