Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260202_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)
=== ===== === ==== ==== === === === ====
Mon 02/02 06Z 0.04 3425 66 23 -10 0.00
Mon 02/02 07Z 0.04 3429 58 24 -8 0.00
Mon 02/02 08Z 0.02 3429 51 26 -8 0.00
Mon 02/02 09Z 0.02 3429 47 27 -8 0.00
Mon 02/02 10Z 0.03 3428 46 27 -8 0.00
Mon 02/02 11Z 0.02 3427 45 25 -8 0.00
Mon 02/02 12Z 0.02 3426 45 22 -8 0.00
Mon 02/02 13Z 0.02 3425 45 19 -9 0.00
Mon 02/02 14Z 0.02 3423 43 17 -9 0.00
Mon 02/02 15Z 0.02 3422 42 14 -9 0.00
Mon 02/02 16Z 0.04 3421 41 13 -9 0.00
Mon 02/02 17Z 0.04 3421 38 12 -9 0.00
Mon 02/02 18Z 0.07 3421 38 12 -9 0.00
Mon 02/02 19Z 0.11 3323 40 11 -9 0.00
Mon 02/02 20Z 0.14 3324 42 11 -9 0.00
Mon 02/02 22Z 0.16 3322 44 12 -9 0.00
Mon 02/02 23Z 0.15 3322 42 15 -9 0.00
Tue 02/03 00Z 0.13 3321 41 23 -8 0.00
Tue 02/03 01Z 0.08 3320 40 41 -8 0.00
Tue 02/03 02Z 0.05 3418 39 56 -8 0.00
Tue 02/03 03Z 0.04 3416 41 54 -8 0.00
Tue 02/03 04Z 0.06 3314 41 52 -8 0.00
Tue 02/03 05Z 0.07 3312 42 51 -8 0.00
Tue 02/03 06Z 0.10 3211 41 53 -8 0.00
Tue 02/03 07Z 0.14 3112 40 55 -8 0.00
Tue 02/03 08Z 0.15 3011 39 53 -8 0.00
Tue 02/03 09Z 0.17 2910 40 49 -9 0.00
Tue 02/03 10Z 0.16 2808 40 25 -9 0.00
Tue 02/03 11Z 0.15 2807 40 10 -9 0.00
Tue 02/03 12Z 0.15 2807 41 13 -9 0.00
Tue 02/03 13Z 0.16 2707 43 16 -9 0.00
Tue 02/03 14Z 0.16 2607 43 20 -9 0.00
Tue 02/03 15Z 0.19 2508 45 65 -9 0.00
Tue 02/03 16Z 0.21 2408 50 90 -10 0.00
Tue 02/03 17Z 0.26 2409 63 90 -10 0.00
Tue 02/03 18Z 0.32 2409 76 85 -11 0.00
Tue 02/03 19Z 0.36 2309 83 67 -11 0.00
Tue 02/03 20Z 0.42 2310 87 29 -12 0.00
Tue 02/03 21Z 0.40 2410 89 24 -12 0.00
Tue 02/03 22Z 0.40 2511 92 37 -12 0.00
Tue 02/03 23Z 0.50 2513 95 51 -13 0.00
Wed 02/04 00Z 0.60 2515 95 72 -13 0.00
Wed 02/04 01Z 0.64 2616 94 76 -13 0.01
Wed 02/04 02Z 0.63 2616 92 75 -13 0.01
Wed 02/04 03Z 0.64 2716 91 68 -14 0.00
Wed 02/04 04Z 0.65 2716 90 51 -14 0.00
Wed 02/04 05Z 0.67 2716 91 37 -14 0.00
Wed 02/04 06Z 0.56 2816 92 34 -14 0.01
Wed 02/04 07Z 0.57 2816 92 38 -15 0.00
Wed 02/04 08Z 0.71 2817 91 43 -16 0.00
Wed 02/04 09Z 0.70 2717 91 36 -16 0.00
Wed 02/04 10Z 0.65 2818 92 35 -17 0.00
Wed 02/04 11Z 0.45 2918 86 36 -17 0.00
Wed 02/04 12Z 0.31 3118 80 37 -16 0.00
Wed 02/04 13Z 0.27 3118 80 37 -15 0.00
Wed 02/04 14Z 0.26 3117 80 38 -15 0.00
Wed 02/04 15Z 0.25 3116 81 35 -15 0.00
Wed 02/04 16Z 0.25 3115 81 34 -14 0.00
Wed 02/04 17Z 0.29 3014 82 34 -14 0.00
Run total areal avg QPF for the Central_Greens is: 0.03 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