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Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260702_0000
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 00Z 0.57 2618 66 58 22 0.00
Thu 07/02 01Z 0.75 2620 74 72 21 0.00
Thu 07/02 02Z 0.83 2623 90 60 20 0.03
Thu 07/02 03Z 0.65 2719 89 59 20 0.07
Thu 07/02 04Z 0.75 2722 92 62 19 0.02
Thu 07/02 05Z 0.67 2822 85 65 19 0.14
Thu 07/02 06Z 0.42 2717 65 54 20 0.01
Thu 07/02 07Z 0.45 2519 70 57 20 0.00
Thu 07/02 08Z 0.58 2725 68 52 20 0.00
Thu 07/02 09Z 0.56 2926 79 54 19 0.00
Thu 07/02 10Z 0.47 3025 75 53 20 0.00
Thu 07/02 11Z 0.46 3026 70 50 20 0.00
Thu 07/02 12Z 0.43 3025 63 47 20 0.00
Thu 07/02 13Z 0.42 3025 64 38 20 0.00
Thu 07/02 14Z 0.38 3022 68 49 20 0.00
Thu 07/02 15Z 0.41 3021 71 42 20 0.00
Thu 07/02 16Z 0.55 2920 80 49 19 0.00
Thu 07/02 17Z 0.59 2817 83 52 19 0.00
Thu 07/02 18Z 0.62 2814 85 58 19 0.00
Thu 07/02 19Z 1.09 2713 90 52 19 0.00
Thu 07/02 20Z 1.74 2614 89 53 19 0.00
Thu 07/02 21Z 2.85 2616 85 60 19 0.01
Thu 07/02 22Z 2.12 2617 83 52 19 0.01
Thu 07/02 23Z 1.75 2619 85 53 19 0.00
Fri 07/03 00Z 1.17 2722 84 54 19 0.00
Fri 07/03 01Z 0.95 2723 88 49 19 0.00
Fri 07/03 02Z 0.94 2725 87 45 19 0.00
Fri 07/03 03Z 0.83 2727 82 46 20 0.00
Fri 07/03 04Z 0.76 2828 81 45 20 0.00
Fri 07/03 05Z 0.75 2829 76 38 20 0.00
Fri 07/03 06Z 0.78 2930 78 45 19 0.00
Fri 07/03 07Z 0.77 2930 77 46 18 0.00
Fri 07/03 08Z 0.77 2930 83 49 18 0.00
Fri 07/03 09Z 0.74 2929 87 49 18 0.00
Fri 07/03 10Z 0.62 2926 85 52 18 0.00
Fri 07/03 11Z 0.58 2925 83 62 18 0.00
Fri 07/03 12Z 0.56 2923 89 53 18 0.00
Fri 07/03 13Z 0.53 2920 88 52 18 0.00
Fri 07/03 14Z 0.57 2819 88 61 18 0.00
Fri 07/03 15Z 0.66 2719 91 63 18 0.00
Fri 07/03 16Z 0.74 2718 93 73 18 0.00
Fri 07/03 17Z 0.88 2719 95 75 17 0.01
Fri 07/03 18Z 0.83 2718 95 74 18 0.01
Fri 07/03 19Z 0.97 2820 93 68 18 0.12
Fri 07/03 20Z 1.04 2820 89 60 18 0.04
Fri 07/03 21Z 1.11 2821 85 34 18 0.01
Fri 07/03 22Z 1.13 2820 76 19 18 0.00
Fri 07/03 23Z 1.60 2823 75 16 17 0.00
Sat 07/04 00Z 1.67 2824 76 15 16 0.00
Sat 07/04 01Z 1.23 2824 79 18 16 0.00
Sat 07/04 02Z 1.01 2925 84 27 16 0.00
Sat 07/04 03Z 0.95 2927 89 23 15 0.00
Sat 07/04 04Z 0.78 3027 88 27 15 0.00
Sat 07/04 05Z 0.68 3127 84 33 15 0.00
Sat 07/04 06Z 0.67 3127 82 27 15 0.00
Sat 07/04 07Z 0.59 3126 83 31 15 0.00
Sat 07/04 08Z 0.53 3125 83 30 15 0.00
Sat 07/04 09Z 0.48 3123 85 36 14 0.00
Sat 07/04 10Z 0.48 3122 84 50 15 0.00
Sat 07/04 11Z 0.45 3022 81 38 15 0.00
Run total areal avg QPF for the Central_Greens is: 0.48 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