National Weather Service United States Department of Commerce

Extreme Heat Warnings and Heat Advisories remain in effect through Friday

Dangerous heat will continue through Friday. Extreme Heat Warnings are in effect for the entire Champlain Valley & eastern Windsor County in Vermont. Heat Advisories in effect for the remainder of our region. Heat index values will peak around 105 degrees in warning areas with locally higher values possible. Advisory areas will see heat index values up to 100 degrees. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260702_1800
Using the MB925 to MB850 layer.
Assumes Central_Greens are orthogonal to 260 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the Central_Greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Thu 07/02 18Z 2.94 2709  87  61  19 0.00
Thu 07/02 19Z 1.70 2511  88  57  19 0.00
Thu 07/02 20Z 0.89 2412  87  57  19 0.03
Thu 07/02 21Z 1.02 2515  86  53  20 0.04
Thu 07/02 22Z 1.17 2516  83  46  20 0.01
Thu 07/02 23Z 1.66 2520  80  39  20 0.00
Fri 07/03 00Z 1.54 2622  81  41  19 0.00
Fri 07/03 01Z 1.24 2724  79  59  19 0.00
Fri 07/03 02Z 1.19 2726  84  52  19 0.01
Fri 07/03 03Z 1.07 2827  89  50  18 0.00
Fri 07/03 04Z 0.73 2925  90  41  18 0.01
Fri 07/03 05Z 0.57 2923  88  26  18 0.00
Fri 07/03 06Z 0.54 2923  84  19  18 0.00
Fri 07/03 07Z 0.56 2923  83  31  18 0.00
Fri 07/03 08Z 0.51 2922  79  33  18 0.00
Fri 07/03 09Z 0.43 3022  75  31  18 0.00
Fri 07/03 10Z 0.37 3021  70  18  18 0.00
Fri 07/03 11Z 0.33 3020  64  19  19 0.00
Fri 07/03 12Z 0.30 3019  61  21  18 0.00
Fri 07/03 13Z 0.29 3017  54  13  19 0.00
Fri 07/03 14Z 0.36 2918  54   5  19 0.00
Fri 07/03 15Z 0.45 2919  58  15  18 0.00
Fri 07/03 16Z 0.59 2919  70  16  18 0.00
Fri 07/03 17Z 0.79 2819  78  24  18 0.00
Fri 07/03 18Z 1.49 2819  81  28  17 0.00
Fri 07/03 19Z 2.88 2820  77  41  17 0.00
Fri 07/03 20Z 5.13 2819  71  50  17 0.00
Fri 07/03 21Z 5.97 2720  66  66  18 0.00
Fri 07/03 22Z 3.49 2821  64  74  18 0.00
Fri 07/03 23Z 1.96 2721  62  61  18 0.00
Sat 07/04 00Z 1.45 2822  59  60  18 0.00
Sat 07/04 01Z 0.88 2920  56  58  18 0.00
Sat 07/04 02Z 0.71 2920  57  61  18 0.00
Sat 07/04 03Z 0.74 2921  62  63  18 0.00
Sat 07/04 04Z 0.74 2921  67  62  17 0.00
Sat 07/04 05Z 0.67 3021  73  65  17 0.00
Sat 07/04 06Z 0.64 3022  78  73  16 0.00
Sat 07/04 07Z 0.55 3020  82  74  16 0.00
Sat 07/04 08Z 0.48 3020  86  77  16 0.00
Sat 07/04 09Z 0.41 3019  90  68  16 0.01
Sat 07/04 10Z 0.35 3117  93  66  16 0.01
Sat 07/04 11Z 0.24 3115  95  59  15 0.01
Sat 07/04 12Z 0.19 3111  91  61  16 0.00
Sat 07/04 13Z 0.22 3111  93  67  15 0.00
Sat 07/04 14Z 0.24 3010  95  57  15 0.00
Sat 07/04 15Z 0.22 3009  96  45  15 0.00
Sat 07/04 16Z 0.25 3109  95  56  14 0.01
Sat 07/04 17Z 0.27 3112  89  72  14 0.05
Sat 07/04 18Z 0.27 3215  85  67  14 0.04
Sat 07/04 19Z 0.32 3216  81  58  14 0.00
Sat 07/04 20Z 0.44 3316  79  40  14 0.00
Sat 07/04 21Z 0.62 3316  74  24  14 0.00
Sat 07/04 22Z 0.36 3318  70  18  14 0.00
Sat 07/04 23Z 0.14 3419  65  13  14 0.00
Sun 07/05 00Z 0.05 3418  66  13  13 0.00
Sun 07/05 01Z 0.08 3518  71  16  13 0.00
Sun 07/05 02Z 0.11 3519  75  16  12 0.00
Sun 07/05 03Z 0.08 3418  76  17  12 0.00
Sun 07/05 04Z 0.06 3417  73  12  12 0.00
Sun 07/05 05Z 0.06 3516  70   7  12 0.00

Run total areal avg QPF for the Central_Greens is: 0.23 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