GFS EXPERIMENTAL Froude Number for the Green Mountains

Extreme Heat Continues; Severe Thunderstorms into Upper Midwest; Strong Bering Sea Storm

Wildfires and poor air quality continue for the Pacific Northwest, Rockies and extended into the Plains. Severe thunderstorms possible for the northern Plains and upper Midwest on Monday along a frontal boundary. Another boundary will focus showers and thunderstorms for the eastern seaboard with localized heavy rainfall possible. For Alaska, a strong Bering Sea storm will bring winds and rainfall. Read More >

Subject: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_20260803_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) === ===== === ==== ==== === === === ==== Mon 08/03 00Z 0.33 1922 80 72 14 0.00 Mon 08/03 03Z 0.11 1819 82 95 14 0.00 Mon 08/03 06Z 0.11 1821 93 93 14 0.04 Mon 08/03 09Z 0.06 1821 97 91 14 0.12 Mon 08/03 12Z 0.15 1921 98 81 15 0.12 Mon 08/03 15Z 0.22 1922 96 87 15 0.04 Mon 08/03 18Z 0.54 2125 95 90 15 0.16 Mon 08/03 21Z 1.05 2628 94 80 12 0.12 Tue 08/04 00Z 1.02 3036 93 56 9 0.02 Tue 08/04 03Z 0.64 3128 68 21 10 0.02 Tue 08/04 06Z 0.74 2926 71 13 11 0.00 Tue 08/04 09Z 0.73 2925 64 5 11 0.00 Tue 08/04 12Z 0.70 2922 55 2 11 0.00 Tue 08/04 15Z 0.81 2914 57 2 11 0.00 Tue 08/04 18Z 1.30 2711 49 4 13 0.00 Tue 08/04 21Z 1.07 2709 44 26 15 0.00 Wed 08/05 00Z 0.34 2508 45 30 15 0.00 Wed 08/05 03Z 0.26 2208 46 26 15 0.00 Wed 08/05 06Z 0.22 2307 49 19 15 0.00 Wed 08/05 09Z 0.14 2105 50 13 15 0.00 Wed 08/05 12Z 0.09 2006 48 8 15 0.00 Wed 08/05 15Z 0.16 2107 54 2 15 0.00 Wed 08/05 18Z 0.54 2109 49 4 15 0.00 Wed 08/05 21Z 0.54 2309 49 4 16 0.00 Run total areal avg QPF for the greens is: 0.64 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