NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260801_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)
=== ===== === ==== ==== === === === ====
Sat 08/01 12Z 0.19 2205  83  70  14 0.00
Sat 08/01 13Z 0.21 2205  84  63  14 0.00
Sat 08/01 14Z 0.31 2206  86  54  14 0.00
Sat 08/01 15Z 0.72 2206  84  38  14 0.00
Sat 08/01 16Z 1.79 2206  79  29  14 0.00
Sat 08/01 17Z 2.49 2307  74  29  15 0.00
Sat 08/01 18Z 2.99 2307  72  24  15 0.00
Sat 08/01 19Z 2.55 2206  70  17  15 0.00
Sat 08/01 20Z 2.29 2106  68  13  16 0.00
Sat 08/01 21Z 1.16 2105  65  10  16 0.00
Sat 08/01 22Z 0.53 2007  63   9  16 0.00
Sat 08/01 23Z 0.33 1908  63  10  16 0.00
Sun 08/02 00Z 0.39 2010  64  14  16 0.00
Sun 08/02 01Z 0.60 2013  70  25  15 0.00
Sun 08/02 02Z 0.66 2116  76  33  15 0.00
Sun 08/02 03Z 0.66 2118  78  47  15 0.00
Sun 08/02 04Z 0.72 2119  82  47  15 0.00
Sun 08/02 05Z 0.70 2220  85  31  15 0.00
Sun 08/02 06Z 0.64 2121  82  47  15 0.00
Sun 08/02 07Z 0.66 2221  78  51  15 0.00
Sun 08/02 08Z 0.69 2222  79  30  15 0.00
Sun 08/02 09Z 0.68 2221  77  33  15 0.00
Sun 08/02 10Z 0.71 2222  84  39  14 0.00
Sun 08/02 11Z 0.68 2221  84  33  14 0.00
Sun 08/02 12Z 0.57 2219  86  39  14 0.00
Sun 08/02 13Z 0.56 2119  90  34  14 0.00
Sun 08/02 14Z 0.55 2118  88  25  14 0.00
Sun 08/02 15Z 0.66 2016  90  16  14 0.00
Sun 08/02 16Z 0.67 1916  92  27  14 0.01
Sun 08/02 17Z 0.71 1918  90  29  14 0.02
Sun 08/02 18Z 0.80 1921  88  35  14 0.02
Sun 08/02 19Z 1.03 1921  86  25  15 0.01
Sun 08/02 20Z 0.75 1822  87  25  15 0.01
Sun 08/02 21Z 0.52 1824  88  37  15 0.00
Sun 08/02 22Z 0.36 1824  87  51  15 0.01
Sun 08/02 23Z 0.34 1925  78  33  15 0.00
Mon 08/03 00Z 0.31 1924  71  28  16 0.00
Mon 08/03 01Z 0.34 1925  67  19  16 0.00
Mon 08/03 02Z 0.35 1925  67  21  16 0.00
Mon 08/03 03Z 0.35 1925  72  32  16 0.00
Mon 08/03 04Z 0.32 1924  90  63  16 0.00
Mon 08/03 05Z 0.32 1925  96  73  16 0.01
Mon 08/03 06Z 0.34 1926  97  75  16 0.02
Mon 08/03 07Z 0.38 1927  97  75  16 0.02
Mon 08/03 08Z 0.48 2028  92  85  16 0.01
Mon 08/03 09Z 0.43 2027  84  95  16 0.02
Mon 08/03 10Z 0.42 2028  81  81  17 0.01
Mon 08/03 11Z 0.44 2028  91  88  16 0.00
Mon 08/03 12Z 0.51 2027  97  98  16 0.04
Mon 08/03 13Z 0.57 2127  98  89  16 0.24
Mon 08/03 14Z 0.64 2222  95  78  16 0.30
Mon 08/03 15Z 0.73 2321  96  82  15 0.02
Mon 08/03 16Z 0.81 2421  98  83  15 0.02
Mon 08/03 17Z 0.84 2618  98  80  15 0.02
Mon 08/03 18Z 0.77 2718  97  76  15 0.12
Mon 08/03 19Z 0.66 2818  96  64  15 0.06
Mon 08/03 20Z 0.53 2918  94  41  14 0.02
Mon 08/03 21Z 0.44 3018  92  29  14 0.01
Mon 08/03 22Z 0.25 3217  87  20  14 0.00
Mon 08/03 23Z 0.14 3317  77  11  14 0.00

Run total areal avg QPF for the Central_Greens is: 1.02 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