GFS EXPERIMENTAL Froude Number for the Green Mountains

Winter Headlines in effect 10 AM today through 10 AM Saturday with heaviest snow in eastern foothills of the Adirondacks and south-central Vermont.

A warm front will approach this afternoon. A brief wintry mix or rain in warmer valleys is likely before a quick transition into moderate to heavy snow takes place during the evening commute. 1-1.5 inch per hour snowfall rates are likely in northeastern New York and much of Vermont. Difficult to very difficult travel is likely this evening. Light snow will continue Friday night into Saturday. Read More >

Subject: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_20260220_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) === ===== === ==== ==== === === === ==== Fri 02/20 00Z 0.04 1905 63 40 -3 0.00 Fri 02/20 03Z 0.09 2007 73 36 -3 0.00 Fri 02/20 06Z 0.05 1906 77 19 -2 0.00 Fri 02/20 09Z 0.02 1705 76 24 -1 0.00 Fri 02/20 12Z 0.03 1708 72 27 -2 0.00 Fri 02/20 15Z 0.03 1710 71 25 -2 0.00 Fri 02/20 18Z 0.09 1613 87 64 -3 0.01 Fri 02/20 21Z 0.24 1315 92 94 -3 0.09 Sat 02/21 00Z 0.31 1418 96 95 -5 0.23 Sat 02/21 03Z 0.24 1515 96 97 -6 0.18 Sat 02/21 06Z 0.03 1710 96 95 -7 0.08 Sat 02/21 09Z 0.17 2406 97 92 -7 0.05 Sat 02/21 12Z 0.12 3004 98 85 -7 0.02 Sat 02/21 15Z 0.06 3202 98 82 -7 0.01 Sat 02/21 18Z 0.07 3402 96 80 -8 0.01 Sat 02/21 21Z 0.11 0405 90 73 -8 0.01 Sun 02/22 00Z 0.24 0709 89 60 -8 0.02 Sun 02/22 03Z 0.34 1111 83 40 -8 0.01 Sun 02/22 06Z 0.22 1312 77 24 -8 0.00 Sun 02/22 09Z 0.25 1212 63 18 -8 0.00 Sun 02/22 12Z 0.30 1214 62 17 -7 0.00 Sun 02/22 15Z 0.31 1316 71 20 -8 0.00 Sun 02/22 18Z 0.71 1215 90 20 -9 0.00 Sun 02/22 21Z 0.71 1116 91 23 -9 0.00 Run total areal avg QPF for the greens is: 0.72 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