
Snow is expected late this morning through Monday night. Across south-central Vermont and portions of the Adirondacks in New York, snowfall rates of 1-2" per hour are likely this evening into tonight. Snow accumulations at least 8" regionwide, 13-19" in southern areas, and locally 2 feet are expected along the spine of the southern Greens. Travel impacts will begin tonight and continue Monday. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260125_1200
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)
=== ===== === ==== ==== === === === ====
Sun 01/25 12Z 0.04 3101 51 21 -17 0.00
Sun 01/25 13Z 0.05 1302 47 38 -16 0.00
Sun 01/25 14Z 0.05 1304 45 55 -16 0.00
Sun 01/25 15Z 0.07 1407 49 70 -16 0.00
Sun 01/25 16Z 0.13 1411 63 84 -16 0.00
Sun 01/25 17Z 0.14 1413 72 86 -16 0.01
Sun 01/25 18Z 0.17 1416 79 86 -16 0.02
Sun 01/25 19Z 0.17 1418 85 86 -15 0.04
Sun 01/25 20Z 0.21 1422 85 87 -15 0.05
Sun 01/25 21Z 0.26 1424 85 88 -15 0.05
Sun 01/25 22Z 0.28 1425 86 89 -14 0.06
Sun 01/25 23Z 0.33 1327 86 89 -14 0.07
Mon 01/26 00Z 0.40 1329 86 90 -14 0.06
Mon 01/26 01Z 0.44 1230 86 91 -14 0.06
Mon 01/26 02Z 0.45 1228 86 90 -14 0.06
Mon 01/26 03Z 0.44 1126 85 89 -13 0.06
Mon 01/26 04Z 0.44 1126 85 89 -12 0.05
Mon 01/26 05Z 0.47 1127 85 90 -12 0.04
Mon 01/26 06Z 0.49 1127 86 89 -13 0.03
Mon 01/26 07Z 0.48 1025 86 92 -13 0.02
Mon 01/26 08Z 0.44 1023 87 94 -13 0.01
Mon 01/26 09Z 0.41 1121 87 93 -12 0.01
Mon 01/26 10Z 0.36 1119 87 93 -12 0.01
Mon 01/26 11Z 0.34 1118 88 92 -12 0.01
Mon 01/26 12Z 0.32 1218 87 88 -12 0.01
Mon 01/26 13Z 0.29 1216 88 88 -13 0.01
Mon 01/26 14Z 0.28 1215 88 87 -12 0.01
Mon 01/26 15Z 0.25 1313 89 89 -13 0.01
Mon 01/26 16Z 0.21 1412 89 87 -12 0.01
Mon 01/26 17Z 0.17 1411 90 87 -12 0.01
Mon 01/26 18Z 0.16 1510 91 89 -12 0.01
Mon 01/26 19Z 0.15 1509 91 92 -12 0.01
Mon 01/26 20Z 0.10 1608 91 91 -13 0.02
Mon 01/26 21Z 0.09 1806 92 90 -13 0.02
Mon 01/26 22Z 0.26 2307 90 86 -14 0.03
Mon 01/26 23Z 0.38 2610 89 81 -14 0.03
Tue 01/27 00Z 0.59 2814 89 81 -15 0.02
Tue 01/27 01Z 0.67 3019 89 83 -17 0.02
Tue 01/27 02Z 0.64 3021 90 82 -18 0.01
Tue 01/27 03Z 0.62 3022 91 79 -18 0.01
Tue 01/27 04Z 0.65 3124 91 78 -19 0.01
Tue 01/27 05Z 0.63 3125 90 74 -19 0.01
Tue 01/27 06Z 0.65 3127 91 68 -19 0.01
Tue 01/27 07Z 0.70 3028 91 60 -19 0.01
Tue 01/27 08Z 0.73 3029 90 54 -19 0.00
Tue 01/27 09Z 0.70 3029 87 47 -19 0.00
Tue 01/27 10Z 0.65 3028 80 30 -19 0.00
Tue 01/27 11Z 0.58 3026 70 24 -19 0.00
Tue 01/27 12Z 0.54 3025 68 42 -19 0.00
Tue 01/27 13Z 0.46 2921 70 45 -18 0.00
Tue 01/27 14Z 0.43 2817 76 58 -19 0.00
Tue 01/27 15Z 0.39 2714 80 75 -18 0.00
Tue 01/27 16Z 0.36 2511 81 82 -18 0.00
Tue 01/27 17Z 0.37 2312 76 82 -18 0.00
Tue 01/27 18Z 0.48 2213 67 80 -18 0.00
Tue 01/27 19Z 0.37 2213 68 81 -17 0.00
Tue 01/27 20Z 0.39 2213 65 82 -18 0.00
Tue 01/27 21Z 0.87 2316 78 82 -18 0.01
Tue 01/27 22Z 0.94 2319 86 79 -19 0.01
Tue 01/27 23Z 1.27 2421 91 77 -19 0.01
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