
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 greens
Model run: BTV_GRID_D2D_NAM3_20260311_1200
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.
925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date Time Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Wed 03/11 12Z 0.11 1625 84 84 8 0.00
Wed 03/11 13Z 0.11 1630 86 83 9 0.00
Wed 03/11 14Z 0.06 1733 85 72 10 0.00
Wed 03/11 15Z 0.04 1735 83 85 10 0.00
Wed 03/11 16Z 0.04 1836 85 92 10 0.02
Wed 03/11 17Z 0.10 1836 84 90 10 0.02
Wed 03/11 18Z 0.15 1937 82 69 11 0.00
Wed 03/11 19Z 0.19 1938 80 58 12 0.00
Wed 03/11 20Z 0.20 1936 80 75 12 0.00
Wed 03/11 21Z 0.22 1939 83 92 12 0.00
Wed 03/11 22Z 0.27 2041 90 88 11 0.01
Wed 03/11 23Z 0.35 2042 93 79 11 0.00
Thu 03/12 00Z 0.42 2043 94 85 11 0.01
Thu 03/12 02Z 0.53 2141 94 91 12 0.02
Thu 03/12 03Z 0.64 2139 97 83 10 0.03
Thu 03/12 04Z 0.84 2334 95 91 10 0.10
Thu 03/12 05Z 0.65 2327 88 78 10 0.11
Thu 03/12 06Z 0.70 2327 94 75 8 0.11
Thu 03/12 07Z 0.82 2328 97 67 8 0.00
Thu 03/12 08Z 0.97 2329 98 87 7 0.02
Thu 03/12 09Z 1.58 2633 98 91 3 0.04
Thu 03/12 10Z 1.03 2634 94 63 0 0.12
Thu 03/12 11Z 0.94 2732 90 54 -3 0.06
Thu 03/12 12Z 1.03 2732 91 36 -6 0.01
Thu 03/12 14Z 1.23 2730 91 4 -9 0.00
Thu 03/12 15Z 1.42 2728 91 9 -10 0.00
Thu 03/12 16Z 2.03 2728 93 3 -11 0.00
Thu 03/12 17Z 3.59 2827 93 2 -11 0.00
Thu 03/12 18Z 4.40 2827 91 11 -12 0.00
Thu 03/12 19Z 3.48 2924 89 24 -12 0.00
Thu 03/12 20Z 3.17 2923 88 20 -12 0.00
Thu 03/12 21Z 2.69 2922 88 28 -13 0.00
Thu 03/12 22Z 1.48 2921 88 36 -13 0.00
Thu 03/12 23Z 1.23 2922 89 41 -13 0.00
Fri 03/13 00Z 1.36 2924 90 50 -13 0.00
Fri 03/13 01Z 1.51 2925 92 55 -13 0.00
Fri 03/13 02Z 1.45 2925 92 55 -13 0.00
Fri 03/13 03Z 1.29 2924 93 55 -13 0.00
Fri 03/13 04Z 1.18 2924 94 53 -13 0.00
Fri 03/13 05Z 1.17 2924 94 54 -13 0.00
Fri 03/13 06Z 1.07 2922 93 50 -13 0.00
Fri 03/13 07Z 0.95 2921 94 40 -13 0.00
Fri 03/13 08Z 0.83 2918 93 30 -13 0.00
Fri 03/13 09Z 0.63 2815 92 16 -12 0.00
Fri 03/13 10Z 0.62 2716 91 8 -12 0.00
Fri 03/13 11Z 0.43 2613 86 4 -11 0.00
Fri 03/13 12Z 0.28 2510 79 3 -11 0.00
Fri 03/13 13Z 0.13 2108 71 7 -10 0.00
Fri 03/13 14Z 0.11 1911 64 11 -10 0.00
Fri 03/13 15Z 0.06 1814 54 21 -9 0.00
Fri 03/13 16Z 0.11 1916 50 54 -8 0.00
Fri 03/13 17Z 0.23 1919 52 86 -8 0.00
Fri 03/13 18Z 0.32 1822 60 89 -9 0.00
Fri 03/13 19Z 0.15 1725 92 88 -9 0.01
Fri 03/13 21Z 0.20 1832 94 88 -8 0.01
Fri 03/13 22Z 0.28 1931 93 81 -8 0.02
Fri 03/13 23Z 0.35 1931 92 91 -7 0.06
Run total areal avg QPF for the greens is: 0.78 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