Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260608_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 06/08 06Z 0.41 0615 72 4 8 0.00
Mon 06/08 07Z 0.41 0614 73 5 8 0.00
Mon 06/08 08Z 0.35 0712 74 5 7 0.00
Mon 06/08 09Z 0.35 0811 69 6 7 0.00
Mon 06/08 10Z 0.31 0810 64 7 7 0.00
Mon 06/08 11Z 0.27 0808 61 6 7 0.00
Mon 06/08 12Z 0.23 0806 60 6 7 0.00
Mon 06/08 13Z 0.19 0705 61 8 7 0.00
Mon 06/08 14Z 0.18 0604 65 9 7 0.00
Mon 06/08 15Z 0.17 0402 69 10 7 0.00
Mon 06/08 16Z 0.17 0401 73 11 8 0.00
Mon 06/08 17Z 0.14 0001 75 10 8 0.00
Mon 06/08 18Z 0.16 3401 76 10 9 0.00
Mon 06/08 19Z 0.21 3001 77 8 9 0.00
Mon 06/08 20Z 0.32 2802 76 7 10 0.00
Mon 06/08 21Z 0.27 2602 74 5 10 0.00
Mon 06/08 22Z 0.38 2504 69 5 10 0.00
Mon 06/08 23Z 0.26 2505 62 4 10 0.00
Tue 06/09 00Z 0.27 2506 54 4 11 0.00
Tue 06/09 01Z 0.39 2509 49 3 11 0.00
Tue 06/09 02Z 0.39 2610 48 2 11 0.00
Tue 06/09 03Z 0.41 2510 48 2 11 0.00
Tue 06/09 04Z 0.51 2613 58 2 11 0.00
Tue 06/09 05Z 0.57 2615 58 2 11 0.00
Tue 06/09 06Z 0.55 2716 60 2 11 0.00
Tue 06/09 07Z 0.53 2816 71 2 11 0.00
Tue 06/09 08Z 0.43 2814 78 2 10 0.00
Tue 06/09 09Z 0.34 2812 79 2 10 0.00
Tue 06/09 10Z 0.35 2713 76 2 11 0.00
Tue 06/09 11Z 0.29 2711 75 2 11 0.01
Tue 06/09 12Z 0.23 2608 77 2 11 0.01
Tue 06/09 13Z 0.25 2609 81 2 11 0.01
Tue 06/09 14Z 0.22 2608 79 2 11 0.01
Tue 06/09 15Z 0.19 2506 77 2 11 0.00
Tue 06/09 16Z 0.25 2507 79 2 11 0.00
Tue 06/09 17Z 0.32 2508 81 2 11 0.00
Tue 06/09 18Z 0.35 2508 80 2 12 0.00
Tue 06/09 19Z 0.38 2509 80 1 12 0.00
Tue 06/09 20Z 0.41 2510 78 1 13 0.00
Tue 06/09 21Z 0.40 2510 74 1 13 0.00
Tue 06/09 22Z 0.36 2610 70 0 14 0.00
Tue 06/09 23Z 0.35 2611 69 0 14 0.00
Wed 06/10 00Z 0.39 2613 74 0 14 0.00
Wed 06/10 01Z 0.38 2613 72 0 14 0.00
Wed 06/10 02Z 0.36 2613 70 0 15 0.00
Wed 06/10 03Z 0.31 2612 64 0 15 0.00
Wed 06/10 04Z 0.27 2611 59 1 16 0.00
Wed 06/10 05Z 0.22 2509 58 2 16 0.00
Wed 06/10 06Z 0.24 2410 62 12 16 0.00
Wed 06/10 07Z 0.24 2410 67 30 16 0.00
Wed 06/10 08Z 0.25 2410 76 40 15 0.00
Wed 06/10 09Z 0.25 2310 83 43 15 0.00
Wed 06/10 10Z 0.25 2211 86 57 15 0.00
Wed 06/10 11Z 0.29 2113 86 75 15 0.00
Wed 06/10 12Z 0.28 2114 84 80 15 0.00
Wed 06/10 13Z 0.23 2013 83 78 16 0.00
Wed 06/10 14Z 0.23 2014 83 73 16 0.00
Wed 06/10 15Z 0.20 1915 83 75 16 0.00
Wed 06/10 16Z 0.31 1914 85 88 15 0.00
Wed 06/10 17Z 0.30 1914 91 94 15 0.00
Run total areal avg QPF for the Central_Greens is: 0.04 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