
An Extreme Cold Watch has been issued for all of northern New York and Vermont for Saturday into Sunday afternoon. Wind chills of 20 to 35 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_20260205_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)
=== ===== === ==== ==== === === === ====
Thu 02/05 06Z 0.40 2915 86 46 -13 0.00
Thu 02/05 07Z 0.45 2917 85 45 -13 0.00
Thu 02/05 08Z 0.50 2919 87 48 -13 0.00
Thu 02/05 09Z 0.50 2919 86 62 -14 0.00
Thu 02/05 10Z 0.49 2920 85 68 -14 0.00
Thu 02/05 11Z 0.47 2920 86 75 -14 0.00
Thu 02/05 12Z 0.44 3021 85 36 -14 0.00
Thu 02/05 13Z 0.41 3022 83 8 -14 0.00
Thu 02/05 14Z 0.36 3121 80 5 -15 0.00
Thu 02/05 15Z 0.32 3118 77 5 -15 0.00
Thu 02/05 16Z 0.29 3117 75 5 -14 0.00
Thu 02/05 17Z 0.26 3115 71 5 -14 0.00
Thu 02/05 18Z 0.23 3113 66 6 -14 0.00
Thu 02/05 19Z 0.20 3212 61 6 -13 0.00
Thu 02/05 20Z 0.17 3212 56 7 -13 0.00
Thu 02/05 21Z 0.15 3211 51 9 -12 0.00
Thu 02/05 22Z 0.12 3311 44 12 -11 0.00
Thu 02/05 23Z 0.10 3310 41 15 -11 0.00
Fri 02/06 00Z 0.07 3309 37 18 -10 0.00
Fri 02/06 01Z 0.05 3307 35 21 -10 0.00
Fri 02/06 02Z 0.02 3405 32 23 -10 0.00
Fri 02/06 03Z 0.02 3402 31 23 -10 0.00
Fri 02/06 04Z 0.02 3301 30 22 -9 0.00
Fri 02/06 05Z 0.02 2600 29 20 -9 0.00
Fri 02/06 06Z 0.03 2601 29 17 -9 0.00
Fri 02/06 07Z 0.04 2302 29 14 -9 0.00
Fri 02/06 08Z 0.03 2003 28 10 -10 0.00
Fri 02/06 09Z 0.02 1805 27 9 -9 0.00
Fri 02/06 10Z 0.02 1807 25 10 -9 0.00
Fri 02/06 11Z 0.03 1808 24 12 -9 0.00
Fri 02/06 12Z 0.05 2008 23 37 -9 0.00
Fri 02/06 13Z 0.07 2008 25 59 -9 0.00
Fri 02/06 14Z 0.08 2008 28 72 -9 0.00
Fri 02/06 15Z 0.08 2008 32 80 -10 0.00
Fri 02/06 16Z 0.07 2007 38 84 -10 0.00
Fri 02/06 17Z 0.06 2006 43 85 -10 0.00
Fri 02/06 18Z 0.05 1906 46 78 -10 0.00
Fri 02/06 19Z 0.06 1906 50 78 -9 0.00
Fri 02/06 20Z 0.07 2006 54 84 -9 0.00
Fri 02/06 21Z 0.09 2007 58 86 -10 0.00
Fri 02/06 22Z 0.11 2008 59 86 -10 0.00
Fri 02/06 23Z 0.13 2109 58 87 -10 0.00
Sat 02/07 00Z 0.15 2110 58 90 -10 0.00
Sat 02/07 01Z 0.14 2010 61 87 -10 0.00
Sat 02/07 02Z 0.15 2010 74 86 -11 0.00
Sat 02/07 03Z 0.22 2112 84 87 -12 0.00
Sat 02/07 04Z 0.27 2112 88 88 -12 0.00
Sat 02/07 05Z 0.24 2112 89 88 -12 0.00
Sat 02/07 06Z 0.21 2210 90 87 -11 0.01
Sat 02/07 07Z 0.18 2208 91 86 -11 0.01
Sat 02/07 08Z 0.15 2306 92 86 -11 0.01
Sat 02/07 09Z 0.13 2305 92 86 -11 0.01
Sat 02/07 10Z 0.12 2404 92 85 -11 0.01
Sat 02/07 11Z 0.14 2704 92 84 -12 0.01
Sat 02/07 12Z 0.20 3108 92 83 -13 0.02
Sat 02/07 13Z 0.14 3313 91 82 -13 0.02
Sat 02/07 14Z 0.10 3414 89 83 -13 0.01
Sat 02/07 15Z 0.08 3416 86 83 -14 0.01
Sat 02/07 16Z 0.10 3317 85 83 -15 0.01
Sat 02/07 17Z 0.13 3319 84 83 -15 0.01
Run total areal avg QPF for the greens is: 0.14 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