
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_20260316_1800
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)
=== ===== === ==== ==== === === === ====
Mon 03/16 18Z 0.04 1832 92 87 8 0.00
Mon 03/16 19Z 0.06 1835 95 79 9 0.02
Mon 03/16 20Z 0.07 1840 97 79 10 0.05
Mon 03/16 21Z 0.11 1844 96 91 10 0.04
Mon 03/16 22Z 0.09 1846 95 86 10 0.02
Mon 03/16 23Z 0.10 1848 94 85 11 0.01
Tue 03/17 00Z 0.06 1845 95 82 11 0.01
Tue 03/17 01Z 0.04 1741 95 89 10 0.05
Tue 03/17 02Z 0.05 1741 92 80 10 0.03
Tue 03/17 03Z 0.06 1744 95 82 10 0.01
Tue 03/17 07Z 0.97 2530 97 97 -3 0.01
Tue 03/17 08Z 1.22 2532 94 90 -5 0.02
Tue 03/17 10Z 5.36 2433 91 4 -10 0.11
Tue 03/17 11Z 8.85 2535 83 11 -12 0.06
Tue 03/17 12Z 6.32 2437 65 16 -13 0.05
Tue 03/17 14Z 20.49 2433 75 14 -15 0.01
Tue 03/17 15Z 18.96 2431 71 13 -16 0.01
Tue 03/17 16Z 20.28 2531 70 15 -16 0.00
Tue 03/17 17Z 19.53 2529 71 17 -16 0.00
Tue 03/17 18Z 18.12 2428 73 21 -16 0.00
Tue 03/17 19Z 17.93 2528 74 36 -16 0.00
Tue 03/17 20Z 18.29 2528 73 47 -16 0.00
Tue 03/17 21Z 18.45 2628 75 48 -17 0.00
Tue 03/17 22Z 15.51 2627 80 51 -17 0.00
Tue 03/17 23Z 11.09 2726 84 50 -18 0.00
Wed 03/18 00Z 8.60 2726 87 47 -19 0.00
Wed 03/18 01Z 5.84 2724 86 52 -19 0.00
Wed 03/18 02Z 4.11 2724 86 52 -19 0.00
Wed 03/18 03Z 3.33 2823 82 54 -18 0.00
Wed 03/18 04Z 2.77 2722 82 57 -18 0.00
Wed 03/18 05Z 2.36 2722 82 60 -18 0.00
Wed 03/18 06Z 2.23 2722 82 42 -18 0.00
Wed 03/18 07Z 1.89 2723 81 28 -18 0.00
Wed 03/18 08Z 1.78 2723 78 16 -19 0.00
Wed 03/18 09Z 1.51 2823 76 10 -19 0.00
Wed 03/18 10Z 1.10 2822 76 7 -19 0.00
Wed 03/18 11Z 0.80 2920 75 5 -19 0.00
Wed 03/18 12Z 0.60 2917 73 4 -19 0.00
Wed 03/18 13Z 0.50 2915 68 5 -19 0.00
Wed 03/18 14Z 0.48 2812 63 5 -18 0.00
Wed 03/18 15Z 0.46 2710 57 6 -18 0.00
Wed 03/18 16Z 0.63 2608 51 7 -17 0.00
Wed 03/18 17Z 1.07 2506 47 8 -16 0.00
Wed 03/18 18Z 1.19 2505 43 8 -16 0.00
Wed 03/18 19Z 1.06 2405 41 8 -15 0.00
Wed 03/18 20Z 0.68 2204 40 7 -14 0.00
Wed 03/18 21Z 0.45 2106 41 8 -13 0.00
Wed 03/18 22Z 0.18 1907 42 7 -13 0.00
Wed 03/18 23Z 0.11 1911 42 9 -12 0.00
Thu 03/19 00Z 0.13 1914 42 15 -12 0.00
Thu 03/19 01Z 0.18 1916 39 25 -12 0.00
Thu 03/19 02Z 0.27 1919 41 51 -11 0.00
Thu 03/19 03Z 0.36 2022 46 84 -11 0.00
Thu 03/19 04Z 0.51 2023 55 90 -11 0.00
Thu 03/19 05Z 0.54 2123 59 86 -11 0.00
Run total areal avg QPF for the greens is: 0.51 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