
A Wind Advisory is in effect for most of northern New York and northwestern Vermont from 8 PM this evening to 8 AM Sunday. South to southeast wind gusts up to 50 mph are expected, with locally higher gusts possible. Strong winds may break limbs or down trees, resulting in isolated power outages. Travel may be difficult for high profile vehicles. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260404_0000
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)
=== ===== === ==== ==== === === === ====
Sat 04/04 00Z 0.99 2437 84 21 10 0.00
Sat 04/04 01Z 1.33 2539 88 16 9 0.00
Sat 04/04 02Z 1.29 2639 96 15 9 0.01
Sat 04/04 03Z 1.36 2738 98 20 7 0.05
Sat 04/04 04Z 1.31 2837 97 21 5 0.04
Sat 04/04 05Z 1.22 2836 96 20 3 0.02
Sat 04/04 06Z 0.92 2933 92 20 2 0.01
Sat 04/04 07Z 0.59 3029 90 18 1 0.01
Sat 04/04 08Z 0.38 3125 89 16 1 0.01
Sat 04/04 09Z 0.23 3223 86 14 1 0.01
Sat 04/04 10Z 0.13 3419 81 12 2 0.00
Sat 04/04 11Z 0.09 3517 77 10 2 0.00
Sat 04/04 12Z 0.10 0115 73 9 3 0.00
Sat 04/04 13Z 0.13 0314 63 8 4 0.00
Sat 04/04 14Z 0.17 0513 56 7 4 0.00
Sat 04/04 15Z 0.19 0712 53 9 4 0.00
Sat 04/04 16Z 0.19 0911 52 15 4 0.00
Sat 04/04 17Z 0.19 1212 56 27 4 0.00
Sat 04/04 18Z 0.20 1314 59 41 4 0.00
Sat 04/04 19Z 0.24 1416 64 63 3 0.00
Sat 04/04 20Z 0.43 1420 67 70 2 0.00
Sat 04/04 21Z 0.58 1422 69 68 2 0.00
Sat 04/04 22Z 0.37 1526 68 73 3 0.00
Sat 04/04 23Z 0.22 1529 65 97 5 0.00
Sun 04/05 00Z 0.15 1632 67 97 5 0.00
Sun 04/05 01Z 0.12 1634 75 93 5 0.00
Sun 04/05 02Z 0.11 1635 79 90 5 0.00
Sun 04/05 03Z 0.08 1736 84 88 6 0.00
Sun 04/05 04Z 0.06 1737 91 88 7 0.01
Sun 04/05 05Z 0.05 1740 95 87 7 0.02
Sun 04/05 06Z 0.04 1843 96 79 8 0.02
Sun 04/05 07Z 0.05 1845 96 90 8 0.02
Sun 04/05 08Z 0.06 1846 96 81 9 0.04
Sun 04/05 09Z 0.09 1845 96 80 9 0.02
Sun 04/05 10Z 0.14 1944 97 89 9 0.04
Sun 04/05 11Z 0.20 1942 97 89 9 0.06
Sun 04/05 12Z 0.32 2039 98 93 7 0.10
Sun 04/05 13Z 0.41 2234 98 98 5 0.11
Sun 04/05 14Z 0.51 2331 98 97 4 0.12
Sun 04/05 15Z 0.63 2430 90 80 3 0.06
Sun 04/05 16Z 0.76 2529 87 39 2 0.01
Sun 04/05 17Z 0.87 2527 91 39 0 0.00
Sun 04/05 18Z 1.07 2526 91 28 0 0.01
Sun 04/05 19Z 2.00 2526 95 21 -1 0.01
Sun 04/05 20Z 3.64 2526 92 24 -2 0.00
Sun 04/05 21Z 7.72 2627 87 16 -2 0.01
Sun 04/05 22Z 9.18 2629 86 20 -4 0.00
Sun 04/05 23Z 3.28 2630 86 24 -5 0.00
Mon 04/06 00Z 2.19 2630 86 28 -5 0.00
Mon 04/06 01Z 2.16 2631 88 35 -6 0.00
Mon 04/06 02Z 1.88 2732 90 43 -7 0.00
Mon 04/06 03Z 1.78 2732 95 59 -8 0.01
Mon 04/06 04Z 1.60 2732 96 67 -8 0.01
Mon 04/06 05Z 1.38 2832 96 69 -8 0.01
Mon 04/06 06Z 1.30 2832 97 67 -8 0.01
Mon 04/06 07Z 1.36 2931 97 65 -8 0.01
Mon 04/06 08Z 1.58 2930 98 50 -9 0.01
Mon 04/06 09Z 1.52 3028 98 43 -10 0.01
Mon 04/06 10Z 1.37 3026 97 34 -10 0.01
Mon 04/06 11Z 1.07 3025 95 21 -10 0.00
Run total areal avg QPF for the greens is: 0.90 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