Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260914_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 09/14 12Z 0.52 3125 92 24 4 0.00
Mon 09/14 13Z 0.40 3228 91 16 5 0.00
Mon 09/14 14Z 0.30 3226 85 15 5 0.00
Mon 09/14 15Z 0.32 3225 82 13 5 0.00
Mon 09/14 16Z 0.41 3223 76 8 4 0.00
Mon 09/14 17Z 1.10 3221 72 6 4 0.00
Mon 09/14 18Z 3.11 3219 73 9 4 0.00
Mon 09/14 19Z 3.97 3219 74 15 4 0.00
Mon 09/14 20Z 3.96 3219 77 18 4 0.00
Mon 09/14 21Z 2.63 3219 81 17 4 0.00
Mon 09/14 22Z 1.04 3219 82 16 3 0.00
Mon 09/14 23Z 0.54 3220 83 15 3 0.00
Tue 09/15 00Z 0.52 3222 83 16 3 0.00
Tue 09/15 01Z 0.25 3321 81 14 4 0.00
Tue 09/15 02Z 0.11 3319 76 11 5 0.00
Tue 09/15 03Z 0.06 3418 69 9 6 0.00
Tue 09/15 04Z 0.03 3515 61 7 6 0.00
Tue 09/15 05Z 0.08 0013 58 7 7 0.00
Tue 09/15 06Z 0.08 0109 55 7 7 0.00
Tue 09/15 07Z 0.04 0006 51 8 8 0.00
Tue 09/15 08Z 0.01 3404 50 8 8 0.00
Tue 09/15 09Z 0.02 0301 48 9 8 0.00
Tue 09/15 10Z 0.02 1201 46 10 8 0.00
Tue 09/15 11Z 0.03 2002 47 10 7 0.00
Tue 09/15 12Z 0.02 1604 46 11 7 0.00
Tue 09/15 13Z 0.06 1905 48 12 7 0.00
Tue 09/15 14Z 0.08 2005 48 13 8 0.00
Tue 09/15 15Z 0.09 2105 50 14 8 0.00
Tue 09/15 16Z 0.09 2006 49 15 9 0.00
Tue 09/15 17Z 0.06 1907 47 16 10 0.00
Tue 09/15 18Z 0.08 1810 47 15 11 0.00
Tue 09/15 19Z 0.12 1911 51 28 11 0.00
Tue 09/15 20Z 0.15 1912 48 42 11 0.00
Tue 09/15 21Z 0.18 2014 43 22 12 0.00
Tue 09/15 22Z 0.20 2016 37 22 13 0.00
Tue 09/15 23Z 0.22 2018 31 67 14 0.00
Wed 09/16 00Z 0.24 2020 25 88 15 0.00
Wed 09/16 01Z 0.26 2022 23 84 16 0.00
Wed 09/16 02Z 0.31 2123 26 84 16 0.00
Wed 09/16 03Z 0.34 2224 29 84 16 0.00
Wed 09/16 04Z 0.40 2224 33 86 16 0.00
Wed 09/16 05Z 0.40 2323 37 84 16 0.00
Wed 09/16 06Z 0.42 2423 37 84 16 0.00
Wed 09/16 07Z 0.50 2425 38 85 15 0.00
Wed 09/16 08Z 0.52 2525 47 87 15 0.00
Wed 09/16 09Z 0.50 2524 57 91 15 0.00
Wed 09/16 10Z 0.45 2621 63 92 15 0.00
Wed 09/16 11Z 0.43 2720 73 87 15 0.00
Wed 09/16 12Z 0.41 2718 83 85 15 0.00
Wed 09/16 13Z 0.38 2717 89 70 14 0.00
Wed 09/16 14Z 0.33 2815 92 57 14 0.00
Wed 09/16 15Z 0.28 2813 94 52 14 0.00
Wed 09/16 16Z 0.25 2811 95 42 14 0.00
Wed 09/16 17Z 0.25 2911 96 46 14 0.00
Wed 09/16 18Z 0.23 2910 92 24 13 0.00
Wed 09/16 19Z 0.21 3009 92 11 13 0.00
Wed 09/16 20Z 0.19 3008 91 10 13 0.00
Wed 09/16 21Z 0.16 3109 88 11 13 0.00
Wed 09/16 22Z 0.12 3108 85 13 13 0.00
Wed 09/16 23Z 0.10 3207 84 12 13 0.00
Run total areal avg QPF for the Central_Greens is: 0.00 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