NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260731_0600
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 07/31 06Z 0.02 3408  82  80  13 0.00
Fri 07/31 07Z 0.09 3311  82  88  13 0.00
Fri 07/31 08Z 0.10 3313  81  94  13 0.00
Fri 07/31 09Z 0.07 3313  81  94  12 0.00
Fri 07/31 10Z 0.06 3413  84  94  12 0.01
Fri 07/31 11Z 0.03 3413  86  90  12 0.01
Fri 07/31 12Z 0.03 3411  88  87  12 0.00
Fri 07/31 13Z 0.03 3411  90  84  12 0.00
Fri 07/31 14Z 0.04 3411  91  81  12 0.00
Fri 07/31 15Z 0.05 3410  92  80  12 0.00
Fri 07/31 16Z 0.06 3308  91  79  12 0.00
Fri 07/31 17Z 0.10 3307  91  75  12 0.00
Fri 07/31 18Z 0.15 3207  89  67  13 0.00
Fri 07/31 19Z 0.28 3108  88  69  13 0.00
Fri 07/31 20Z 0.42 3110  88  64  13 0.00
Fri 07/31 21Z 0.40 3210  90  51  13 0.00
Fri 07/31 22Z 0.26 3211  87  37  13 0.00
Fri 07/31 23Z 0.20 3210  83  33  13 0.00
Sat 08/01 00Z 0.17 3211  80  30  13 0.00
Sat 08/01 01Z 0.14 3311  74  26  14 0.00
Sat 08/01 02Z 0.11 3310  69  24  14 0.00
Sat 08/01 03Z 0.12 3309  68  26  14 0.00
Sat 08/01 04Z 0.09 3307  67  33  14 0.00
Sat 08/01 05Z 0.11 3207  68  39  13 0.00
Sat 08/01 06Z 0.12 3206  69  43  13 0.00
Sat 08/01 07Z 0.13 3105  70  46  13 0.00
Sat 08/01 08Z 0.14 3004  73  42  13 0.00
Sat 08/01 09Z 0.15 2803  76  33  13 0.00
Sat 08/01 10Z 0.15 2503  78  28  12 0.00
Sat 08/01 11Z 0.13 2203  79  24  12 0.00
Sat 08/01 12Z 0.20 2204  79  22  12 0.00
Sat 08/01 13Z 0.24 2205  79  18  12 0.00
Sat 08/01 14Z 0.29 2105  80  15  12 0.00
Sat 08/01 15Z 0.44 2005  81  13  13 0.00
Sat 08/01 16Z 1.02 2005  82  14  13 0.00
Sat 08/01 17Z 1.19 2006  81  13  13 0.00
Sat 08/01 18Z 1.29 2005  80  12  13 0.00
Sat 08/01 19Z 0.99 2005  77  13  14 0.00
Sat 08/01 20Z 0.32 1905  75  14  14 0.00
Sat 08/01 21Z 0.19 1806  73  14  14 0.00
Sat 08/01 22Z 0.21 1809  75  15  14 0.00
Sat 08/01 23Z 0.21 1811  78  18  14 0.00
Sun 08/02 00Z 0.26 1812  81  25  14 0.00
Sun 08/02 01Z 0.31 1914  83  38  14 0.00
Sun 08/02 02Z 0.36 1915  85  55  14 0.00
Sun 08/02 03Z 0.38 1916  89  59  14 0.00
Sun 08/02 04Z 0.34 1917  93  62  14 0.00
Sun 08/02 05Z 0.30 1917  93  52  14 0.00
Sun 08/02 06Z 0.36 2018  93  50  14 0.00
Sun 08/02 07Z 0.39 2119  89  42  14 0.00
Sun 08/02 08Z 0.33 2117  87  29  15 0.00
Sun 08/02 09Z 0.38 2118  95  24  14 0.00
Sun 08/02 10Z 0.37 2117  97  20  14 0.01
Sun 08/02 11Z 0.39 2118  97  28  14 0.02
Sun 08/02 12Z 0.37 2117  92  21  14 0.01
Sun 08/02 13Z 0.31 2017  88  15  14 0.00
Sun 08/02 14Z 0.35 2017  90  15  14 0.00
Sun 08/02 15Z 0.37 2016  93  13  14 0.00
Sun 08/02 16Z 0.37 2015  95   9  13 0.00
Sun 08/02 17Z 0.38 1914  94  10  14 0.00

Run total areal avg QPF for the Central_Greens is: 0.06 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