Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260608_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)
=== ===== === ==== ==== === === === ====
Mon 06/08 00Z 0.15 0115 91 22 9 0.00
Mon 06/08 01Z 0.18 0118 87 3 9 0.00
Mon 06/08 02Z 0.33 0223 75 0 9 0.00
Mon 06/08 03Z 0.66 0327 66 0 8 0.00
Mon 06/08 04Z 0.81 0527 51 0 8 0.00
Mon 06/08 05Z 0.85 0525 45 1 8 0.00
Mon 06/08 06Z 0.90 0625 41 3 8 0.00
Mon 06/08 07Z 0.94 0724 40 4 8 0.00
Mon 06/08 08Z 0.87 0822 39 4 7 0.00
Mon 06/08 09Z 0.85 0820 40 5 7 0.00
Mon 06/08 10Z 0.69 0816 42 4 7 0.00
Mon 06/08 11Z 0.55 0813 44 6 7 0.00
Mon 06/08 12Z 0.47 0711 45 10 7 0.00
Mon 06/08 13Z 0.43 0609 47 13 7 0.00
Mon 06/08 14Z 0.46 0607 50 13 7 0.00
Mon 06/08 15Z 0.66 0404 54 12 7 0.00
Mon 06/08 16Z 0.65 0303 57 12 8 0.00
Mon 06/08 17Z 0.29 3101 61 12 8 0.00
Mon 06/08 18Z 0.36 2501 64 13 9 0.00
Mon 06/08 19Z 0.77 2502 66 13 9 0.00
Mon 06/08 20Z 0.79 2403 66 12 10 0.00
Mon 06/08 21Z 0.84 2405 65 10 10 0.00
Mon 06/08 22Z 0.60 2506 60 11 10 0.00
Mon 06/08 23Z 0.41 2607 57 12 10 0.00
Tue 06/09 00Z 0.38 2508 54 12 11 0.00
Tue 06/09 01Z 0.42 2510 49 9 11 0.00
Tue 06/09 02Z 0.45 2611 43 6 11 0.00
Tue 06/09 03Z 0.42 2511 47 5 11 0.00
Tue 06/09 04Z 0.49 2513 49 3 11 0.00
Tue 06/09 05Z 0.47 2514 50 3 12 0.00
Tue 06/09 06Z 0.50 2615 53 2 12 0.00
Tue 06/09 07Z 0.52 2616 60 3 11 0.00
Tue 06/09 08Z 0.53 2618 67 3 12 0.00
Tue 06/09 09Z 0.54 2620 74 3 12 0.00
Tue 06/09 10Z 0.49 2620 74 3 12 0.01
Tue 06/09 11Z 0.39 2717 71 3 12 0.01
Tue 06/09 12Z 0.39 2716 76 3 12 0.01
Tue 06/09 13Z 0.31 2713 74 2 12 0.01
Tue 06/09 14Z 0.21 2809 74 3 12 0.00
Tue 06/09 15Z 0.26 2708 74 5 12 0.00
Tue 06/09 16Z 0.30 2507 71 4 12 0.00
Tue 06/09 17Z 0.54 2408 72 5 12 0.00
Tue 06/09 18Z 0.66 2408 70 5 13 0.00
Tue 06/09 19Z 0.65 2409 68 5 13 0.00
Tue 06/09 20Z 0.66 2410 67 5 13 0.00
Tue 06/09 21Z 0.63 2412 67 5 14 0.00
Tue 06/09 22Z 0.63 2514 73 4 14 0.00
Tue 06/09 23Z 0.60 2515 76 4 14 0.00
Wed 06/10 00Z 0.62 2516 77 3 14 0.00
Wed 06/10 01Z 0.62 2617 76 2 14 0.00
Wed 06/10 02Z 0.55 2617 74 1 14 0.00
Wed 06/10 03Z 0.47 2616 69 1 15 0.00
Wed 06/10 04Z 0.36 2713 63 1 16 0.00
Wed 06/10 05Z 0.30 2611 60 1 16 0.00
Wed 06/10 06Z 0.25 2610 58 2 16 0.00
Wed 06/10 07Z 0.21 2408 58 4 16 0.00
Wed 06/10 08Z 0.18 2307 60 14 15 0.00
Wed 06/10 09Z 0.19 2208 64 43 15 0.00
Wed 06/10 10Z 0.20 2109 73 65 15 0.00
Wed 06/10 11Z 0.20 2109 80 69 14 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