
Additional river rises are expected with minor and localized ice jam flooding possible late tonight into Thursday. Also, minor open water flooding is forecasted on the Ausable River and Otter Creek, with Action Stage possible on the Lamoille, Winooski and Missisquoi Rivers on Thursday. The threat for flooding ends by Thursday night. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260311_1800
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)
=== ===== === ==== ==== === === === ====
Wed 03/11 18Z 0.15 1832 75 84 11 0.00
Wed 03/11 19Z 0.19 1834 75 75 11 0.00
Wed 03/11 20Z 0.22 1835 77 90 12 0.00
Wed 03/11 21Z 0.26 1936 80 88 11 0.00
Wed 03/11 22Z 0.24 1838 93 90 11 0.03
Wed 03/11 23Z 0.36 1940 97 86 11 0.04
Thu 03/12 00Z 0.58 2142 99 95 11 0.09
Thu 03/12 01Z 0.84 2239 98 94 11 0.08
Thu 03/12 02Z 0.91 2239 98 93 11 0.09
Thu 03/12 03Z 0.94 2237 96 91 11 0.07
Thu 03/12 04Z 0.83 2233 97 82 11 0.10
Thu 03/12 05Z 1.05 2333 97 79 10 0.10
Thu 03/12 06Z 0.83 2327 96 79 10 0.06
Thu 03/12 07Z 0.92 2330 95 95 9 0.05
Thu 03/12 08Z 0.90 2330 96 85 9 0.08
Thu 03/12 09Z 1.37 2632 97 79 5 0.08
Thu 03/12 10Z 0.99 2632 93 55 1 0.04
Thu 03/12 11Z 0.94 2732 90 58 -2 0.01
Thu 03/12 12Z 0.85 2730 91 47 -4 0.00
Thu 03/12 13Z 1.00 2730 92 28 -7 0.00
Thu 03/12 14Z 1.07 2828 91 20 -8 0.00
Thu 03/12 15Z 1.15 2827 91 32 -9 0.00
Thu 03/12 16Z 1.65 2826 90 19 -10 0.00
Thu 03/12 17Z 2.51 2824 90 11 -10 0.00
Thu 03/12 18Z 1.94 2822 88 12 -10 0.00
Thu 03/12 19Z 2.17 2821 88 11 -11 0.00
Thu 03/12 20Z 2.32 2920 88 23 -11 0.00
Thu 03/12 21Z 1.84 2919 87 25 -11 0.00
Thu 03/12 22Z 1.91 2921 88 36 -12 0.00
Thu 03/12 23Z 1.22 2922 88 43 -12 0.00
Fri 03/13 00Z 1.16 2923 90 51 -12 0.00
Fri 03/13 01Z 1.30 2925 91 55 -12 0.00
Fri 03/13 02Z 1.17 2925 92 63 -12 0.00
Fri 03/13 03Z 1.04 2924 94 64 -12 0.00
Fri 03/13 04Z 1.05 2923 96 65 -12 0.00
Fri 03/13 05Z 1.05 2921 97 60 -13 0.00
Fri 03/13 06Z 1.18 2922 96 61 -13 0.00
Fri 03/13 07Z 1.06 2921 95 57 -13 0.00
Fri 03/13 08Z 1.00 2922 93 51 -12 0.00
Fri 03/13 09Z 0.75 2818 92 36 -12 0.00
Fri 03/13 10Z 0.49 2814 90 10 -12 0.00
Fri 03/13 11Z 0.53 2715 89 5 -12 0.00
Fri 03/13 12Z 0.27 2609 80 4 -10 0.00
Fri 03/13 13Z 0.26 2409 73 4 -10 0.00
Fri 03/13 14Z 0.13 2008 57 12 -9 0.00
Fri 03/13 15Z 0.11 1812 49 37 -8 0.00
Fri 03/13 16Z 0.26 1916 49 86 -8 0.00
Fri 03/13 17Z 0.41 1919 49 86 -8 0.00
Fri 03/13 18Z 2.82 1822 70 90 -10 0.00
Fri 03/13 19Z 0.14 1730 93 88 -9 0.04
Fri 03/13 20Z 0.24 1833 92 92 -9 0.05
Fri 03/13 21Z 0.43 1833 94 88 -9 0.02
Fri 03/13 22Z 0.50 1933 93 90 -8 0.01
Fri 03/13 23Z 0.53 1933 93 86 -7 0.00
Sat 03/14 00Z 0.52 1933 92 80 -6 0.00
Sat 03/14 01Z 0.43 1933 90 88 -5 0.00
Sat 03/14 02Z 0.61 2034 93 77 -5 0.01
Sat 03/14 03Z 0.91 2136 95 33 -5 0.02
Sat 03/14 04Z 1.18 2335 97 12 -6 0.01
Sat 03/14 05Z 1.79 2433 97 7 -8 0.02
Run total areal avg QPF for the Central_Greens is: 1.10 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