Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260424_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 04/24 00Z 0.39 3321 44 30 1 0.00
Fri 04/24 01Z 0.35 3322 44 26 0 0.00
Fri 04/24 02Z 0.26 3320 45 10 0 0.00
Fri 04/24 03Z 0.18 3417 48 4 0 0.00
Fri 04/24 04Z 0.14 3514 56 4 -1 0.00
Fri 04/24 05Z 0.13 0013 62 4 -2 0.00
Fri 04/24 06Z 0.10 0012 65 5 -3 0.00
Fri 04/24 07Z 0.05 3512 63 7 -4 0.00
Fri 04/24 08Z 0.06 3412 62 7 -5 0.00
Fri 04/24 09Z 0.09 3415 61 5 -5 0.00
Fri 04/24 10Z 0.06 3417 59 4 -6 0.00
Fri 04/24 11Z 0.04 3417 58 5 -5 0.00
Fri 04/24 12Z 0.03 3516 59 13 -5 0.00
Fri 04/24 13Z 0.03 3514 59 31 -5 0.00
Fri 04/24 14Z 0.06 3512 59 39 -5 0.00
Fri 04/24 15Z 0.46 3410 60 37 -5 0.00
Fri 04/24 16Z 0.98 3310 61 32 -4 0.00
Fri 04/24 17Z 1.41 3310 61 22 -4 0.00
Fri 04/24 18Z 0.99 3310 60 13 -3 0.00
Fri 04/24 19Z 1.21 3310 59 13 -3 0.00
Fri 04/24 20Z 0.78 3411 58 14 -2 0.00
Fri 04/24 21Z 0.30 3412 60 15 -2 0.00
Fri 04/24 22Z 0.52 3511 63 14 -2 0.00
Fri 04/24 23Z 0.53 0012 68 12 -2 0.00
Sat 04/25 00Z 0.45 0114 71 11 -3 0.00
Sat 04/25 01Z 0.62 0216 73 13 -3 0.00
Sat 04/25 02Z 0.69 0316 73 16 -4 0.00
Sat 04/25 03Z 0.74 0417 72 17 -4 0.00
Sat 04/25 04Z 0.66 0518 68 15 -3 0.00
Sat 04/25 05Z 0.52 0515 64 10 -4 0.00
Sat 04/25 06Z 0.38 0710 63 5 -3 0.00
Sat 04/25 07Z 0.28 0908 64 3 -3 0.00
Sat 04/25 08Z 0.23 1008 64 3 -3 0.00
Sat 04/25 09Z 0.13 1308 64 3 -3 0.00
Sat 04/25 10Z 0.12 1308 66 2 -3 0.00
Sat 04/25 11Z 0.13 1308 69 3 -2 0.00
Sat 04/25 12Z 0.13 1208 69 3 -2 0.00
Sat 04/25 13Z 0.13 1207 70 2 -2 0.00
Sat 04/25 14Z 0.13 1306 70 2 -3 0.00
Sat 04/25 15Z 0.25 1305 67 3 -2 0.00
Sat 04/25 16Z 0.63 1205 63 3 -2 0.00
Sat 04/25 17Z 1.06 1204 61 3 -1 0.00
Sat 04/25 18Z 1.29 1204 61 3 -1 0.00
Sat 04/25 19Z 1.06 1303 60 3 -1 0.00
Sat 04/25 20Z 1.28 1203 59 3 0 0.00
Sat 04/25 21Z 1.23 1104 58 3 0 0.00
Sat 04/25 22Z 0.45 1104 57 4 0 0.00
Sat 04/25 23Z 0.33 1105 56 5 0 0.00
Sun 04/26 00Z 0.31 1106 56 6 0 0.00
Sun 04/26 01Z 0.37 1108 57 8 0 0.00
Sun 04/26 02Z 0.38 1109 58 8 0 0.00
Sun 04/26 03Z 0.28 1208 57 7 0 0.00
Sun 04/26 04Z 0.22 1307 57 9 0 0.00
Sun 04/26 05Z 0.24 1208 57 9 0 0.00
Sun 04/26 06Z 0.26 1209 57 7 0 0.00
Sun 04/26 07Z 0.34 1110 55 7 0 0.00
Sun 04/26 08Z 0.36 1110 54 6 0 0.00
Sun 04/26 09Z 0.37 1210 57 8 0 0.00
Sun 04/26 10Z 0.35 1210 58 12 -1 0.00
Sun 04/26 11Z 0.42 1210 62 28 -1 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