Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260805_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)
=== ===== === ==== ==== === === === ====
Wed 08/05 18Z 2.09 2307 75 17 14 0.00
Wed 08/05 19Z 1.41 2308 72 14 15 0.00
Wed 08/05 20Z 0.86 2308 71 13 15 0.00
Wed 08/05 21Z 0.49 2208 68 14 16 0.00
Wed 08/05 22Z 0.46 2208 69 16 16 0.00
Wed 08/05 23Z 0.37 2209 73 17 16 0.00
Thu 08/06 00Z 0.38 2210 75 14 16 0.00
Thu 08/06 01Z 0.39 2310 75 12 16 0.00
Thu 08/06 02Z 0.42 2311 75 14 16 0.00
Thu 08/06 03Z 0.44 2312 76 20 16 0.00
Thu 08/06 04Z 0.47 2314 81 32 16 0.00
Thu 08/06 05Z 0.51 2415 83 43 16 0.00
Thu 08/06 06Z 0.48 2414 85 50 16 0.00
Thu 08/06 07Z 0.46 2514 87 51 16 0.00
Thu 08/06 08Z 0.36 2511 86 47 16 0.00
Thu 08/06 09Z 0.27 2509 83 38 16 0.00
Thu 08/06 10Z 0.20 2507 80 39 17 0.00
Thu 08/06 11Z 0.15 2405 78 45 17 0.00
Thu 08/06 12Z 0.14 2206 78 51 17 0.00
Thu 08/06 13Z 0.13 2206 80 52 16 0.00
Thu 08/06 14Z 0.13 2205 83 50 16 0.00
Thu 08/06 15Z 0.13 2104 86 51 16 0.00
Thu 08/06 16Z 0.15 2104 87 51 16 0.00
Thu 08/06 17Z 0.17 2103 86 64 16 0.00
Thu 08/06 18Z 0.33 2304 84 79 16 0.00
Thu 08/06 19Z 0.33 2204 81 81 17 0.00
Thu 08/06 20Z 0.31 2303 81 76 17 0.00
Thu 08/06 21Z 0.15 2003 81 73 17 0.00
Thu 08/06 22Z 0.12 2003 83 71 17 0.00
Thu 08/06 23Z 0.14 2005 84 68 17 0.00
Fri 08/07 00Z 0.22 2205 84 71 17 0.00
Fri 08/07 01Z 0.22 2306 83 67 17 0.00
Fri 08/07 02Z 0.26 2208 81 71 18 0.00
Fri 08/07 03Z 0.33 2311 82 72 18 0.00
Fri 08/07 04Z 0.38 2412 86 70 18 0.00
Fri 08/07 05Z 0.40 2412 90 71 17 0.00
Fri 08/07 06Z 0.40 2512 93 75 17 0.01
Fri 08/07 07Z 0.38 2611 95 75 17 0.01
Fri 08/07 08Z 0.37 2711 95 69 17 0.02
Fri 08/07 09Z 0.27 2809 94 67 17 0.01
Fri 08/07 10Z 0.21 3009 92 63 17 0.00
Fri 08/07 11Z 0.17 3109 93 44 16 0.00
Fri 08/07 12Z 0.14 3107 93 30 16 0.00
Fri 08/07 13Z 0.14 3107 92 39 16 0.00
Fri 08/07 14Z 0.15 3007 89 43 16 0.00
Fri 08/07 15Z 0.14 3006 83 45 16 0.00
Fri 08/07 16Z 0.15 2906 78 34 17 0.00
Fri 08/07 17Z 0.15 3006 73 22 17 0.00
Fri 08/07 18Z 0.22 3006 72 23 17 0.00
Fri 08/07 19Z 0.27 3006 74 24 17 0.00
Fri 08/07 20Z 0.20 3005 76 24 17 0.00
Fri 08/07 21Z 0.19 2905 76 21 18 0.00
Fri 08/07 22Z 0.18 2905 77 24 18 0.00
Fri 08/07 23Z 0.18 2805 80 27 17 0.00
Sat 08/08 00Z 0.20 2705 83 28 17 0.00
Sat 08/08 01Z 0.23 2706 86 26 17 0.00
Sat 08/08 02Z 0.20 2605 86 26 17 0.00
Sat 08/08 03Z 0.21 2505 86 27 17 0.00
Sat 08/08 04Z 0.16 2304 85 25 17 0.00
Sat 08/08 05Z 0.23 2207 85 34 17 0.00
Run total areal avg QPF for the Central_Greens is: 0.05 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