Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260605_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)
=== ===== === ==== ==== === === === ====
Fri 06/05 00Z 0.83 2813 46 19 14 0.00
Fri 06/05 01Z 0.81 2916 46 18 14 0.00
Fri 06/05 02Z 0.75 2918 45 19 14 0.00
Fri 06/05 03Z 0.68 3019 41 18 13 0.00
Fri 06/05 04Z 0.56 3018 41 16 13 0.00
Fri 06/05 05Z 0.47 3018 47 16 13 0.00
Fri 06/05 06Z 0.44 3118 57 16 13 0.00
Fri 06/05 07Z 0.46 3118 60 13 13 0.00
Fri 06/05 08Z 0.40 3118 56 8 13 0.00
Fri 06/05 09Z 0.37 3116 51 5 13 0.00
Fri 06/05 10Z 0.34 3114 49 5 13 0.00
Fri 06/05 11Z 0.33 3113 48 5 13 0.00
Fri 06/05 12Z 0.31 3112 47 7 13 0.00
Fri 06/05 13Z 0.29 3010 46 11 13 0.00
Fri 06/05 14Z 0.30 3008 46 15 13 0.00
Fri 06/05 15Z 0.56 2907 48 19 13 0.00
Fri 06/05 16Z 2.03 2807 49 20 13 0.00
Fri 06/05 17Z 3.32 2807 49 21 13 0.00
Fri 06/05 18Z 4.26 2707 49 25 13 0.00
Fri 06/05 19Z 4.24 2707 53 31 14 0.00
Fri 06/05 20Z 4.18 2607 59 34 14 0.00
Fri 06/05 21Z 3.41 2508 61 30 14 0.00
Fri 06/05 22Z 1.32 2509 60 25 14 0.00
Fri 06/05 23Z 0.88 2610 57 12 14 0.00
Sat 06/06 00Z 0.90 2610 56 7 14 0.00
Sat 06/06 01Z 0.84 2611 59 7 14 0.00
Sat 06/06 02Z 0.85 2512 65 15 14 0.00
Sat 06/06 03Z 0.85 2512 65 15 14 0.00
Sat 06/06 04Z 0.85 2413 63 8 14 0.00
Sat 06/06 05Z 0.93 2415 61 23 14 0.00
Sat 06/06 06Z 1.15 2317 63 32 14 0.00
Sat 06/06 07Z 1.17 2318 67 33 13 0.00
Sat 06/06 08Z 1.10 2221 69 50 13 0.00
Sat 06/06 09Z 0.98 2221 69 45 13 0.00
Sat 06/06 10Z 0.86 2220 70 46 13 0.00
Sat 06/06 11Z 0.86 2321 74 42 13 0.00
Sat 06/06 12Z 0.86 2320 77 39 13 0.00
Sat 06/06 13Z 0.95 2220 78 70 13 0.00
Sat 06/06 14Z 1.59 2221 82 86 13 0.00
Sat 06/06 15Z 1.88 2123 83 93 13 0.00
Sat 06/06 16Z 4.01 2225 84 95 13 0.01
Sat 06/06 17Z 1.06 2327 95 73 13 0.03
Sat 06/06 18Z 1.21 2326 95 73 14 0.02
Sat 06/06 19Z 1.28 2431 98 69 14 0.09
Sat 06/06 20Z 1.27 2629 96 54 14 0.03
Sat 06/06 21Z 1.18 2625 95 64 13 0.02
Sat 06/06 22Z 1.05 2723 93 69 13 0.01
Sat 06/06 23Z 0.90 2722 90 67 13 0.01
Sun 06/07 00Z 0.84 2722 89 77 14 0.00
Sun 06/07 01Z 0.84 2722 90 86 13 0.00
Sun 06/07 02Z 0.77 2720 94 84 13 0.01
Sun 06/07 03Z 0.70 2821 92 73 13 0.01
Sun 06/07 04Z 0.67 2821 92 59 13 0.00
Sun 06/07 05Z 0.62 2820 92 51 12 0.01
Sun 06/07 06Z 0.54 2919 93 37 12 0.01
Sun 06/07 07Z 0.49 2919 94 36 12 0.01
Sun 06/07 08Z 0.46 3019 95 45 12 0.01
Sun 06/07 09Z 0.50 3019 97 52 11 0.02
Sun 06/07 10Z 0.48 3019 96 56 10 0.02
Sun 06/07 11Z 0.45 3019 96 60 10 0.02
Run total areal avg QPF for the Central_Greens is: 0.34 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