Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260605_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)
=== ===== === ==== ==== === === === ====
Fri 06/05 12Z 0.27 3011 60 6 13 0.00
Fri 06/05 13Z 0.29 2910 59 7 13 0.00
Fri 06/05 14Z 0.34 2909 58 9 13 0.00
Fri 06/05 15Z 0.43 2909 57 10 13 0.00
Fri 06/05 16Z 0.76 2808 55 11 13 0.00
Fri 06/05 17Z 1.77 2908 53 12 13 0.00
Fri 06/05 18Z 2.51 2908 51 14 13 0.00
Fri 06/05 19Z 3.83 2808 54 14 13 0.00
Fri 06/05 20Z 4.07 2708 59 11 14 0.00
Fri 06/05 21Z 2.96 2708 60 8 14 0.00
Fri 06/05 22Z 1.12 2608 62 7 14 0.00
Fri 06/05 23Z 0.69 2609 59 8 14 0.00
Sat 06/06 00Z 0.86 2610 56 17 14 0.00
Sat 06/06 01Z 0.86 2610 59 11 14 0.00
Sat 06/06 02Z 0.84 2610 60 13 14 0.00
Sat 06/06 03Z 0.94 2512 61 16 14 0.00
Sat 06/06 04Z 1.11 2514 61 27 14 0.00
Sat 06/06 05Z 1.23 2516 63 27 14 0.00
Sat 06/06 06Z 1.10 2516 66 24 13 0.00
Sat 06/06 07Z 1.06 2515 70 24 13 0.00
Sat 06/06 08Z 0.86 2414 75 40 13 0.00
Sat 06/06 09Z 0.75 2314 77 51 13 0.01
Sat 06/06 10Z 0.76 2216 78 59 13 0.00
Sat 06/06 11Z 0.78 2218 76 53 13 0.00
Sat 06/06 12Z 0.84 2119 75 41 13 0.00
Sat 06/06 13Z 1.03 2120 75 47 13 0.00
Sat 06/06 14Z 1.05 2220 79 82 13 0.00
Sat 06/06 15Z 0.98 2222 87 96 12 0.01
Sat 06/06 16Z 0.78 2224 90 97 12 0.03
Sat 06/06 17Z 0.80 2126 93 96 12 0.04
Sat 06/06 18Z 0.81 2128 87 90 13 0.03
Sat 06/06 19Z 0.84 2129 94 87 13 0.03
Sat 06/06 20Z 0.81 2229 94 80 14 0.07
Sat 06/06 21Z 0.92 2328 96 75 14 0.06
Sat 06/06 22Z 1.05 2426 95 67 14 0.01
Sat 06/06 23Z 0.93 2425 94 76 14 0.04
Sun 06/07 00Z 0.94 2424 94 80 14 0.03
Sun 06/07 01Z 0.94 2425 92 67 14 0.10
Sun 06/07 02Z 1.10 2429 96 71 13 0.02
Sun 06/07 03Z 1.23 2530 97 65 12 0.03
Sun 06/07 04Z 1.09 2629 98 81 11 0.04
Sun 06/07 05Z 0.92 2829 98 89 11 0.05
Sun 06/07 06Z 0.87 2930 98 93 10 0.08
Sun 06/07 07Z 0.89 3032 98 93 10 0.10
Sun 06/07 08Z 0.87 3031 97 81 9 0.06
Sun 06/07 09Z 0.92 2931 98 59 9 0.04
Sun 06/07 10Z 0.90 3033 98 59 8 0.04
Sun 06/07 11Z 0.72 3132 97 67 8 0.03
Sun 06/07 12Z 0.65 3130 97 67 8 0.01
Sun 06/07 13Z 0.63 3127 98 67 8 0.01
Sun 06/07 14Z 0.57 3126 98 65 7 0.02
Sun 06/07 15Z 0.46 3225 98 66 7 0.04
Sun 06/07 16Z 0.33 3226 98 59 7 0.02
Sun 06/07 17Z 0.23 3326 96 58 6 0.01
Sun 06/07 18Z 0.14 3325 95 59 6 0.00
Sun 06/07 19Z 0.11 3425 94 56 5 0.00
Sun 06/07 20Z 0.16 3525 93 38 4 0.00
Sun 06/07 21Z 0.13 3524 91 15 4 0.00
Sun 06/07 22Z 0.29 3526 93 3 3 0.00
Sun 06/07 23Z 0.57 0029 87 3 4 0.00
Run total areal avg QPF for the Central_Greens is: 1.06 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