
A Flood Watch remains in effect for south-central Vermont and eastern slopes of the Adirondacks due to the potential for heavy rain. Additional rainfall amounts of 1-3 inches with localized amounts of 3-5 inches along the spine of the southern Greens could produce excessive runoff and cause flooding in low-lying or flood prone areas. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260729_0600
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.
925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date Time Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Wed 07/29 06Z 0.08 1715 93 96 13 0.00
Wed 07/29 07Z 0.15 1619 93 94 13 0.00
Wed 07/29 08Z 0.18 1621 93 93 13 0.01
Wed 07/29 09Z 0.23 1622 93 91 13 0.01
Wed 07/29 10Z 0.33 1526 91 91 13 0.01
Wed 07/29 11Z 0.39 1528 90 88 13 0.01
Wed 07/29 12Z 0.37 1528 86 85 13 0.01
Wed 07/29 13Z 0.34 1524 86 81 13 0.01
Wed 07/29 14Z 0.40 1422 84 71 13 0.00
Wed 07/29 15Z 0.58 1322 89 69 13 0.00
Wed 07/29 16Z 0.76 1322 91 66 12 0.01
Wed 07/29 17Z 0.93 1322 93 69 12 0.01
Wed 07/29 18Z 0.79 1321 94 72 12 0.01
Wed 07/29 19Z 0.74 1220 94 74 12 0.01
Wed 07/29 20Z 0.69 1220 93 79 12 0.02
Wed 07/29 21Z 0.62 1120 91 79 12 0.04
Wed 07/29 22Z 0.58 1121 86 79 12 0.01
Wed 07/29 23Z 0.55 1120 81 79 13 0.00
Thu 07/30 00Z 0.51 1019 80 80 13 0.01
Thu 07/30 01Z 0.51 0919 81 85 13 0.01
Thu 07/30 02Z 0.51 0919 79 90 12 0.01
Thu 07/30 03Z 0.49 0918 76 92 13 0.00
Thu 07/30 04Z 0.47 0817 76 94 13 0.00
Thu 07/30 05Z 0.41 0715 78 93 12 0.00
Thu 07/30 06Z 0.40 0615 78 94 12 0.01
Thu 07/30 07Z 0.44 0616 82 93 12 0.02
Thu 07/30 08Z 0.46 0617 84 93 11 0.02
Thu 07/30 09Z 0.45 0616 87 91 11 0.02
Thu 07/30 10Z 0.44 0517 86 89 11 0.02
Thu 07/30 11Z 0.43 0517 85 89 11 0.02
Thu 07/30 12Z 0.40 0417 83 89 11 0.01
Thu 07/30 13Z 0.42 0418 79 89 11 0.01
Thu 07/30 14Z 0.37 0418 75 89 12 0.00
Thu 07/30 15Z 0.39 0318 80 90 11 0.00
Thu 07/30 16Z 0.65 0217 83 86 11 0.00
Thu 07/30 17Z 0.60 0217 86 90 11 0.00
Thu 07/30 18Z 0.71 0318 89 95 11 0.01
Thu 07/30 19Z 0.53 0319 88 96 11 0.01
Thu 07/30 20Z 0.47 0320 88 94 11 0.01
Thu 07/30 21Z 0.44 0320 85 86 11 0.01
Thu 07/30 22Z 0.46 0419 87 80 11 0.00
Thu 07/30 23Z 0.46 0419 85 78 11 0.00
Fri 07/31 00Z 0.44 0418 84 80 11 0.00
Fri 07/31 01Z 0.40 0517 86 77 11 0.00
Fri 07/31 02Z 0.32 0414 87 72 11 0.00
Fri 07/31 03Z 0.26 0313 86 73 11 0.00
Fri 07/31 04Z 0.21 0312 87 74 11 0.00
Fri 07/31 05Z 0.16 0212 87 72 11 0.00
Fri 07/31 06Z 0.15 0212 86 66 11 0.00
Fri 07/31 07Z 0.15 0113 87 62 11 0.00
Fri 07/31 08Z 0.16 0114 89 60 11 0.00
Fri 07/31 09Z 0.17 0215 89 55 11 0.00
Fri 07/31 10Z 0.20 0215 87 52 11 0.00
Fri 07/31 11Z 0.17 0214 87 52 11 0.00
Fri 07/31 12Z 0.13 0113 88 55 11 0.00
Fri 07/31 13Z 0.13 0112 90 57 11 0.00
Fri 07/31 14Z 0.13 0210 91 59 11 0.00
Fri 07/31 15Z 0.10 0108 92 59 11 0.00
Fri 07/31 16Z 0.05 0007 92 58 11 0.00
Fri 07/31 17Z 0.08 3507 92 56 11 0.00
Run total areal avg QPF for the greens is: 0.37 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