NAM3 EXPERIMENTAL Froude Number for the Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260724_0600
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 06Z 0.29 2905  70   8  10 0.00
Fri 07/24 07Z 0.35 2905  68   9  10 0.00
Fri 07/24 08Z 0.38 2905  66   9  10 0.00
Fri 07/24 09Z 0.39 2805  66   9   9 0.00
Fri 07/24 10Z 0.35 2704  66  11   9 0.00
Fri 07/24 11Z 0.30 2504  67  13   9 0.00
Fri 07/24 12Z 0.23 2204  69  14   9 0.00
Fri 07/24 13Z 0.22 2106  71  15   9 0.00
Fri 07/24 14Z 0.48 2106  72  17   9 0.00
Fri 07/24 15Z 1.37 2206  74  22   9 0.00
Fri 07/24 16Z 1.69 2306  73  27  10 0.00
Fri 07/24 17Z 1.90 2306  70  34  10 0.00
Fri 07/24 18Z 1.97 2405  66  41  11 0.00
Fri 07/24 19Z 1.45 2504  62  45  11 0.00
Fri 07/24 20Z 0.86 2503  61  46  11 0.00
Fri 07/24 21Z 0.40 2602  60  47  12 0.00
Fri 07/24 22Z 0.14 2101  60  48  12 0.00
Fri 07/24 23Z 0.09 1902  61  49  12 0.00
Sat 07/25 00Z 0.09 2003  61  49  12 0.00
Sat 07/25 01Z 0.08 2002  60  46  12 0.00
Sat 07/25 02Z 0.07 2002  61  47  12 0.00
Sat 07/25 03Z 0.07 1903  61  46  12 0.00
Sat 07/25 04Z 0.11 2104  62  48  12 0.00
Sat 07/25 05Z 0.09 2003  63  49  12 0.00
Sat 07/25 06Z 0.06 2002  62  49  12 0.00
Sat 07/25 07Z 0.04 1802  61  47  12 0.00
Sat 07/25 08Z 0.03 1802  59  46  12 0.00
Sat 07/25 09Z 0.04 1602  58  42  12 0.00
Sat 07/25 10Z 0.03 1803  59  42  12 0.00
Sat 07/25 11Z 0.04 1803  60  41  12 0.00
Sat 07/25 12Z 0.03 1804  62  40  11 0.00
Sat 07/25 13Z 0.03 1803  64  40  11 0.00
Sat 07/25 14Z 0.07 1603  67  38  11 0.00
Sat 07/25 15Z 0.25 1602  71  34  11 0.00
Sat 07/25 16Z 0.62 1503  73  31  11 0.00
Sat 07/25 17Z 1.02 1404  74  27  12 0.00
Sat 07/25 18Z 1.10 1505  73  23  12 0.00
Sat 07/25 19Z 1.30 1506  72  19  13 0.00
Sat 07/25 20Z 1.13 1506  72  16  13 0.00
Sat 07/25 21Z 0.73 1606  73  14  13 0.00
Sat 07/25 22Z 0.56 1606  74  11  13 0.00
Sat 07/25 23Z 0.30 1607  77   9  12 0.00
Sun 07/26 00Z 0.20 1609  80   7  12 0.00
Sun 07/26 01Z 0.11 1710  83   6  12 0.00
Sun 07/26 02Z 0.08 1810  85   6  12 0.00
Sun 07/26 03Z 0.12 1910  85   5  12 0.00
Sun 07/26 04Z 0.17 2009  84   5  12 0.00
Sun 07/26 05Z 0.23 2107  83   5  12 0.00
Sun 07/26 06Z 0.25 2206  83   5  11 0.00
Sun 07/26 07Z 0.25 2405  84   5  11 0.00
Sun 07/26 08Z 0.28 2605  85   6  11 0.00
Sun 07/26 09Z 0.22 2704  85   6  11 0.00
Sun 07/26 10Z 0.16 2803  85   6  11 0.00
Sun 07/26 11Z 0.07 3201  84   6  11 0.00
Sun 07/26 12Z 0.08 0301  83   6  11 0.00
Sun 07/26 13Z 0.12 0901  85   6  11 0.00
Sun 07/26 14Z 0.19 1102  86   6  11 0.00
Sun 07/26 15Z 0.21 1302  88   6  11 0.00
Sun 07/26 16Z 0.22 1302  87   7  11 0.00
Sun 07/26 17Z 0.26 1401  86   7  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