National Weather Service United States Department of Commerce

Dangerous Cold Expected This Weekend

Extreme Cold Warnings and Cold Weather Advisories are in effect across the region for this weekend. 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 Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260206_1200
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)
=== ===== === ==== ==== === === === ====
Fri 02/06 12Z 0.04 1710  63  56 -11 0.00
Fri 02/06 13Z 0.10 1912  65  64 -11 0.00
Fri 02/06 14Z 0.17 2012  66  68 -11 0.00
Fri 02/06 15Z 0.15 2010  65  76 -11 0.00
Fri 02/06 16Z 0.12 1909  67  82 -11 0.00
Fri 02/06 17Z 0.15 1907  68  82 -11 0.00
Fri 02/06 18Z 0.22 2007  68  84 -11 0.00
Fri 02/06 19Z 0.25 2006  70  84 -11 0.00
Fri 02/06 20Z 0.22 2006  72  78 -11 0.00
Fri 02/06 21Z 0.13 1906  75  74 -11 0.00
Fri 02/06 22Z 0.05 1708  79  74 -11 0.00
Fri 02/06 23Z 0.05 1711  85  67 -11 0.00
Sat 02/07 01Z 0.19 1912  91  79 -12 0.00
Sat 02/07 04Z 0.44 2213  93  69 -12 0.00
Sat 02/07 05Z 0.38 2212  92  80 -12 0.00
Sat 02/07 06Z 0.25 2109  93  89 -12 0.00
Sat 02/07 07Z 0.14 2006  92  87 -12 0.00
Sat 02/07 08Z 0.07 1905  92  86 -12 0.00
Sat 02/07 09Z 0.04 1705  92  86 -12 0.00
Sat 02/07 10Z 0.04 1705  92  86 -12 0.01
Sat 02/07 11Z 0.03 1704  93  85 -12 0.02
Sat 02/07 12Z 0.03 1901  93  86 -12 0.02
Sat 02/07 13Z 0.06 3304  92  83 -13 0.01
Sat 02/07 14Z 0.16 3409  90  80 -13 0.01
Sat 02/07 15Z 0.11 3414  88  80 -14 0.01
Sat 02/07 16Z 0.05 3416  86  80 -15 0.02
Sat 02/07 17Z 0.06 3417  84  81 -15 0.03
Sat 02/07 18Z 0.07 3318  84  82 -16 0.02
Sat 02/07 19Z 0.10 3320  84  83 -17 0.01
Sat 02/07 20Z 0.11 3321  84  83 -17 0.01
Sat 02/07 21Z 0.11 3323  84  83 -18 0.01
Sat 02/07 22Z 0.11 3324  84  81 -19 0.01
Sat 02/07 23Z 0.12 3325  85  78 -19 0.01
Sun 02/08 00Z 0.12 3326  84  78 -20 0.01
Sun 02/08 01Z 0.11 3326  84  77 -20 0.00
Sun 02/08 02Z 0.11 3326  84  76 -20 0.00
Sun 02/08 03Z 0.10 3325  84  75 -20 0.00
Sun 02/08 04Z 0.10 3324  83  77 -20 0.00
Sun 02/08 05Z 0.09 3323  82  78 -19 0.00
Sun 02/08 06Z 0.07 3323  82  79 -19 0.00
Sun 02/08 07Z 0.08 3323  81  77 -19 0.00
Sun 02/08 08Z 0.09 3324  81  76 -20 0.00
Sun 02/08 09Z 0.09 3325  81  75 -20 0.00
Sun 02/08 10Z 0.08 3324  80  75 -20 0.00
Sun 02/08 11Z 0.06 3424  80  75 -19 0.00
Sun 02/08 12Z 0.03 3423  80  76 -19 0.00
Sun 02/08 13Z 0.02 3523  79  76 -18 0.00
Sun 02/08 14Z 0.02 3522  79  75 -17 0.00
Sun 02/08 15Z 0.02 3422  78  72 -17 0.00
Sun 02/08 16Z 0.02 3423  76  69 -17 0.00
Sun 02/08 17Z 0.02 3423  75  65 -16 0.00
Sun 02/08 18Z 0.03 3424  72  61 -16 0.00
Sun 02/08 19Z 0.04 3424  68  55 -15 0.00
Sun 02/08 20Z 0.05 3425  64  41 -15 0.00
Sun 02/08 21Z 0.07 3326  59  24 -15 0.00
Sun 02/08 22Z 0.07 3427  55  20 -14 0.00
Sun 02/08 23Z 0.06 3427  51  19 -13 0.00

Run total areal avg QPF for the Central_Greens is: 0.21 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