Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260920_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)
=== ===== === ==== ==== === === === ====
Sun 09/20 06Z 0.26 2014 82 20 6 0.00
Sun 09/20 07Z 0.26 2014 85 25 6 0.00
Sun 09/20 08Z 0.20 1914 88 39 7 0.00
Sun 09/20 09Z 0.15 1914 86 74 7 0.00
Sun 09/20 10Z 0.17 1917 90 93 6 0.00
Sun 09/20 11Z 0.19 1918 92 98 6 0.01
Sun 09/20 12Z 0.14 1819 94 99 6 0.02
Sun 09/20 13Z 0.07 1718 94 99 6 0.03
Sun 09/20 14Z 0.05 1717 94 99 6 0.06
Sun 09/20 15Z 0.06 1715 96 99 7 0.07
Sun 09/20 16Z 0.09 1815 98 100 7 0.07
Sun 09/20 17Z 0.11 1815 98 100 7 0.06
Sun 09/20 18Z 0.12 1816 98 99 7 0.05
Sun 09/20 19Z 0.09 1817 98 99 8 0.05
Sun 09/20 20Z 0.09 1818 98 99 8 0.05
Sun 09/20 21Z 0.12 1817 99 93 8 0.06
Sun 09/20 22Z 0.10 1815 98 80 8 0.05
Sun 09/20 23Z 0.10 1812 98 65 8 0.03
Mon 09/21 00Z 0.05 1808 98 46 8 0.02
Mon 09/21 01Z 0.05 1804 99 41 7 0.01
Mon 09/21 02Z 0.03 1801 99 33 7 0.01
Mon 09/21 03Z 0.05 0501 99 37 6 0.00
Mon 09/21 04Z 0.05 0104 98 37 6 0.00
Mon 09/21 05Z 0.08 0108 97 36 6 0.00
Mon 09/21 06Z 0.09 0010 93 22 6 0.00
Mon 09/21 07Z 0.10 0011 88 10 6 0.00
Mon 09/21 08Z 0.11 0013 87 4 6 0.00
Mon 09/21 09Z 0.13 0016 87 2 5 0.00
Mon 09/21 10Z 0.15 0017 87 1 5 0.00
Mon 09/21 11Z 0.18 0118 89 1 4 0.00
Mon 09/21 12Z 0.19 0118 88 2 4 0.00
Mon 09/21 13Z 0.15 0018 84 2 4 0.00
Mon 09/21 14Z 0.13 0016 81 3 4 0.00
Mon 09/21 15Z 0.10 0013 79 2 4 0.00
Mon 09/21 16Z 0.13 0113 73 2 4 0.00
Mon 09/21 17Z 0.13 0112 70 2 4 0.00
Mon 09/21 18Z 0.13 0112 65 1 5 0.00
Mon 09/21 19Z 0.15 0112 58 1 5 0.00
Mon 09/21 20Z 0.15 0211 51 2 5 0.00
Mon 09/21 21Z 0.14 0211 47 2 6 0.00
Mon 09/21 22Z 0.15 0211 44 2 6 0.00
Mon 09/21 23Z 0.18 0312 41 2 6 0.00
Tue 09/22 00Z 0.19 0312 40 2 6 0.00
Tue 09/22 01Z 0.21 0413 38 2 6 0.00
Tue 09/22 02Z 0.22 0412 38 2 6 0.00
Tue 09/22 03Z 0.21 0510 38 2 6 0.00
Tue 09/22 04Z 0.19 0609 41 2 5 0.00
Tue 09/22 05Z 0.17 0807 47 2 4 0.00
Tue 09/22 06Z 0.14 0906 52 2 4 0.00
Tue 09/22 07Z 0.13 1106 56 2 4 0.00
Tue 09/22 08Z 0.11 1206 62 2 3 0.00
Tue 09/22 09Z 0.13 1207 67 2 3 0.00
Tue 09/22 10Z 0.15 1208 70 2 3 0.00
Tue 09/22 11Z 0.14 1207 71 2 3 0.00
Tue 09/22 12Z 0.16 1107 72 2 3 0.00
Tue 09/22 13Z 0.17 0907 71 2 3 0.00
Tue 09/22 14Z 0.19 0807 70 2 3 0.00
Tue 09/22 15Z 0.18 0706 71 3 3 0.00
Tue 09/22 16Z 0.22 0706 74 3 3 0.00
Tue 09/22 17Z 0.29 0606 73 3 2 0.00
Run total areal avg QPF for the Central_Greens is: 0.65 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