Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260203_0600
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)
=== ===== === ==== ==== === === === ====
Tue 02/03 06Z 0.08 3312 63 57 -9 0.00
Tue 02/03 07Z 0.08 3312 64 60 -9 0.00
Tue 02/03 08Z 0.07 3312 63 56 -9 0.00
Tue 02/03 09Z 0.08 3311 62 54 -8 0.00
Tue 02/03 10Z 0.09 3211 61 54 -8 0.00
Tue 02/03 11Z 0.08 3209 61 53 -8 0.00
Tue 02/03 12Z 0.06 3207 60 46 -8 0.00
Tue 02/03 13Z 0.07 3106 60 30 -8 0.00
Tue 02/03 14Z 0.10 2905 61 14 -8 0.00
Tue 02/03 15Z 0.11 2705 63 11 -9 0.00
Tue 02/03 16Z 0.12 2605 66 27 -9 0.00
Tue 02/03 17Z 0.12 2504 71 69 -9 0.00
Tue 02/03 18Z 0.14 2404 71 88 -10 0.00
Tue 02/03 19Z 0.17 2305 67 89 -10 0.00
Tue 02/03 20Z 0.20 2305 59 87 -10 0.00
Tue 02/03 21Z 0.21 2306 55 79 -11 0.00
Tue 02/03 22Z 0.25 2307 55 68 -11 0.00
Tue 02/03 23Z 0.30 2409 63 70 -11 0.00
Wed 02/04 00Z 0.34 2510 86 61 -12 0.00
Wed 02/04 01Z 0.37 2511 93 56 -12 0.00
Wed 02/04 02Z 0.40 2612 92 72 -12 0.00
Wed 02/04 03Z 0.47 2614 90 79 -12 0.00
Wed 02/04 04Z 0.62 2616 90 76 -13 0.00
Wed 02/04 05Z 0.67 2617 93 61 -13 0.00
Wed 02/04 06Z 0.69 2617 94 43 -13 0.01
Wed 02/04 07Z 0.67 2718 93 42 -13 0.01
Wed 02/04 08Z 0.70 2818 94 48 -14 0.01
Wed 02/04 09Z 0.61 2716 91 55 -15 0.01
Wed 02/04 10Z 0.62 2716 87 56 -16 0.00
Wed 02/04 11Z 0.45 2714 86 48 -16 0.00
Wed 02/04 12Z 0.28 2914 82 49 -15 0.00
Wed 02/04 13Z 0.17 3216 82 52 -15 0.00
Wed 02/04 14Z 0.16 3218 85 52 -14 0.00
Wed 02/04 15Z 0.20 3219 85 45 -14 0.00
Wed 02/04 16Z 0.24 3219 89 39 -14 0.00
Wed 02/04 17Z 0.27 3218 90 37 -14 0.00
Wed 02/04 18Z 0.30 3117 86 34 -14 0.00
Wed 02/04 19Z 0.32 3114 79 31 -13 0.00
Wed 02/04 20Z 0.39 3013 80 29 -13 0.00
Wed 02/04 21Z 0.44 2914 84 29 -14 0.00
Wed 02/04 22Z 0.50 2915 87 27 -14 0.00
Wed 02/04 23Z 0.49 2916 88 25 -14 0.00
Thu 02/05 00Z 0.39 3016 87 25 -13 0.00
Thu 02/05 01Z 0.30 3015 85 28 -13 0.00
Thu 02/05 02Z 0.24 3013 85 30 -13 0.00
Thu 02/05 03Z 0.19 3112 85 31 -13 0.00
Thu 02/05 04Z 0.17 3111 87 27 -13 0.00
Thu 02/05 05Z 0.19 3011 89 30 -14 0.00
Thu 02/05 06Z 0.21 3011 90 36 -14 0.00
Thu 02/05 07Z 0.23 3012 90 32 -14 0.00
Thu 02/05 08Z 0.26 2912 91 23 -14 0.00
Thu 02/05 09Z 0.30 2913 93 22 -15 0.00
Thu 02/05 10Z 0.33 2915 93 29 -15 0.00
Thu 02/05 11Z 0.34 3016 93 49 -16 0.00
Thu 02/05 12Z 0.36 3118 92 75 -16 0.00
Thu 02/05 13Z 0.40 3120 90 75 -17 0.00
Thu 02/05 14Z 0.49 3119 90 70 -18 0.01
Thu 02/05 15Z 0.58 3118 92 58 -18 0.00
Thu 02/05 16Z 0.75 3116 93 39 -18 0.00
Thu 02/05 17Z 0.80 3116 93 16 -18 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