
A Fire Weather Watch has been issued for all of northern New York and western Vermont from 11 AM to 7 PM Tuesday. Critically low relative humidity values to 20 to 25 percent, with south winds gusting up to 30 MPH will lead to critical fire weather concerns. Should any fires start, weather and fuels will make fire containment difficult. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260427_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)
=== ===== === ==== ==== === === === ====
Mon 04/27 18Z 0.87 0800 52 46 7 0.00
Mon 04/27 19Z 0.78 0001 54 62 7 0.00
Mon 04/27 20Z 0.69 0301 57 69 7 0.00
Mon 04/27 21Z 0.45 0701 57 70 7 0.00
Mon 04/27 22Z 0.59 1002 58 65 7 0.00
Mon 04/27 23Z 0.11 1501 57 53 7 0.00
Tue 04/28 00Z 0.20 1303 57 28 7 0.00
Tue 04/28 01Z 0.26 1406 57 18 7 0.00
Tue 04/28 02Z 0.17 1509 57 16 6 0.00
Tue 04/28 03Z 0.05 1710 57 15 6 0.00
Tue 04/28 04Z 0.03 1610 57 13 6 0.00
Tue 04/28 05Z 0.04 1711 56 11 6 0.00
Tue 04/28 06Z 0.06 1711 56 9 6 0.00
Tue 04/28 07Z 0.13 1812 56 8 6 0.00
Tue 04/28 08Z 0.15 1813 57 6 6 0.00
Tue 04/28 09Z 0.09 1812 58 5 5 0.00
Tue 04/28 10Z 0.08 1713 58 5 5 0.00
Tue 04/28 11Z 0.05 1715 56 4 5 0.00
Tue 04/28 12Z 0.04 1617 55 4 5 0.00
Tue 04/28 13Z 0.05 1619 55 3 5 0.00
Tue 04/28 14Z 0.14 1619 58 3 4 0.00
Tue 04/28 15Z 0.36 1520 62 3 4 0.00
Tue 04/28 16Z 1.29 1519 65 4 4 0.00
Tue 04/28 17Z 1.96 1517 66 4 4 0.00
Tue 04/28 18Z 1.19 1617 65 6 4 0.00
Tue 04/28 19Z 1.88 1617 63 7 5 0.00
Tue 04/28 20Z 2.32 1517 63 6 5 0.00
Tue 04/28 21Z 1.10 1616 62 11 5 0.00
Tue 04/28 22Z 0.44 1618 63 62 4 0.00
Tue 04/28 23Z 0.15 1620 66 75 4 0.00
Wed 04/29 00Z 0.06 1720 68 86 4 0.00
Wed 04/29 01Z 0.09 1721 68 83 4 0.00
Wed 04/29 02Z 0.17 1821 71 80 3 0.00
Wed 04/29 03Z 0.20 1920 78 74 3 0.00
Wed 04/29 04Z 0.19 1919 77 68 3 0.00
Wed 04/29 05Z 0.24 1920 73 67 3 0.00
Wed 04/29 06Z 0.41 2022 75 62 3 0.00
Wed 04/29 07Z 0.34 2121 82 48 5 0.00
Wed 04/29 08Z 0.28 2118 85 41 6 0.00
Wed 04/29 09Z 0.28 2117 88 41 6 0.00
Wed 04/29 10Z 0.21 2113 89 34 6 0.00
Wed 04/29 11Z 0.19 2112 89 32 6 0.00
Wed 04/29 12Z 0.14 2110 89 25 7 0.00
Wed 04/29 13Z 0.12 2009 90 22 6 0.00
Wed 04/29 14Z 0.07 1810 89 18 6 0.00
Wed 04/29 15Z 0.05 1710 86 18 6 0.00
Wed 04/29 16Z 0.05 1610 82 25 6 0.00
Wed 04/29 17Z 0.10 1710 79 47 5 0.00
Wed 04/29 18Z 0.25 1609 76 67 5 0.00
Wed 04/29 19Z 1.35 1510 74 58 5 0.00
Wed 04/29 20Z 1.46 1511 75 54 5 0.00
Wed 04/29 21Z 1.99 1511 78 59 5 0.00
Wed 04/29 22Z 1.26 1413 81 52 5 0.00
Wed 04/29 23Z 0.35 1415 86 43 5 0.00
Thu 04/30 00Z 0.17 1416 88 42 6 0.00
Thu 04/30 01Z 0.15 1419 87 46 6 0.00
Thu 04/30 02Z 0.18 1422 82 43 6 0.00
Thu 04/30 03Z 0.20 1424 77 41 6 0.00
Thu 04/30 04Z 0.25 1429 89 42 6 0.01
Thu 04/30 05Z 0.30 1434 95 43 6 0.02
Run total areal avg QPF for the Central_Greens is: 0.03 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