NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260724_1800
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 07/24 18Z 2.01 2403  67  24  11 0.00
Fri 07/24 19Z 1.28 2602  65  27  11 0.00
Fri 07/24 20Z 1.11 2602  64  28  12 0.00
Fri 07/24 21Z 0.66 2602  63  27  12 0.00
Fri 07/24 22Z 0.31 2402  63  29  12 0.00
Fri 07/24 23Z 0.18 2202  62  33  12 0.00
Sat 07/25 00Z 0.14 2202  62  36  12 0.00
Sat 07/25 01Z 0.16 2103  61  39  12 0.00
Sat 07/25 02Z 0.13 2004  61  41  12 0.00
Sat 07/25 03Z 0.11 2005  62  41  12 0.00
Sat 07/25 04Z 0.14 2005  63  41  12 0.00
Sat 07/25 05Z 0.16 2005  64  42  12 0.00
Sat 07/25 06Z 0.17 2104  65  43  11 0.00
Sat 07/25 07Z 0.10 2103  65  44  11 0.00
Sat 07/25 08Z 0.08 2002  64  41  11 0.00
Sat 07/25 09Z 0.11 2202  64  40  11 0.00
Sat 07/25 10Z 0.09 2102  64  37  11 0.00
Sat 07/25 11Z 0.11 2202  64  36  11 0.00
Sat 07/25 12Z 0.09 2103  64  36  11 0.00
Sat 07/25 13Z 0.05 1704  64  36  11 0.00
Sat 07/25 14Z 0.14 1604  66  35  11 0.00
Sat 07/25 15Z 0.18 1703  68  33  11 0.00
Sat 07/25 16Z 0.42 1703  69  29  12 0.00
Sat 07/25 17Z 0.56 1603  70  27  12 0.00
Sat 07/25 18Z 0.75 1603  70  26  12 0.00
Sat 07/25 19Z 1.19 1505  70  25  13 0.00
Sat 07/25 20Z 1.09 1505  71  25  13 0.00
Sat 07/25 21Z 1.24 1507  72  24  13 0.00
Sat 07/25 22Z 0.67 1608  74  23  13 0.00
Sat 07/25 23Z 0.29 1609  76  16  13 0.00
Sun 07/26 00Z 0.17 1610  79  11  12 0.00
Sun 07/26 01Z 0.13 1711  81  11  12 0.00
Sun 07/26 02Z 0.08 1812  83  11  12 0.00
Sun 07/26 03Z 0.15 1912  83  11  12 0.00
Sun 07/26 04Z 0.20 2011  82  11  12 0.00
Sun 07/26 05Z 0.26 2010  83  10  11 0.00
Sun 07/26 06Z 0.29 2109  84  10  11 0.00
Sun 07/26 07Z 0.33 2208  85  10  11 0.00
Sun 07/26 08Z 0.37 2308  85  10  11 0.00
Sun 07/26 09Z 0.33 2307  83  10  11 0.00
Sun 07/26 10Z 0.24 2305  80  10  11 0.00
Sun 07/26 11Z 0.15 2204  78  10  11 0.00
Sun 07/26 12Z 0.08 1904  78  10  11 0.00
Sun 07/26 13Z 0.05 1704  80  10  11 0.00
Sun 07/26 14Z 0.18 1604  82  11  11 0.00
Sun 07/26 15Z 0.29 1604  85  12  11 0.00
Sun 07/26 16Z 0.30 1505  86  14  11 0.00
Sun 07/26 17Z 0.32 1605  87  15  11 0.00
Sun 07/26 18Z 0.28 1605  87  15  12 0.00
Sun 07/26 19Z 0.21 1705  86  15  12 0.00
Sun 07/26 20Z 0.18 1805  85  14  12 0.00
Sun 07/26 21Z 0.11 1804  84  13  12 0.00
Sun 07/26 22Z 0.13 1804  84  13  12 0.00
Sun 07/26 23Z 0.11 1805  83  14  12 0.00
Mon 07/27 00Z 0.10 1805  83  16  12 0.00
Mon 07/27 01Z 0.09 1806  83  17  12 0.00
Mon 07/27 02Z 0.09 1807  83  18  12 0.00
Mon 07/27 03Z 0.21 2007  82  20  12 0.00
Mon 07/27 04Z 0.22 2106  82  19  12 0.00
Mon 07/27 05Z 0.17 2105  81  20  12 0.00

Run total areal avg QPF for the greens is: 0.00 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