
A High Wind Warning remains in effect for the Adirondacks and their northern slopes, with Wind Advisories for the rest of the area through 11 AM Tue. Isolated to scattered power outages and difficult travel are possible. South winds 25 to 35 mph with gusts up to 60 mph anticipated. Sharply colder temperatures will arrive tonight, with light snowfall accumulations possible. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260317_0600
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)
=== ===== === ==== ==== === === === ====
Tue 03/17 06Z 0.34 2021 98 98 5 0.00
Tue 03/17 07Z 1.80 2631 97 92 -3 0.11
Tue 03/17 08Z 1.37 2633 95 95 -6 0.05
Tue 03/17 09Z 1.09 2530 92 88 -7 0.02
Tue 03/17 10Z 2.24 2432 92 36 -9 0.00
Tue 03/17 11Z 7.01 2533 86 27 -11 0.00
Tue 03/17 12Z 10.22 2433 78 28 -12 0.00
Tue 03/17 13Z 14.36 2535 74 23 -13 0.00
Tue 03/17 14Z 20.03 2533 75 19 -15 0.00
Tue 03/17 15Z 19.92 2531 76 17 -15 0.00
Tue 03/17 16Z 18.49 2529 78 18 -15 0.00
Tue 03/17 17Z 17.15 2428 77 23 -15 0.00
Tue 03/17 18Z 17.88 2528 73 25 -15 0.00
Tue 03/17 19Z 18.95 2528 70 31 -15 0.00
Tue 03/17 20Z 18.90 2628 72 35 -15 0.00
Tue 03/17 21Z 16.79 2627 75 39 -15 0.00
Tue 03/17 22Z 13.33 2626 77 46 -16 0.00
Tue 03/17 23Z 12.63 2727 78 52 -17 0.00
Wed 03/18 00Z 10.07 2726 82 48 -18 0.00
Wed 03/18 01Z 7.32 2824 88 42 -18 0.00
Wed 03/18 02Z 5.18 2823 85 46 -19 0.00
Wed 03/18 03Z 3.10 2822 85 54 -19 0.00
Wed 03/18 04Z 2.49 2823 86 54 -19 0.00
Wed 03/18 05Z 2.67 2823 84 41 -19 0.00
Wed 03/18 06Z 2.21 2823 83 26 -19 0.00
Wed 03/18 07Z 1.75 2823 82 16 -19 0.00
Wed 03/18 08Z 1.42 2823 79 10 -19 0.00
Wed 03/18 09Z 1.16 2823 73 7 -19 0.00
Wed 03/18 10Z 0.99 2822 71 6 -19 0.00
Wed 03/18 11Z 0.78 2920 69 5 -20 0.00
Wed 03/18 12Z 0.59 2917 65 5 -19 0.00
Wed 03/18 13Z 0.53 2916 63 6 -19 0.00
Wed 03/18 14Z 0.46 2914 56 7 -18 0.00
Wed 03/18 15Z 0.41 2811 49 8 -18 0.00
Wed 03/18 16Z 0.42 2809 44 8 -17 0.00
Wed 03/18 17Z 0.72 2707 40 9 -16 0.00
Wed 03/18 18Z 0.84 2606 37 9 -16 0.00
Wed 03/18 19Z 0.82 2505 35 9 -15 0.00
Wed 03/18 20Z 0.74 2404 36 9 -14 0.00
Wed 03/18 21Z 0.34 2104 36 8 -13 0.00
Wed 03/18 22Z 0.15 1906 37 8 -13 0.00
Wed 03/18 23Z 0.09 1810 38 7 -13 0.00
Thu 03/19 00Z 0.10 1813 39 9 -12 0.00
Thu 03/19 01Z 0.18 1916 38 12 -12 0.00
Thu 03/19 02Z 0.28 2017 38 23 -12 0.00
Thu 03/19 03Z 0.34 2019 42 39 -12 0.00
Thu 03/19 04Z 0.45 2020 48 71 -11 0.00
Thu 03/19 05Z 0.49 2121 53 88 -11 0.00
Thu 03/19 06Z 0.49 2121 58 87 -11 0.00
Thu 03/19 09Z 0.52 2121 66 87 -10 0.00
Thu 03/19 10Z 0.48 2121 73 86 -11 0.00
Thu 03/19 11Z 0.41 2121 79 89 -10 0.00
Thu 03/19 12Z 0.34 2022 83 88 -10 0.00
Thu 03/19 13Z 0.32 2022 86 90 -9 0.00
Thu 03/19 14Z 0.32 2021 88 89 -9 0.00
Thu 03/19 15Z 0.34 2020 87 81 -9 0.00
Thu 03/19 16Z 0.58 2018 84 69 -8 0.00
Thu 03/19 17Z 0.91 2018 80 47 -8 0.00
Run total areal avg QPF for the greens is: 0.18 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