Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260615_1200
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)
=== ===== === ==== ==== === === === ====
Mon 06/15 12Z 0.41 3218 99 68 7 0.00
Mon 06/15 13Z 0.50 3117 97 53 7 0.01
Mon 06/15 14Z 0.75 3018 97 43 7 0.01
Mon 06/15 15Z 0.69 3017 97 37 7 0.01
Mon 06/15 16Z 0.92 3015 95 40 7 0.01
Mon 06/15 17Z 0.82 3016 96 29 8 0.02
Mon 06/15 18Z 2.30 3116 91 9 7 0.01
Mon 06/15 19Z 3.24 3014 89 5 7 0.00
Mon 06/15 20Z 3.51 3013 87 8 7 0.00
Mon 06/15 21Z 3.05 3013 85 11 7 0.00
Mon 06/15 22Z 1.69 3013 87 13 7 0.00
Mon 06/15 23Z 0.74 3016 93 15 6 0.00
Tue 06/16 00Z 0.69 3018 94 13 6 0.01
Tue 06/16 01Z 0.68 3019 92 11 6 0.00
Tue 06/16 02Z 0.62 3020 92 11 5 0.00
Tue 06/16 03Z 0.53 3021 93 12 5 0.00
Tue 06/16 04Z 0.49 3122 95 10 5 0.00
Tue 06/16 05Z 0.44 3122 95 3 5 0.01
Tue 06/16 06Z 0.42 3122 96 1 4 0.01
Tue 06/16 07Z 0.40 3223 94 2 4 0.00
Tue 06/16 08Z 0.33 3222 88 5 4 0.00
Tue 06/16 09Z 0.25 3221 83 7 5 0.00
Tue 06/16 10Z 0.18 3319 79 8 5 0.00
Tue 06/16 11Z 0.16 3216 76 9 6 0.00
Tue 06/16 12Z 0.18 3214 73 10 6 0.00
Tue 06/16 13Z 0.23 3113 70 11 6 0.00
Tue 06/16 14Z 0.33 3112 67 17 6 0.00
Tue 06/16 15Z 1.26 3011 65 26 6 0.00
Tue 06/16 16Z 3.04 2910 62 33 7 0.00
Tue 06/16 17Z 4.41 2809 63 42 7 0.00
Tue 06/16 18Z 5.51 2709 66 46 8 0.00
Tue 06/16 19Z 6.19 2609 69 44 8 0.00
Tue 06/16 20Z 6.24 2509 72 39 9 0.00
Tue 06/16 21Z 5.35 2410 73 35 9 0.00
Tue 06/16 22Z 2.87 2409 70 27 9 0.00
Tue 06/16 23Z 0.80 2309 63 22 9 0.00
Wed 06/17 00Z 0.65 2311 58 12 9 0.00
Wed 06/17 01Z 0.69 2314 58 6 9 0.00
Wed 06/17 02Z 0.78 2315 62 11 9 0.00
Wed 06/17 03Z 0.76 2416 65 22 9 0.00
Wed 06/17 04Z 0.76 2416 68 23 9 0.00
Wed 06/17 05Z 0.67 2414 71 22 9 0.00
Wed 06/17 06Z 0.63 2313 72 24 8 0.00
Wed 06/17 07Z 0.56 2312 74 19 8 0.00
Wed 06/17 08Z 0.50 2311 75 20 8 0.00
Wed 06/17 09Z 0.44 2210 78 17 8 0.00
Wed 06/17 10Z 0.42 2110 80 14 8 0.00
Wed 06/17 11Z 0.42 2111 82 13 8 0.00
Wed 06/17 12Z 0.48 2011 84 11 7 0.00
Wed 06/17 13Z 1.60 1910 85 7 7 0.00
Wed 06/17 14Z 1.87 1910 85 3 8 0.00
Wed 06/17 15Z 2.08 1910 83 4 8 0.00
Wed 06/17 16Z 1.63 1910 76 8 8 0.00
Wed 06/17 17Z 1.50 1812 75 50 9 0.00
Wed 06/17 18Z 0.66 1812 73 87 9 0.00
Wed 06/17 19Z 0.37 1713 74 93 9 0.00
Wed 06/17 20Z 0.27 1714 79 94 9 0.00
Wed 06/17 21Z 0.21 1714 83 81 10 0.00
Wed 06/17 22Z 0.33 1816 82 53 10 0.00
Wed 06/17 23Z 0.43 1816 87 42 10 0.01
Run total areal avg QPF for the Central_Greens is: 0.11 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