National Weather Service United States Department of Commerce

Dangerous Cold Expected This Weekend

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_0000
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 00Z 0.12 3006  58  17 -11 0.00
Fri 02/06 01Z 0.09 3106  59  18 -11 0.00
Fri 02/06 02Z 0.09 3105  63  20 -11 0.00
Fri 02/06 03Z 0.05 3203  65  20 -11 0.00
Fri 02/06 04Z 0.03 3302  63  21 -11 0.00
Fri 02/06 05Z 0.04 0400  59  21 -11 0.00
Fri 02/06 06Z 0.04 1602  55  20 -10 0.00
Fri 02/06 07Z 0.03 1604  51  17 -10 0.00
Fri 02/06 08Z 0.03 1707  52  13 -10 0.00
Fri 02/06 09Z 0.02 1708  54   9 -11 0.00
Fri 02/06 10Z 0.02 1809  55   6 -11 0.00
Fri 02/06 11Z 0.03 1809  57  11 -11 0.00
Fri 02/06 12Z 0.03 1811  61  29 -12 0.00
Fri 02/06 13Z 0.03 1812  65  47 -12 0.00
Fri 02/06 14Z 0.06 1914  68  58 -12 0.00
Fri 02/06 15Z 0.09 1913  70  64 -11 0.00
Fri 02/06 16Z 0.11 1912  71  73 -11 0.00
Fri 02/06 17Z 0.11 2010  74  84 -11 0.00
Fri 02/06 18Z 0.12 2008  78  87 -11 0.00
Fri 02/06 19Z 0.15 2007  81  88 -11 0.00
Fri 02/06 20Z 0.08 1907  83  90 -11 0.00
Fri 02/06 21Z 0.05 1807  85  89 -11 0.00
Fri 02/06 22Z 0.05 1808  85  86 -11 0.00
Fri 02/06 23Z 0.07 1910  85  85 -11 0.00
Sat 02/07 00Z 0.08 1910  86  88 -11 0.00
Sat 02/07 01Z 0.11 1912  89  90 -12 0.00
Sat 02/07 02Z 0.14 1912  92  87 -12 0.00
Sat 02/07 03Z 0.16 1913  92  87 -12 0.01
Sat 02/07 04Z 0.14 1913  92  87 -11 0.01
Sat 02/07 05Z 0.13 1913  92  86 -11 0.01
Sat 02/07 06Z 0.12 1913  91  85 -11 0.01
Sat 02/07 07Z 0.11 1912  92  85 -11 0.01
Sat 02/07 08Z 0.11 1911  91  84 -11 0.01
Sat 02/07 09Z 0.12 2009  92  84 -11 0.01
Sat 02/07 10Z 0.13 2106  92  84 -12 0.01
Sat 02/07 11Z 0.15 2304  93  84 -12 0.01
Sat 02/07 12Z 0.15 3106  92  82 -13 0.03
Sat 02/07 13Z 0.10 3310  89  82 -13 0.02
Sat 02/07 14Z 0.10 3414  88  82 -13 0.02
Sat 02/07 15Z 0.09 3415  87  82 -14 0.01
Sat 02/07 16Z 0.10 3315  85  82 -15 0.01
Sat 02/07 17Z 0.12 3316  84  83 -15 0.01
Sat 02/07 18Z 0.14 3317  84  83 -16 0.01
Sat 02/07 19Z 0.16 3319  83  83 -17 0.01
Sat 02/07 20Z 0.18 3321  84  82 -18 0.01
Sat 02/07 21Z 0.19 3323  85  80 -18 0.01
Sat 02/07 22Z 0.19 3325  86  78 -18 0.00
Sat 02/07 23Z 0.20 3326  86  75 -19 0.00
Sun 02/08 00Z 0.20 3327  86  72 -19 0.00
Sun 02/08 01Z 0.22 3328  85  72 -20 0.00
Sun 02/08 02Z 0.21 3327  84  71 -20 0.00
Sun 02/08 03Z 0.22 3226  84  73 -20 0.00
Sun 02/08 04Z 0.21 3225  83  74 -20 0.00
Sun 02/08 05Z 0.19 3224  82  74 -20 0.00
Sun 02/08 06Z 0.20 3225  81  68 -20 0.00
Sun 02/08 07Z 0.20 3225  81  63 -20 0.00
Sun 02/08 08Z 0.22 3226  80  61 -21 0.00
Sun 02/08 09Z 0.24 3227  78  57 -21 0.00
Sun 02/08 10Z 0.25 3229  76  53 -21 0.00
Sun 02/08 11Z 0.24 3229  73  42 -21 0.00

Run total areal avg QPF for the greens is: 0.23 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