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Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260628_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)
=== ===== === ==== ==== === === === ====
Sun 06/28 00Z 0.03 3406 86 65 12 0.00
Sun 06/28 01Z 0.02 3405 85 63 12 0.00
Sun 06/28 02Z 0.07 0005 82 66 12 0.00
Sun 06/28 03Z 0.10 0105 79 68 12 0.00
Sun 06/28 04Z 0.10 0205 77 72 12 0.00
Sun 06/28 05Z 0.09 0105 76 76 12 0.00
Sun 06/28 06Z 0.06 0004 74 76 12 0.00
Sun 06/28 07Z 0.10 0106 71 63 12 0.00
Sun 06/28 08Z 0.09 0107 67 48 12 0.00
Sun 06/28 09Z 0.09 0008 64 41 12 0.00
Sun 06/28 10Z 0.11 0009 62 35 12 0.00
Sun 06/28 11Z 0.14 0110 64 30 11 0.00
Sun 06/28 12Z 0.19 0110 67 28 11 0.00
Sun 06/28 13Z 0.28 0209 72 29 11 0.00
Sun 06/28 14Z 0.41 0108 76 33 11 0.00
Sun 06/28 15Z 0.94 0106 78 31 11 0.00
Sun 06/28 16Z 1.16 0105 78 34 11 0.00
Sun 06/28 17Z 0.77 0003 76 43 12 0.03
Sun 06/28 18Z 0.33 3403 74 40 12 0.03
Sun 06/28 19Z 0.37 3304 75 39 12 0.01
Sun 06/28 20Z 0.47 3305 75 32 12 0.01
Sun 06/28 21Z 0.28 3306 73 23 13 0.01
Sun 06/28 22Z 0.21 3307 68 28 13 0.00
Sun 06/28 23Z 0.09 3307 61 26 13 0.00
Mon 06/29 00Z 0.03 3408 55 26 13 0.00
Mon 06/29 01Z 0.09 0008 54 20 13 0.00
Mon 06/29 02Z 0.13 0008 55 18 13 0.00
Mon 06/29 03Z 0.12 0008 53 19 13 0.00
Mon 06/29 04Z 0.08 0008 53 22 13 0.00
Mon 06/29 05Z 0.13 0008 53 22 12 0.00
Mon 06/29 06Z 0.16 0108 56 20 12 0.00
Mon 06/29 07Z 0.14 0108 58 20 12 0.00
Mon 06/29 08Z 0.13 0008 60 18 12 0.00
Mon 06/29 09Z 0.11 0008 63 14 12 0.00
Mon 06/29 10Z 0.09 3508 66 14 11 0.00
Mon 06/29 11Z 0.11 0008 68 11 11 0.00
Mon 06/29 12Z 0.08 3507 70 10 11 0.00
Mon 06/29 13Z 0.11 3506 72 9 11 0.00
Mon 06/29 14Z 0.30 3505 72 5 11 0.00
Mon 06/29 15Z 0.23 3403 73 5 12 0.00
Mon 06/29 16Z 0.31 3303 74 11 12 0.00
Mon 06/29 17Z 0.62 3103 73 13 12 0.00
Mon 06/29 18Z 0.86 3104 69 9 13 0.00
Mon 06/29 19Z 0.89 3004 65 6 13 0.00
Mon 06/29 20Z 0.98 3004 61 4 13 0.00
Mon 06/29 21Z 0.98 3006 58 5 13 0.00
Mon 06/29 22Z 0.42 3005 59 8 13 0.00
Mon 06/29 23Z 0.23 3004 62 11 13 0.00
Tue 06/30 00Z 0.23 2903 65 10 13 0.00
Tue 06/30 01Z 0.29 2704 69 15 13 0.00
Tue 06/30 02Z 0.38 2605 71 18 13 0.00
Tue 06/30 03Z 0.49 2507 73 21 13 0.00
Tue 06/30 04Z 0.62 2508 74 20 13 0.00
Tue 06/30 05Z 0.71 2509 76 21 13 0.00
Tue 06/30 06Z 0.74 2610 75 22 13 0.00
Tue 06/30 07Z 0.75 2511 77 20 13 0.00
Tue 06/30 08Z 0.72 2611 75 22 13 0.00
Tue 06/30 09Z 0.61 2611 74 27 13 0.00
Tue 06/30 10Z 0.55 2610 74 30 13 0.00
Tue 06/30 11Z 0.57 2611 74 32 13 0.00
Run total areal avg QPF for the Central_Greens is: 0.09 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