National Weather Service United States Department of Commerce

Several Rounds of Strong Winds Expected Into Tuesday

A High Wind Warning remains in effect for the Adirondacks and their northern slopes, with Wind Advisories for the rest of the area through 11 AM Tue. Isolated to scattered power outages and difficult travel are possible. South winds 25 to 35 mph with gusts up to 60 mph anticipated. Sharply colder temperatures will arrive tonight, with light snowfall accumulations possible. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260317_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)
=== ===== === ==== ==== === === === ====
Tue 03/17 00Z 0.05 1840  92  96   9 0.00
Tue 03/17 01Z 0.04 1742  94  94   9 0.02
Tue 03/17 02Z 0.04 1741  96  87   9 0.01
Tue 03/17 03Z 0.04 1842  95  89   9 0.01
Tue 03/17 04Z 0.05 1742  96  86   9 0.02
Tue 03/17 05Z 0.11 1741  96  92   9 0.01
Tue 03/17 06Z 0.16 1738  98  97   9 0.06
Tue 03/17 07Z 0.60 2525  96  90   0 0.18
Tue 03/17 08Z 1.33 2533  96  96  -5 0.03
Tue 03/17 09Z 1.21 2534  94  92  -7 0.03
Tue 03/17 10Z 1.44 2431  93  21  -9 0.01
Tue 03/17 11Z 5.85 2531  90   9 -11 0.00
Tue 03/17 12Z 15.83 2433  75  11 -13 0.00
Tue 03/17 13Z 20.50 2434  71  16 -14 0.00
Tue 03/17 14Z 20.06 2432  74  21 -15 0.00
Tue 03/17 15Z 20.80 2532  74  19 -15 0.00
Tue 03/17 16Z 20.08 2531  76  18 -15 0.00
Tue 03/17 17Z 20.23 2530  74  18 -16 0.00
Tue 03/17 18Z 20.02 2530  71  20 -16 0.00
Tue 03/17 19Z 19.72 2530  71  31 -16 0.00
Tue 03/17 20Z 19.43 2529  71  38 -16 0.00
Tue 03/17 21Z 18.28 2628  73  47 -17 0.00
Tue 03/17 22Z 18.15 2628  77  50 -17 0.00
Tue 03/17 23Z 13.12 2727  81  47 -18 0.00
Wed 03/18 00Z 9.58 2726  86  47 -19 0.00
Wed 03/18 01Z 5.49 2725  85  49 -19 0.00
Wed 03/18 02Z 3.61 2724  85  50 -19 0.00
Wed 03/18 03Z 2.79 2823  85  54 -19 0.00
Wed 03/18 04Z 2.75 2822  84  55 -19 0.00
Wed 03/18 05Z 2.65 2722  84  36 -18 0.00
Wed 03/18 06Z 2.21 2722  81  24 -18 0.00
Wed 03/18 07Z 2.18 2722  81  16 -19 0.00
Wed 03/18 08Z 1.85 2823  77  11 -19 0.00
Wed 03/18 09Z 1.42 2822  73   8 -19 0.00
Wed 03/18 10Z 1.02 2821  71   6 -19 0.00
Wed 03/18 11Z 0.77 2920  70   5 -20 0.00
Wed 03/18 12Z 0.54 2916  68   5 -19 0.00
Wed 03/18 13Z 0.44 2913  65   5 -19 0.00
Wed 03/18 14Z 0.42 2812  60   5 -19 0.00
Wed 03/18 15Z 0.42 2810  53   6 -18 0.00
Wed 03/18 16Z 0.55 2708  47   7 -17 0.00
Wed 03/18 17Z 0.72 2606  42   8 -17 0.00
Wed 03/18 18Z 0.72 2504  37   8 -16 0.00
Wed 03/18 19Z 0.79 2404  35   8 -15 0.00
Wed 03/18 20Z 0.59 2204  34   8 -14 0.00
Wed 03/18 21Z 0.33 2105  34   7 -13 0.00
Wed 03/18 22Z 0.18 1906  35   7 -13 0.00
Wed 03/18 23Z 0.08 1810  36   9 -13 0.00
Thu 03/19 00Z 0.08 1813  37  20 -12 0.00
Thu 03/19 01Z 0.17 1916  35  39 -12 0.00
Thu 03/19 02Z 0.24 1918  34  68 -12 0.00
Thu 03/19 03Z 0.31 1920  40  89 -12 0.00
Thu 03/19 04Z 0.43 2022  48  90 -11 0.00
Thu 03/19 05Z 0.52 2123  55  86 -11 0.00
Thu 03/19 06Z 0.53 2123  60  87 -11 0.00
Thu 03/19 07Z 0.55 2123  63  87 -11 0.00
Thu 03/19 08Z 0.56 2221  66  86 -11 0.00
Thu 03/19 09Z 0.51 2120  71  86 -11 0.00
Thu 03/19 10Z 0.38 2119  81  84 -11 0.00
Thu 03/19 11Z 0.27 2019  87  83 -10 0.00

Run total areal avg QPF for the greens is: 0.38 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