Subject: NAM12 EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_NAM12_20251007_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) === ===== === ==== ==== === === === ==== Tue 10/07 00Z 0.71 2317 52 6 14 0.00 Tue 10/07 03Z 1.21 2519 54 5 13 0.00 Tue 10/07 06Z 1.13 2619 62 10 13 0.00 Tue 10/07 09Z 0.82 2517 66 19 13 0.00 Tue 10/07 12Z 0.79 2418 65 22 13 0.00 Tue 10/07 15Z 0.60 2220 67 55 13 0.00 Tue 10/07 18Z 0.99 2123 78 73 13 0.00 Tue 10/07 21Z 0.71 2228 95 93 12 0.05 Wed 10/08 00Z 0.78 2230 95 80 12 0.13 Wed 10/08 03Z 0.67 2135 95 74 12 0.11 Wed 10/08 06Z 0.70 2139 97 92 12 0.26 Wed 10/08 09Z 0.43 3018 98 96 9 0.55 Wed 10/08 12Z 0.30 3321 85 77 5 0.05 Wed 10/08 15Z 0.36 3319 86 28 2 0.01 Wed 10/08 18Z 5.23 3220 81 4 1 0.00 Wed 10/08 21Z 2.78 3224 88 8 0 0.00 Thu 10/09 00Z 0.60 3326 93 5 -2 0.00 Thu 10/09 03Z 0.47 3325 94 7 -4 0.00 Thu 10/09 06Z 0.30 3424 94 9 -5 0.00 Thu 10/09 09Z 0.20 3423 89 10 -6 0.00 Thu 10/09 12Z 0.21 3426 83 13 -7 0.00 Thu 10/09 15Z 0.35 3423 77 13 -7 0.00 Thu 10/09 18Z 3.81 3320 70 6 -6 0.00 Thu 10/09 21Z 0.34 3423 77 11 -7 0.00 Fri 10/10 00Z 0.73 3323 55 4 -4 0.00 Fri 10/10 03Z 0.25 3419 48 7 -2 0.00 Fri 10/10 06Z 0.19 3314 39 10 -1 0.00 Fri 10/10 09Z 0.27 3115 30 13 0 0.00 Fri 10/10 12Z 0.29 3016 25 12 1 0.00 Run total areal avg QPF for the greens is: 1.16 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