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_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)
=== ===== === ==== ==== === === === ====
Sat 08/15 00Z 0.03 3414  88  40   9 0.00
Sat 08/15 01Z 0.04 3515  83  31   9 0.00
Sat 08/15 02Z 0.05 3516  79  25   9 0.00
Sat 08/15 03Z 0.08 3517  78  17   8 0.00
Sat 08/15 04Z 0.11 3514  77  10   8 0.00
Sat 08/15 05Z 0.09 3512  80   8   8 0.00
Sat 08/15 06Z 0.05 3510  81   8   8 0.00
Sat 08/15 07Z 0.08 3408  81   8   8 0.00
Sat 08/15 08Z 0.14 3309  79   8   8 0.00
Sat 08/15 09Z 0.20 3212  77   8   8 0.00
Sat 08/15 10Z 0.24 3213  76   7   8 0.00
Sat 08/15 11Z 0.24 3214  77   4   8 0.00
Sat 08/15 12Z 0.18 3315  76   4   8 0.00
Sat 08/15 13Z 0.13 3315  75   5   7 0.00
Sat 08/15 14Z 0.11 3314  77   8   7 0.00
Sat 08/15 15Z 0.17 3311  80  11   7 0.00
Sat 08/15 16Z 0.55 3209  82  13   7 0.00
Sat 08/15 17Z 0.68 3110  82  14   8 0.00
Sat 08/15 18Z 0.56 3212  77  15   8 0.00
Sat 08/15 19Z 0.95 3214  71  16   8 0.00
Sat 08/15 20Z 1.18 3213  75  16   8 0.00
Sat 08/15 21Z 0.78 3214  78  15   8 0.00
Sat 08/15 22Z 0.25 3313  75  11   8 0.00
Sat 08/15 23Z 0.08 3412  70  10   9 0.00
Sun 08/16 00Z 0.06 3412  67   9   9 0.00
Sun 08/16 01Z 0.04 3411  62   9   9 0.00
Sun 08/16 02Z 0.05 3410  59   9   9 0.00
Sun 08/16 03Z 0.04 3510  61  10   9 0.00
Sun 08/16 04Z 0.05 3509  61  10   9 0.00
Sun 08/16 05Z 0.06 0008  63  10   9 0.00
Sun 08/16 06Z 0.06 0105  63  10   9 0.00
Sun 08/16 07Z 0.04 0202  61   9  10 0.00
Sun 08/16 08Z 0.02 3401  60   8   9 0.00
Sun 08/16 09Z 0.05 2601  57   7   9 0.00
Sun 08/16 10Z 0.04 2002  56   6  10 0.00
Sun 08/16 11Z 0.04 1904  56   7  10 0.00
Sun 08/16 12Z 0.13 2106  59   9   9 0.00
Sun 08/16 13Z 0.17 2107  63  10   9 0.00
Sun 08/16 14Z 0.20 2107  70   9   9 0.00
Sun 08/16 15Z 0.47 2109  78   8   9 0.00
Sun 08/16 16Z 0.88 2109  84   7   9 0.00
Sun 08/16 17Z 0.68 2008  83   6   9 0.00
Sun 08/16 18Z 0.43 1908  83   8  10 0.00
Sun 08/16 19Z 0.37 1811  85  25  11 0.00
Sun 08/16 20Z 0.33 1812  87  52  11 0.00
Sun 08/16 21Z 0.30 1814  92  92  11 0.00
Sun 08/16 22Z 0.21 1817  97  96  11 0.01
Sun 08/16 23Z 0.15 1820  97  98  12 0.01
Mon 08/17 00Z 0.17 1822  97  98  12 0.02
Mon 08/17 01Z 0.18 1826  98  97  12 0.05
Mon 08/17 02Z 0.23 1829  98  98  12 0.04
Mon 08/17 03Z 0.26 1830  98  98  12 0.07
Mon 08/17 04Z 0.30 1831  98  95  12 0.07
Mon 08/17 05Z 0.33 1930  98  95  12 0.07
Mon 08/17 06Z 0.36 1928  99  96  12 0.08
Mon 08/17 07Z 0.38 2026  99  96  13 0.11
Mon 08/17 08Z 0.39 2124  99  97  15 0.08
Mon 08/17 09Z 0.38 2121  99  95  15 0.09
Mon 08/17 10Z 0.39 2219  99  92  15 0.21
Mon 08/17 11Z 0.35 2415  99  94  15 0.06

Run total areal avg QPF for the Central_Greens is: 0.97 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