GFS EXPERIMENTAL Froude Number for the Green Mountains

Winter Storm Warnings and Winter Weather Advisories for Tuesday

Snow will develop across the region on Tuesday morning and become heavy at times across portions of central and southern Vermont, with total accumulations of 5 to 9 inches. Snowfall from Essex County, NY to Essex County, VT will be 3 to 7 inches, with lighter amounts near the International Border. Travel will be difficult during both the morning and evening commutes on Tuesday. Read More >

Subject: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_20251201_0600 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) === ===== === ==== ==== === === === ==== Mon 12/01 06Z 1.13 2528 90 75 -7 0.00 Mon 12/01 09Z 1.18 2831 96 66 -9 0.01 Mon 12/01 12Z 0.69 3026 91 53 -11 0.01 Mon 12/01 15Z 0.54 3120 90 4 -13 0.01 Mon 12/01 18Z 0.41 3116 73 10 -13 0.00 Mon 12/01 21Z 0.18 3110 49 5 -10 0.00 Tue 12/02 00Z 0.10 2905 42 4 -8 0.00 Tue 12/02 03Z 0.03 1907 33 5 -6 0.00 Tue 12/02 06Z 0.03 1814 35 6 -6 0.00 Tue 12/02 09Z 0.09 1918 47 45 -8 0.00 Tue 12/02 12Z 0.15 1919 85 95 -10 0.01 Tue 12/02 15Z 0.10 1918 95 96 -8 0.06 Tue 12/02 18Z 0.08 1914 96 96 -6 0.10 Tue 12/02 21Z 0.05 1401 96 95 -6 0.11 Wed 12/03 00Z 0.08 0206 96 96 -6 0.07 Wed 12/03 03Z 0.03 3514 96 97 -7 0.03 Wed 12/03 06Z 0.15 3418 95 78 -9 0.01 Wed 12/03 09Z 0.17 3319 86 18 -9 0.01 Wed 12/03 12Z 0.12 3316 68 5 -9 0.00 Wed 12/03 15Z 0.22 3010 68 10 -9 0.00 Wed 12/03 18Z 0.26 2609 70 12 -8 0.00 Wed 12/03 21Z 0.39 2415 70 21 -8 0.00 Thu 12/04 00Z 0.48 2320 73 86 -7 0.00 Thu 12/04 03Z 0.56 2325 77 95 -6 0.00 Run total areal avg QPF for the greens is: 0.43 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