NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260815_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 08/15 12Z 0.11 3310  85   8   8 0.00
Sat 08/15 13Z 0.04 3410  85   5   8 0.00
Sat 08/15 14Z 0.09 3309  84   5   8 0.00
Sat 08/15 15Z 0.08 3410  83   9   8 0.00
Sat 08/15 16Z 0.09 3307  83  15   8 0.00
Sat 08/15 17Z 0.31 3207  81  16   8 0.00
Sat 08/15 18Z 0.63 3109  79  15   8 0.00
Sat 08/15 19Z 0.79 3210  77  18   8 0.00
Sat 08/15 20Z 0.68 3311  77  22   8 0.00
Sat 08/15 21Z 0.37 3311  78  17   8 0.00
Sat 08/15 22Z 0.12 3410  75  13   8 0.00
Sat 08/15 23Z 0.07 3409  72  11   8 0.00
Sun 08/16 00Z 0.04 3509  71  10   8 0.00
Sun 08/16 01Z 0.04 3410  67   9   8 0.00
Sun 08/16 02Z 0.05 3509  60   8   9 0.00
Sun 08/16 03Z 0.05 0008  59   8   9 0.00
Sun 08/16 04Z 0.06 0005  54   8   9 0.00
Sun 08/16 05Z 0.05 3504  52   8   9 0.00
Sun 08/16 06Z 0.05 0003  49   8  10 0.00
Sun 08/16 07Z 0.04 3502  48   8  10 0.00
Sun 08/16 08Z 0.04 3502  46   7  10 0.00
Sun 08/16 09Z 0.03 0101  48   7  10 0.00
Sun 08/16 10Z 0.02 3401  48   8  10 0.00
Sun 08/16 11Z 0.04 2201  46   7  11 0.00
Sun 08/16 12Z 0.09 2204  47   7  10 0.00
Sun 08/16 13Z 0.12 2106  49   7  10 0.00
Sun 08/16 14Z 0.14 2106  54   6  10 0.00
Sun 08/16 15Z 0.20 2107  63   5  10 0.00
Sun 08/16 16Z 0.34 2107  72   5   9 0.00
Sun 08/16 17Z 0.50 2007  76   6  10 0.00
Sun 08/16 18Z 0.60 1908  79   7  10 0.00
Sun 08/16 19Z 0.52 1910  78   6  11 0.00
Sun 08/16 20Z 0.36 1810  77   7  11 0.00
Sun 08/16 21Z 0.38 1912  86  12  11 0.00
Sun 08/16 22Z 0.34 1914  92  27  11 0.00
Sun 08/16 23Z 0.32 2016  95  34  12 0.00
Mon 08/17 00Z 0.31 1918  96  70  12 0.01
Mon 08/17 01Z 0.30 1922  97  79  12 0.01
Mon 08/17 02Z 0.35 1924  98  72  12 0.01
Mon 08/17 03Z 0.45 2027  97  85  13 0.02
Mon 08/17 04Z 0.43 2027  96  96  13 0.01
Mon 08/17 05Z 0.43 2028  95  97  12 0.02
Mon 08/17 06Z 0.47 2030  95  96  12 0.02
Mon 08/17 07Z 0.43 1929  98  94  12 0.01
Mon 08/17 08Z 0.42 1926  99  95  11 0.04
Mon 08/17 09Z 0.40 2024  99  96  12 0.09
Mon 08/17 10Z 0.35 1924  99  95  12 0.08
Mon 08/17 11Z 0.31 1924  99  95  12 0.09
Mon 08/17 12Z 0.33 2023  99  94  12 0.07
Mon 08/17 13Z 0.33 2022  99  95  12 0.04
Mon 08/17 14Z 0.30 2019  99  96  12 0.03
Mon 08/17 15Z 0.26 2016  99  94  12 0.02
Mon 08/17 16Z 0.22 2013  99  92  12 0.02
Mon 08/17 17Z 0.18 2109  99  85  13 0.01
Mon 08/17 18Z 0.13 2206  99  72  13 0.01
Mon 08/17 19Z 0.12 2604  97  64  14 0.00
Mon 08/17 20Z 0.10 3004  96  55  15 0.00
Mon 08/17 21Z 0.08 3205  95  51  15 0.00
Mon 08/17 22Z 0.06 3306  95  43  15 0.00
Mon 08/17 23Z 0.05 3307  95  34  14 0.00

Run total areal avg QPF for the Central_Greens is: 0.61 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