Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260804_0600
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 08/04 06Z 0.70 3023 85 3 10 0.00
Tue 08/04 07Z 0.78 3024 80 0 10 0.00
Tue 08/04 08Z 0.65 3023 74 1 11 0.00
Tue 08/04 09Z 0.62 3023 70 1 11 0.00
Tue 08/04 10Z 0.66 3023 64 1 11 0.00
Tue 08/04 11Z 0.65 3023 57 1 12 0.00
Tue 08/04 12Z 0.63 3022 53 1 12 0.00
Tue 08/04 13Z 0.65 3022 52 1 12 0.00
Tue 08/04 14Z 0.72 2920 53 2 12 0.00
Tue 08/04 15Z 0.76 2918 54 2 12 0.00
Tue 08/04 16Z 0.76 2915 53 3 12 0.00
Tue 08/04 17Z 0.64 2912 54 4 13 0.00
Tue 08/04 18Z 0.68 2910 57 7 13 0.00
Tue 08/04 19Z 0.68 2808 62 10 13 0.00
Tue 08/04 20Z 0.58 2708 67 14 14 0.00
Tue 08/04 21Z 0.52 2607 71 19 14 0.00
Tue 08/04 22Z 0.36 2507 71 22 14 0.00
Tue 08/04 23Z 0.26 2407 65 29 16 0.00
Wed 08/05 00Z 0.25 2408 61 38 16 0.00
Wed 08/05 01Z 0.27 2309 59 42 16 0.00
Wed 08/05 02Z 0.25 2309 57 46 17 0.00
Wed 08/05 03Z 0.24 2309 53 47 17 0.00
Wed 08/05 04Z 0.23 2309 51 46 17 0.00
Wed 08/05 05Z 0.22 2408 51 44 17 0.00
Wed 08/05 06Z 0.21 2508 51 42 18 0.00
Wed 08/05 07Z 0.23 2509 51 43 17 0.00
Wed 08/05 08Z 0.22 2608 50 40 17 0.00
Wed 08/05 09Z 0.22 2608 47 35 17 0.00
Wed 08/05 10Z 0.20 2608 46 28 17 0.00
Wed 08/05 11Z 0.16 2706 45 19 17 0.00
Wed 08/05 12Z 0.18 2607 49 13 16 0.00
Wed 08/05 13Z 0.20 2707 55 6 16 0.00
Wed 08/05 14Z 0.19 2706 58 2 15 0.00
Wed 08/05 15Z 0.16 2505 58 1 15 0.00
Wed 08/05 16Z 0.16 2304 58 1 15 0.00
Wed 08/05 17Z 0.36 2206 59 1 15 0.00
Wed 08/05 18Z 0.51 2207 56 2 15 0.00
Wed 08/05 19Z 0.59 2208 54 2 16 0.00
Wed 08/05 20Z 0.36 2209 54 3 16 0.00
Wed 08/05 21Z 0.35 2310 55 5 17 0.00
Wed 08/05 22Z 0.39 2411 62 16 17 0.00
Wed 08/05 23Z 0.39 2412 70 31 17 0.00
Thu 08/06 00Z 0.39 2412 73 31 17 0.00
Thu 08/06 01Z 0.40 2413 76 41 17 0.00
Thu 08/06 02Z 0.39 2412 78 49 17 0.00
Thu 08/06 03Z 0.44 2414 78 56 16 0.00
Thu 08/06 04Z 0.46 2514 78 62 16 0.00
Thu 08/06 05Z 0.50 2515 80 67 16 0.00
Thu 08/06 06Z 0.49 2516 81 68 16 0.00
Thu 08/06 07Z 0.49 2516 81 60 16 0.00
Thu 08/06 08Z 0.49 2516 78 53 16 0.00
Thu 08/06 09Z 0.46 2615 79 55 16 0.00
Thu 08/06 10Z 0.39 2613 79 49 17 0.00
Thu 08/06 11Z 0.31 2711 79 36 17 0.00
Thu 08/06 12Z 0.25 2708 80 23 16 0.00
Thu 08/06 13Z 0.22 2607 82 19 16 0.00
Thu 08/06 14Z 0.21 2606 83 13 16 0.00
Thu 08/06 15Z 0.18 2505 83 9 16 0.00
Thu 08/06 16Z 0.21 2404 83 12 16 0.00
Thu 08/06 17Z 0.33 2405 82 16 16 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