GFS 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: GFS EXPERIMENTAL Froude Number for the greens Model run: BTV_GRID_D2D_GFS_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 0.57 2518 84 56 15 0.00 Wed 07/17 15Z 0.98 2317 81 63 15 0.01 Wed 07/17 18Z 1.18 2317 74 64 16 0.05 Wed 07/17 21Z 0.88 2613 72 75 17 0.04 Thu 07/18 00Z 0.66 2713 72 82 15 0.07 Thu 07/18 03Z 0.47 2510 71 70 14 0.04 Thu 07/18 06Z 0.48 2613 71 71 14 0.00 Thu 07/18 09Z 0.37 2711 70 73 13 0.00 Thu 07/18 12Z 0.37 2811 72 75 12 0.00 Thu 07/18 15Z 1.15 2813 74 27 11 0.01 Thu 07/18 18Z 4.64 2915 56 21 12 0.00 Thu 07/18 21Z 1.52 3014 61 35 12 0.00 Fri 07/19 00Z 0.39 3216 73 23 10 0.00 Fri 07/19 03Z 0.35 3214 76 20 9 0.00 Fri 07/19 06Z 0.22 3313 75 19 9 0.00 Fri 07/19 09Z 0.16 3311 78 22 8 0.00 Fri 07/19 12Z 0.18 3310 77 25 8 0.00 Fri 07/19 15Z 0.44 3208 73 25 8 0.00 Fri 07/19 18Z 1.21 3007 61 17 10 0.00 Fri 07/19 21Z 0.94 2806 58 14 12 0.00 Sat 07/20 00Z 0.48 2707 58 16 12 0.00 Sat 07/20 03Z 0.40 2608 58 22 12 0.00 Sat 07/20 06Z 0.42 2609 58 24 12 0.00 Sat 07/20 09Z 0.50 2512 59 28 11 0.00 Run total areal avg QPF for the greens is: 0.22 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