National Weather Service United States Department of Commerce

Significant Heat on Sunday Afternoon

Heat and humidity will gradually build over the weekend and peak on Sunday. The warmest temperatures and highest heat index values will occur on Sunday between Noon and 6 PM across the Champlain Valley of 95-98 F. Stay hydrated, take breaks in air-conditioned rooms if possible, seek shade often, and check up on relatives and neighbors. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20250602_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)
=== ===== === ==== ==== === === === ====
Mon 06/02 06Z 0.72 2717  96  61   0 0.00
Mon 06/02 07Z 0.71 2718  95  72   0 0.01
Mon 06/02 08Z 0.71 2720  96  80   0 0.02
Mon 06/02 09Z 0.72 2820  96  91   0 0.02
Mon 06/02 10Z 0.67 2919  93  93   0 0.01
Mon 06/02 11Z 0.66 2919  92  82   1 0.00
Mon 06/02 12Z 0.68 2819  92  61   1 0.00
Mon 06/02 13Z 0.69 2819  90  38   2 0.00
Mon 06/02 14Z 0.73 2818  84  16   2 0.00
Mon 06/02 15Z 1.23 2717  85   5   2 0.00
Mon 06/02 16Z 7.61 2716  85   2   2 0.00
Mon 06/02 17Z 9.90 2716  76   6   3 0.00
Mon 06/02 18Z 9.20 2715  71  10   3 0.00
Mon 06/02 19Z 9.30 2714  66  11   4 0.00
Mon 06/02 20Z 7.97 2713  65  11   4 0.00
Mon 06/02 21Z 5.60 2712  66  12   4 0.00
Mon 06/02 22Z 2.22 2712  66  16   5 0.00
Mon 06/02 23Z 1.06 2712  65  23   5 0.00
Tue 06/03 00Z 1.02 2814  64  19   5 0.00
Tue 06/03 01Z 1.50 2915  60  22   5 0.00
Tue 06/03 02Z 1.03 3015  60  20   5 0.00
Tue 06/03 03Z 0.94 3014  60  18   5 0.00
Tue 06/03 04Z 0.97 2913  62  15   5 0.00
Tue 06/03 05Z 0.70 2910  58  14   5 0.00
Tue 06/03 06Z 0.69 2910  55  12   5 0.00
Tue 06/03 07Z 0.65 2909  54  11   5 0.00
Tue 06/03 08Z 0.52 2908  53   9   5 0.00
Tue 06/03 09Z 0.38 3007  50   9   6 0.00
Tue 06/03 10Z 0.32 3007  48   9   6 0.00
Tue 06/03 11Z 0.23 3005  45   9   6 0.00
Tue 06/03 12Z 0.21 3004  45   8   6 0.00
Tue 06/03 13Z 0.33 2604  47   6   6 0.00
Tue 06/03 14Z 0.61 2505  49   4   7 0.00
Tue 06/03 15Z 1.18 2405  49   4   7 0.00
Tue 06/03 16Z 2.34 2506  48   7   7 0.00
Tue 06/03 17Z 2.46 2506  46  27   8 0.00
Tue 06/03 18Z 2.16 2506  43  63   9 0.00
Tue 06/03 19Z 1.51 2507  45  80   9 0.00
Tue 06/03 20Z 0.93 2507  51  91   9 0.00
Tue 06/03 21Z 0.44 2507  53  84  10 0.00
Tue 06/03 22Z 0.33 2407  56  70  11 0.00
Tue 06/03 23Z 0.28 2307  61  54  11 0.00
Wed 06/04 00Z 0.24 2307  63  42  12 0.00
Wed 06/04 01Z 0.26 2309  60  35  12 0.00
Wed 06/04 02Z 0.29 2310  57  35  13 0.00
Wed 06/04 03Z 0.30 2311  57  31  13 0.00
Wed 06/04 04Z 0.27 2311  56  29  13 0.00
Wed 06/04 05Z 0.24 2310  55  25  14 0.00
Wed 06/04 06Z 0.25 2211  54  22  14 0.00
Wed 06/04 07Z 0.29 2312  53  16  14 0.00
Wed 06/04 08Z 0.32 2313  54  16  14 0.00
Wed 06/04 09Z 0.41 2315  56  16  14 0.00
Wed 06/04 10Z 0.46 2416  56  18  14 0.00
Wed 06/04 11Z 0.53 2417  56  18  13 0.00
Wed 06/04 12Z 0.55 2416  57  18  13 0.00
Wed 06/04 13Z 0.49 2315  56  15  13 0.00
Wed 06/04 14Z 0.41 2213  55  14  14 0.00
Wed 06/04 15Z 0.34 2112  55  12  14 0.00
Wed 06/04 16Z 0.34 2011  57  14  14 0.00
Wed 06/04 17Z 0.37 1911  59  14  14 0.00

Run total areal avg QPF for the greens is: 0.06 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