Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260812_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)
=== ===== === ==== ==== === === === ====
Wed 08/12 00Z 0.37 3109 74 71 13 0.00
Wed 08/12 01Z 0.49 3110 75 76 12 0.00
Wed 08/12 02Z 0.45 3113 77 77 12 0.00
Wed 08/12 03Z 0.34 3111 76 78 12 0.00
Wed 08/12 04Z 0.34 3111 73 77 12 0.00
Wed 08/12 05Z 0.40 3112 74 69 12 0.00
Wed 08/12 06Z 0.38 3111 74 66 12 0.00
Wed 08/12 07Z 0.30 3210 73 60 12 0.00
Wed 08/12 08Z 0.25 3109 73 54 12 0.00
Wed 08/12 09Z 0.26 3109 73 52 12 0.00
Wed 08/12 10Z 0.26 3109 72 51 12 0.00
Wed 08/12 11Z 0.26 3109 69 47 12 0.00
Wed 08/12 12Z 0.29 3009 67 49 12 0.00
Wed 08/12 13Z 0.32 3008 68 52 12 0.00
Wed 08/12 14Z 0.54 2808 70 58 12 0.00
Wed 08/12 15Z 1.51 2808 70 58 12 0.00
Wed 08/12 16Z 2.87 2807 69 59 12 0.00
Wed 08/12 17Z 3.50 2806 67 67 12 0.00
Wed 08/12 18Z 3.26 2706 68 81 12 0.00
Wed 08/12 19Z 2.01 2607 70 83 12 0.02
Wed 08/12 20Z 0.83 2610 77 89 12 0.02
Wed 08/12 21Z 0.57 2410 78 80 12 0.02
Wed 08/12 22Z 0.46 2609 76 66 13 0.00
Wed 08/12 23Z 0.40 2708 73 74 13 0.00
Thu 08/13 00Z 0.36 2607 73 79 13 0.00
Thu 08/13 01Z 0.48 2508 75 81 13 0.00
Thu 08/13 02Z 0.62 2510 77 88 13 0.00
Thu 08/13 03Z 0.57 2410 76 89 13 0.00
Thu 08/13 04Z 0.48 2410 75 80 13 0.00
Thu 08/13 05Z 0.39 2309 76 81 13 0.00
Thu 08/13 06Z 0.37 2210 80 90 13 0.00
Thu 08/13 07Z 0.41 2113 85 90 13 0.01
Thu 08/13 08Z 0.32 2112 86 86 13 0.01
Thu 08/13 09Z 0.27 2111 87 95 13 0.01
Thu 08/13 10Z 0.17 2009 87 93 13 0.01
Thu 08/13 11Z 0.15 2008 91 80 12 0.00
Thu 08/13 12Z 0.17 2305 96 68 12 0.00
Thu 08/13 13Z 0.23 2707 97 63 12 0.01
Thu 08/13 14Z 0.27 2809 97 69 12 0.01
Thu 08/13 15Z 0.26 2909 98 66 12 0.01
Thu 08/13 16Z 0.29 3111 98 63 11 0.01
Thu 08/13 17Z 0.26 3213 97 50 11 0.01
Thu 08/13 18Z 0.28 3214 95 45 11 0.00
Thu 08/13 19Z 0.37 3215 92 41 11 0.01
Thu 08/13 20Z 0.35 3217 88 33 12 0.01
Thu 08/13 21Z 0.24 3317 82 31 12 0.00
Thu 08/13 22Z 0.30 3218 83 32 12 0.00
Thu 08/13 23Z 0.38 3219 87 30 11 0.00
Fri 08/14 00Z 0.46 3121 85 32 11 0.00
Fri 08/14 01Z 0.50 3123 86 32 11 0.00
Fri 08/14 02Z 0.50 3224 82 32 10 0.00
Fri 08/14 03Z 0.40 3223 80 30 10 0.00
Fri 08/14 04Z 0.38 3224 79 29 10 0.00
Fri 08/14 05Z 0.33 3223 78 27 9 0.00
Fri 08/14 06Z 0.33 3222 77 29 9 0.00
Fri 08/14 07Z 0.32 3220 77 31 9 0.00
Fri 08/14 08Z 0.34 3220 76 34 9 0.00
Fri 08/14 09Z 0.35 3220 71 35 9 0.00
Fri 08/14 10Z 0.35 3221 69 45 9 0.00
Fri 08/14 11Z 0.33 3221 74 48 9 0.00
Run total areal avg QPF for the Central_Greens is: 0.17 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