NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260816_0000
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)
=== ===== === ==== ==== === === === ====
Sun 08/16 00Z 0.03 3407  75  11   9 0.00
Sun 08/16 01Z 0.03 3506  72  10   9 0.00
Sun 08/16 02Z 0.03 0004  71  11   9 0.00
Sun 08/16 03Z 0.03 3302  70  13   9 0.00
Sun 08/16 04Z 0.05 3102  67  14  10 0.00
Sun 08/16 05Z 0.08 2903  65  14  10 0.00
Sun 08/16 06Z 0.08 2803  62  14  10 0.00
Sun 08/16 07Z 0.07 2602  59  14  10 0.00
Sun 08/16 08Z 0.07 2602  58  13  10 0.00
Sun 08/16 09Z 0.06 2601  58  11  10 0.00
Sun 08/16 10Z 0.07 2302  60   8  10 0.00
Sun 08/16 11Z 0.05 1903  62   6  10 0.00
Sun 08/16 12Z 0.09 1905  67   5   9 0.00
Sun 08/16 13Z 0.16 2008  72   5   9 0.00
Sun 08/16 14Z 0.23 2009  77   3   9 0.00
Sun 08/16 15Z 0.33 2010  81   3   9 0.00
Sun 08/16 16Z 0.75 1910  85   5   9 0.00
Sun 08/16 17Z 0.82 1910  87   5  10 0.00
Sun 08/16 18Z 0.69 1911  87   2  10 0.00
Sun 08/16 19Z 0.52 1912  85   7  11 0.00
Sun 08/16 20Z 0.60 1913  85  27  11 0.00
Sun 08/16 21Z 0.57 1913  87  53  11 0.00
Sun 08/16 22Z 0.34 1914  92  71  12 0.00
Sun 08/16 23Z 0.24 1916  97  80  12 0.01
Mon 08/17 00Z 0.27 1918  99  95  12 0.04
Mon 08/17 01Z 0.30 1920  98  98  12 0.03
Mon 08/17 02Z 0.39 1925  98  98  12 0.04
Mon 08/17 03Z 0.49 2028  98  95  12 0.04
Mon 08/17 04Z 0.52 2028  98  92  12 0.03
Mon 08/17 05Z 0.49 2028  98  92  12 0.03
Mon 08/17 06Z 0.52 2028  98  93  12 0.03
Mon 08/17 07Z 0.48 2027  99  96  12 0.02
Mon 08/17 08Z 0.47 2025  98  97  12 0.03
Mon 08/17 09Z 0.46 2024  99  96  12 0.03
Mon 08/17 10Z 0.46 2124  99  96  12 0.03
Mon 08/17 11Z 0.45 2124  99  95  12 0.04
Mon 08/17 12Z 0.43 2121  99  94  13 0.03
Mon 08/17 13Z 0.44 2220  99  96  13 0.03
Mon 08/17 14Z 0.39 2217  99  96  13 0.03
Mon 08/17 15Z 0.35 2215  99  88  13 0.02
Mon 08/17 16Z 0.29 2212  99  85  14 0.01
Mon 08/17 17Z 0.21 2308  98  82  14 0.01
Mon 08/17 18Z 0.12 2504  95  75  15 0.00
Mon 08/17 19Z 0.11 2904  94  67  15 0.00
Mon 08/17 20Z 0.06 3204  94  64  15 0.00
Mon 08/17 21Z 0.05 3304  95  61  15 0.00
Mon 08/17 22Z 0.06 3204  97  55  14 0.00
Mon 08/17 23Z 0.03 3305  97  60  14 0.00
Tue 08/18 00Z 0.04 3305  98  46  14 0.00
Tue 08/18 01Z 0.04 3406  98  32  14 0.01
Tue 08/18 02Z 0.04 3507  98  27  13 0.01
Tue 08/18 03Z 0.04 3507  98  19  13 0.01
Tue 08/18 04Z 0.06 0007  97  21  13 0.01
Tue 08/18 05Z 0.04 3506  96  16  13 0.01
Tue 08/18 06Z 0.02 3506  94  11  13 0.00
Tue 08/18 07Z 0.02 3505  92   9  13 0.00
Tue 08/18 08Z 0.04 3306  91   6  13 0.00
Tue 08/18 09Z 0.05 3306  91   4  12 0.01
Tue 08/18 10Z 0.07 3307  92   4  12 0.01
Tue 08/18 11Z 0.06 3305  91   2  12 0.00

Run total areal avg QPF for the Central_Greens is: 0.60 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