Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260607_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 06/07 18Z 0.18 3321 98 94 10 0.00
Sun 06/07 19Z 0.12 3422 97 92 10 0.02
Sun 06/07 20Z 0.11 3521 97 85 9 0.02
Sun 06/07 21Z 0.15 3522 97 86 9 0.01
Sun 06/07 22Z 0.22 0023 97 82 9 0.01
Sun 06/07 23Z 0.29 0125 90 70 9 0.00
Mon 06/08 00Z 0.37 0226 80 42 9 0.00
Mon 06/08 01Z 0.46 0326 79 17 9 0.00
Mon 06/08 02Z 0.55 0425 72 4 9 0.00
Mon 06/08 03Z 0.62 0524 66 1 8 0.00
Mon 06/08 04Z 0.65 0622 63 1 8 0.00
Mon 06/08 05Z 0.65 0621 57 2 8 0.00
Mon 06/08 06Z 0.67 0720 52 2 8 0.00
Mon 06/08 07Z 0.70 0720 42 3 7 0.00
Mon 06/08 08Z 0.79 0720 37 3 7 0.00
Mon 06/08 09Z 0.68 0717 40 4 7 0.00
Mon 06/08 10Z 0.55 0713 44 6 7 0.00
Mon 06/08 11Z 0.49 0611 47 9 7 0.00
Mon 06/08 12Z 0.42 0609 49 12 7 0.00
Mon 06/08 13Z 0.32 0407 52 12 7 0.00
Mon 06/08 14Z 0.47 0306 56 12 7 0.00
Mon 06/08 15Z 0.59 0403 59 13 7 0.00
Mon 06/08 16Z 0.32 0102 61 13 8 0.00
Mon 06/08 17Z 0.35 3001 64 13 8 0.00
Mon 06/08 18Z 0.57 2902 66 12 9 0.00
Mon 06/08 19Z 0.86 2703 68 11 9 0.00
Mon 06/08 20Z 0.75 2803 67 10 10 0.00
Mon 06/08 21Z 0.80 2705 62 9 10 0.00
Mon 06/08 22Z 0.51 2706 56 8 10 0.00
Mon 06/08 23Z 0.34 2707 53 7 11 0.00
Tue 06/09 00Z 0.38 2709 49 5 11 0.00
Tue 06/09 01Z 0.39 2710 50 5 11 0.00
Tue 06/09 02Z 0.39 2710 49 4 11 0.00
Tue 06/09 03Z 0.38 2709 51 3 11 0.00
Tue 06/09 04Z 0.55 2614 52 3 11 0.00
Tue 06/09 05Z 0.50 2613 55 3 11 0.00
Tue 06/09 06Z 0.61 2615 60 4 11 0.00
Tue 06/09 07Z 0.54 2715 66 3 11 0.00
Tue 06/09 08Z 0.46 2715 71 3 11 0.00
Tue 06/09 09Z 0.34 2713 71 2 12 0.00
Tue 06/09 10Z 0.33 2713 69 2 12 0.00
Tue 06/09 11Z 0.29 2612 66 1 12 0.00
Tue 06/09 12Z 0.24 2609 69 1 11 0.00
Tue 06/09 13Z 0.20 2607 71 1 11 0.00
Tue 06/09 14Z 0.21 2507 70 1 11 0.00
Tue 06/09 15Z 0.25 2606 70 1 11 0.00
Tue 06/09 16Z 0.52 2507 71 2 11 0.00
Tue 06/09 17Z 0.69 2608 68 2 12 0.00
Tue 06/09 18Z 0.56 2607 62 2 12 0.00
Tue 06/09 19Z 0.55 2607 59 1 13 0.00
Tue 06/09 20Z 0.48 2607 61 2 14 0.00
Tue 06/09 21Z 0.41 2608 65 2 14 0.00
Tue 06/09 22Z 0.40 2509 71 2 14 0.00
Tue 06/09 23Z 0.37 2510 75 1 14 0.00
Wed 06/10 00Z 0.40 2612 74 1 15 0.00
Wed 06/10 01Z 0.41 2613 75 1 15 0.00
Wed 06/10 02Z 0.37 2612 73 2 15 0.00
Wed 06/10 03Z 0.31 2611 69 3 15 0.00
Wed 06/10 04Z 0.22 2507 67 3 15 0.00
Wed 06/10 05Z 0.19 2506 69 2 15 0.00
Run total areal avg QPF for the Central_Greens is: 0.06 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