GFS EXPERIMENTAL Froude Number for the Green Mountains

Cold Weather Advisory through Sunday Morning, then heavy snow Sunday through Monday.

A Cold Weather Advisory will conclude for portions of northern New York and Vermont this morning with cold conditions of -15F to -25F ongoing. A Winter Storm Warning is in effect across Vermont and northern New York starting 1 PM Today through 1 AM Tuesday. Total snow accumulations between 8 and 16 inches north and 13 to 19 inches south will create very hazardous conditions for travel. Read More >

Subject: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_20260125_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) === ===== === ==== ==== === === === ==== Sun 01/25 00Z 0.30 3018 68 16 -22 0.00 Sun 01/25 03Z 0.25 3016 57 16 -20 0.00 Sun 01/25 06Z 0.17 3112 46 10 -19 0.00 Sun 01/25 09Z 0.10 3208 37 12 -18 0.00 Sun 01/25 12Z 0.02 3400 30 48 -16 0.00 Sun 01/25 15Z 0.05 1608 37 88 -16 0.00 Sun 01/25 18Z 0.11 1511 88 97 -16 0.02 Sun 01/25 21Z 0.16 1416 97 96 -15 0.09 Mon 01/26 00Z 0.30 1423 96 96 -15 0.12 Mon 01/26 03Z 0.42 1223 95 96 -14 0.11 Mon 01/26 06Z 0.49 1121 96 97 -14 0.13 Mon 01/26 09Z 0.37 1016 96 97 -13 0.07 Mon 01/26 12Z 0.27 1213 96 98 -13 0.04 Mon 01/26 15Z 0.17 1411 96 99 -13 0.03 Mon 01/26 18Z 0.02 1709 96 99 -13 0.04 Mon 01/26 21Z 0.36 2310 96 100 -14 0.05 Tue 01/27 00Z 0.60 2918 95 96 -16 0.06 Tue 01/27 03Z 0.82 2923 96 85 -19 0.03 Tue 01/27 06Z 1.05 2925 96 87 -21 0.01 Tue 01/27 09Z 0.64 3024 91 44 -20 0.01 Tue 01/27 12Z 0.50 2921 84 57 -20 0.00 Tue 01/27 15Z 0.42 2716 85 82 -19 0.00 Tue 01/27 18Z 0.36 2312 98 99 -19 0.01 Tue 01/27 21Z 0.55 2214 97 99 -19 0.02 Run total areal avg QPF for the greens is: 0.84 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