
An Extreme Cold Warning is in effect for northern New York and Vermont this evening through Saturday morning. Dangerously cold wind chills of -20F to -40F are expected. In addition, a Winter Weather Advisory remains in effect for southern St Lawrence County today. A lake effect band will produce additional snow accumulations between 2 and 4 inches with highest amounts along and south of Route 3. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260123_0600
Using the MB925 to MB850 layer.
Assumes Central_Greens are orthogonal to 260 degree winds.
925-850 mb Layer Average Wind/RH. Avg QPF over the Central_Greens.
Date Time Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 01/23 06Z 1.13 2625 83 36 -15 0.00
Fri 01/23 07Z 2.53 2625 88 27 -16 0.00
Fri 01/23 08Z 3.73 2625 86 27 -16 0.00
Fri 01/23 09Z 1.83 2624 85 33 -17 0.00
Fri 01/23 10Z 1.42 2623 86 35 -17 0.01
Fri 01/23 11Z 1.44 2623 88 44 -17 0.00
Fri 01/23 12Z 1.25 2624 87 55 -17 0.01
Fri 01/23 13Z 1.26 2624 86 66 -17 0.01
Fri 01/23 14Z 3.93 2620 88 64 -18 0.00
Fri 01/23 15Z 4.70 2519 88 67 -17 0.01
Fri 01/23 16Z 7.28 2518 86 62 -17 0.01
Fri 01/23 17Z 10.44 2620 81 60 -17 0.01
Fri 01/23 18Z 10.45 2621 79 57 -18 0.01
Fri 01/23 19Z 10.26 2622 80 55 -18 0.01
Fri 01/23 20Z 12.22 2623 75 59 -18 0.01
Fri 01/23 21Z 10.85 2724 78 61 -19 0.01
Fri 01/23 22Z 5.00 2825 82 71 -20 0.01
Fri 01/23 23Z 5.49 2926 76 69 -21 0.01
Sat 01/24 00Z 8.86 2828 67 45 -22 0.00
Sat 01/24 01Z 8.31 2830 73 55 -23 0.00
Sat 01/24 02Z 14.03 2833 71 28 -25 0.00
Sat 01/24 03Z 10.45 2930 74 28 -26 0.00
Sat 01/24 04Z 2.79 3028 72 25 -26 0.00
Sat 01/24 05Z 4.35 3029 75 20 -27 0.00
Sat 01/24 06Z 4.26 3028 71 22 -28 0.00
Sat 01/24 07Z 1.54 3029 60 19 -29 0.00
Sat 01/24 08Z 0.79 3028 59 17 -28 0.00
Sat 01/24 09Z 0.51 3127 59 19 -28 0.00
Sat 01/24 10Z 0.43 3127 62 19 -27 0.00
Sat 01/24 11Z 0.37 3127 61 19 -26 0.00
Sat 01/24 12Z 0.33 3128 58 19 -25 0.00
Sat 01/24 13Z 0.32 3128 55 19 -25 0.00
Sat 01/24 14Z 0.30 3127 51 19 -24 0.00
Sat 01/24 15Z 0.31 3126 48 19 -24 0.00
Sat 01/24 16Z 0.32 3125 46 21 -24 0.00
Sat 01/24 17Z 0.33 3124 47 21 -24 0.00
Sat 01/24 18Z 0.34 3123 49 19 -24 0.00
Sat 01/24 19Z 0.35 3022 53 16 -24 0.00
Sat 01/24 20Z 0.37 3021 56 13 -24 0.00
Sat 01/24 21Z 0.40 3020 57 13 -24 0.00
Sat 01/24 22Z 0.40 3020 55 12 -24 0.00
Sat 01/24 23Z 0.39 3020 53 11 -23 0.00
Sun 01/25 00Z 0.33 3020 50 11 -22 0.00
Sun 01/25 01Z 0.27 3120 48 13 -21 0.00
Sun 01/25 02Z 0.25 3120 46 14 -21 0.00
Sun 01/25 03Z 0.23 3120 42 14 -20 0.00
Sun 01/25 04Z 0.20 3119 37 13 -20 0.00
Sun 01/25 05Z 0.18 3118 33 10 -19 0.00
Sun 01/25 06Z 0.18 3117 31 9 -19 0.00
Sun 01/25 07Z 0.16 3116 29 9 -18 0.00
Sun 01/25 08Z 0.16 3115 29 9 -18 0.00
Sun 01/25 09Z 0.16 3114 28 9 -18 0.00
Sun 01/25 10Z 0.13 3111 26 10 -17 0.00
Sun 01/25 11Z 0.15 3011 25 12 -17 0.00
Sun 01/25 12Z 0.13 2908 25 15 -17 0.00
Sun 01/25 13Z 0.09 2906 23 19 -16 0.00
Sun 01/25 14Z 0.07 2905 22 27 -16 0.00
Sun 01/25 15Z 0.05 2502 22 45 -15 0.00
Sun 01/25 16Z 0.03 2002 24 65 -15 0.00
Sun 01/25 17Z 0.04 1904 27 81 -15 0.00
Run total areal avg QPF for the Central_Greens is: 0.12 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