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 of 95-98 F will occur on Sunday between 1 PM and 5 PM across the Champlain Valley and eastern Windsor County in Vermont. Stay hydrated, take breaks in air-conditioned rooms if possible, seek shade often, and check up on relatives and neighbors. Read More >

Subject: NAM12 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM12_20250701_1200
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 07/01 12Z 0.48 2124  96  96  16 0.00
Tue 07/01 15Z 0.67 2418  95  87  16 0.37
Tue 07/01 18Z 0.56 2514  91  73  16 0.13
Tue 07/01 21Z 0.94 2418  93  59  17 0.03
Wed 07/02 00Z 1.38 2624  84  62  16 0.04
Wed 07/02 03Z 0.83 2621  82  49  15 0.00
Wed 07/02 06Z 0.63 2819  87  51  14 0.00
Wed 07/02 09Z 0.54 2917  82  35  14 0.00
Wed 07/02 12Z 0.47 2714  71  22  14 0.00
Wed 07/02 15Z 0.49 2713  69  18  14 0.00
Wed 07/02 18Z 1.86 2709  78  12  13 0.00
Wed 07/02 21Z 5.21 2709  77  15  14 0.00
Thu 07/03 00Z 0.92 2711  79  18  14 0.00
Thu 07/03 03Z 0.99 2812  71  23  14 0.00
Thu 07/03 06Z 0.63 2812  64  38  14 0.00
Thu 07/03 09Z 0.79 2714  68  38  14 0.00
Thu 07/03 12Z 0.77 2616  71  46  13 0.00
Thu 07/03 15Z 1.02 2715  60  87  13 0.00
Thu 07/03 18Z 3.43 2713  75  76  13 0.00
Thu 07/03 21Z 5.30 2913  75  52  12 0.09
Fri 07/04 00Z 1.30 3114  77  55  11 0.01
Fri 07/04 03Z 0.95 3216  70  56  10 0.00
Fri 07/04 06Z 0.85 3216  67  66   9 0.00
Fri 07/04 09Z 0.86 3115  71  59  10 0.00
Fri 07/04 12Z 0.73 3113  72  42   7 0.00
Fri 07/04 15Z 3.79 2913  76  32   7 0.00
Fri 07/04 18Z 8.87 2814  76  28   9 0.00
Fri 07/04 21Z 3.22 2913  72  29  10 0.00
Sat 07/05 00Z 0.72 3013  67  26  10 0.00

Run total areal avg QPF for the greens is: 0.67 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