Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260127_0600
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)
=== ===== === ==== ==== === === === ====
Tue 01/27 06Z 0.51 3022 85 68 -21 0.00
Tue 01/27 07Z 0.55 3025 89 60 -21 0.00
Tue 01/27 08Z 0.59 3027 84 52 -21 0.00
Tue 01/27 09Z 0.57 3028 81 43 -20 0.00
Tue 01/27 10Z 0.49 3027 76 29 -20 0.00
Tue 01/27 11Z 0.47 3028 77 30 -20 0.00
Tue 01/27 12Z 0.44 3028 72 41 -19 0.00
Tue 01/27 13Z 0.43 3025 71 42 -19 0.00
Tue 01/27 14Z 0.43 2820 71 52 -19 0.00
Tue 01/27 15Z 0.51 2718 81 72 -19 0.00
Tue 01/27 16Z 0.57 2616 84 78 -19 0.00
Tue 01/27 17Z 0.53 2515 83 80 -18 0.01
Tue 01/27 18Z 0.49 2413 80 81 -18 0.01
Tue 01/27 19Z 0.50 2312 84 82 -18 0.01
Tue 01/27 20Z 2.20 2313 85 81 -19 0.00
Tue 01/27 21Z 1.29 2216 86 81 -19 0.01
Tue 01/27 22Z 1.68 2318 89 79 -19 0.01
Tue 01/27 23Z 2.28 2522 91 75 -20 0.01
Wed 01/28 00Z 1.56 2623 82 71 -20 0.00
Wed 01/28 01Z 1.28 2722 77 69 -20 0.00
Wed 01/28 02Z 0.84 2721 76 70 -20 0.00
Wed 01/28 03Z 0.79 2721 83 71 -19 0.00
Wed 01/28 04Z 0.78 2721 86 70 -19 0.00
Wed 01/28 05Z 0.77 2821 87 71 -20 0.01
Wed 01/28 06Z 0.74 2820 87 68 -20 0.01
Wed 01/28 07Z 0.71 2921 88 64 -20 0.00
Wed 01/28 08Z 0.68 2921 89 61 -20 0.00
Wed 01/28 09Z 0.62 2921 89 56 -20 0.00
Wed 01/28 10Z 0.52 3020 88 53 -20 0.00
Wed 01/28 11Z 0.42 3019 88 44 -20 0.00
Wed 01/28 12Z 0.43 3019 90 37 -20 0.00
Wed 01/28 13Z 0.39 3018 87 29 -20 0.00
Wed 01/28 14Z 0.34 3015 83 29 -20 0.00
Wed 01/28 15Z 0.37 2912 81 32 -20 0.00
Wed 01/28 16Z 0.44 2810 80 32 -19 0.00
Wed 01/28 17Z 0.87 2707 77 33 -19 0.00
Wed 01/28 18Z 2.32 2707 76 36 -19 0.00
Wed 01/28 19Z 4.20 2708 77 38 -19 0.00
Wed 01/28 20Z 2.78 2808 77 41 -19 0.00
Wed 01/28 21Z 0.83 2807 80 41 -19 0.00
Wed 01/28 22Z 0.54 2708 86 43 -19 0.00
Wed 01/28 23Z 0.56 2609 91 43 -19 0.00
Thu 01/29 00Z 0.56 2710 92 48 -19 0.00
Thu 01/29 01Z 0.51 2910 90 62 -19 0.00
Thu 01/29 02Z 0.41 3011 86 75 -19 0.00
Thu 01/29 03Z 0.35 3111 85 79 -19 0.00
Thu 01/29 04Z 0.34 3112 84 79 -19 0.00
Thu 01/29 05Z 0.37 3113 85 79 -19 0.01
Thu 01/29 06Z 0.43 3113 87 78 -20 0.01
Thu 01/29 07Z 0.42 3114 89 77 -20 0.00
Thu 01/29 08Z 0.38 3115 90 75 -20 0.00
Thu 01/29 09Z 0.37 3217 92 74 -20 0.00
Thu 01/29 10Z 0.41 3117 93 70 -20 0.00
Thu 01/29 11Z 0.41 3117 92 68 -20 0.00
Thu 01/29 12Z 0.38 3116 91 67 -19 0.00
Thu 01/29 13Z 0.36 3115 92 70 -19 0.00
Thu 01/29 14Z 0.38 3014 91 70 -19 0.00
Thu 01/29 15Z 0.41 3013 91 68 -19 0.00
Thu 01/29 16Z 0.53 3013 89 64 -19 0.00
Thu 01/29 17Z 1.51 3014 88 61 -19 0.00
Run total areal avg QPF for the Central_Greens is: 0.10 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