Subject: NAM12 EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_NAM12_20251015_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) === ===== === ==== ==== === === === ==== Wed 10/15 00Z 0.13 3313 86 73 9 0.00 Wed 10/15 03Z 0.21 3319 85 58 7 0.00 Wed 10/15 06Z 0.32 3319 85 23 6 0.00 Wed 10/15 09Z 0.18 3418 86 13 4 0.00 Wed 10/15 12Z 0.18 3318 89 11 1 0.00 Wed 10/15 15Z 0.31 3321 77 15 0 0.00 Wed 10/15 18Z 0.45 3422 72 17 -2 0.00 Wed 10/15 21Z 1.66 3422 79 21 -3 0.00 Thu 10/16 00Z 0.61 3424 86 8 -4 0.00 Thu 10/16 03Z 0.34 3426 89 9 -5 0.00 Thu 10/16 06Z 0.21 3525 91 7 -6 0.00 Thu 10/16 09Z 0.29 3525 91 15 -6 0.00 Thu 10/16 12Z 0.28 3526 91 24 -6 0.00 Thu 10/16 15Z 0.38 3422 90 29 -6 0.00 Thu 10/16 18Z 1.31 3421 85 57 -4 0.00 Thu 10/16 21Z 1.74 3424 83 73 -4 0.00 Fri 10/17 00Z 0.07 3528 77 80 -2 0.00 Fri 10/17 03Z 0.16 0126 78 75 0 0.00 Fri 10/17 06Z 0.20 0124 85 66 0 0.00 Fri 10/17 09Z 0.13 0119 85 52 0 0.00 Fri 10/17 12Z 0.10 0120 79 37 2 0.00 Fri 10/17 15Z 0.04 3515 80 22 1 0.00 Fri 10/17 18Z 0.13 3413 72 8 1 0.00 Fri 10/17 21Z 0.02 3516 77 22 1 0.00 Sat 10/18 00Z 0.10 3420 49 8 3 0.00 Sat 10/18 03Z 0.03 3516 49 41 3 0.00 Sat 10/18 06Z 0.07 3414 48 65 4 0.00 Sat 10/18 09Z 0.06 3412 37 72 4 0.00 Sat 10/18 12Z 0.06 3411 30 72 6 0.00 Run total areal avg QPF for the greens is: 0.00 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