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 through 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_1800
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 18Z 0.12 2109  55  68  -5 0.00
Tue 02/10 19Z 0.07 1910  48  85  -4 0.00
Tue 02/10 20Z 0.05 1814  47  97  -5 0.00
Tue 02/10 21Z 0.04 1818  64  95  -6 0.00
Tue 02/10 23Z 0.04 1825  95  97  -4 0.05
Wed 02/11 00Z 0.15 1926  95  96  -4 0.07
Wed 02/11 01Z 0.26 2025  95  95  -5 0.08
Wed 02/11 02Z 0.31 2124  96  95  -5 0.08
Wed 02/11 03Z 0.37 2223  97  95  -4 0.07
Wed 02/11 04Z 0.41 2321  97  94  -4 0.05
Wed 02/11 05Z 0.45 2520  97  68  -5 0.05
Wed 02/11 06Z 0.48 2619  97  37  -6 0.03
Wed 02/11 07Z 0.47 2718  97  21  -6 0.02
Wed 02/11 08Z 0.48 2718  96  17  -6 0.01
Wed 02/11 09Z 0.51 2819  97  20  -7 0.01
Wed 02/11 11Z 0.49 2819  97  45  -7 0.01
Wed 02/11 12Z 0.49 2919  96  55  -8 0.01
Wed 02/11 13Z 0.50 2919  96  65  -8 0.01
Wed 02/11 14Z 0.55 2819  97  76  -9 0.01
Wed 02/11 15Z 0.63 2818  97  81  -9 0.01
Wed 02/11 16Z 0.75 2818  96  84  -9 0.01
Wed 02/11 17Z 0.95 2817  96  86  -9 0.01
Wed 02/11 18Z 1.19 2817  96  85  -9 0.01
Wed 02/11 19Z 1.18 2918  96  85 -10 0.01
Wed 02/11 20Z 1.06 2919  96  85 -10 0.01
Wed 02/11 21Z 0.90 3019  96  85 -10 0.02
Wed 02/11 22Z 0.93 3020  95  84 -11 0.02
Wed 02/11 23Z 0.84 3121  95  83 -11 0.02
Thu 02/12 00Z 0.68 3222  96  82 -12 0.02
Thu 02/12 01Z 0.51 3223  96  83 -12 0.02
Thu 02/12 02Z 0.41 3324  96  83 -12 0.01
Thu 02/12 03Z 0.37 3323  96  84 -12 0.01
Thu 02/12 04Z 0.35 3323  95  84 -11 0.01
Thu 02/12 05Z 0.29 3323  94  82 -11 0.01
Thu 02/12 06Z 0.25 3423  94  79 -11 0.01
Thu 02/12 07Z 0.21 3424  94  78 -11 0.01
Thu 02/12 09Z 0.17 3422  94  78 -11 0.01
Thu 02/12 10Z 0.17 3423  94  78 -11 0.01
Thu 02/12 11Z 0.16 3424  94  75 -12 0.01
Thu 02/12 12Z 0.17 3424  94  74 -12 0.01
Thu 02/12 13Z 0.20 3423  94  71 -12 0.01
Thu 02/12 14Z 0.19 3423  93  69 -12 0.01
Thu 02/12 15Z 0.18 3423  93  68 -12 0.01
Thu 02/12 16Z 0.18 3422  93  67 -11 0.01
Thu 02/12 17Z 0.18 3423  92  64 -11 0.01
Thu 02/12 18Z 0.19 3323  92  61 -11 0.00
Thu 02/12 19Z 0.20 3323  91  52 -11 0.00
Thu 02/12 20Z 0.22 3323  90  35 -11 0.00
Thu 02/12 21Z 0.24 3324  86  24 -11 0.00
Thu 02/12 22Z 0.21 3324  75  15 -11 0.00
Thu 02/12 23Z 0.16 3425  67  10 -10 0.00
Fri 02/13 00Z 0.13 3425  64  13 -10 0.00
Fri 02/13 01Z 0.13 3425  66  15 -10 0.00
Fri 02/13 02Z 0.13 3425  69  16 -10 0.00
Fri 02/13 04Z 0.11 3423  67  16  -9 0.00
Fri 02/13 05Z 0.10 3422  65  16  -9 0.00

Run total areal avg QPF for the greens is: 0.87 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