
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 greens
Model run: BTV_GRID_D2D_NAM3_20260310_0600
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)
=== ===== === ==== ==== === === === ====
Tue 03/10 06Z 1.07 2632 37 45 8 0.00
Tue 03/10 07Z 1.13 2632 37 49 8 0.00
Tue 03/10 08Z 1.11 2730 39 54 8 0.00
Tue 03/10 09Z 1.09 2828 43 56 7 0.00
Tue 03/10 10Z 0.91 2825 48 53 7 0.00
Tue 03/10 11Z 0.74 2822 52 50 7 0.00
Tue 03/10 12Z 0.60 2719 54 53 7 0.00
Tue 03/10 13Z 0.51 2617 53 55 8 0.00
Tue 03/10 14Z 0.48 2516 52 55 8 0.00
Tue 03/10 15Z 0.50 2418 50 48 8 0.00
Tue 03/10 16Z 0.55 2320 49 44 8 0.00
Tue 03/10 17Z 0.64 2420 51 43 8 0.00
Tue 03/10 18Z 0.72 2419 55 29 7 0.00
Tue 03/10 19Z 0.84 2418 62 34 7 0.00
Tue 03/10 20Z 0.94 2516 70 48 7 0.00
Tue 03/10 21Z 0.98 2516 79 45 6 0.00
Tue 03/10 22Z 0.83 2617 85 41 6 0.00
Tue 03/10 23Z 0.65 2617 89 39 6 0.00
Wed 03/11 00Z 0.50 2614 93 40 6 0.00
Wed 03/11 01Z 0.36 2612 95 43 6 0.01
Wed 03/11 02Z 0.25 2709 97 51 6 0.02
Wed 03/11 03Z 0.18 2707 97 60 6 0.01
Wed 03/11 04Z 0.13 2706 98 52 7 0.01
Wed 03/11 05Z 0.11 2605 98 65 7 0.02
Wed 03/11 06Z 0.08 2205 98 56 7 0.01
Wed 03/11 07Z 0.06 1907 98 57 7 0.01
Wed 03/11 08Z 0.04 1810 98 54 7 0.01
Wed 03/11 09Z 0.04 1716 98 54 7 0.01
Wed 03/11 10Z 0.08 1622 98 44 8 0.02
Wed 03/11 11Z 0.08 1728 98 50 8 0.03
Wed 03/11 12Z 0.06 1731 97 51 8 0.03
Wed 03/11 13Z 0.04 1732 97 46 9 0.02
Wed 03/11 14Z 0.08 1835 97 56 9 0.02
Wed 03/11 15Z 0.13 1937 96 58 10 0.02
Wed 03/11 16Z 0.17 1938 96 74 10 0.03
Wed 03/11 17Z 0.21 1939 96 63 10 0.04
Wed 03/11 18Z 0.22 1940 93 37 10 0.01
Wed 03/11 19Z 0.26 2043 94 27 10 0.01
Wed 03/11 20Z 0.26 2044 91 52 11 0.00
Wed 03/11 21Z 0.26 2043 90 83 12 0.01
Wed 03/11 22Z 0.26 1945 90 92 12 0.01
Wed 03/11 23Z 0.35 2047 94 93 11 0.05
Thu 03/12 01Z 0.44 2048 93 83 12 0.02
Thu 03/12 02Z 0.46 2047 92 80 12 0.01
Thu 03/12 03Z 0.41 2046 92 89 13 0.00
Thu 03/12 04Z 0.88 2243 96 96 11 0.00
Thu 03/12 05Z 0.87 2435 94 84 8 0.28
Thu 03/12 06Z 1.35 2438 98 56 5 0.24
Thu 03/12 07Z 1.65 2540 92 50 0 0.02
Thu 03/12 08Z 2.15 2541 93 38 -5 0.04
Thu 03/12 09Z 2.51 2539 94 6 -8 0.00
Thu 03/12 10Z 3.24 2638 94 5 -10 0.00
Thu 03/12 11Z 4.46 2640 93 3 -12 0.00
Thu 03/12 12Z 7.68 2739 92 6 -13 0.01
Thu 03/12 13Z 9.68 2736 92 10 -14 0.00
Thu 03/12 14Z 10.07 2735 88 15 -15 0.00
Thu 03/12 15Z 14.51 2832 87 21 -14 0.00
Thu 03/12 16Z 15.68 2830 82 29 -14 0.00
Thu 03/12 17Z 16.60 2827 80 36 -13 0.00
Run total areal avg QPF for the greens is: 1.03 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