Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260324_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)
=== ===== === ==== ==== === === === ====
Tue 03/24 00Z 0.16 3321 92 26 -10 0.00
Tue 03/24 01Z 0.24 3326 92 24 -10 0.00
Tue 03/24 02Z 0.42 3329 94 37 -11 0.00
Tue 03/24 03Z 0.44 3326 94 34 -11 0.00
Tue 03/24 04Z 0.35 3324 91 30 -11 0.01
Tue 03/24 05Z 0.27 3323 93 18 -10 0.01
Tue 03/24 06Z 0.16 3321 93 17 -11 0.00
Tue 03/24 07Z 0.12 3420 93 18 -11 0.00
Tue 03/24 08Z 0.09 3419 92 15 -11 0.00
Tue 03/24 09Z 0.08 3418 90 9 -11 0.00
Tue 03/24 10Z 0.11 3317 87 6 -11 0.00
Tue 03/24 11Z 0.14 3317 83 5 -11 0.00
Tue 03/24 12Z 0.18 3317 82 7 -11 0.00
Tue 03/24 13Z 0.20 3215 80 10 -11 0.00
Tue 03/24 14Z 0.25 3212 74 12 -11 0.00
Tue 03/24 15Z 0.40 3109 66 10 -11 0.00
Tue 03/24 16Z 0.63 2906 55 6 -10 0.00
Tue 03/24 17Z 0.81 2606 45 5 -9 0.00
Tue 03/24 18Z 1.67 2508 44 5 -9 0.00
Tue 03/24 19Z 1.25 2408 41 3 -8 0.00
Tue 03/24 20Z 1.41 2311 40 6 -8 0.00
Tue 03/24 21Z 1.17 2314 41 8 -7 0.00
Tue 03/24 22Z 0.90 2318 42 17 -7 0.00
Tue 03/24 23Z 0.93 2422 42 40 -6 0.00
Wed 03/25 00Z 1.23 2427 43 17 -6 0.00
Wed 03/25 01Z 1.70 2530 45 26 -7 0.00
Wed 03/25 02Z 3.46 2532 55 46 -8 0.00
Wed 03/25 03Z 3.23 2631 71 91 -8 0.00
Wed 03/25 04Z 1.82 2729 78 91 -9 0.00
Wed 03/25 05Z 1.08 2827 86 17 -9 0.01
Wed 03/25 06Z 1.15 2827 88 14 -9 0.00
Wed 03/25 07Z 0.83 2824 84 6 -9 0.00
Wed 03/25 08Z 0.60 2923 73 14 -8 0.00
Wed 03/25 09Z 0.49 2922 66 23 -7 0.00
Wed 03/25 10Z 0.55 2822 67 23 -8 0.00
Wed 03/25 11Z 0.45 2820 56 25 -7 0.00
Wed 03/25 12Z 0.40 2819 43 13 -5 0.00
Wed 03/25 13Z 0.36 2816 33 11 -4 0.00
Wed 03/25 14Z 0.34 2715 33 8 -4 0.00
Wed 03/25 15Z 0.40 2715 41 8 -5 0.00
Wed 03/25 16Z 0.41 2614 37 5 -4 0.00
Wed 03/25 17Z 0.45 2513 32 3 -4 0.00
Wed 03/25 18Z 0.48 2412 30 16 -4 0.00
Wed 03/25 19Z 0.57 2313 28 64 -4 0.00
Wed 03/25 20Z 1.06 2214 36 93 -4 0.00
Wed 03/25 21Z 2.00 2316 55 91 -4 0.00
Wed 03/25 22Z 1.84 2317 73 92 -5 0.00
Wed 03/25 23Z 0.74 2218 79 92 -4 0.00
Thu 03/26 00Z 0.75 2121 74 79 -3 0.00
Thu 03/26 01Z 0.84 2224 73 76 -3 0.00
Thu 03/26 02Z 0.78 2125 69 82 -2 0.00
Thu 03/26 03Z 0.94 2228 80 77 -2 0.00
Thu 03/26 04Z 0.89 2230 83 88 -2 0.00
Thu 03/26 05Z 0.75 2327 74 91 -1 0.00
Thu 03/26 06Z 0.77 2330 81 93 -1 0.00
Thu 03/26 07Z 0.78 2430 83 93 -1 0.00
Thu 03/26 08Z 0.69 2428 79 92 0 0.00
Thu 03/26 09Z 0.64 2426 73 94 0 0.00
Thu 03/26 10Z 0.60 2327 68 92 0 0.00
Thu 03/26 11Z 0.61 2426 72 93 1 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