National Weather Service United States Department of Commerce

Hazardous Travel for This Evening's Commute and Wednesday Morning's Commute in Locally Heavy Snow

Snow accumulations between 3 and 6 inches are expected across much of the area from 10 AM today to 7 AM Wednesday. Some locally higher amounts are expected in the northern Adirondacks. The heaviest snowfall rates are anticipated during this evening's commute. Plan on slippery road conditions. Roads, especially bridges and overpasses, will become slick. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260210_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 02/10 00Z 0.26 3121  55  63 -10 0.00
Tue 02/10 01Z 0.25 3222  58  64  -9 0.00
Tue 02/10 02Z 0.21 3221  59  68  -9 0.00
Tue 02/10 03Z 0.17 3319  58  69  -8 0.00
Tue 02/10 04Z 0.14 3317  59  75  -8 0.00
Tue 02/10 05Z 0.14 3317  61  80  -8 0.00
Tue 02/10 08Z 0.17 3114  79  88  -8 0.00
Tue 02/10 09Z 0.17 3113  83  88  -8 0.00
Tue 02/10 10Z 0.16 3112  83  86  -7 0.00
Tue 02/10 11Z 0.15 3110  79  84  -7 0.00
Tue 02/10 12Z 0.16 3009  74  82  -7 0.00
Tue 02/10 13Z 0.13 2907  64  74  -7 0.00
Tue 02/10 14Z 0.13 2706  53  64  -6 0.00
Tue 02/10 15Z 0.13 2506  47  60  -6 0.00
Tue 02/10 16Z 0.12 2306  43  53  -6 0.00
Tue 02/10 17Z 0.10 2107  40  50  -6 0.00
Tue 02/10 18Z 0.12 2109  37  65  -5 0.00
Tue 02/10 19Z 0.12 2010  40  86  -5 0.00
Tue 02/10 20Z 0.13 1914  57  93  -6 0.00
Tue 02/10 21Z 0.05 1816  77  93  -5 0.00
Tue 02/10 22Z 0.03 1819  92  93  -4 0.00
Tue 02/10 23Z 0.06 1823  94  93  -4 0.00
Wed 02/11 00Z 0.09 1925  95  95  -4 0.01
Wed 02/11 01Z 0.20 2025  95  96  -5 0.06
Wed 02/11 02Z 0.29 2124  97  96  -5 0.09
Wed 02/11 03Z 0.33 2222  97  98  -5 0.09
Wed 02/11 04Z 0.34 2319  97  96  -5 0.07
Wed 02/11 05Z 0.34 2417  97  88  -5 0.05
Wed 02/11 06Z 0.34 2415  98  43  -5 0.04
Wed 02/11 07Z 0.37 2515  98  23  -6 0.03
Wed 02/11 08Z 0.43 2616  98  19  -6 0.02
Wed 02/11 09Z 0.49 2717  98  34  -7 0.02
Wed 02/11 10Z 0.57 2818  98  42  -8 0.02
Wed 02/11 11Z 0.60 2919  97  52  -9 0.02
Wed 02/11 12Z 0.56 2920  96  65  -9 0.02
Wed 02/11 13Z 0.55 2921  96  76  -9 0.02
Wed 02/11 14Z 0.57 2920  95  82 -10 0.01
Wed 02/11 15Z 0.62 3020  95  83 -10 0.01
Wed 02/11 16Z 0.74 3019  94  83 -11 0.01
Wed 02/11 17Z 1.32 3019  95  84 -11 0.01
Wed 02/11 18Z 2.28 3018  94  86 -11 0.01
Wed 02/11 19Z 2.20 3018  94  87 -11 0.01
Wed 02/11 20Z 1.57 3119  95  88 -11 0.01
Wed 02/11 21Z 1.01 3120  95  87 -12 0.01
Wed 02/11 22Z 0.80 3223  96  85 -12 0.01
Wed 02/11 23Z 0.66 3324  96  84 -13 0.01
Thu 02/12 00Z 0.61 3324  96  83 -12 0.01
Thu 02/12 01Z 0.51 3325  96  81 -12 0.01
Thu 02/12 02Z 0.43 3324  96  81 -12 0.01
Thu 02/12 03Z 0.33 3323  96  82 -12 0.01
Thu 02/12 04Z 0.27 3422  95  81 -12 0.01
Thu 02/12 05Z 0.24 3422  95  80 -12 0.01
Thu 02/12 06Z 0.23 3423  93  77 -12 0.01
Thu 02/12 07Z 0.21 3424  93  76 -12 0.01
Thu 02/12 08Z 0.21 3424  93  75 -12 0.00
Thu 02/12 09Z 0.23 3425  94  74 -12 0.00
Thu 02/12 10Z 0.26 3426  95  75 -13 0.00
Thu 02/12 11Z 0.30 3326  95  75 -13 0.01

Run total areal avg QPF for the greens is: 0.75 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