Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260703_1800
Using the MB925 to MB850 layer.
Assumes Central_Greens are orthogonal to 260 degree winds.
925-850 mb Layer Average Wind/RH. Avg QPF over the Central_Greens.
Date Time Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 07/03 18Z 5.97 2712 86 58 17 0.00
Fri 07/03 19Z 4.11 2714 83 62 18 0.00
Fri 07/03 20Z 3.62 2715 83 74 18 0.01
Fri 07/03 21Z 1.57 2915 77 79 18 0.01
Fri 07/03 22Z 1.24 2814 77 74 18 0.00
Fri 07/03 23Z 0.94 2816 79 80 18 0.01
Sat 07/04 00Z 0.88 2819 82 75 18 0.01
Sat 07/04 01Z 0.67 2918 72 77 18 0.01
Sat 07/04 02Z 0.51 3017 68 73 18 0.01
Sat 07/04 03Z 0.48 2916 66 68 18 0.00
Sat 07/04 04Z 0.48 2916 63 71 18 0.00
Sat 07/04 05Z 0.49 2917 67 70 18 0.00
Sat 07/04 06Z 0.42 3018 69 66 18 0.00
Sat 07/04 07Z 0.51 3020 75 63 17 0.00
Sat 07/04 08Z 0.48 3020 81 57 17 0.00
Sat 07/04 09Z 0.45 3020 85 51 16 0.00
Sat 07/04 10Z 0.43 3020 90 51 16 0.00
Sat 07/04 11Z 0.41 2918 91 53 16 0.00
Sat 07/04 12Z 0.34 3017 89 49 16 0.00
Sat 07/04 13Z 0.29 3117 87 41 16 0.00
Sat 07/04 14Z 0.27 3216 86 48 15 0.00
Sat 07/04 15Z 0.38 3115 86 52 14 0.00
Sat 07/04 16Z 0.80 3114 85 51 14 0.00
Sat 07/04 17Z 1.46 3113 83 48 14 0.00
Sat 07/04 18Z 2.64 3114 80 46 14 0.02
Sat 07/04 19Z 2.24 3114 80 30 14 0.01
Sat 07/04 20Z 2.08 3114 79 26 14 0.00
Sat 07/04 21Z 1.00 3115 77 23 14 0.00
Sat 07/04 22Z 0.65 3114 76 20 14 0.00
Sat 07/04 23Z 0.38 3213 75 18 14 0.00
Sun 07/05 00Z 0.20 3314 73 17 14 0.00
Sun 07/05 01Z 0.10 3415 73 13 13 0.00
Sun 07/05 02Z 0.08 3415 72 13 13 0.00
Sun 07/05 03Z 0.04 3415 72 15 13 0.00
Sun 07/05 04Z 0.06 3514 70 12 13 0.00
Sun 07/05 05Z 0.12 0012 69 12 13 0.00
Sun 07/05 06Z 0.14 0109 67 13 13 0.00
Sun 07/05 07Z 0.15 0206 64 21 13 0.00
Sun 07/05 08Z 0.15 0304 61 25 13 0.00
Sun 07/05 09Z 0.13 0603 61 30 13 0.00
Sun 07/05 10Z 0.16 0903 62 29 12 0.00
Sun 07/05 11Z 0.18 1004 63 35 12 0.00
Sun 07/05 12Z 0.18 1005 64 39 12 0.00
Sun 07/05 13Z 0.18 1105 68 38 12 0.00
Sun 07/05 14Z 0.28 1305 73 36 12 0.00
Sun 07/05 15Z 0.62 1305 78 30 11 0.00
Sun 07/05 16Z 0.64 1305 81 26 11 0.00
Sun 07/05 17Z 1.02 1205 82 28 12 0.01
Sun 07/05 18Z 1.04 1204 81 32 12 0.01
Sun 07/05 19Z 0.69 1203 81 29 12 0.00
Sun 07/05 20Z 0.30 1202 82 26 12 0.00
Sun 07/05 21Z 0.32 0902 83 24 13 0.00
Sun 07/05 22Z 0.42 0904 82 24 13 0.00
Sun 07/05 23Z 0.39 0905 84 23 12 0.00
Mon 07/06 00Z 0.37 1007 86 21 12 0.00
Mon 07/06 01Z 0.33 1108 88 20 12 0.01
Mon 07/06 02Z 0.31 1210 87 18 12 0.00
Mon 07/06 03Z 0.31 1211 83 18 12 0.00
Mon 07/06 04Z 0.32 1314 78 17 12 0.00
Mon 07/06 05Z 0.29 1315 75 20 12 0.00
Run total areal avg QPF for the Central_Greens is: 0.12 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