National Weather Service United States Department of Commerce

Winter Storm Warnings and Winter Weather Advisories in Effect Until 10 AM This Morning

Winter Storm Warnings and Winter Weather Weather Advisories remain in effect until 10 AM this morning. The period of heaviest snow has ended, with light snow continuing through this morning and afternoon. Additional snow accumulations up to 1 inch are possible. Slippery travel conditions are possible, especially on untreated roads and surfaces. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260221_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)
=== ===== === ==== ==== === === === ====
Sat 02/21 06Z 0.07 1910  96  83  -6 0.00
Sat 02/21 07Z 0.19 2110  97  77  -7 0.00
Sat 02/21 08Z 0.24 2308  98  82  -7 0.01
Sat 02/21 09Z 0.25 2408  98  91  -7 0.01
Sat 02/21 10Z 0.24 2607  98  91  -7 0.02
Sat 02/21 11Z 0.18 2905  98  93  -7 0.02
Sat 02/21 12Z 0.14 3004  98  90  -7 0.01
Sat 02/21 13Z 0.10 3202  98  84  -7 0.01
Sat 02/21 14Z 0.08 0002  98  77  -7 0.01
Sat 02/21 15Z 0.08 0302  98  71  -7 0.00
Sat 02/21 16Z 0.11 0402  98  69  -8 0.00
Sat 02/21 17Z 0.12 0501  96  69  -8 0.00
Sat 02/21 18Z 0.11 0501  93  67  -8 0.01
Sat 02/21 19Z 0.11 0403  89  61  -8 0.00
Sat 02/21 20Z 0.13 0404  86  54  -8 0.00
Sat 02/21 21Z 0.14 0405  83  49  -8 0.00
Sat 02/21 22Z 0.18 0505  80  47  -8 0.00
Sat 02/21 23Z 0.22 0606  78  48  -8 0.00
Sun 02/22 00Z 0.26 0707  76  47  -8 0.00
Sun 02/22 01Z 0.28 0808  77  45  -8 0.00
Sun 02/22 02Z 0.29 0909  75  42  -8 0.00
Sun 02/22 03Z 0.30 1010  65  41  -7 0.00
Sun 02/22 04Z 0.31 1111  51  40  -7 0.00
Sun 02/22 05Z 0.30 1313  47  39  -7 0.00
Sun 02/22 06Z 0.29 1415  46  41  -8 0.00
Sun 02/22 07Z 0.26 1415  49  46  -8 0.00
Sun 02/22 08Z 0.22 1516  52  52  -8 0.00
Sun 02/22 09Z 0.19 1515  55  56  -7 0.00
Sun 02/22 10Z 0.18 1414  55  59  -7 0.00
Sun 02/22 11Z 0.19 1413  52  64  -7 0.00
Sun 02/22 12Z 0.19 1413  51  68  -7 0.00
Sun 02/22 13Z 0.20 1413  52  65  -7 0.00
Sun 02/22 14Z 0.22 1314  53  67  -7 0.00
Sun 02/22 15Z 0.24 1314  57  65  -7 0.00
Sun 02/22 16Z 0.27 1314  60  64  -7 0.00
Sun 02/22 17Z 0.31 1214  64  61  -7 0.00
Sun 02/22 18Z 0.33 1313  69  59  -7 0.00
Sun 02/22 19Z 0.36 1313  72  62  -7 0.00
Sun 02/22 20Z 0.39 1313  75  67  -7 0.00
Sun 02/22 21Z 0.40 1213  76  73  -8 0.00
Sun 02/22 22Z 0.39 1213  77  76  -8 0.00
Sun 02/22 23Z 0.43 1113  79  76  -8 0.00
Mon 02/23 00Z 0.47 1015  80  71  -8 0.00
Mon 02/23 01Z 0.50 0916  80  66  -8 0.00
Mon 02/23 02Z 0.52 0918  78  55  -7 0.00
Mon 02/23 03Z 0.56 0921  78  59  -8 0.00
Mon 02/23 04Z 0.54 0921  72  50  -7 0.00
Mon 02/23 05Z 0.51 0921  62  57  -7 0.00
Mon 02/23 06Z 0.53 0922  55  63  -7 0.00
Mon 02/23 07Z 0.49 0822  52  70  -7 0.00
Mon 02/23 08Z 0.48 0722  48  74  -6 0.00
Mon 02/23 09Z 0.50 0724  44  76  -6 0.00
Mon 02/23 10Z 0.55 0727  38  78  -6 0.00
Mon 02/23 11Z 0.58 0730  34  75  -6 0.00
Mon 02/23 12Z 0.59 0632  34  77  -6 0.00
Mon 02/23 13Z 0.60 0632  34  80  -6 0.00
Mon 02/23 14Z 0.59 0531  34  77  -7 0.00
Mon 02/23 15Z 0.55 0528  38  76  -7 0.00
Mon 02/23 16Z 0.53 0426  42  72  -8 0.00
Mon 02/23 17Z 0.48 0426  50  79  -9 0.00

Run total areal avg QPF for the greens is: 0.10 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