
Cold Weather Advisory has been issued for St. Lawrence, Franklin, western Clinton, and western Essex counties of New York Thursday 7 PM through Friday 10 AM. Cold temperatures and breezy winds will cause wind chills to fall into the -20F to -30F range. The risk of frostbite and hypothermia will be elevated, especially for vulnerable populations. Wear appropriate clothing, a hat, and gloves. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260128_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 01/28 12Z 0.47 2917 81 35 -19 0.00
Wed 01/28 13Z 0.51 2917 83 31 -19 0.00
Wed 01/28 14Z 0.47 2916 84 31 -19 0.00
Wed 01/28 15Z 0.49 2816 82 39 -19 0.00
Wed 01/28 16Z 0.48 2814 76 45 -19 0.00
Wed 01/28 17Z 0.54 2813 73 53 -19 0.00
Wed 01/28 18Z 0.58 2812 72 62 -18 0.00
Wed 01/28 19Z 0.63 2812 74 66 -18 0.00
Wed 01/28 20Z 0.68 2811 79 61 -18 0.00
Wed 01/28 21Z 0.79 2711 86 58 -19 0.00
Wed 01/28 22Z 0.73 2812 83 56 -19 0.00
Wed 01/28 23Z 0.76 2914 78 56 -18 0.00
Thu 01/29 00Z 0.67 2914 77 57 -18 0.00
Thu 01/29 01Z 0.56 2912 79 60 -18 0.00
Thu 01/29 02Z 0.51 2911 84 60 -18 0.00
Thu 01/29 03Z 0.48 2810 88 62 -18 0.00
Thu 01/29 04Z 0.45 2810 90 65 -18 0.00
Thu 01/29 05Z 0.43 2810 90 67 -18 0.00
Thu 01/29 06Z 0.42 2811 88 66 -18 0.00
Thu 01/29 07Z 0.43 2811 84 65 -19 0.00
Thu 01/29 08Z 0.42 2912 85 61 -19 0.00
Thu 01/29 09Z 0.40 2811 86 57 -19 0.00
Thu 01/29 10Z 0.41 2812 86 56 -19 0.00
Thu 01/29 11Z 0.41 2812 86 57 -19 0.00
Thu 01/29 12Z 0.39 2813 84 59 -19 0.00
Thu 01/29 13Z 0.37 2913 84 64 -19 0.00
Thu 01/29 14Z 0.35 3012 85 67 -19 0.00
Thu 01/29 15Z 0.36 3012 88 69 -19 0.00
Thu 01/29 16Z 0.43 3012 89 67 -19 0.00
Thu 01/29 17Z 0.62 3013 90 65 -19 0.00
Thu 01/29 18Z 1.27 3014 90 61 -19 0.00
Thu 01/29 19Z 1.96 3016 92 58 -19 0.00
Thu 01/29 20Z 1.53 3016 93 58 -19 0.00
Thu 01/29 21Z 1.34 3017 93 56 -19 0.01
Thu 01/29 22Z 1.40 3019 93 51 -20 0.01
Thu 01/29 23Z 1.25 3022 92 47 -21 0.01
Fri 01/30 00Z 0.93 3024 88 43 -21 0.00
Fri 01/30 01Z 0.88 3025 86 39 -22 0.00
Fri 01/30 02Z 0.96 3026 86 38 -23 0.00
Fri 01/30 03Z 0.95 3027 84 36 -23 0.00
Fri 01/30 04Z 0.88 3027 83 36 -24 0.00
Fri 01/30 05Z 0.83 2927 82 34 -24 0.00
Fri 01/30 06Z 0.79 2927 80 33 -24 0.00
Fri 01/30 07Z 0.71 2929 76 32 -24 0.00
Fri 01/30 08Z 0.63 2930 72 36 -23 0.00
Fri 01/30 09Z 0.56 3029 71 42 -23 0.00
Fri 01/30 10Z 0.50 3029 70 46 -23 0.00
Fri 01/30 11Z 0.45 3028 69 52 -22 0.00
Fri 01/30 12Z 0.41 3028 70 61 -22 0.00
Fri 01/30 13Z 0.38 3027 72 69 -21 0.00
Fri 01/30 14Z 0.35 3025 74 76 -21 0.00
Fri 01/30 15Z 0.34 3023 76 80 -20 0.00
Fri 01/30 16Z 0.33 3022 79 82 -20 0.00
Fri 01/30 17Z 0.33 3020 80 81 -20 0.00
Fri 01/30 18Z 0.33 3020 80 79 -19 0.00
Fri 01/30 19Z 0.34 2919 80 76 -19 0.00
Fri 01/30 20Z 0.36 2919 82 71 -19 0.00
Fri 01/30 21Z 0.38 2919 83 66 -19 0.00
Fri 01/30 22Z 0.38 3020 84 63 -18 0.00
Fri 01/30 23Z 0.34 3021 85 62 -18 0.00
Run total areal avg QPF for the greens is: 0.03 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