Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260516_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)
=== ===== === ==== ==== === === === ====
Sat 05/16 06Z 0.39 2511 90 50 6 0.00
Sat 05/16 07Z 0.48 2614 87 30 5 0.00
Sat 05/16 08Z 0.47 2714 84 10 5 0.00
Sat 05/16 09Z 0.47 2815 79 3 5 0.00
Sat 05/16 10Z 0.50 2714 75 6 5 0.00
Sat 05/16 11Z 0.59 2717 73 8 5 0.00
Sat 05/16 12Z 0.65 2619 72 28 5 0.00
Sat 05/16 13Z 0.69 2619 69 74 5 0.00
Sat 05/16 14Z 0.74 2519 59 57 6 0.00
Sat 05/16 15Z 0.78 2418 57 50 6 0.00
Sat 05/16 16Z 0.88 2417 53 62 7 0.00
Sat 05/16 17Z 1.11 2315 50 42 8 0.00
Sat 05/16 18Z 1.42 2216 50 30 9 0.00
Sat 05/16 19Z 3.43 2217 57 32 9 0.00
Sat 05/16 20Z 4.89 2219 71 25 9 0.00
Sat 05/16 21Z 2.66 2221 76 14 9 0.00
Sat 05/16 22Z 1.18 2122 74 10 10 0.00
Sat 05/16 23Z 1.00 2126 76 12 10 0.00
Sun 05/17 00Z 0.92 2130 73 74 11 0.00
Sun 05/17 01Z 1.26 2237 80 83 10 0.02
Sun 05/17 02Z 1.21 2340 89 71 10 0.01
Sun 05/17 03Z 1.26 2440 93 80 10 0.05
Sun 05/17 04Z 1.19 2536 94 66 10 0.06
Sun 05/17 05Z 1.08 2732 97 28 9 0.02
Sun 05/17 06Z 1.05 2831 95 3 9 0.01
Sun 05/17 07Z 0.77 2930 81 4 10 0.01
Sun 05/17 08Z 0.68 2931 68 5 9 0.00
Sun 05/17 09Z 0.75 2933 63 8 9 0.00
Sun 05/17 10Z 0.73 2936 47 7 9 0.00
Sun 05/17 11Z 0.68 3036 46 20 9 0.00
Sun 05/17 12Z 0.65 3033 52 17 8 0.00
Sun 05/17 13Z 0.61 3031 55 52 8 0.00
Sun 05/17 14Z 0.76 3030 61 61 7 0.00
Sun 05/17 15Z 0.90 3028 66 61 7 0.00
Sun 05/17 16Z 1.31 2927 70 66 7 0.00
Sun 05/17 17Z 5.01 2926 74 57 6 0.00
Sun 05/17 18Z 5.38 2923 73 34 6 0.00
Sun 05/17 19Z 5.81 2921 73 29 7 0.00
Sun 05/17 20Z 5.11 2919 74 25 7 0.00
Sun 05/17 21Z 4.15 2917 76 25 7 0.00
Sun 05/17 22Z 1.01 2917 75 21 7 0.00
Sun 05/17 23Z 0.67 3017 75 20 7 0.00
Mon 05/18 00Z 0.51 3017 76 16 7 0.00
Mon 05/18 01Z 0.45 3117 77 12 7 0.00
Mon 05/18 02Z 0.37 3117 73 11 7 0.00
Mon 05/18 03Z 0.31 3015 68 13 8 0.00
Mon 05/18 04Z 0.28 3014 62 18 8 0.00
Mon 05/18 05Z 0.25 2912 57 29 9 0.00
Mon 05/18 06Z 0.23 2911 51 41 10 0.00
Mon 05/18 07Z 0.22 2810 46 21 10 0.00
Mon 05/18 08Z 0.24 2710 44 30 11 0.00
Mon 05/18 09Z 0.21 2809 44 30 11 0.00
Mon 05/18 10Z 0.17 2708 43 28 12 0.00
Mon 05/18 11Z 0.17 2508 40 27 12 0.00
Mon 05/18 12Z 0.23 2311 44 19 13 0.00
Mon 05/18 13Z 0.29 2214 62 24 12 0.00
Mon 05/18 14Z 0.32 2217 84 36 12 0.00
Mon 05/18 15Z 0.41 2221 91 52 12 0.00
Mon 05/18 16Z 0.48 2222 92 55 13 0.00
Mon 05/18 17Z 0.53 2321 90 50 13 0.00
Run total areal avg QPF for the Central_Greens is: 0.18 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