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Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260625_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 06/25 18Z 4.17 2208 78 36 11 0.00
Thu 06/25 19Z 4.01 2209 79 37 11 0.00
Thu 06/25 20Z 4.08 2311 77 43 11 0.02
Thu 06/25 21Z 2.68 2211 74 47 11 0.01
Thu 06/25 22Z 0.81 2211 72 50 11 0.01
Thu 06/25 23Z 0.47 2209 67 59 12 0.00
Fri 06/26 00Z 0.38 2109 66 84 12 0.00
Fri 06/26 01Z 0.33 2009 66 94 11 0.00
Fri 06/26 02Z 0.26 1810 71 98 11 0.00
Fri 06/26 03Z 0.09 1710 83 97 10 0.02
Fri 06/26 04Z 0.08 1714 90 96 10 0.04
Fri 06/26 05Z 0.13 1715 94 95 10 0.07
Fri 06/26 06Z 0.16 1818 96 93 10 0.10
Fri 06/26 07Z 0.10 1719 96 86 10 0.14
Fri 06/26 08Z 0.09 1718 98 86 10 0.08
Fri 06/26 09Z 0.17 1818 97 85 10 0.03
Fri 06/26 10Z 0.23 1920 98 83 10 0.02
Fri 06/26 11Z 0.37 2019 99 85 10 0.04
Fri 06/26 12Z 0.45 2218 97 73 10 0.04
Fri 06/26 13Z 0.50 2317 94 66 11 0.02
Fri 06/26 14Z 0.49 2215 97 60 10 0.01
Fri 06/26 15Z 0.45 2313 99 57 11 0.01
Fri 06/26 16Z 0.45 2411 98 59 11 0.01
Fri 06/26 17Z 0.51 2510 96 63 11 0.01
Fri 06/26 18Z 0.54 2509 95 58 11 0.00
Fri 06/26 19Z 0.52 2507 93 61 11 0.03
Fri 06/26 20Z 0.49 2408 92 66 12 0.14
Fri 06/26 21Z 0.50 2710 91 73 12 0.17
Fri 06/26 22Z 0.46 2813 91 73 12 0.16
Fri 06/26 23Z 0.36 3012 87 64 12 0.05
Sat 06/27 00Z 0.38 3013 89 56 11 0.01
Sat 06/27 01Z 0.39 2913 93 55 11 0.00
Sat 06/27 02Z 0.27 3010 91 49 11 0.00
Sat 06/27 03Z 0.28 2910 91 46 11 0.00
Sat 06/27 04Z 0.24 2909 93 47 11 0.00
Sat 06/27 05Z 0.22 3009 93 46 11 0.00
Sat 06/27 06Z 0.20 3008 92 45 11 0.00
Sat 06/27 07Z 0.19 3008 93 45 11 0.00
Sat 06/27 08Z 0.18 3007 94 45 11 0.00
Sat 06/27 09Z 0.17 3007 95 46 11 0.00
Sat 06/27 10Z 0.13 3006 96 49 10 0.00
Sat 06/27 11Z 0.07 3205 95 48 10 0.00
Sat 06/27 12Z 0.02 3404 94 47 11 0.00
Sat 06/27 13Z 0.04 3203 95 52 10 0.00
Sat 06/27 14Z 0.03 3302 94 54 10 0.00
Sat 06/27 15Z 0.05 2801 95 55 11 0.01
Sat 06/27 16Z 0.05 2701 95 55 11 0.03
Sat 06/27 17Z 0.07 2601 95 58 11 0.04
Sat 06/27 18Z 0.09 2802 95 54 11 0.04
Sat 06/27 19Z 0.07 3001 94 51 11 0.02
Sat 06/27 20Z 0.05 3302 93 48 11 0.03
Sat 06/27 21Z 0.05 3302 93 49 12 0.04
Sat 06/27 22Z 0.06 3402 93 50 12 0.04
Sat 06/27 23Z 0.06 3503 92 49 12 0.03
Sun 06/28 00Z 0.09 0203 92 48 12 0.03
Sun 06/28 01Z 0.09 0103 93 50 11 0.01
Sun 06/28 02Z 0.11 0304 92 51 11 0.01
Sun 06/28 03Z 0.13 0304 93 54 11 0.00
Sun 06/28 04Z 0.11 0205 94 56 11 0.00
Sun 06/28 05Z 0.10 0205 95 60 11 0.00
Run total areal avg QPF for the Central_Greens is: 1.57 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