
Temperatures across northern New York and Grand Isle County in Vermont will drop below freezing tonight as rain moves into the region. A glaze up to a tenth of an inch of freezing rain will be possible through Wednesday afternoon. Flooding remains possible through Thursday due to snow melt, ice jams, and widespread rainfall Wednesday and Thursday. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260310_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)
=== ===== === ==== ==== === === === ====
Tue 03/10 12Z 0.57 2619 47 42 8 0.00
Tue 03/10 13Z 0.57 2619 46 41 8 0.00
Tue 03/10 14Z 0.57 2519 46 43 8 0.00
Tue 03/10 15Z 0.57 2518 48 47 8 0.00
Tue 03/10 16Z 0.56 2417 49 43 8 0.00
Tue 03/10 17Z 0.61 2416 49 43 8 0.00
Tue 03/10 18Z 0.66 2316 49 40 8 0.00
Tue 03/10 19Z 0.75 2318 50 46 8 0.00
Tue 03/10 20Z 0.87 2419 56 43 8 0.00
Tue 03/10 21Z 0.95 2520 67 41 8 0.00
Tue 03/10 22Z 0.99 2622 78 40 7 0.00
Tue 03/10 23Z 0.78 2621 87 40 7 0.01
Wed 03/11 00Z 0.60 2719 91 40 7 0.01
Wed 03/11 01Z 0.46 2716 93 42 7 0.00
Wed 03/11 02Z 0.36 2714 95 38 7 0.00
Wed 03/11 03Z 0.29 2712 97 41 7 0.00
Wed 03/11 04Z 0.24 2710 97 47 7 0.00
Wed 03/11 05Z 0.17 2607 98 83 7 0.00
Wed 03/11 06Z 0.11 2306 99 83 8 0.01
Wed 03/11 07Z 0.08 2007 99 84 8 0.01
Wed 03/11 08Z 0.06 1812 99 85 8 0.01
Wed 03/11 09Z 0.02 1717 99 86 8 0.03
Wed 03/11 10Z 0.03 1622 98 72 8 0.03
Wed 03/11 11Z 0.04 1627 98 55 8 0.03
Wed 03/11 12Z 0.03 1729 98 38 8 0.03
Wed 03/11 13Z 0.07 1730 98 38 9 0.03
Wed 03/11 14Z 0.11 1832 98 44 9 0.03
Wed 03/11 15Z 0.14 1833 97 56 10 0.03
Wed 03/11 16Z 0.18 1834 95 66 9 0.03
Wed 03/11 17Z 0.20 1935 94 41 9 0.01
Wed 03/11 18Z 0.20 1936 94 27 9 0.01
Wed 03/11 19Z 0.21 1937 94 55 10 0.01
Wed 03/11 20Z 0.24 1937 94 70 11 0.01
Wed 03/11 21Z 0.26 1939 93 86 11 0.01
Wed 03/11 22Z 0.29 1941 91 83 12 0.00
Wed 03/11 23Z 0.32 1941 96 90 11 0.03
Thu 03/12 00Z 0.36 2041 94 95 11 0.02
Thu 03/12 01Z 0.48 2041 95 87 11 0.01
Thu 03/12 02Z 0.59 2145 96 91 12 0.01
Thu 03/12 03Z 0.63 2046 96 77 12 0.02
Thu 03/12 04Z 0.77 2044 98 90 11 0.05
Thu 03/12 05Z 1.25 2336 98 58 9 0.09
Thu 03/12 06Z 1.21 2437 97 51 9 0.02
Thu 03/12 07Z 1.38 2434 99 74 7 0.04
Thu 03/12 08Z 1.29 2536 96 57 0 0.07
Thu 03/12 09Z 1.83 2639 89 30 -4 0.03
Thu 03/12 10Z 2.92 2637 87 17 -8 0.00
Thu 03/12 11Z 2.30 2636 92 3 -10 0.00
Thu 03/12 12Z 2.12 2638 94 1 -11 0.00
Thu 03/12 13Z 8.02 2738 91 3 -12 0.01
Thu 03/12 14Z 15.15 2738 86 8 -13 0.00
Thu 03/12 15Z 14.52 2735 86 12 -12 0.00
Thu 03/12 16Z 17.91 2832 86 17 -12 0.00
Thu 03/12 17Z 16.36 2829 78 22 -12 0.00
Thu 03/12 18Z 17.04 2827 74 28 -12 0.00
Thu 03/12 19Z 15.67 2826 70 38 -11 0.00
Thu 03/12 20Z 16.50 2826 72 41 -11 0.00
Thu 03/12 21Z 15.02 2825 76 44 -11 0.00
Thu 03/12 22Z 8.36 2824 82 49 -11 0.00
Thu 03/12 23Z 2.90 2824 86 56 -11 0.00
Run total areal avg QPF for the Central_Greens is: 0.74 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