Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens Model run: BTV_GRID_D2D_NAM3_20250308_0000 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) === ===== === ==== ==== === === === ==== Sat 03/08 00Z 3.08 2826 74 48 -11 0.00 Sat 03/08 01Z 2.51 2730 73 43 -11 0.00 Sat 03/08 02Z 2.01 2732 70 20 -12 0.00 Sat 03/08 03Z 1.91 2733 71 22 -12 0.00 Sat 03/08 04Z 1.78 2832 72 27 -12 0.00 Sat 03/08 05Z 1.81 2732 73 33 -12 0.00 Sat 03/08 06Z 1.37 2831 73 46 -12 0.00 Sat 03/08 07Z 1.24 2730 77 67 -11 0.00 Sat 03/08 08Z 1.12 2729 83 87 -11 0.00 Sat 03/08 09Z 1.03 2727 91 85 -11 0.01 Sat 03/08 10Z 1.09 2725 94 75 -12 0.01 Sat 03/08 11Z 1.33 2825 93 53 -13 0.01 Sat 03/08 12Z 1.50 2827 87 33 -13 0.01 Sat 03/08 13Z 4.22 2826 88 49 -14 0.01 Sat 03/08 14Z 10.83 2826 86 55 -15 0.00 Sat 03/08 15Z 15.75 2826 80 57 -15 0.00 Sat 03/08 16Z 15.15 2827 80 64 -15 0.00 Sat 03/08 17Z 16.50 2827 75 68 -15 0.00 Sat 03/08 18Z 16.63 2828 76 70 -15 0.00 Sat 03/08 19Z 16.05 2828 77 71 -15 0.00 Sat 03/08 20Z 15.51 2829 76 71 -14 0.00 Sat 03/08 21Z 13.48 2930 78 73 -14 0.00 Sat 03/08 22Z 8.78 2932 79 74 -14 0.00 Sat 03/08 23Z 2.57 2934 74 72 -14 0.00 Sun 03/09 00Z 1.96 2935 72 70 -13 0.00 Sun 03/09 01Z 1.57 2935 73 58 -13 0.00 Sun 03/09 02Z 1.34 2935 72 47 -13 0.00 Sun 03/09 03Z 1.18 3035 72 36 -13 0.00 Sun 03/09 04Z 1.10 3034 75 32 -13 0.00 Sun 03/09 05Z 1.01 3033 77 27 -13 0.00 Sun 03/09 06Z 0.88 3032 79 20 -13 0.00 Sun 03/09 07Z 0.81 3030 82 18 -13 0.00 Sun 03/09 08Z 0.73 3028 84 16 -13 0.00 Sun 03/09 09Z 0.61 3026 82 25 -13 0.00 Sun 03/09 10Z 0.46 3024 77 40 -12 0.00 Sun 03/09 11Z 0.42 3021 76 47 -12 0.00 Sun 03/09 12Z 0.36 2918 74 56 -11 0.00 Sun 03/09 13Z 0.36 2816 72 59 -11 0.00 Sun 03/09 14Z 0.37 2814 69 77 -11 0.00 Sun 03/09 15Z 0.46 2713 66 85 -11 0.00 Sun 03/09 16Z 0.79 2713 73 85 -11 0.00 Sun 03/09 17Z 1.74 2712 85 89 -11 0.00 Sun 03/09 18Z 2.07 2613 90 86 -11 0.00 Sun 03/09 19Z 3.33 2515 91 68 -10 0.00 Sun 03/09 20Z 2.90 2516 92 33 -10 0.00 Sun 03/09 21Z 1.29 2620 96 31 -9 0.01 Sun 03/09 22Z 2.07 2823 95 4 -10 0.02 Sun 03/09 23Z 1.95 2925 91 2 -11 0.01 Mon 03/10 00Z 1.35 2922 87 2 -11 0.00 Mon 03/10 01Z 0.93 2921 92 4 -11 0.00 Mon 03/10 02Z 0.96 2721 97 9 -11 0.01 Mon 03/10 03Z 1.01 2822 94 20 -11 0.01 Mon 03/10 04Z 0.86 2822 89 56 -11 0.00 Mon 03/10 05Z 0.67 2720 83 84 -10 0.00 Mon 03/10 06Z 0.55 2721 70 85 -8 0.00 Mon 03/10 07Z 0.59 2624 74 87 -8 0.00 Mon 03/10 08Z 0.58 2624 92 92 -7 0.01 Mon 03/10 09Z 0.57 2526 95 95 -5 0.01 Mon 03/10 10Z 0.60 2528 95 94 -4 0.03 Mon 03/10 11Z 0.65 2531 93 82 -4 0.02 Run total areal avg QPF for the Central_Greens is: 0.18 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