NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20240816_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)
=== ===== === ==== ==== === === === ====
Fri 08/16 12Z 0.05 0006  84  53  13 0.00
Fri 08/16 13Z 0.09 0205  84  53  13 0.00
Fri 08/16 14Z 0.09 0303  86  54  13 0.00
Fri 08/16 15Z 0.06 0401  88  55  13 0.00
Fri 08/16 16Z 0.05 0800  88  56  13 0.01
Fri 08/16 17Z 0.08 1101  88  58  14 0.04
Fri 08/16 18Z 0.16 1202  88  61  14 0.05
Fri 08/16 19Z 0.25 1303  88  64  14 0.05
Fri 08/16 20Z 0.31 1304  86  66  14 0.04
Fri 08/16 21Z 0.22 1405  84  61  14 0.03
Fri 08/16 22Z 0.14 1506  83  57  14 0.00
Fri 08/16 23Z 0.12 1509  83  52  15 0.00
Sat 08/17 00Z 0.07 1611  82  46  15 0.00
Sat 08/17 01Z 0.04 1712  82  43  15 0.00
Sat 08/17 02Z 0.13 1813  84  45  14 0.00
Sat 08/17 03Z 0.18 1913  86  41  14 0.00
Sat 08/17 04Z 0.24 2012  87  38  14 0.00
Sat 08/17 05Z 0.32 2113  89  38  14 0.00
Sat 08/17 06Z 0.31 2114  93  35  14 0.00
Sat 08/17 07Z 0.25 2012  90  33  14 0.00
Sat 08/17 08Z 0.25 2014  91  31  14 0.00
Sat 08/17 09Z 0.24 2015  91  21  14 0.00
Sat 08/17 10Z 0.28 2016  89  26  13 0.00
Sat 08/17 11Z 0.24 1916  84  20  13 0.00
Sat 08/17 12Z 0.21 1916  81  17  14 0.00
Sat 08/17 13Z 0.19 1916  81  24  14 0.00
Sat 08/17 14Z 0.20 1916  82  33  14 0.00
Sat 08/17 15Z 0.21 1916  80  45  14 0.00
Sat 08/17 16Z 0.19 1817  80  60  14 0.00
Sat 08/17 17Z 0.19 1818  81  79  14 0.00
Sat 08/17 18Z 0.17 1819  77  90  14 0.00
Sat 08/17 19Z 0.17 1819  81  94  14 0.00
Sat 08/17 20Z 0.22 1819  81  95  14 0.00
Sat 08/17 21Z 0.31 1818  82  95  13 0.00
Sat 08/17 22Z 0.16 1719  81  96  13 0.00
Sat 08/17 23Z 0.13 1721  81  92  13 0.00
Sun 08/18 00Z 0.18 1823  84  93  13 0.00
Sun 08/18 01Z 0.25 1823  87  93  12 0.00
Sun 08/18 02Z 0.36 1923  92  92  12 0.01
Sun 08/18 03Z 0.31 1923  89  93  12 0.02
Sun 08/18 04Z 0.23 1824  88  89  12 0.05
Sun 08/18 05Z 0.16 1825  90  83  12 0.06
Sun 08/18 06Z 0.17 1824  87  84  12 0.03
Sun 08/18 07Z 0.19 1825  85  88  12 0.03
Sun 08/18 08Z 0.22 1827  84  91  12 0.01
Sun 08/18 09Z 0.13 1726  84  91  12 0.03
Sun 08/18 10Z 0.10 1727  83  94  12 0.01
Sun 08/18 11Z 0.10 1726  82  89  12 0.04
Sun 08/18 12Z 0.14 1727  80  93  12 0.01
Sun 08/18 13Z 0.16 1828  81  94  12 0.01
Sun 08/18 14Z 0.14 1728  81  89  12 0.02
Sun 08/18 15Z 0.14 1727  82  90  12 0.01
Sun 08/18 16Z 0.13 1725  81  93  12 0.01
Sun 08/18 17Z 0.16 1825  81  89  13 0.00
Sun 08/18 18Z 0.13 1724  80  89  13 0.00
Sun 08/18 19Z 0.13 1723  86  90  13 0.00
Sun 08/18 20Z 0.09 1721  89  90  13 0.00
Sun 08/18 21Z 0.09 1622  91  95  13 0.01
Sun 08/18 22Z 0.10 1622  95  91  13 0.01
Sun 08/18 23Z 0.10 1624  96  89  13 0.01

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