
An Extreme Cold Watch remains in effect for all of northern New York and Vermont for Saturday into Sunday afternoon. Wind chills of 20 to 40 below zero are possible, especially Saturday afternoon through Sunday morning. The risk of frostbite and hypothermia will be elevated, especially for vulnerable populations. Prepare now for the extreme cold, especially if you plan to be outdoors. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260206_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)
=== ===== === ==== ==== === === === ====
Fri 02/06 06Z 0.04 1906 61 23 -10 0.00
Fri 02/06 07Z 0.04 2006 58 20 -10 0.00
Fri 02/06 08Z 0.05 2005 58 21 -10 0.00
Fri 02/06 09Z 0.07 2008 60 28 -10 0.00
Fri 02/06 10Z 0.05 1909 62 44 -11 0.00
Fri 02/06 11Z 0.05 1911 63 61 -11 0.00
Fri 02/06 12Z 0.06 1910 66 67 -11 0.00
Fri 02/06 13Z 0.04 1811 69 71 -11 0.00
Fri 02/06 14Z 0.04 1814 71 78 -11 0.00
Fri 02/06 15Z 0.08 1915 73 81 -11 0.00
Fri 02/06 16Z 0.12 2013 75 85 -11 0.00
Fri 02/06 17Z 0.12 2011 75 87 -11 0.00
Fri 02/06 18Z 0.11 1910 76 87 -11 0.00
Fri 02/06 19Z 0.11 1909 79 86 -11 0.00
Fri 02/06 21Z 0.07 1908 85 89 -11 0.00
Fri 02/06 22Z 0.05 1810 86 90 -11 0.00
Sat 02/07 01Z 0.11 1913 89 88 -11 0.00
Sat 02/07 02Z 0.16 2014 91 87 -11 0.00
Sat 02/07 03Z 0.18 2014 92 86 -11 0.00
Sat 02/07 04Z 0.15 1913 91 86 -11 0.00
Sat 02/07 05Z 0.11 1913 91 86 -11 0.01
Sat 02/07 08Z 0.07 1812 91 85 -11 0.01
Sat 02/07 09Z 0.07 1910 92 85 -11 0.01
Sat 02/07 10Z 0.08 1908 92 85 -12 0.01
Sat 02/07 11Z 0.10 2005 93 84 -12 0.01
Sat 02/07 12Z 0.12 2802 92 83 -12 0.02
Sat 02/07 13Z 0.08 3307 91 82 -13 0.01
Sat 02/07 15Z 0.09 3413 87 81 -14 0.01
Sat 02/07 16Z 0.10 3314 86 82 -14 0.01
Sat 02/07 18Z 0.14 3316 84 83 -15 0.01
Sat 02/07 19Z 0.16 3318 84 83 -16 0.02
Sat 02/07 20Z 0.19 3320 84 83 -17 0.02
Sat 02/07 21Z 0.21 3322 85 82 -18 0.02
Sat 02/07 22Z 0.21 3324 85 80 -19 0.01
Sat 02/07 23Z 0.21 3325 85 78 -19 0.01
Sun 02/08 00Z 0.21 3326 85 77 -19 0.01
Sun 02/08 01Z 0.21 3326 85 76 -20 0.01
Sun 02/08 02Z 0.20 3326 85 77 -20 0.01
Sun 02/08 03Z 0.20 3325 84 78 -20 0.01
Sun 02/08 04Z 0.18 3324 84 80 -20 0.01
Sun 02/08 05Z 0.17 3323 83 79 -19 0.01
Sun 02/08 06Z 0.16 3322 83 76 -19 0.00
Sun 02/08 07Z 0.16 3322 82 75 -19 0.00
Sun 02/08 08Z 0.19 3224 82 72 -19 0.00
Sun 02/08 09Z 0.21 3225 81 70 -20 0.00
Sun 02/08 10Z 0.21 3226 80 69 -20 0.00
Sun 02/08 11Z 0.21 3226 76 65 -20 0.00
Sun 02/08 12Z 0.21 3227 71 57 -20 0.00
Sun 02/08 13Z 0.20 3227 67 52 -20 0.00
Sun 02/08 14Z 0.20 3226 65 46 -21 0.00
Sun 02/08 15Z 0.20 3224 66 38 -21 0.00
Sun 02/08 16Z 0.20 3223 66 36 -22 0.00
Sun 02/08 17Z 0.23 3222 67 40 -22 0.00
Run total areal avg QPF for the greens is: 0.25 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