NAM12 EXPERIMENTAL Froude Number for the Green Mountains

Heat Continues for the East and South-Central U.S.; Strong to Severe Storms Across the Mid-Atlantic and Northeast

The extremely dangerous heat wave continues across the East Coast and much of the South-Central U.S. today. Record high temperatures are expected for some areas especially across the Mid-Atlantic where extreme heat risk conditions reside. There is a Slight Risk (level 2 of 5) of severe thunderstorms today for the northern Mid-Atlantic into portions of southern New England. Read More >

Subject: NAM12 EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_NAM12_20240717_1200 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) === ===== === ==== ==== === === === ==== Wed 07/17 12Z 0.52 2516 88 82 15 0.00 Wed 07/17 15Z 0.69 2317 84 71 16 0.02 Wed 07/17 18Z 2.32 2214 81 85 16 0.07 Wed 07/17 21Z 0.73 2416 87 79 16 0.24 Thu 07/18 00Z 0.62 2613 85 62 16 0.02 Thu 07/18 03Z 0.79 2715 87 60 15 0.01 Thu 07/18 06Z 0.72 2816 71 64 14 0.00 Thu 07/18 09Z 0.53 2913 77 69 13 0.00 Thu 07/18 12Z 0.45 3015 74 69 12 0.00 Thu 07/18 15Z 0.74 2913 76 19 10 0.00 Thu 07/18 18Z 8.26 2913 78 16 10 0.00 Thu 07/18 21Z 5.01 2914 80 22 10 0.00 Fri 07/19 00Z 0.94 3017 82 27 9 0.00 Fri 07/19 03Z 0.58 3119 85 29 9 0.00 Fri 07/19 06Z 0.25 3317 83 28 9 0.00 Fri 07/19 09Z 0.12 3412 79 22 9 0.00 Fri 07/19 12Z 0.12 3309 74 19 9 0.00 Fri 07/19 15Z 0.15 3105 79 21 9 0.00 Fri 07/19 18Z 1.51 2805 79 19 10 0.00 Fri 07/19 21Z 1.91 2706 76 14 11 0.00 Sat 07/20 00Z 0.60 2609 80 15 11 0.00 Sat 07/20 03Z 0.93 2612 80 21 10 0.00 Sat 07/20 06Z 0.74 2715 65 29 10 0.00 Sat 07/20 09Z 0.71 2612 75 22 10 0.00 Sat 07/20 12Z 0.53 2817 53 26 11 0.00 Sat 07/20 15Z 0.64 2715 69 25 11 0.00 Sat 07/20 18Z 5.98 2614 82 27 11 0.00 Sat 07/20 21Z 7.97 2714 78 30 12 0.00 Sun 07/21 00Z 1.71 2715 75 38 12 0.00 Run total areal avg QPF for the greens is: 0.36 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