National Weather Service United States Department of Commerce

Extreme Heat Warnings and Heat Advisories remain in effect through Friday

Dangerous heat will build today and 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_20260701_1200
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)
=== ===== === ==== ==== === === === ====
Wed 07/01 12Z 0.21 3112  77  57  18 0.00
Wed 07/01 13Z 0.23 3012  79  48  18 0.00
Wed 07/01 14Z 0.23 3010  76  38  18 0.00
Wed 07/01 15Z 0.28 2909  73  24  18 0.00
Wed 07/01 16Z 0.42 2808  73  18  18 0.00
Wed 07/01 17Z 0.73 2708  72  17  18 0.00
Wed 07/01 18Z 1.00 2508  72  19  18 0.00
Wed 07/01 19Z 1.10 2409  75  31  19 0.00
Wed 07/01 20Z 1.52 2411  79  46  19 0.00
Wed 07/01 21Z 0.98 2314  80  47  19 0.00
Wed 07/01 22Z 0.83 2417  87  46  19 0.00
Wed 07/01 23Z 0.97 2423  91  54  19 0.00
Thu 07/02 00Z 0.94 2522  87  52  20 0.00
Thu 07/02 01Z 0.80 2624  78  51  20 0.00
Thu 07/02 02Z 0.63 2823  82  50  20 0.00
Thu 07/02 03Z 0.61 2722  78  50  20 0.00
Thu 07/02 04Z 0.61 2723  77  54  20 0.00
Thu 07/02 05Z 0.53 2822  68  52  21 0.00
Thu 07/02 06Z 0.50 2821  70  54  21 0.00
Thu 07/02 07Z 0.53 2822  81  60  20 0.00
Thu 07/02 08Z 0.46 2820  79  63  20 0.00
Thu 07/02 09Z 0.40 2919  83  62  20 0.00
Thu 07/02 10Z 0.36 2918  81  61  19 0.00
Thu 07/02 11Z 0.31 2916  74  52  20 0.00
Thu 07/02 12Z 0.30 3017  70  55  20 0.00
Thu 07/02 13Z 0.35 2918  70  43  20 0.00
Thu 07/02 14Z 0.40 2918  75  42  19 0.00
Thu 07/02 15Z 0.45 2917  78  49  19 0.00
Thu 07/02 16Z 0.53 2916  82  53  19 0.00
Thu 07/02 17Z 0.55 2815  82  56  19 0.00
Thu 07/02 18Z 0.54 2716  75  59  20 0.00
Thu 07/02 19Z 0.81 2718  83  59  20 0.00
Thu 07/02 20Z 1.14 2619  88  55  19 0.00
Thu 07/02 21Z 1.04 2520  93  46  19 0.00
Thu 07/02 22Z 1.05 2622  90  46  20 0.01
Thu 07/02 23Z 1.04 2623  85  39  20 0.01
Fri 07/03 00Z 1.01 2624  88  44  20 0.01
Fri 07/03 01Z 1.02 2626  88  63  20 0.00
Fri 07/03 02Z 1.06 2728  92  69  19 0.01
Fri 07/03 03Z 0.96 2728  91  65  19 0.04
Fri 07/03 04Z 0.89 2728  87  59  19 0.01
Fri 07/03 05Z 0.87 2829  82  58  19 0.00
Fri 07/03 06Z 0.76 2929  74  60  19 0.00
Fri 07/03 07Z 0.66 2928  70  54  18 0.00
Fri 07/03 08Z 0.61 2927  70  44  19 0.00
Fri 07/03 09Z 0.53 2926  67  40  19 0.00
Fri 07/03 10Z 0.46 3026  60  40  19 0.00
Fri 07/03 11Z 0.42 3024  60  36  19 0.00
Fri 07/03 12Z 0.39 3021  57  33  19 0.00
Fri 07/03 13Z 0.37 2919  55  34  19 0.00
Fri 07/03 14Z 0.40 2918  50  48  19 0.00
Fri 07/03 15Z 0.53 2818  56  45  18 0.00
Fri 07/03 16Z 0.64 2819  60  64  18 0.00
Fri 07/03 17Z 1.01 2719  73  63  18 0.00
Fri 07/03 18Z 6.00 2718  77  69  17 0.00
Fri 07/03 19Z 8.46 2718  77  64  17 0.00
Fri 07/03 20Z 6.21 2818  79  68  17 0.00
Fri 07/03 21Z 3.06 2819  80  61  18 0.03
Fri 07/03 22Z 1.99 2919  80  41  18 0.00
Fri 07/03 23Z 1.23 2919  78  31  18 0.00

Run total areal avg QPF for the Central_Greens is: 0.12 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