
Snow accumulations between 3 and 6 inches are expected across much of the area from 10 AM today to 7 AM Wednesday. Some locally higher amounts are expected in the northern Adirondacks. The heaviest snowfall rates are anticipated during this evening's commute. Plan on slippery road conditions. Roads, especially bridges and overpasses, will become slick. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260210_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)
=== ===== === ==== ==== === === === ====
Tue 02/10 12Z 0.10 3005 60 79 -6 0.00
Tue 02/10 13Z 0.11 2805 62 71 -6 0.00
Tue 02/10 14Z 0.12 2805 63 65 -6 0.00
Tue 02/10 15Z 0.11 2605 62 65 -6 0.00
Tue 02/10 16Z 0.09 2205 59 60 -6 0.00
Tue 02/10 17Z 0.08 2007 55 57 -5 0.00
Tue 02/10 20Z 0.16 2015 43 93 -5 0.00
Tue 02/10 21Z 0.09 1818 64 93 -6 0.00
Tue 02/10 22Z 0.05 1820 91 94 -5 0.00
Tue 02/10 23Z 0.02 1823 95 95 -3 0.00
Wed 02/11 00Z 0.09 1826 95 94 -3 0.01
Wed 02/11 02Z 0.29 2125 95 96 -5 0.06
Wed 02/11 03Z 0.34 2224 96 97 -5 0.07
Wed 02/11 04Z 0.36 2321 97 96 -4 0.08
Wed 02/11 05Z 0.37 2419 97 95 -5 0.09
Wed 02/11 06Z 0.41 2517 98 73 -5 0.07
Wed 02/11 07Z 0.41 2616 98 46 -6 0.05
Wed 02/11 08Z 0.43 2615 97 34 -6 0.04
Wed 02/11 09Z 0.47 2716 97 42 -7 0.03
Wed 02/11 10Z 0.49 2717 97 53 -7 0.02
Wed 02/11 11Z 0.53 2818 97 59 -8 0.02
Wed 02/11 12Z 0.53 2818 97 61 -8 0.02
Wed 02/11 13Z 0.52 2919 96 66 -9 0.01
Wed 02/11 14Z 0.55 2919 96 74 -9 0.01
Wed 02/11 15Z 0.60 2918 96 80 -9 0.01
Wed 02/11 16Z 0.66 2917 95 84 -10 0.01
Wed 02/11 17Z 0.86 2917 95 87 -10 0.01
Wed 02/11 18Z 1.02 2916 95 87 -9 0.01
Wed 02/11 19Z 1.15 2916 96 86 -9 0.01
Wed 02/11 20Z 1.02 2917 96 85 -10 0.01
Wed 02/11 21Z 0.86 3019 95 84 -10 0.01
Wed 02/11 22Z 0.89 3020 96 84 -10 0.02
Wed 02/11 23Z 0.83 3121 96 82 -11 0.02
Thu 02/12 00Z 0.72 3222 96 82 -11 0.02
Thu 02/12 01Z 0.64 3222 97 83 -12 0.02
Thu 02/12 02Z 0.66 3221 97 84 -12 0.02
Thu 02/12 03Z 0.53 3221 97 85 -12 0.01
Thu 02/12 04Z 0.43 3221 96 83 -12 0.01
Thu 02/12 05Z 0.39 3321 95 83 -12 0.01
Thu 02/12 06Z 0.37 3321 95 81 -12 0.01
Thu 02/12 07Z 0.35 3323 95 79 -12 0.01
Thu 02/12 08Z 0.32 3323 95 80 -12 0.01
Thu 02/12 09Z 0.26 3324 95 80 -12 0.01
Thu 02/12 10Z 0.22 3425 94 78 -12 0.01
Thu 02/12 11Z 0.19 3425 94 75 -12 0.01
Thu 02/12 12Z 0.19 3425 94 74 -12 0.01
Thu 02/12 13Z 0.23 3425 94 73 -12 0.01
Thu 02/12 14Z 0.25 3325 94 72 -13 0.01
Thu 02/12 15Z 0.27 3324 94 71 -12 0.01
Thu 02/12 16Z 0.29 3325 94 70 -12 0.01
Thu 02/12 18Z 0.29 3325 94 63 -12 0.01
Thu 02/12 19Z 0.33 3325 92 48 -12 0.01
Thu 02/12 20Z 0.36 3326 85 29 -12 0.00
Thu 02/12 21Z 0.35 3327 73 19 -11 0.00
Thu 02/12 22Z 0.28 3329 69 13 -11 0.00
Thu 02/12 23Z 0.25 3330 72 16 -11 0.00
Run total areal avg QPF for the greens is: 0.91 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