
Significant heat is expected to build from Wednesday through Friday. Extreme Heat Warnings are now in effect for the entire Champlain Valley & eastern Windsor County in Vermont. Heat Advisories are now in effect for the remainder of the area in northern New York & Vermont. Heat index values are expected to peak around 105 degrees in warning areas, and mid 90s to lower 100s in advisory areas. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260701_0000
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)
=== ===== === ==== ==== === === === ====
Wed 07/01 00Z 0.37 2214 82 94 16 0.00
Wed 07/01 01Z 0.47 2416 87 97 16 0.08
Wed 07/01 02Z 0.56 2419 90 90 16 0.09
Wed 07/01 03Z 0.63 2421 88 84 17 0.06
Wed 07/01 04Z 0.73 2425 87 72 17 0.02
Wed 07/01 05Z 0.75 2525 90 62 17 0.00
Wed 07/01 06Z 0.77 2525 92 55 17 0.01
Wed 07/01 07Z 0.82 2626 93 54 18 0.01
Wed 07/01 08Z 0.81 2626 93 53 18 0.00
Wed 07/01 09Z 0.85 2727 96 50 18 0.01
Wed 07/01 10Z 0.79 2725 96 50 18 0.02
Wed 07/01 11Z 0.71 2723 96 48 18 0.03
Wed 07/01 12Z 0.64 2821 94 45 18 0.02
Wed 07/01 13Z 0.49 2816 95 42 18 0.01
Wed 07/01 14Z 0.38 2812 95 38 18 0.01
Wed 07/01 15Z 0.34 2709 94 40 18 0.01
Wed 07/01 16Z 0.37 2609 91 40 18 0.00
Wed 07/01 17Z 0.40 2509 90 38 18 0.00
Wed 07/01 18Z 0.48 2511 89 40 19 0.00
Wed 07/01 19Z 0.56 2412 90 49 19 0.00
Wed 07/01 20Z 0.63 2515 91 46 19 0.00
Wed 07/01 21Z 0.63 2516 92 48 20 0.00
Wed 07/01 22Z 0.59 2417 92 46 20 0.00
Wed 07/01 23Z 0.69 2419 94 43 20 0.00
Thu 07/02 00Z 0.82 2521 92 42 20 0.00
Thu 07/02 01Z 0.85 2622 92 41 20 0.01
Thu 07/02 02Z 0.75 2623 90 38 20 0.00
Thu 07/02 03Z 0.80 2624 93 39 20 0.01
Thu 07/02 04Z 0.71 2723 91 38 20 0.00
Thu 07/02 05Z 0.71 2824 93 41 20 0.00
Thu 07/02 06Z 0.67 2823 91 39 20 0.01
Thu 07/02 07Z 0.68 2924 92 39 19 0.01
Thu 07/02 08Z 0.71 2925 93 46 19 0.01
Thu 07/02 09Z 0.68 2924 91 53 19 0.01
Thu 07/02 10Z 0.63 2923 92 40 19 0.01
Thu 07/02 11Z 0.63 2923 88 35 19 0.01
Thu 07/02 12Z 0.49 2920 74 45 20 0.01
Thu 07/02 13Z 0.53 2820 76 37 20 0.01
Thu 07/02 14Z 0.53 2820 76 52 20 0.01
Thu 07/02 15Z 0.54 2820 76 38 20 0.00
Thu 07/02 16Z 0.55 2718 77 30 20 0.00
Thu 07/02 17Z 0.53 2716 81 26 20 0.00
Thu 07/02 18Z 0.57 2617 80 27 21 0.00
Thu 07/02 19Z 0.68 2517 86 30 20 0.00
Thu 07/02 20Z 0.89 2518 89 32 20 0.00
Thu 07/02 21Z 1.48 2521 86 35 20 0.00
Thu 07/02 22Z 1.85 2622 85 33 20 0.00
Thu 07/02 23Z 1.20 2624 86 42 20 0.00
Fri 07/03 00Z 1.11 2626 88 49 20 0.00
Fri 07/03 01Z 1.04 2628 89 48 20 0.00
Fri 07/03 02Z 1.01 2630 88 58 20 0.00
Fri 07/03 03Z 0.97 2730 89 58 19 0.00
Fri 07/03 04Z 0.97 2730 88 58 19 0.00
Fri 07/03 05Z 0.97 2829 86 59 18 0.00
Fri 07/03 06Z 1.00 2829 89 51 18 0.00
Fri 07/03 07Z 0.86 2928 87 34 17 0.00
Fri 07/03 08Z 0.68 3027 84 25 18 0.01
Fri 07/03 09Z 0.58 3025 76 25 18 0.01
Fri 07/03 10Z 0.51 3024 67 19 18 0.01
Fri 07/03 11Z 0.50 3024 72 16 17 0.01
Run total areal avg QPF for the greens is: 0.53 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