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_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)
=== ===== === ==== ==== === === === ====
Sat 08/15 06Z 0.05 3508  82  14  10 0.00
Sat 08/15 07Z 0.05 3508  84  16   9 0.00
Sat 08/15 08Z 0.04 3408  84  18   9 0.00
Sat 08/15 09Z 0.04 3406  83  17   9 0.00
Sat 08/15 10Z 0.08 3307  82  19   9 0.00
Sat 08/15 11Z 0.12 3208  80  19   9 0.00
Sat 08/15 12Z 0.10 3309  79  16   9 0.00
Sat 08/15 13Z 0.09 3312  79  13   9 0.00
Sat 08/15 14Z 0.06 3412  79  14   9 0.00
Sat 08/15 15Z 0.10 3310  78  18   9 0.00
Sat 08/15 16Z 0.24 3209  78  18   9 0.00
Sat 08/15 17Z 0.75 3210  77  25   9 0.00
Sat 08/15 18Z 0.81 3211  76  31   9 0.00
Sat 08/15 19Z 0.74 3212  76  27   9 0.00
Sat 08/15 20Z 0.77 3212  80  31   9 0.00
Sat 08/15 21Z 0.40 3212  79  19   9 0.00
Sat 08/15 22Z 0.30 3212  80   9   9 0.00
Sat 08/15 23Z 0.19 3312  80  10   9 0.00
Sun 08/16 00Z 0.12 3311  79  10   9 0.00
Sun 08/16 01Z 0.12 3310  78   9   8 0.00
Sun 08/16 02Z 0.08 3309  76   9   8 0.00
Sun 08/16 03Z 0.13 3208  76   8   8 0.00
Sun 08/16 04Z 0.12 3207  76   8   9 0.00
Sun 08/16 05Z 0.09 3206  76   8   9 0.00
Sun 08/16 06Z 0.06 3204  73   8   9 0.00
Sun 08/16 07Z 0.08 3104  74   8   9 0.00
Sun 08/16 08Z 0.09 2903  74   8   9 0.00
Sun 08/16 09Z 0.11 2603  75   8   8 0.00
Sun 08/16 10Z 0.17 2504  76   8   8 0.00
Sun 08/16 11Z 0.15 2404  76   8   9 0.00
Sun 08/16 12Z 0.15 2205  76   8   9 0.00
Sun 08/16 13Z 0.15 2106  77   7   9 0.00
Sun 08/16 14Z 0.21 2108  81   7   9 0.00
Sun 08/16 15Z 0.40 2109  89   6   9 0.00
Sun 08/16 16Z 0.43 2010  93   5   9 0.00
Sun 08/16 17Z 0.37 2009  92  11  10 0.00
Sun 08/16 18Z 0.30 2009  89  11  10 0.00
Sun 08/16 19Z 0.26 1909  89  13  11 0.00
Sun 08/16 20Z 0.17 1810  89  14  11 0.00
Sun 08/16 21Z 0.13 1813  89  19  11 0.00
Sun 08/16 22Z 0.14 1816  92  41  12 0.00
Sun 08/16 23Z 0.19 1818  93  87  12 0.00
Mon 08/17 00Z 0.20 1820  96  97  12 0.00
Mon 08/17 01Z 0.21 1821  98  98  12 0.01
Mon 08/17 02Z 0.24 1921  96  99  12 0.01
Mon 08/17 03Z 0.24 1922  96  99  12 0.02
Mon 08/17 04Z 0.22 1824  95  95  12 0.02
Mon 08/17 05Z 0.27 1928  97  91  12 0.02
Mon 08/17 06Z 0.28 1929  98  85  13 0.03
Mon 08/17 07Z 0.28 1929  98  92  13 0.02
Mon 08/17 08Z 0.27 1928  98  98  13 0.02
Mon 08/17 09Z 0.26 1926  98  97  13 0.02
Mon 08/17 10Z 0.28 1924  98  95  13 0.02
Mon 08/17 11Z 0.27 2022  98  92  13 0.02
Mon 08/17 12Z 0.24 2019  99  91  14 0.03
Mon 08/17 13Z 0.21 2017  99  89  14 0.03
Mon 08/17 14Z 0.21 2014  99  84  14 0.03
Mon 08/17 15Z 0.18 2110  99  78  14 0.01
Mon 08/17 16Z 0.15 2207  98  81  15 0.01
Mon 08/17 17Z 0.15 2506  98  86  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.32 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