Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260710_0000
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 07/10 00Z 0.61 2713 68 56 17 0.00
Fri 07/10 01Z 0.38 2912 73 52 17 0.00
Fri 07/10 02Z 0.28 3010 77 51 16 0.00
Fri 07/10 03Z 0.28 2809 84 57 15 0.00
Fri 07/10 04Z 0.35 2610 88 65 15 0.00
Fri 07/10 05Z 0.47 2613 92 79 15 0.04
Fri 07/10 06Z 0.53 2715 94 84 14 0.05
Fri 07/10 07Z 0.54 2816 94 84 14 0.02
Fri 07/10 08Z 0.51 2917 93 80 14 0.00
Fri 07/10 09Z 0.47 2917 95 81 14 0.01
Fri 07/10 10Z 0.35 3117 95 79 14 0.02
Fri 07/10 11Z 0.26 3218 94 69 13 0.01
Fri 07/10 12Z 0.18 3316 92 62 13 0.01
Fri 07/10 13Z 0.16 3315 89 56 13 0.01
Fri 07/10 14Z 0.09 3414 87 46 13 0.00
Fri 07/10 15Z 0.09 3413 88 40 12 0.00
Fri 07/10 16Z 0.10 3512 85 31 12 0.00
Fri 07/10 17Z 0.16 3510 84 28 12 0.00
Fri 07/10 18Z 0.21 3509 81 25 12 0.00
Fri 07/10 19Z 0.21 3409 76 29 13 0.00
Fri 07/10 20Z 0.39 3410 74 34 13 0.00
Fri 07/10 21Z 0.52 3311 72 39 13 0.00
Fri 07/10 22Z 0.19 3411 68 39 13 0.00
Fri 07/10 23Z 0.07 3412 69 39 13 0.00
Sat 07/11 00Z 0.04 3512 73 32 12 0.00
Sat 07/11 01Z 0.05 3514 72 20 12 0.00
Sat 07/11 02Z 0.12 3514 72 22 12 0.00
Sat 07/11 03Z 0.14 3415 69 19 11 0.00
Sat 07/11 04Z 0.12 3416 67 16 11 0.00
Sat 07/11 05Z 0.07 3416 65 10 11 0.00
Sat 07/11 06Z 0.07 3514 63 9 11 0.00
Sat 07/11 07Z 0.16 0013 64 12 10 0.00
Sat 07/11 08Z 0.19 0011 65 11 10 0.00
Sat 07/11 09Z 0.26 0110 65 12 10 0.00
Sat 07/11 10Z 0.27 0209 65 17 10 0.00
Sat 07/11 11Z 0.20 0107 64 17 10 0.00
Sat 07/11 12Z 0.14 0007 63 19 9 0.00
Sat 07/11 13Z 0.11 3506 63 15 9 0.00
Sat 07/11 14Z 0.22 3406 64 15 9 0.00
Sat 07/11 15Z 0.48 3306 64 18 10 0.00
Sat 07/11 16Z 0.84 3307 63 20 10 0.00
Sat 07/11 17Z 0.94 3308 61 19 10 0.00
Sat 07/11 18Z 0.37 3409 60 15 10 0.00
Sat 07/11 19Z 0.36 3509 62 15 11 0.00
Sat 07/11 20Z 0.33 3509 64 14 11 0.00
Sat 07/11 21Z 0.34 3510 67 15 11 0.00
Sat 07/11 22Z 0.42 3511 72 17 11 0.00
Sat 07/11 23Z 0.36 0012 75 21 10 0.00
Sun 07/12 00Z 0.27 0014 76 25 10 0.00
Sun 07/12 01Z 0.38 0115 74 29 10 0.00
Sun 07/12 02Z 0.47 0117 73 30 10 0.00
Sun 07/12 03Z 0.52 0216 74 31 9 0.00
Sun 07/12 04Z 0.57 0216 76 30 9 0.00
Sun 07/12 05Z 0.58 0316 75 30 9 0.00
Sun 07/12 06Z 0.57 0315 74 29 9 0.00
Sun 07/12 07Z 0.53 0314 74 26 9 0.00
Sun 07/12 08Z 0.46 0212 76 23 9 0.00
Sun 07/12 09Z 0.37 0212 76 19 9 0.00
Sun 07/12 10Z 0.27 0112 76 16 9 0.00
Sun 07/12 11Z 0.23 0112 75 15 9 0.00
Run total areal avg QPF for the Central_Greens is: 0.17 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