Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260301_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)
=== ===== === ==== ==== === === === ====
Sun 03/01 06Z 0.26 2911 59 87 -5 0.00
Sun 03/01 07Z 0.30 2913 67 82 -6 0.00
Sun 03/01 08Z 0.30 2913 74 90 -7 0.00
Sun 03/01 09Z 0.23 2912 76 81 -7 0.00
Sun 03/01 11Z 0.19 3115 86 93 -9 0.00
Sun 03/01 12Z 0.21 3118 89 89 -11 0.01
Sun 03/01 13Z 0.23 3220 87 86 -12 0.01
Sun 03/01 14Z 0.27 3123 81 77 -13 0.01
Sun 03/01 15Z 0.29 3123 62 62 -13 0.00
Sun 03/01 16Z 0.29 3123 53 46 -13 0.00
Sun 03/01 17Z 0.33 3122 57 36 -14 0.00
Sun 03/01 18Z 0.37 3120 61 28 -15 0.00
Sun 03/01 19Z 0.46 3120 67 31 -16 0.00
Sun 03/01 20Z 0.53 3119 71 34 -17 0.00
Sun 03/01 21Z 0.65 3020 76 39 -18 0.00
Sun 03/01 22Z 0.57 3021 74 38 -18 0.00
Sun 03/01 23Z 0.51 3122 70 31 -19 0.00
Mon 03/02 00Z 0.48 3122 69 22 -19 0.00
Mon 03/02 01Z 0.39 3122 64 16 -19 0.00
Mon 03/02 02Z 0.31 3122 56 13 -19 0.00
Mon 03/02 03Z 0.26 3222 51 11 -19 0.00
Mon 03/02 04Z 0.23 3221 47 11 -19 0.00
Mon 03/02 05Z 0.21 3220 45 9 -19 0.00
Mon 03/02 06Z 0.20 3219 44 7 -19 0.00
Mon 03/02 07Z 0.20 3219 43 5 -19 0.00
Mon 03/02 08Z 0.22 3118 43 5 -19 0.00
Mon 03/02 09Z 0.22 3117 43 7 -19 0.00
Mon 03/02 10Z 0.24 3116 41 10 -19 0.00
Mon 03/02 11Z 0.25 3016 39 12 -19 0.00
Mon 03/02 12Z 0.28 3017 38 17 -19 0.00
Mon 03/02 13Z 0.30 3017 39 20 -19 0.00
Mon 03/02 14Z 0.32 2916 43 18 -19 0.00
Mon 03/02 15Z 0.35 2815 45 20 -19 0.00
Mon 03/02 16Z 0.39 2815 41 15 -19 0.00
Mon 03/02 17Z 0.40 2815 38 11 -18 0.00
Mon 03/02 18Z 0.39 2914 41 16 -17 0.00
Mon 03/02 19Z 0.41 2814 47 19 -17 0.00
Mon 03/02 20Z 0.39 2813 51 12 -16 0.00
Mon 03/02 21Z 0.35 2812 52 9 -15 0.00
Mon 03/02 22Z 0.34 2712 51 16 -14 0.00
Mon 03/02 23Z 0.36 2613 50 25 -14 0.00
Tue 03/03 00Z 0.39 2515 44 38 -13 0.00
Tue 03/03 01Z 0.39 2417 35 58 -11 0.00
Tue 03/03 02Z 0.42 2419 28 56 -10 0.00
Tue 03/03 03Z 0.49 2423 23 55 -9 0.00
Tue 03/03 04Z 0.51 2425 23 67 -9 0.00
Tue 03/03 05Z 0.51 2425 28 60 -8 0.00
Tue 03/03 06Z 0.51 2426 29 64 -7 0.00
Tue 03/03 07Z 0.51 2526 28 57 -6 0.00
Tue 03/03 08Z 0.50 2526 29 54 -5 0.00
Tue 03/03 09Z 0.50 2426 28 53 -5 0.00
Tue 03/03 10Z 0.49 2425 26 43 -4 0.00
Tue 03/03 11Z 0.47 2424 27 35 -4 0.00
Tue 03/03 12Z 0.46 2425 32 32 -4 0.00
Tue 03/03 13Z 0.46 2426 40 27 -3 0.00
Tue 03/03 14Z 0.45 2326 45 23 -3 0.00
Tue 03/03 15Z 0.43 2326 53 19 -2 0.00
Tue 03/03 16Z 0.43 2326 63 16 -2 0.00
Tue 03/03 17Z 0.46 2326 79 15 -2 0.00
Run total areal avg QPF for the Central_Greens is: 0.03 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