Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260215_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)
=== ===== === ==== ==== === === === ====
Sun 02/15 00Z 0.78 2818 87 15 -10 0.00
Sun 02/15 01Z 0.90 2822 86 14 -10 0.00
Sun 02/15 02Z 0.91 2824 86 13 -10 0.00
Sun 02/15 03Z 0.87 2925 88 14 -10 0.00
Sun 02/15 04Z 0.94 2928 92 17 -10 0.00
Sun 02/15 05Z 0.78 3028 87 18 -10 0.00
Sun 02/15 06Z 0.66 3026 87 19 -10 0.00
Sun 02/15 07Z 0.58 3026 87 20 -10 0.00
Sun 02/15 08Z 0.50 3025 84 19 -11 0.01
Sun 02/15 09Z 0.39 3024 77 17 -10 0.00
Sun 02/15 10Z 0.27 3123 67 16 -9 0.00
Sun 02/15 11Z 0.17 3223 54 14 -9 0.00
Sun 02/15 12Z 0.09 3322 41 14 -9 0.00
Sun 02/15 13Z 0.04 3418 32 14 -8 0.00
Sun 02/15 14Z 0.04 3513 27 15 -8 0.00
Sun 02/15 15Z 0.05 0010 25 19 -7 0.00
Sun 02/15 16Z 0.07 0206 26 23 -7 0.00
Sun 02/15 17Z 0.07 0404 27 31 -7 0.00
Sun 02/15 18Z 0.07 0703 28 40 -7 0.00
Sun 02/15 19Z 0.04 1302 29 44 -6 0.00
Sun 02/15 20Z 0.03 1503 29 45 -6 0.00
Sun 02/15 21Z 0.02 1604 27 38 -5 0.00
Sun 02/15 22Z 0.02 1606 23 24 -4 0.00
Sun 02/15 23Z 0.03 1809 24 16 -4 0.00
Mon 02/16 00Z 0.04 1811 25 17 -4 0.00
Mon 02/16 01Z 0.09 1912 30 31 -5 0.00
Mon 02/16 02Z 0.10 1912 38 49 -4 0.00
Mon 02/16 03Z 0.12 1913 47 61 -4 0.00
Mon 02/16 04Z 0.14 1914 61 77 -5 0.00
Mon 02/16 05Z 0.14 1914 79 75 -5 0.00
Mon 02/16 06Z 0.11 1914 90 86 -5 0.01
Mon 02/16 07Z 0.11 1915 91 88 -5 0.01
Mon 02/16 08Z 0.12 1915 93 86 -4 0.02
Mon 02/16 09Z 0.12 1915 95 90 -4 0.02
Mon 02/16 10Z 0.15 1914 95 91 -5 0.02
Mon 02/16 11Z 0.15 2013 96 89 -5 0.02
Mon 02/16 12Z 0.16 2112 97 82 -4 0.01
Mon 02/16 13Z 0.14 2111 96 75 -4 0.01
Mon 02/16 14Z 0.14 2111 96 70 -4 0.01
Mon 02/16 15Z 0.14 2110 97 62 -4 0.01
Mon 02/16 16Z 0.13 2109 97 56 -4 0.00
Mon 02/16 17Z 0.15 2110 97 49 -4 0.00
Mon 02/16 18Z 0.16 2110 97 48 -4 0.00
Mon 02/16 19Z 0.19 2111 97 42 -4 0.00
Mon 02/16 20Z 0.25 2212 97 33 -5 0.00
Mon 02/16 21Z 0.28 2212 97 42 -5 0.00
Mon 02/16 22Z 0.30 2213 97 42 -5 0.00
Mon 02/16 23Z 0.34 2314 96 80 -4 0.00
Tue 02/17 00Z 0.33 2315 93 84 -3 0.00
Tue 02/17 01Z 0.39 2417 92 81 -3 0.00
Tue 02/17 02Z 0.42 2418 90 91 -3 0.01
Tue 02/17 03Z 0.41 2517 92 90 -3 0.01
Tue 02/17 04Z 0.41 2617 95 89 -2 0.02
Tue 02/17 05Z 0.42 2717 86 89 -2 0.01
Tue 02/17 06Z 0.42 2617 80 88 -3 0.00
Tue 02/17 07Z 0.42 2717 83 91 -3 0.01
Tue 02/17 08Z 0.39 2716 88 86 -3 0.01
Tue 02/17 09Z 0.34 2815 90 84 -2 0.00
Tue 02/17 10Z 0.31 2813 87 82 -2 0.00
Tue 02/17 11Z 0.30 2812 89 74 -2 0.00
Run total areal avg QPF for the Central_Greens is: 0.22 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