Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260226_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)
=== ===== === ==== ==== === === === ====
Thu 02/26 00Z 0.57 2119 83 81 -7 0.00
Thu 02/26 01Z 0.57 2122 81 85 -6 0.00
Thu 02/26 02Z 0.73 2226 85 83 -6 0.01
Thu 02/26 03Z 0.75 2326 93 92 -5 0.02
Thu 02/26 04Z 0.84 2522 95 84 -7 0.03
Thu 02/26 05Z 1.33 2623 94 42 -8 0.01
Thu 02/26 06Z 1.68 2625 92 25 -9 0.01
Thu 02/26 07Z 1.82 2626 87 31 -10 0.01
Thu 02/26 08Z 2.16 2627 82 17 -11 0.00
Thu 02/26 09Z 1.98 2627 79 15 -12 0.00
Thu 02/26 10Z 2.41 2628 80 16 -13 0.00
Thu 02/26 11Z 2.04 2727 75 24 -14 0.00
Thu 02/26 12Z 1.35 2727 69 8 -14 0.00
Thu 02/26 13Z 1.24 2726 66 1 -14 0.00
Thu 02/26 14Z 1.54 2724 66 2 -14 0.00
Thu 02/26 15Z 4.93 2722 69 4 -14 0.00
Thu 02/26 16Z 9.76 2619 74 5 -14 0.00
Thu 02/26 17Z 12.15 2618 79 6 -13 0.00
Thu 02/26 18Z 10.60 2617 80 9 -13 0.00
Thu 02/26 19Z 8.55 2616 80 15 -13 0.00
Thu 02/26 20Z 6.24 2615 79 18 -12 0.00
Thu 02/26 21Z 4.44 2616 77 21 -12 0.00
Thu 02/26 22Z 1.31 2715 77 28 -12 0.00
Thu 02/26 23Z 0.88 2815 76 44 -12 0.00
Fri 02/27 00Z 0.78 2915 76 51 -12 0.00
Fri 02/27 01Z 0.66 2915 75 48 -12 0.00
Fri 02/27 02Z 0.52 2915 72 46 -12 0.00
Fri 02/27 03Z 0.42 2915 66 44 -12 0.00
Fri 02/27 04Z 0.34 2915 61 38 -12 0.00
Fri 02/27 05Z 0.29 2914 59 35 -11 0.00
Fri 02/27 06Z 0.27 2913 58 43 -11 0.00
Fri 02/27 08Z 0.26 2813 56 70 -11 0.00
Fri 02/27 09Z 0.28 2813 58 78 -11 0.00
Fri 02/27 10Z 0.28 2814 57 79 -10 0.00
Fri 02/27 11Z 0.31 2714 59 80 -10 0.00
Fri 02/27 12Z 0.35 2616 63 79 -10 0.00
Fri 02/27 13Z 0.39 2618 72 77 -9 0.00
Fri 02/27 14Z 0.43 2519 77 66 -9 0.00
Fri 02/27 16Z 0.55 2521 67 44 -8 0.00
Fri 02/27 17Z 0.58 2522 77 37 -7 0.00
Fri 02/27 18Z 0.63 2522 81 28 -7 0.00
Fri 02/27 19Z 0.69 2522 81 29 -6 0.00
Fri 02/27 20Z 0.75 2522 81 42 -6 0.00
Fri 02/27 21Z 0.72 2423 80 53 -5 0.00
Fri 02/27 22Z 0.66 2424 78 63 -4 0.00
Fri 02/27 23Z 0.67 2427 77 69 -3 0.00
Sat 02/28 00Z 0.71 2329 74 67 -3 0.00
Sat 02/28 01Z 0.71 2331 69 62 -2 0.00
Sat 02/28 02Z 0.71 2233 64 59 -1 0.00
Sat 02/28 03Z 0.74 2235 64 56 -1 0.00
Sat 02/28 04Z 0.73 2237 61 52 -1 0.00
Sat 02/28 05Z 0.79 2240 58 48 0 0.00
Sat 02/28 06Z 0.82 2244 55 44 0 0.00
Sat 02/28 07Z 0.84 2246 49 44 0 0.00
Sat 02/28 08Z 0.86 2248 48 50 1 0.00
Sat 02/28 09Z 0.86 2348 52 57 1 0.00
Sat 02/28 10Z 0.84 2346 59 51 1 0.00
Sat 02/28 11Z 0.82 2344 63 51 1 0.00
Run total areal avg QPF for the Central_Greens is: 0.09 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