Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260520_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)
=== ===== === ==== ==== === === === ====
Wed 05/20 00Z 1.08 2617 73 41 16 0.00
Wed 05/20 01Z 1.20 2520 70 44 16 0.00
Wed 05/20 02Z 1.26 2525 68 50 16 0.00
Wed 05/20 03Z 1.36 2530 66 58 17 0.00
Wed 05/20 04Z 1.49 2533 71 77 17 0.00
Wed 05/20 05Z 1.59 2435 73 66 17 0.00
Wed 05/20 06Z 1.78 2540 78 63 16 0.00
Wed 05/20 07Z 1.59 2636 81 63 16 0.01
Wed 05/20 08Z 1.41 2636 81 72 15 0.00
Wed 05/20 09Z 1.31 2634 81 70 15 0.00
Wed 05/20 10Z 1.29 2631 86 63 15 0.00
Wed 05/20 11Z 1.13 2629 90 60 15 0.00
Wed 05/20 12Z 0.97 2627 91 62 15 0.00
Wed 05/20 13Z 0.98 2626 92 70 14 0.01
Wed 05/20 14Z 1.15 2627 95 76 14 0.02
Wed 05/20 15Z 1.40 2727 93 87 13 0.03
Wed 05/20 16Z 2.42 2724 90 76 12 0.01
Wed 05/20 17Z 9.54 2722 85 66 11 0.00
Wed 05/20 18Z 11.87 2722 78 56 11 0.00
Wed 05/20 19Z 12.27 2820 72 46 11 0.00
Wed 05/20 20Z 9.89 2820 72 42 11 0.00
Wed 05/20 21Z 7.60 2921 72 44 10 0.00
Wed 05/20 22Z 3.17 3021 77 42 9 0.00
Wed 05/20 23Z 0.93 3121 82 40 8 0.00
Thu 05/21 00Z 0.62 3123 81 36 7 0.00
Thu 05/21 01Z 0.55 3124 80 28 6 0.00
Thu 05/21 02Z 0.46 3123 77 18 5 0.00
Thu 05/21 03Z 0.34 3223 74 13 5 0.00
Thu 05/21 04Z 0.28 3224 63 9 4 0.00
Thu 05/21 05Z 0.24 3225 62 6 3 0.00
Thu 05/21 06Z 0.19 3325 58 5 3 0.00
Thu 05/21 07Z 0.16 3325 59 2 2 0.00
Thu 05/21 08Z 0.12 3326 60 2 1 0.00
Thu 05/21 09Z 0.07 3425 54 2 1 0.00
Thu 05/21 10Z 0.06 3426 48 3 0 0.00
Thu 05/21 11Z 0.05 3425 45 3 0 0.00
Thu 05/21 12Z 0.07 3423 45 3 0 0.00
Thu 05/21 13Z 0.07 3420 44 3 0 0.00
Thu 05/21 14Z 0.09 3318 43 3 0 0.00
Thu 05/21 15Z 0.10 3317 43 2 0 0.00
Thu 05/21 16Z 0.14 3417 42 2 0 0.00
Thu 05/21 17Z 0.23 3317 41 3 0 0.00
Thu 05/21 18Z 0.22 3417 39 3 0 0.00
Thu 05/21 19Z 0.20 3417 37 3 0 0.00
Thu 05/21 20Z 0.13 3417 34 5 1 0.00
Thu 05/21 21Z 0.13 3417 32 5 1 0.00
Thu 05/21 22Z 0.05 3417 29 5 2 0.00
Thu 05/21 23Z 0.03 3418 26 7 2 0.00
Fri 05/22 00Z 0.02 3520 22 7 3 0.00
Fri 05/22 01Z 0.06 3520 22 8 3 0.00
Fri 05/22 02Z 0.07 3519 26 8 3 0.00
Fri 05/22 03Z 0.06 3518 31 9 3 0.00
Fri 05/22 04Z 0.07 3517 35 8 3 0.00
Fri 05/22 05Z 0.09 0018 37 6 2 0.00
Fri 05/22 06Z 0.13 0017 37 6 2 0.00
Fri 05/22 07Z 0.18 0117 37 6 2 0.00
Fri 05/22 08Z 0.23 0115 36 6 2 0.00
Fri 05/22 09Z 0.20 0112 36 5 2 0.00
Fri 05/22 10Z 0.15 0110 38 6 1 0.00
Fri 05/22 11Z 0.16 0110 41 6 1 0.00
Run total areal avg QPF for the Central_Greens is: 0.08 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