Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260610_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)
=== ===== === ==== ==== === === === ====
Wed 06/10 00Z 0.38 2509 73 0 16 0.00
Wed 06/10 01Z 0.48 2512 73 0 16 0.00
Wed 06/10 02Z 0.53 2613 71 0 16 0.00
Wed 06/10 03Z 0.47 2712 68 0 16 0.00
Wed 06/10 04Z 0.45 2812 64 1 16 0.00
Wed 06/10 05Z 0.45 2811 64 2 15 0.00
Wed 06/10 06Z 0.45 2911 67 4 15 0.00
Wed 06/10 07Z 0.42 2810 71 7 15 0.00
Wed 06/10 08Z 0.39 2809 74 14 15 0.00
Wed 06/10 09Z 0.32 2607 78 27 15 0.00
Wed 06/10 10Z 0.29 2407 81 46 15 0.00
Wed 06/10 11Z 0.32 2309 84 75 15 0.00
Wed 06/10 12Z 0.29 2210 89 92 15 0.00
Wed 06/10 13Z 0.29 2211 93 85 15 0.03
Wed 06/10 14Z 0.26 2209 92 80 15 0.01
Wed 06/10 15Z 0.28 2110 89 84 15 0.00
Wed 06/10 16Z 0.30 2009 88 79 16 0.00
Wed 06/10 17Z 0.46 1908 89 79 16 0.00
Wed 06/10 18Z 0.68 1909 87 86 16 0.01
Wed 06/10 19Z 1.56 2110 85 85 16 0.01
Wed 06/10 20Z 1.08 1910 85 91 16 0.00
Wed 06/10 21Z 0.62 1911 88 80 16 0.00
Wed 06/10 22Z 0.42 2014 93 81 16 0.04
Wed 06/10 23Z 0.45 2216 94 76 16 0.12
Thu 06/11 00Z 0.50 2120 97 82 16 0.01
Thu 06/11 01Z 0.47 2119 98 84 16 0.07
Thu 06/11 02Z 0.52 2219 98 81 16 0.29
Thu 06/11 03Z 0.46 2216 93 81 16 0.18
Thu 06/11 04Z 0.57 2320 91 88 16 0.20
Thu 06/11 05Z 0.53 2418 93 89 16 0.08
Thu 06/11 06Z 0.55 2419 96 84 16 0.02
Thu 06/11 07Z 0.55 2518 96 85 16 0.02
Thu 06/11 08Z 0.56 2619 96 88 15 0.02
Thu 06/11 09Z 0.53 2718 96 75 15 0.01
Thu 06/11 10Z 0.52 2718 97 66 15 0.01
Thu 06/11 11Z 0.50 2717 95 59 15 0.01
Thu 06/11 12Z 0.47 2817 94 63 16 0.01
Thu 06/11 13Z 0.47 2816 94 62 15 0.00
Thu 06/11 14Z 0.42 2814 96 57 15 0.01
Thu 06/11 15Z 0.36 2914 96 49 16 0.01
Thu 06/11 16Z 0.26 3012 94 35 16 0.00
Thu 06/11 17Z 0.26 2909 90 36 17 0.00
Thu 06/11 18Z 0.44 2711 90 59 17 0.00
Thu 06/11 19Z 0.52 2712 90 62 17 0.00
Thu 06/11 20Z 0.58 2613 95 78 17 0.00
Thu 06/11 21Z 0.62 2614 97 79 17 0.02
Thu 06/11 22Z 0.74 2718 94 73 17 0.10
Thu 06/11 23Z 0.75 2917 92 68 16 0.03
Fri 06/12 00Z 0.77 2917 92 72 16 0.00
Fri 06/12 01Z 0.61 2815 93 67 16 0.01
Fri 06/12 02Z 0.62 2715 93 69 15 0.00
Fri 06/12 03Z 0.38 2811 92 59 16 0.00
Fri 06/12 04Z 0.39 2812 94 43 16 0.00
Fri 06/12 05Z 0.35 2811 95 42 15 0.00
Fri 06/12 06Z 0.28 2911 97 48 15 0.01
Fri 06/12 07Z 0.23 3009 97 67 15 0.01
Fri 06/12 08Z 0.26 2910 97 84 15 0.01
Fri 06/12 09Z 0.25 2910 98 89 15 0.01
Fri 06/12 10Z 0.29 2911 99 94 15 0.06
Fri 06/12 11Z 0.27 2911 97 91 15 0.03
Run total areal avg QPF for the Central_Greens is: 1.46 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