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Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260619_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 06/19 12Z 1.07 2724 93 57 7 0.00
Fri 06/19 13Z 1.44 2627 94 51 7 0.00
Fri 06/19 14Z 2.06 2628 94 52 8 0.00
Fri 06/19 15Z 2.14 2627 95 53 8 0.01
Fri 06/19 16Z 2.85 2627 95 57 8 0.01
Fri 06/19 17Z 4.78 2627 93 64 8 0.01
Fri 06/19 18Z 8.76 2626 91 57 8 0.00
Fri 06/19 19Z 11.22 2726 87 46 9 0.00
Fri 06/19 20Z 15.28 2725 82 38 9 0.00
Fri 06/19 21Z 15.85 2625 75 34 9 0.00
Fri 06/19 22Z 13.17 2625 75 38 9 0.00
Fri 06/19 23Z 7.48 2627 78 46 9 0.00
Sat 06/20 00Z 2.40 2728 81 63 9 0.01
Sat 06/20 01Z 2.13 2728 85 68 8 0.01
Sat 06/20 02Z 1.76 2729 88 69 8 0.01
Sat 06/20 03Z 1.53 2729 89 68 7 0.01
Sat 06/20 04Z 1.32 2729 91 69 7 0.01
Sat 06/20 05Z 1.11 2829 93 74 7 0.01
Sat 06/20 06Z 0.95 2830 95 90 7 0.05
Sat 06/20 07Z 0.89 2830 97 91 7 0.08
Sat 06/20 08Z 0.81 2828 97 92 7 0.08
Sat 06/20 09Z 0.76 2928 97 87 7 0.06
Sat 06/20 10Z 0.76 2929 96 81 7 0.03
Sat 06/20 11Z 0.72 3029 97 77 7 0.02
Sat 06/20 12Z 0.70 3028 97 71 7 0.01
Sat 06/20 13Z 0.68 3025 95 69 7 0.01
Sat 06/20 14Z 0.79 3022 96 70 7 0.01
Sat 06/20 15Z 1.05 2920 97 67 7 0.01
Sat 06/20 16Z 1.09 2920 96 69 8 0.01
Sat 06/20 17Z 0.97 2922 96 72 8 0.03
Sat 06/20 18Z 1.49 2922 95 65 8 0.02
Sat 06/20 19Z 2.17 2921 93 61 8 0.01
Sat 06/20 20Z 1.97 2919 91 60 8 0.00
Sat 06/20 21Z 2.10 2918 90 58 9 0.00
Sat 06/20 22Z 1.43 2918 91 58 9 0.00
Sat 06/20 23Z 0.71 3017 93 59 9 0.00
Sun 06/21 00Z 0.49 3017 95 64 9 0.01
Sun 06/21 01Z 0.40 3117 95 60 9 0.01
Sun 06/21 02Z 0.37 3117 95 59 9 0.01
Sun 06/21 03Z 0.36 3116 96 54 9 0.01
Sun 06/21 04Z 0.32 3115 96 63 8 0.03
Sun 06/21 05Z 0.27 3114 95 72 8 0.05
Sun 06/21 06Z 0.24 3113 96 72 8 0.02
Sun 06/21 07Z 0.27 3112 96 77 8 0.02
Sun 06/21 08Z 0.25 3011 93 72 9 0.01
Sun 06/21 09Z 0.24 3010 92 65 9 0.00
Sun 06/21 10Z 0.25 2910 91 64 9 0.00
Sun 06/21 11Z 0.25 2909 91 65 9 0.00
Sun 06/21 12Z 0.23 2808 89 66 9 0.01
Sun 06/21 13Z 0.24 2708 90 65 9 0.00
Sun 06/21 14Z 0.27 2708 90 59 9 0.00
Sun 06/21 15Z 0.32 2709 90 61 9 0.00
Sun 06/21 16Z 0.40 2809 91 64 9 0.00
Sun 06/21 17Z 0.75 2908 91 69 9 0.00
Sun 06/21 18Z 1.16 2908 91 70 9 0.00
Sun 06/21 19Z 1.34 2908 91 73 9 0.00
Sun 06/21 20Z 0.97 2908 90 76 10 0.00
Sun 06/21 21Z 0.33 3008 80 77 10 0.05
Sun 06/21 22Z 0.26 3007 78 66 10 0.01
Sun 06/21 23Z 0.36 2808 79 65 10 0.00
Run total areal avg QPF for the Central_Greens is: 0.76 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