Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260204_1200
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)
=== ===== === ==== ==== === === === ====
Wed 02/04 12Z 0.76 2815 87 74 -15 0.00
Wed 02/04 13Z 0.65 2917 92 70 -15 0.00
Wed 02/04 14Z 0.58 2918 92 73 -16 0.00
Wed 02/04 15Z 0.43 3017 90 73 -15 0.00
Wed 02/04 16Z 0.37 3016 87 67 -15 0.00
Wed 02/04 17Z 0.43 3016 86 52 -14 0.00
Wed 02/04 18Z 0.45 3115 86 36 -14 0.00
Wed 02/04 19Z 0.43 3114 85 30 -14 0.00
Wed 02/04 20Z 0.55 3014 86 35 -14 0.00
Wed 02/04 21Z 0.60 2915 87 35 -13 0.00
Wed 02/04 22Z 0.56 2916 87 32 -13 0.00
Wed 02/04 23Z 0.44 3017 87 27 -13 0.00
Thu 02/05 00Z 0.28 3117 85 23 -12 0.00
Thu 02/05 01Z 0.27 3117 87 24 -12 0.00
Thu 02/05 02Z 0.28 3016 88 28 -12 0.00
Thu 02/05 03Z 0.27 3015 87 29 -12 0.00
Thu 02/05 04Z 0.27 2914 86 30 -12 0.00
Thu 02/05 05Z 0.30 2914 86 31 -12 0.00
Thu 02/05 06Z 0.29 2915 84 32 -12 0.00
Thu 02/05 07Z 0.29 2915 84 34 -12 0.00
Thu 02/05 08Z 0.30 2916 85 28 -13 0.00
Thu 02/05 09Z 0.33 2916 86 36 -13 0.00
Thu 02/05 10Z 0.34 2916 87 52 -14 0.00
Thu 02/05 11Z 0.34 3017 88 63 -14 0.00
Thu 02/05 12Z 0.33 3017 87 46 -14 0.00
Thu 02/05 13Z 0.33 3017 88 5 -15 0.00
Thu 02/05 14Z 0.28 3117 86 4 -15 0.00
Thu 02/05 15Z 0.25 3116 84 3 -15 0.00
Thu 02/05 16Z 0.25 3115 83 3 -15 0.00
Thu 02/05 17Z 0.25 3114 82 4 -15 0.00
Thu 02/05 18Z 0.23 3113 77 3 -15 0.00
Thu 02/05 19Z 0.22 3113 71 4 -14 0.00
Thu 02/05 20Z 0.19 3214 64 4 -13 0.00
Thu 02/05 21Z 0.16 3214 60 4 -13 0.00
Thu 02/05 22Z 0.12 3214 57 4 -12 0.00
Thu 02/05 23Z 0.10 3314 54 5 -12 0.00
Fri 02/06 00Z 0.08 3313 52 5 -11 0.00
Fri 02/06 01Z 0.06 3311 51 6 -11 0.00
Fri 02/06 02Z 0.05 3309 49 7 -11 0.00
Fri 02/06 03Z 0.04 3306 44 8 -10 0.00
Fri 02/06 04Z 0.03 3305 40 10 -10 0.00
Fri 02/06 05Z 0.04 3205 37 12 -9 0.00
Fri 02/06 06Z 0.04 3103 36 15 -9 0.00
Fri 02/06 07Z 0.05 2603 38 22 -10 0.00
Fri 02/06 08Z 0.06 2104 41 28 -10 0.00
Fri 02/06 09Z 0.07 2105 40 33 -10 0.00
Fri 02/06 10Z 0.08 2205 37 32 -10 0.00
Fri 02/06 11Z 0.08 2205 34 28 -9 0.00
Fri 02/06 12Z 0.10 2306 33 19 -9 0.00
Fri 02/06 13Z 0.09 2206 35 13 -10 0.00
Fri 02/06 14Z 0.08 2106 38 10 -10 0.00
Fri 02/06 15Z 0.08 2007 39 10 -10 0.00
Fri 02/06 16Z 0.11 2008 42 7 -10 0.00
Fri 02/06 17Z 0.12 2008 42 18 -10 0.00
Fri 02/06 18Z 0.12 2008 46 69 -10 0.00
Fri 02/06 19Z 0.14 2008 53 85 -10 0.00
Fri 02/06 20Z 0.19 2009 58 87 -11 0.00
Fri 02/06 21Z 0.19 2010 56 85 -10 0.00
Fri 02/06 22Z 0.16 1911 59 87 -10 0.00
Fri 02/06 23Z 0.16 1912 64 83 -11 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