Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260328_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 03/28 06Z 0.17 3312 80 13 -15 0.00
Sat 03/28 07Z 0.27 3214 79 17 -15 0.00
Sat 03/28 08Z 0.31 3213 79 18 -16 0.00
Sat 03/28 09Z 0.44 3213 82 37 -16 0.00
Sat 03/28 10Z 0.55 3214 85 46 -17 0.00
Sat 03/28 11Z 0.49 3214 86 56 -17 0.00
Sat 03/28 12Z 0.52 3111 86 62 -17 0.00
Sat 03/28 13Z 1.36 3110 84 59 -17 0.00
Sat 03/28 14Z 2.44 3009 79 59 -16 0.00
Sat 03/28 15Z 3.33 3009 73 57 -16 0.00
Sat 03/28 16Z 4.71 2910 71 56 -15 0.00
Sat 03/28 17Z 7.14 2711 72 60 -15 0.00
Sat 03/28 18Z 8.98 2613 71 66 -14 0.00
Sat 03/28 19Z 9.68 2715 72 71 -13 0.00
Sat 03/28 20Z 7.47 2718 78 68 -13 0.00
Sat 03/28 21Z 11.15 2819 67 49 -13 0.00
Sat 03/28 22Z 8.54 2819 71 60 -13 0.00
Sat 03/28 23Z 3.91 2720 82 56 -14 0.00
Sun 03/29 00Z 5.16 2825 83 55 -14 0.01
Sun 03/29 01Z 4.17 2926 75 41 -14 0.00
Sun 03/29 02Z 1.93 2824 71 24 -14 0.00
Sun 03/29 03Z 1.82 2823 70 10 -14 0.00
Sun 03/29 04Z 1.68 2823 77 21 -14 0.00
Sun 03/29 05Z 1.52 2824 85 63 -14 0.00
Sun 03/29 06Z 1.32 2823 88 76 -14 0.00
Sun 03/29 07Z 1.21 2823 90 73 -14 0.00
Sun 03/29 08Z 1.10 2823 91 78 -14 0.00
Sun 03/29 09Z 1.01 2822 92 74 -13 0.00
Sun 03/29 10Z 0.93 2722 92 74 -13 0.00
Sun 03/29 11Z 0.78 2720 92 70 -12 0.00
Sun 03/29 12Z 0.75 2621 91 77 -12 0.00
Sun 03/29 13Z 0.75 2621 85 80 -11 0.00
Sun 03/29 14Z 0.77 2621 84 77 -10 0.00
Sun 03/29 15Z 0.90 2619 78 78 -9 0.00
Sun 03/29 16Z 0.92 2418 66 85 -8 0.00
Sun 03/29 17Z 1.56 2320 58 89 -8 0.00
Sun 03/29 18Z 1.64 2321 55 79 -7 0.00
Sun 03/29 19Z 2.89 2323 54 76 -7 0.00
Sun 03/29 20Z 3.45 2324 54 56 -6 0.00
Sun 03/29 21Z 1.75 2325 56 74 -5 0.00
Sun 03/29 22Z 1.37 2427 56 43 -4 0.00
Sun 03/29 23Z 1.42 2429 55 24 -4 0.00
Mon 03/30 00Z 1.40 2430 53 9 -3 0.00
Mon 03/30 01Z 1.42 2430 52 6 -3 0.00
Mon 03/30 02Z 1.61 2532 51 9 -2 0.00
Mon 03/30 03Z 1.68 2532 55 16 -2 0.00
Mon 03/30 04Z 1.29 2529 54 48 -2 0.00
Mon 03/30 05Z 1.15 2528 59 84 -2 0.00
Mon 03/30 06Z 0.95 2428 69 82 -1 0.00
Mon 03/30 07Z 0.92 2526 66 85 -1 0.00
Mon 03/30 08Z 0.81 2426 77 61 -1 0.00
Mon 03/30 09Z 0.79 2426 82 56 -2 0.00
Mon 03/30 10Z 0.81 2526 84 68 -2 0.00
Mon 03/30 11Z 0.85 2526 84 84 -2 0.00
Mon 03/30 12Z 0.84 2525 80 93 -2 0.00
Mon 03/30 13Z 0.85 2526 84 88 -2 0.00
Mon 03/30 14Z 0.91 2526 82 70 -1 0.00
Mon 03/30 15Z 0.90 2525 67 75 0 0.00
Mon 03/30 16Z 1.04 2526 69 81 0 0.00
Mon 03/30 17Z 1.19 2525 68 78 0 0.00
Run total areal avg QPF for the Central_Greens is: 0.01 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