
A wintry mix of snow, sleet, and freezing rain will spread northward late Thursday through Friday Morning, mainly in southern Vermont and western Essex County in New York. Precipitation will likely start as a wintry mix of freezing rain and sleet, before transitioning to mainly snow. Total snow and sleet accumulations up to two inches and ice accumulations up to one tenth of an inch are expected. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260305_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)
=== ===== === ==== ==== === === === ====
Thu 03/05 12Z 0.07 2603 51 18 2 0.00
Thu 03/05 13Z 0.04 2702 50 19 2 0.00
Thu 03/05 14Z 0.02 0600 49 21 2 0.00
Thu 03/05 15Z 0.04 1303 51 22 2 0.00
Thu 03/05 16Z 0.11 1307 56 25 1 0.00
Thu 03/05 17Z 0.13 1309 60 25 1 0.00
Thu 03/05 18Z 0.13 1411 64 25 1 0.00
Thu 03/05 19Z 0.13 1412 70 28 0 0.00
Thu 03/05 20Z 0.15 1311 78 30 0 0.00
Thu 03/05 21Z 0.15 1312 83 32 0 0.00
Thu 03/05 22Z 0.11 1413 82 39 0 0.01
Thu 03/05 23Z 0.10 1413 80 49 1 0.01
Fri 03/06 00Z 0.13 1315 77 55 1 0.00
Fri 03/06 01Z 0.14 1316 79 62 1 0.00
Fri 03/06 02Z 0.14 1317 82 67 1 0.01
Fri 03/06 03Z 0.15 1318 85 70 1 0.01
Fri 03/06 04Z 0.14 1318 89 72 1 0.00
Fri 03/06 05Z 0.14 1317 91 72 1 0.01
Fri 03/06 06Z 0.13 1417 94 75 0 0.01
Fri 03/06 07Z 0.13 1417 96 74 0 0.01
Fri 03/06 08Z 0.13 1417 97 75 0 0.02
Fri 03/06 09Z 0.12 1417 96 73 0 0.01
Fri 03/06 10Z 0.12 1416 95 65 0 0.01
Fri 03/06 11Z 0.12 1416 95 56 0 0.00
Fri 03/06 12Z 0.11 1416 95 49 0 0.00
Fri 03/06 13Z 0.10 1415 95 43 0 0.00
Fri 03/06 14Z 0.08 1515 95 38 0 0.00
Fri 03/06 15Z 0.06 1515 95 34 0 0.00
Fri 03/06 16Z 0.04 1615 96 34 0 0.00
Fri 03/06 17Z 0.04 1614 96 31 0 0.00
Fri 03/06 18Z 0.04 1714 95 29 0 0.00
Fri 03/06 19Z 0.04 1714 94 27 0 0.00
Fri 03/06 20Z 0.04 1716 93 20 0 0.00
Fri 03/06 21Z 0.08 1817 94 33 0 0.00
Fri 03/06 22Z 0.12 1819 95 49 0 0.00
Fri 03/06 23Z 0.15 1821 95 59 0 0.00
Sat 03/07 00Z 0.18 1923 95 63 0 0.00
Sat 03/07 01Z 0.22 1925 95 52 0 0.00
Sat 03/07 02Z 0.25 1927 95 53 0 0.00
Sat 03/07 03Z 0.26 1928 95 48 1 0.00
Sat 03/07 04Z 0.24 1928 94 40 2 0.00
Sat 03/07 05Z 0.25 1929 94 18 3 0.00
Sat 03/07 06Z 0.28 2029 95 22 3 0.00
Sat 03/07 07Z 0.30 2029 95 45 4 0.01
Sat 03/07 08Z 0.33 2030 96 56 5 0.01
Sat 03/07 09Z 0.34 2032 97 81 5 0.02
Sat 03/07 10Z 0.39 2133 98 45 6 0.03
Sat 03/07 11Z 0.40 2132 97 84 7 0.04
Sat 03/07 12Z 0.41 2232 97 92 8 0.03
Sat 03/07 13Z 0.44 2231 97 92 8 0.02
Sat 03/07 14Z 0.45 2331 96 86 9 0.02
Sat 03/07 15Z 0.44 2330 95 80 10 0.01
Sat 03/07 16Z 0.46 2231 96 54 10 0.01
Sat 03/07 17Z 0.49 2233 95 35 10 0.01
Sat 03/07 19Z 0.54 2235 92 40 11 0.01
Sat 03/07 20Z 0.55 2335 91 70 12 0.00
Sat 03/07 21Z 0.55 2336 92 74 12 0.00
Sat 03/07 22Z 0.58 2238 94 59 12 0.01
Sat 03/07 23Z 0.67 2341 93 50 11 0.01
Run total areal avg QPF for the Central_Greens is: 0.35 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