
A warm front will approach Friday afternoon. A brief wintry mix or rain in warmer valleys is possible before a quick transition into moderate to heavy snow takes place during the Friday evening commute. 1-1.5 inch per hour snowfall rates are likely in northeastern New York and much of Vermont. Difficult travel is likely Friday Evening. Light snow will continue Friday night into Saturday. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260219_1800
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 02/19 18Z 0.10 1203 56 29 -4 0.00
Thu 02/19 19Z 0.11 1304 57 32 -4 0.00
Thu 02/19 20Z 0.04 1605 57 36 -4 0.00
Thu 02/19 21Z 0.03 1704 56 40 -4 0.00
Thu 02/19 22Z 0.05 1903 57 47 -4 0.00
Thu 02/19 23Z 0.07 1904 57 52 -4 0.00
Fri 02/20 00Z 0.03 1903 53 41 -3 0.00
Fri 02/20 01Z 0.02 1603 52 21 -3 0.00
Fri 02/20 02Z 0.02 1604 55 13 -3 0.00
Fri 02/20 03Z 0.03 1805 57 11 -3 0.00
Fri 02/20 06Z 0.02 1707 63 9 -3 0.00
Fri 02/20 07Z 0.05 1809 66 9 -3 0.00
Fri 02/20 08Z 0.02 1709 68 9 -2 0.00
Fri 02/20 09Z 0.02 1609 69 10 -2 0.00
Fri 02/20 10Z 0.03 1610 67 10 -2 0.00
Fri 02/20 11Z 0.02 1712 65 11 -1 0.00
Fri 02/20 12Z 0.02 1615 64 11 -1 0.00
Fri 02/20 13Z 0.02 1716 63 10 -2 0.00
Fri 02/20 14Z 0.02 1617 61 13 -2 0.00
Fri 02/20 15Z 0.02 1617 62 22 -3 0.00
Fri 02/20 16Z 0.02 1618 62 30 -3 0.00
Fri 02/20 17Z 0.03 1618 66 61 -3 0.00
Fri 02/20 18Z 0.09 1516 79 91 -2 0.00
Fri 02/20 19Z 0.10 1518 92 94 0 0.00
Fri 02/20 20Z 0.14 1419 96 94 0 0.01
Fri 02/20 21Z 0.22 1322 95 97 0 0.04
Fri 02/20 22Z 0.30 1325 94 99 -1 0.08
Fri 02/20 23Z 0.37 1227 94 99 -1 0.08
Sat 02/21 00Z 0.37 1225 96 98 -2 0.07
Sat 02/21 01Z 0.36 1321 96 96 -4 0.05
Sat 02/21 02Z 0.38 1319 96 97 -5 0.09
Sat 02/21 03Z 0.42 1317 95 99 -7 0.16
Sat 02/21 04Z 0.37 1316 95 96 -7 0.11
Sat 02/21 05Z 0.27 1414 95 95 -8 0.07
Sat 02/21 06Z 0.13 1511 95 97 -8 0.03
Sat 02/21 07Z 0.06 1608 94 93 -8 0.02
Sat 02/21 08Z 0.04 1606 94 91 -8 0.02
Sat 02/21 09Z 0.05 1804 95 89 -8 0.02
Sat 02/21 10Z 0.11 2203 96 88 -8 0.01
Sat 02/21 11Z 0.11 2602 96 87 -8 0.01
Sat 02/21 12Z 0.09 2802 98 87 -8 0.01
Sat 02/21 13Z 0.07 2801 99 88 -8 0.01
Sat 02/21 14Z 0.06 3201 99 89 -8 0.01
Sat 02/21 15Z 0.06 0101 99 88 -8 0.01
Sat 02/21 16Z 0.08 0303 98 86 -8 0.00
Sat 02/21 17Z 0.14 0304 97 81 -8 0.00
Sat 02/21 18Z 0.12 0204 96 84 -8 0.00
Sat 02/21 19Z 0.15 0205 90 81 -8 0.00
Sat 02/21 20Z 0.20 0305 83 81 -8 0.00
Sat 02/21 21Z 0.28 0407 75 69 -8 0.00
Sat 02/21 22Z 0.37 0608 73 53 -8 0.00
Sat 02/21 23Z 0.37 0710 75 42 -8 0.00
Sun 02/22 00Z 0.30 0810 63 29 -8 0.00
Sun 02/22 02Z 0.28 1011 53 16 -8 0.00
Sun 02/22 03Z 0.25 1010 56 13 -8 0.00
Sun 02/22 04Z 0.22 1109 56 13 -8 0.00
Sun 02/22 05Z 0.19 1108 56 14 -8 0.00
Run total areal avg QPF for the Central_Greens is: 0.91 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