
Severe weather and flooding threats will continue for portions of the central U.S. through Thursday, focused from the central High Plains to the Mid-Mississippi Valley. Hot and dry conditions will fuel fire weather concerns for the Intermountain West, and dry thunderstorms may spark additional wildfires. Dangerous heat will build across the southern U.S. Friday into the weekend. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260624_1800
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 06/24 18Z 4.01 3012 86 66 9 0.00
Wed 06/24 19Z 4.82 2915 84 61 9 0.01
Wed 06/24 20Z 4.62 2915 83 55 10 0.01
Wed 06/24 21Z 4.38 2916 80 49 10 0.01
Wed 06/24 22Z 4.28 2918 77 34 10 0.00
Wed 06/24 23Z 3.44 2920 76 33 10 0.00
Thu 06/25 00Z 2.91 2922 77 30 10 0.00
Thu 06/25 01Z 2.54 2923 78 32 9 0.00
Thu 06/25 02Z 1.60 2923 78 31 9 0.00
Thu 06/25 03Z 1.05 3021 79 30 9 0.00
Thu 06/25 04Z 0.78 3021 80 32 9 0.00
Thu 06/25 05Z 0.71 3020 78 30 9 0.00
Thu 06/25 06Z 0.64 3017 76 26 9 0.00
Thu 06/25 07Z 0.63 3017 75 24 9 0.00
Thu 06/25 08Z 0.56 3014 74 19 9 0.00
Thu 06/25 09Z 0.53 3013 73 21 9 0.00
Thu 06/25 10Z 0.55 2913 73 19 9 0.00
Thu 06/25 11Z 0.54 2913 73 19 9 0.00
Thu 06/25 12Z 0.50 2912 73 21 9 0.00
Thu 06/25 13Z 0.50 2909 73 20 9 0.00
Thu 06/25 14Z 1.04 2807 73 20 9 0.00
Thu 06/25 15Z 2.04 2806 72 19 9 0.00
Thu 06/25 16Z 2.43 2705 71 22 10 0.00
Thu 06/25 17Z 2.38 2604 70 26 10 0.00
Thu 06/25 18Z 2.40 2404 69 33 11 0.00
Thu 06/25 19Z 1.68 2204 69 33 11 0.00
Thu 06/25 20Z 1.70 2105 71 34 11 0.00
Thu 06/25 21Z 0.90 2006 73 34 11 0.00
Thu 06/25 22Z 0.63 2007 74 38 11 0.00
Thu 06/25 23Z 0.23 2007 73 49 11 0.00
Fri 06/26 00Z 0.12 1909 68 69 11 0.00
Fri 06/26 01Z 0.11 1811 67 74 11 0.00
Fri 06/26 02Z 0.07 1813 68 72 11 0.01
Fri 06/26 03Z 0.09 1815 71 79 11 0.00
Fri 06/26 04Z 0.12 1817 73 88 11 0.00
Fri 06/26 05Z 0.14 1819 76 88 11 0.00
Fri 06/26 06Z 0.28 1922 81 93 11 0.00
Fri 06/26 07Z 0.21 1923 87 95 11 0.06
Fri 06/26 08Z 0.20 1924 88 92 11 0.10
Fri 06/26 09Z 0.19 1924 90 82 11 0.07
Fri 06/26 10Z 0.13 1824 90 84 11 0.03
Fri 06/26 11Z 0.19 1920 92 73 11 0.03
Fri 06/26 12Z 0.29 2020 95 68 11 0.01
Fri 06/26 13Z 0.31 2117 93 63 11 0.01
Fri 06/26 14Z 0.31 2116 95 67 11 0.01
Fri 06/26 15Z 0.31 2114 96 66 11 0.01
Fri 06/26 16Z 0.33 2113 96 58 11 0.01
Fri 06/26 17Z 0.34 2112 95 47 11 0.00
Fri 06/26 18Z 0.43 2112 92 49 11 0.00
Fri 06/26 19Z 0.77 2111 88 62 11 0.01
Fri 06/26 20Z 1.03 2212 89 72 11 0.03
Fri 06/26 21Z 0.67 2217 91 67 12 0.12
Fri 06/26 22Z 0.70 2418 94 74 12 0.08
Fri 06/26 23Z 0.74 2619 92 68 11 0.08
Sat 06/27 00Z 0.80 2720 96 48 10 0.04
Sat 06/27 01Z 0.70 2820 96 41 10 0.02
Sat 06/27 02Z 0.57 2919 94 39 10 0.01
Sat 06/27 03Z 0.54 2918 96 40 9 0.01
Sat 06/27 04Z 0.51 2917 96 41 9 0.01
Sat 06/27 05Z 0.52 2817 95 37 10 0.02
Run total areal avg QPF for the greens is: 0.81 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