Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260828_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)
=== ===== === ==== ==== === === === ====
Fri 08/28 00Z 0.53 2120 92 80 13 0.00
Fri 08/28 01Z 0.60 2122 94 73 13 0.00
Fri 08/28 02Z 0.62 2224 94 75 14 0.01
Fri 08/28 03Z 0.63 2224 86 74 14 0.01
Fri 08/28 04Z 0.68 2422 88 63 14 0.01
Fri 08/28 05Z 0.64 2521 94 69 14 0.01
Fri 08/28 06Z 0.61 2519 92 61 13 0.02
Fri 08/28 07Z 0.53 2616 88 51 13 0.01
Fri 08/28 08Z 0.40 2613 86 51 13 0.00
Fri 08/28 09Z 0.32 2711 84 53 13 0.00
Fri 08/28 10Z 0.28 2810 86 54 12 0.00
Fri 08/28 11Z 0.24 2908 86 60 12 0.00
Fri 08/28 12Z 0.20 2907 86 61 12 0.00
Fri 08/28 13Z 0.18 2806 86 56 12 0.00
Fri 08/28 14Z 0.20 2706 86 39 12 0.00
Fri 08/28 15Z 0.23 2706 87 35 12 0.00
Fri 08/28 16Z 0.28 2807 87 35 11 0.00
Fri 08/28 17Z 0.32 2807 87 31 11 0.00
Fri 08/28 18Z 0.36 2807 87 33 11 0.00
Fri 08/28 19Z 0.38 2908 88 21 11 0.01
Fri 08/28 20Z 0.37 2909 91 36 12 0.02
Fri 08/28 21Z 0.23 3010 89 22 11 0.02
Fri 08/28 22Z 0.24 3010 86 21 11 0.00
Fri 08/28 23Z 0.24 3011 79 19 11 0.00
Sat 08/29 00Z 0.20 3112 73 19 11 0.00
Sat 08/29 01Z 0.17 3113 70 15 10 0.00
Sat 08/29 02Z 0.15 3213 67 8 10 0.00
Sat 08/29 03Z 0.15 3213 64 6 10 0.00
Sat 08/29 04Z 0.14 3214 61 6 9 0.00
Sat 08/29 05Z 0.13 3215 59 6 9 0.00
Sat 08/29 06Z 0.12 3214 58 7 9 0.00
Sat 08/29 07Z 0.12 3214 59 7 9 0.00
Sat 08/29 08Z 0.12 3212 57 9 9 0.00
Sat 08/29 09Z 0.13 3213 54 12 9 0.00
Sat 08/29 10Z 0.13 3214 52 14 9 0.00
Sat 08/29 11Z 0.13 3213 50 12 9 0.00
Sat 08/29 12Z 0.13 3213 51 11 9 0.00
Sat 08/29 13Z 0.13 3211 53 11 9 0.00
Sat 08/29 14Z 0.14 3108 57 22 8 0.00
Sat 08/29 15Z 0.18 3007 61 29 8 0.00
Sat 08/29 16Z 0.21 2906 61 24 8 0.00
Sat 08/29 17Z 0.32 2907 59 18 8 0.00
Sat 08/29 18Z 0.39 2908 58 8 9 0.00
Sat 08/29 19Z 0.36 2908 62 12 9 0.00
Sat 08/29 20Z 0.44 2808 70 9 9 0.00
Sat 08/29 21Z 0.55 2709 76 15 9 0.00
Sat 08/29 22Z 0.58 2610 81 16 9 0.00
Sat 08/29 23Z 0.62 2612 84 5 9 0.00
Sun 08/30 00Z 0.73 2615 86 5 9 0.00
Sun 08/30 01Z 0.90 2618 88 8 9 0.00
Sun 08/30 02Z 1.03 2618 88 13 9 0.00
Sun 08/30 03Z 0.92 2720 83 16 9 0.00
Sun 08/30 04Z 0.84 2821 79 17 9 0.00
Sun 08/30 05Z 0.91 2821 85 24 9 0.00
Sun 08/30 06Z 0.90 2721 86 25 9 0.00
Sun 08/30 07Z 1.03 2622 86 26 9 0.00
Sun 08/30 08Z 1.01 2623 88 28 9 0.00
Sun 08/30 09Z 1.03 2623 86 26 10 0.00
Sun 08/30 10Z 1.10 2624 85 27 9 0.00
Sun 08/30 11Z 1.02 2624 84 22 10 0.00
Run total areal avg QPF for the Central_Greens is: 0.12 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