National Weather Service United States Department of Commerce

Winter Weather Advisory in Effect for Portions of Northern New York and Vermont Through Monday Morning

A Winter Weather Advisory is in effect until 8 AM Monday for the northern Adirondack region of NY and the spine of the Green Mountains eastward in Vermont. Most snow should taper off this afternoon changing to rain and freezing drizzle. Freezing drizzle is expected to form this evening into Monday morning with icing amounts ranging from a glaze up to 0.05". Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260322_1800
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)
=== ===== === ==== ==== === === === ====
Sun 03/22 18Z 0.32 2119  99  98   0 0.00
Sun 03/22 19Z 0.41 2219  99  94   0 0.07
Sun 03/22 20Z 0.46 2419  99  87   0 0.06
Sun 03/22 21Z 0.55 2619  99  69   0 0.06
Sun 03/22 22Z 0.52 2917  99  52  -1 0.03
Sun 03/22 23Z 0.41 3018  98  35  -2 0.01
Mon 03/23 00Z 0.19 3219  94  32  -2 0.01
Mon 03/23 01Z 0.11 3318  89  25  -3 0.00
Mon 03/23 02Z 0.04 3415  85  21  -3 0.00
Mon 03/23 03Z 0.06 3513  86  16  -4 0.00
Mon 03/23 04Z 0.09 0012  86  14  -4 0.00
Mon 03/23 05Z 0.15 0112  88  10  -5 0.00
Mon 03/23 06Z 0.15 0112  87   7  -5 0.00
Mon 03/23 07Z 0.14 0211  87   7  -5 0.00
Mon 03/23 08Z 0.17 0211  86   7  -5 0.00
Mon 03/23 09Z 0.22 0312  89   8  -6 0.00
Mon 03/23 10Z 0.23 0311  92   8  -7 0.00
Mon 03/23 11Z 0.25 0410  93  10  -7 0.00
Mon 03/23 12Z 0.27 0509  95  11  -8 0.00
Mon 03/23 13Z 0.28 0509  96  15  -8 0.01
Mon 03/23 14Z 0.25 0407  96  11  -9 0.00
Mon 03/23 15Z 0.19 0405  96  10  -9 0.00
Mon 03/23 16Z 0.19 0304  95  14  -9 0.00
Mon 03/23 17Z 0.15 0203  96  10  -9 0.00
Mon 03/23 18Z 0.07 3503  97  10  -9 0.00
Mon 03/23 19Z 0.07 3306  97  11  -8 0.00
Mon 03/23 20Z 0.09 3309  96  14  -9 0.00
Mon 03/23 21Z 0.12 3313  96  21  -9 0.01
Mon 03/23 22Z 0.12 3416  96  31  -9 0.01
Mon 03/23 23Z 0.10 3419  95  37  -9 0.01
Tue 03/24 00Z 0.08 3421  94  48  -9 0.01
Tue 03/24 01Z 0.10 3423  92  55 -10 0.01
Tue 03/24 02Z 0.10 3425  85  59 -10 0.00
Tue 03/24 03Z 0.08 3428  76  65 -10 0.00
Tue 03/24 04Z 0.07 3428  72  66 -11 0.00
Tue 03/24 05Z 0.08 3427  76  55 -11 0.00
Tue 03/24 06Z 0.08 3425  80  38 -11 0.00
Tue 03/24 07Z 0.10 3423  82  23 -11 0.00
Tue 03/24 08Z 0.11 3421  81  10 -12 0.00
Tue 03/24 09Z 0.08 3419  79   3 -12 0.00
Tue 03/24 10Z 0.11 3417  78   5 -12 0.00
Tue 03/24 11Z 0.10 3416  75   9 -12 0.00
Tue 03/24 12Z 0.14 3315  74   9 -12 0.00
Tue 03/24 13Z 0.20 3314  73  11 -12 0.00
Tue 03/24 14Z 0.22 3211  67  10 -11 0.00
Tue 03/24 15Z 0.28 3009  62   7 -11 0.00
Tue 03/24 16Z 0.38 2809  54   5 -10 0.00
Tue 03/24 17Z 0.47 2609  50   4  -9 0.00
Tue 03/24 18Z 0.43 2409  42  11  -8 0.00
Tue 03/24 19Z 0.45 2411  36  15  -7 0.00
Tue 03/24 20Z 0.53 2314  33  12  -6 0.00
Tue 03/24 21Z 0.83 2418  40   9  -7 0.00
Tue 03/24 22Z 0.96 2422  42   8  -7 0.00
Tue 03/24 23Z 1.08 2426  43  12  -6 0.00
Wed 03/25 00Z 1.22 2531  36  18  -6 0.00
Wed 03/25 01Z 1.32 2534  32  15  -6 0.00
Wed 03/25 02Z 1.68 2635  47  88  -7 0.00
Wed 03/25 03Z 1.90 2633  66  85  -8 0.00
Wed 03/25 04Z 1.46 2731  73  77  -8 0.00
Wed 03/25 05Z 1.04 2828  85  38  -8 0.00

Run total areal avg QPF for the Central_Greens is: 0.30 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