Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260201_1800
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)
=== ===== === ==== ==== === === === ====
Sun 02/01 18Z 0.06 0013 79 11 -11 0.00
Sun 02/01 19Z 0.06 3516 78 11 -10 0.00
Sun 02/01 20Z 0.07 0019 76 11 -10 0.00
Sun 02/01 21Z 0.09 0021 70 11 -9 0.00
Sun 02/01 22Z 0.10 0025 64 11 -9 0.00
Sun 02/01 23Z 0.10 0027 57 10 -9 0.00
Mon 02/02 00Z 0.09 0028 55 10 -9 0.00
Mon 02/02 01Z 0.10 0029 54 10 -9 0.00
Mon 02/02 02Z 0.09 0029 53 11 -10 0.00
Mon 02/02 03Z 0.06 3527 53 12 -10 0.00
Mon 02/02 04Z 0.03 3525 53 15 -9 0.00
Mon 02/02 05Z 0.02 3425 52 21 -9 0.00
Mon 02/02 06Z 0.02 3524 48 29 -9 0.00
Mon 02/02 07Z 0.02 3525 43 34 -9 0.00
Mon 02/02 08Z 0.02 3525 42 35 -9 0.00
Mon 02/02 10Z 0.02 3525 39 33 -8 0.00
Mon 02/02 11Z 0.02 3525 37 30 -8 0.00
Mon 02/02 12Z 0.02 3425 38 31 -8 0.00
Mon 02/02 13Z 0.02 3425 37 32 -8 0.00
Mon 02/02 14Z 0.02 3525 37 29 -8 0.00
Mon 02/02 15Z 0.02 3423 38 27 -8 0.00
Mon 02/02 16Z 0.03 3422 39 24 -8 0.00
Mon 02/02 17Z 0.05 3421 36 19 -9 0.00
Mon 02/02 18Z 0.09 3322 38 16 -9 0.00
Mon 02/02 19Z 0.10 3323 41 14 -9 0.00
Mon 02/02 20Z 0.09 3323 39 12 -9 0.00
Mon 02/02 21Z 0.09 3322 38 10 -9 0.00
Mon 02/02 22Z 0.09 3322 37 9 -9 0.00
Mon 02/02 23Z 0.10 3321 37 9 -9 0.00
Tue 02/03 00Z 0.10 3319 37 11 -9 0.00
Tue 02/03 01Z 0.08 3318 34 22 -8 0.00
Tue 02/03 02Z 0.06 3417 33 40 -8 0.00
Tue 02/03 03Z 0.07 3316 38 48 -9 0.00
Tue 02/03 04Z 0.05 3314 39 49 -9 0.00
Tue 02/03 05Z 0.07 3313 41 48 -9 0.00
Tue 02/03 06Z 0.08 3313 42 48 -9 0.00
Tue 02/03 07Z 0.09 3212 42 48 -9 0.00
Tue 02/03 08Z 0.11 3212 42 48 -9 0.00
Tue 02/03 09Z 0.11 3210 42 57 -9 0.00
Tue 02/03 10Z 0.13 3109 41 56 -9 0.00
Tue 02/03 11Z 0.12 3007 41 44 -9 0.00
Tue 02/03 12Z 0.10 3006 40 24 -9 0.00
Tue 02/03 13Z 0.09 2904 39 16 -9 0.00
Tue 02/03 14Z 0.11 2604 39 13 -9 0.00
Tue 02/03 15Z 0.13 2405 40 16 -9 0.00
Tue 02/03 16Z 0.18 2307 42 29 -9 0.00
Tue 02/03 17Z 0.22 2308 42 82 -10 0.00
Tue 02/03 18Z 0.26 2308 40 89 -10 0.00
Tue 02/03 19Z 0.30 2208 48 73 -10 0.00
Tue 02/03 20Z 0.34 2308 65 51 -11 0.00
Tue 02/03 21Z 0.35 2309 80 31 -11 0.00
Tue 02/03 22Z 0.34 2509 86 26 -11 0.00
Tue 02/03 23Z 0.34 2510 91 30 -12 0.00
Wed 02/04 00Z 0.43 2512 94 36 -12 0.00
Wed 02/04 01Z 0.50 2513 93 60 -12 0.00
Wed 02/04 02Z 0.50 2614 91 75 -12 0.00
Wed 02/04 03Z 0.51 2614 86 80 -12 0.00
Wed 02/04 04Z 0.59 2716 92 82 -13 0.00
Wed 02/04 05Z 0.60 2715 94 77 -13 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