Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260704_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)
=== ===== === ==== ==== === === === ====
Sat 07/04 00Z 0.66 2919 71 87 19 0.00
Sat 07/04 01Z 0.67 2920 74 93 18 0.00
Sat 07/04 02Z 0.69 3020 78 91 18 0.00
Sat 07/04 03Z 0.71 2921 78 86 17 0.00
Sat 07/04 04Z 0.69 3021 77 89 16 0.00
Sat 07/04 05Z 0.67 3021 83 88 16 0.00
Sat 07/04 06Z 0.56 3021 86 82 16 0.00
Sat 07/04 07Z 0.48 3019 89 81 17 0.00
Sat 07/04 08Z 0.45 3018 88 78 16 0.00
Sat 07/04 09Z 0.44 3018 89 77 16 0.00
Sat 07/04 10Z 0.42 3017 90 67 15 0.00
Sat 07/04 11Z 0.40 3017 91 62 15 0.00
Sat 07/04 12Z 0.41 3016 92 64 15 0.00
Sat 07/04 13Z 0.43 3016 91 64 15 0.00
Sat 07/04 14Z 0.47 3015 90 61 15 0.00
Sat 07/04 15Z 0.50 3014 87 62 15 0.00
Sat 07/04 16Z 0.71 3112 86 73 15 0.01
Sat 07/04 17Z 0.89 3115 88 71 15 0.11
Sat 07/04 18Z 1.02 3114 89 71 15 0.03
Sat 07/04 19Z 1.51 3213 86 72 14 0.01
Sat 07/04 20Z 1.31 3215 81 68 14 0.03
Sat 07/04 21Z 1.18 3214 77 60 14 0.00
Sat 07/04 22Z 0.54 3214 74 61 14 0.00
Sat 07/04 23Z 0.31 3313 71 61 14 0.00
Sun 07/05 00Z 0.15 3312 68 59 14 0.00
Sun 07/05 01Z 0.11 3412 67 54 14 0.00
Sun 07/05 02Z 0.10 3411 67 47 13 0.00
Sun 07/05 03Z 0.09 3411 67 46 13 0.00
Sun 07/05 04Z 0.05 3409 67 41 13 0.00
Sun 07/05 05Z 0.06 3410 65 42 13 0.00
Sun 07/05 06Z 0.03 3408 64 40 13 0.00
Sun 07/05 07Z 0.02 3407 63 40 13 0.00
Sun 07/05 08Z 0.03 3405 63 35 12 0.00
Sun 07/05 09Z 0.05 3504 64 23 12 0.00
Sun 07/05 10Z 0.04 3502 63 29 12 0.00
Sun 07/05 11Z 0.04 0002 62 35 12 0.00
Sun 07/05 12Z 0.06 0501 65 34 12 0.00
Sun 07/05 13Z 0.07 1301 69 29 12 0.00
Sun 07/05 14Z 0.15 1501 73 25 12 0.00
Sun 07/05 15Z 0.18 1900 76 19 12 0.00
Sun 07/05 16Z 0.19 2900 78 10 12 0.00
Sun 07/05 17Z 0.21 3101 78 12 12 0.01
Sun 07/05 18Z 0.25 3102 77 8 12 0.00
Sun 07/05 19Z 0.20 3303 76 4 13 0.00
Sun 07/05 20Z 0.12 3403 75 2 13 0.00
Sun 07/05 21Z 0.27 0003 75 2 13 0.00
Sun 07/05 22Z 0.21 0004 75 3 13 0.00
Sun 07/05 23Z 0.29 0205 76 3 13 0.00
Mon 07/06 00Z 0.31 0405 77 3 13 0.00
Mon 07/06 01Z 0.38 0506 76 3 13 0.00
Mon 07/06 02Z 0.56 0609 76 4 12 0.00
Mon 07/06 03Z 0.68 0711 77 4 12 0.00
Mon 07/06 04Z 0.67 0811 75 3 12 0.00
Mon 07/06 05Z 0.59 1011 77 3 12 0.00
Mon 07/06 06Z 0.42 1211 81 3 12 0.00
Mon 07/06 07Z 0.31 1311 83 3 12 0.00
Mon 07/06 08Z 0.28 1313 86 4 12 0.00
Mon 07/06 09Z 0.21 1414 89 5 12 0.00
Mon 07/06 10Z 0.18 1515 86 5 12 0.00
Mon 07/06 11Z 0.21 1416 85 6 11 0.00
Run total areal avg QPF for the Central_Greens is: 0.20 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