Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260521_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)
=== ===== === ==== ==== === === === ====
Thu 05/21 00Z 0.42 3116 71 44 10 0.00
Thu 05/21 01Z 0.44 3218 75 26 8 0.00
Thu 05/21 02Z 0.46 3220 77 16 7 0.00
Thu 05/21 03Z 0.50 3223 76 15 6 0.00
Thu 05/21 04Z 0.39 3324 73 15 5 0.00
Thu 05/21 05Z 0.23 3324 68 15 4 0.00
Thu 05/21 06Z 0.09 3422 65 19 4 0.00
Thu 05/21 07Z 0.05 3421 64 19 3 0.00
Thu 05/21 08Z 0.04 3421 64 17 2 0.00
Thu 05/21 09Z 0.04 3421 65 13 1 0.00
Thu 05/21 10Z 0.03 3420 66 8 1 0.00
Thu 05/21 11Z 0.03 3419 65 5 1 0.00
Thu 05/21 12Z 0.04 3416 58 3 0 0.00
Thu 05/21 13Z 0.06 3413 51 3 1 0.00
Thu 05/21 14Z 0.08 3312 46 3 1 0.00
Thu 05/21 15Z 0.09 3312 42 3 0 0.00
Thu 05/21 16Z 0.12 3312 42 3 0 0.00
Thu 05/21 17Z 0.22 3313 41 4 0 0.00
Thu 05/21 18Z 0.37 3314 38 4 1 0.00
Thu 05/21 19Z 0.38 3314 35 4 1 0.00
Thu 05/21 20Z 0.33 3315 33 5 1 0.00
Thu 05/21 21Z 0.26 3316 34 5 1 0.00
Thu 05/21 22Z 0.15 3316 35 5 1 0.00
Thu 05/21 23Z 0.13 3316 35 5 1 0.00
Fri 05/22 00Z 0.08 3418 35 5 1 0.00
Fri 05/22 01Z 0.03 3418 35 5 1 0.00
Fri 05/22 02Z 0.05 3517 35 3 1 0.00
Fri 05/22 03Z 0.07 3516 38 2 1 0.00
Fri 05/22 04Z 0.08 3515 43 1 1 0.00
Fri 05/22 05Z 0.12 0014 46 1 0 0.00
Fri 05/22 06Z 0.16 0113 47 2 0 0.00
Fri 05/22 07Z 0.18 0112 46 2 0 0.00
Fri 05/22 08Z 0.18 0112 43 2 0 0.00
Fri 05/22 09Z 0.21 0212 39 2 1 0.00
Fri 05/22 10Z 0.25 0313 33 3 1 0.00
Fri 05/22 11Z 0.25 0312 30 3 1 0.00
Fri 05/22 12Z 0.26 0411 28 4 1 0.00
Fri 05/22 13Z 0.23 0409 27 5 1 0.00
Fri 05/22 14Z 0.25 0408 28 5 1 0.00
Fri 05/22 15Z 0.45 0405 33 6 1 0.00
Fri 05/22 16Z 0.94 0404 37 7 1 0.00
Fri 05/22 17Z 0.79 0202 40 9 2 0.00
Fri 05/22 18Z 0.96 0302 42 10 3 0.00
Fri 05/22 19Z 0.68 0202 45 11 3 0.00
Fri 05/22 20Z 0.25 0001 47 12 4 0.00
Fri 05/22 21Z 0.17 0101 50 12 4 0.00
Fri 05/22 22Z 0.10 3201 52 12 4 0.00
Fri 05/22 23Z 0.07 0201 53 14 4 0.00
Sat 05/23 00Z 0.13 0302 52 15 4 0.00
Sat 05/23 01Z 0.15 0402 50 15 4 0.00
Sat 05/23 02Z 0.23 0604 48 18 4 0.00
Sat 05/23 03Z 0.30 0605 47 22 4 0.00
Sat 05/23 04Z 0.38 0608 44 24 4 0.00
Sat 05/23 05Z 0.44 0808 45 26 4 0.00
Sat 05/23 06Z 0.51 0810 47 27 4 0.00
Sat 05/23 07Z 0.54 0811 46 24 4 0.00
Sat 05/23 08Z 0.60 0912 44 21 4 0.00
Sat 05/23 09Z 0.63 1014 42 17 4 0.00
Sat 05/23 10Z 0.63 1015 41 11 4 0.00
Sat 05/23 11Z 0.62 1117 42 7 4 0.00
Run total areal avg QPF for the Central_Greens is: 0.00 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