GFS EXPERIMENTAL Froude Number for the Green Mountains

Heavy Rainfall Threat Continues in the Southwest on Monday; Record Warmth in the Plains and Midwest

Remnant moisture from Tropical Storm Rachel will persist over portions of the Great Basin and Southwest on Monday, bringing a potential heavy to excessive rainfall risk. Well above average and potentially record breaking temperatures will develop across the Plains and Midwest early this week, spreading into the Lower Mississippi Valley and Southeast midweek. Read More >

Subject: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_20261012_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 10/12 06Z 0.17 2607 98 97 9 0.00 Mon 10/12 09Z 0.17 3110 97 84 8 0.03 Mon 10/12 12Z 0.24 3215 97 48 7 0.00 Mon 10/12 15Z 0.22 3113 89 31 9 0.00 Mon 10/12 18Z 0.40 3016 94 73 8 0.00 Mon 10/12 21Z 0.48 3018 96 87 8 0.01 Tue 10/13 00Z 0.25 3112 98 87 7 0.01 Tue 10/13 03Z 0.07 3404 98 99 6 0.01 Tue 10/13 06Z 0.02 1903 98 99 7 0.06 Tue 10/13 09Z 0.07 1711 100 99 6 0.13 Tue 10/13 12Z 0.03 1817 99 97 6 0.07 Tue 10/13 15Z 0.04 1824 99 96 7 0.08 Tue 10/13 18Z 0.06 1829 99 96 7 0.27 Tue 10/13 21Z 0.14 1928 99 99 9 0.14 Wed 10/14 00Z 0.28 2130 99 91 11 0.08 Wed 10/14 03Z 0.42 2228 99 79 12 0.05 Wed 10/14 06Z 0.55 2425 97 79 12 0.04 Wed 10/14 09Z 0.74 2624 98 29 11 0.02 Wed 10/14 12Z 0.69 2722 98 31 9 0.01 Wed 10/14 15Z 0.50 2819 92 76 9 0.00 Wed 10/14 18Z 0.67 2722 95 84 7 0.00 Wed 10/14 21Z 0.58 2819 95 76 6 0.00 Thu 10/15 00Z 0.62 2920 98 63 4 0.00 Thu 10/15 03Z 0.61 3021 98 51 3 0.00 Run total areal avg QPF for the greens is: 1.01 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