Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260602_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 06/02 00Z 0.03 3405 72 66 5 0.00
Tue 06/02 01Z 0.03 3507 70 62 5 0.00
Tue 06/02 02Z 0.10 3509 69 56 5 0.00
Tue 06/02 03Z 0.17 0010 69 56 5 0.00
Tue 06/02 04Z 0.18 0011 69 65 5 0.00
Tue 06/02 05Z 0.12 3510 67 69 5 0.00
Tue 06/02 06Z 0.14 3411 66 65 5 0.00
Tue 06/02 07Z 0.18 3311 65 60 5 0.00
Tue 06/02 08Z 0.22 3213 65 65 5 0.00
Tue 06/02 09Z 0.22 3214 63 64 6 0.00
Tue 06/02 10Z 0.20 3315 60 65 6 0.00
Tue 06/02 11Z 0.18 3316 57 62 6 0.00
Tue 06/02 12Z 0.16 3316 52 54 6 0.00
Tue 06/02 13Z 0.15 3316 47 47 7 0.00
Tue 06/02 14Z 0.14 3417 42 39 7 0.00
Tue 06/02 15Z 0.63 3316 44 34 7 0.00
Tue 06/02 16Z 1.68 3317 43 24 7 0.00
Tue 06/02 17Z 2.56 3319 41 14 7 0.00
Tue 06/02 18Z 2.83 3320 40 11 7 0.00
Tue 06/02 19Z 2.55 3319 44 14 7 0.00
Tue 06/02 20Z 2.31 3320 45 26 7 0.00
Tue 06/02 21Z 1.18 3420 45 45 7 0.00
Tue 06/02 22Z 0.50 3421 45 70 7 0.00
Tue 06/02 23Z 0.07 3421 44 81 7 0.00
Wed 06/03 00Z 0.08 3523 45 69 7 0.00
Wed 06/03 01Z 0.21 3523 46 51 7 0.00
Wed 06/03 02Z 0.35 0023 44 42 8 0.00
Wed 06/03 03Z 0.37 0021 42 45 8 0.00
Wed 06/03 04Z 0.35 0019 43 47 8 0.00
Wed 06/03 05Z 0.37 0117 43 31 8 0.00
Wed 06/03 06Z 0.34 0016 43 21 8 0.00
Wed 06/03 07Z 0.28 0015 44 18 8 0.00
Wed 06/03 08Z 0.35 0014 44 23 8 0.00
Wed 06/03 09Z 0.39 0113 45 36 8 0.00
Wed 06/03 10Z 0.24 0011 45 56 8 0.00
Wed 06/03 11Z 0.11 3511 46 75 8 0.00
Wed 06/03 12Z 0.09 3510 46 75 8 0.00
Wed 06/03 13Z 0.04 3410 47 76 8 0.00
Wed 06/03 14Z 0.21 3309 49 75 9 0.00
Wed 06/03 15Z 0.71 3210 51 75 9 0.00
Wed 06/03 16Z 1.41 3210 51 72 9 0.00
Wed 06/03 17Z 1.89 3210 50 67 9 0.00
Wed 06/03 18Z 1.97 3210 50 63 10 0.00
Wed 06/03 19Z 1.72 3209 50 56 10 0.00
Wed 06/03 20Z 2.12 3109 52 54 11 0.00
Wed 06/03 21Z 1.83 3109 54 53 11 0.00
Wed 06/03 22Z 0.80 3009 56 53 11 0.00
Wed 06/03 23Z 0.47 3010 57 57 11 0.00
Thu 06/04 00Z 0.43 2909 58 53 11 0.00
Thu 06/04 01Z 0.47 2910 60 50 11 0.00
Thu 06/04 02Z 0.46 2910 61 43 11 0.00
Thu 06/04 03Z 0.45 3010 63 36 11 0.00
Thu 06/04 04Z 0.33 3110 63 31 11 0.00
Thu 06/04 05Z 0.29 3110 61 27 11 0.00
Thu 06/04 06Z 0.32 2909 58 25 11 0.00
Thu 06/04 07Z 0.40 2810 56 27 11 0.00
Thu 06/04 08Z 0.40 2810 51 31 11 0.00
Thu 06/04 09Z 0.36 2910 47 36 11 0.00
Thu 06/04 10Z 0.37 2910 48 39 11 0.00
Thu 06/04 11Z 0.38 2911 48 39 11 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