
Severe weather and flooding threats continue for portions of the central U.S., with impactful flash flooding possible from southern Kansas to southwestern Missouri. Extremely Critical fire weather conditions will develop across the Great Basin and Southwest on Friday, with dry and windy conditions through the weekend. Dangerous heat will increase across the southern and central U.S. this weekend. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the greens
Model run: BTV_GRID_D2D_NAM3_20260625_1800
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)
=== ===== === ==== ==== === === === ====
Thu 06/25 18Z 2.73 2306 79 50 11 0.00
Thu 06/25 19Z 2.50 2307 80 51 11 0.02
Thu 06/25 20Z 2.60 2309 79 56 11 0.04
Thu 06/25 21Z 1.64 2209 76 59 11 0.03
Thu 06/25 22Z 0.51 2209 74 62 11 0.03
Thu 06/25 23Z 0.31 2109 70 68 11 0.02
Fri 06/26 00Z 0.31 2109 68 80 11 0.00
Fri 06/26 01Z 0.28 2009 69 88 11 0.00
Fri 06/26 02Z 0.16 1909 72 94 11 0.00
Fri 06/26 03Z 0.10 1710 80 97 10 0.01
Fri 06/26 04Z 0.11 1713 85 97 10 0.03
Fri 06/26 05Z 0.14 1715 90 96 10 0.05
Fri 06/26 06Z 0.18 1717 95 95 10 0.09
Fri 06/26 07Z 0.12 1719 95 90 10 0.11
Fri 06/26 08Z 0.06 1719 96 89 10 0.06
Fri 06/26 09Z 0.09 1819 97 88 10 0.03
Fri 06/26 10Z 0.12 1920 98 83 10 0.03
Fri 06/26 11Z 0.22 2019 99 82 10 0.03
Fri 06/26 12Z 0.30 2116 97 78 10 0.03
Fri 06/26 13Z 0.35 2215 94 75 10 0.02
Fri 06/26 14Z 0.37 2214 97 69 10 0.01
Fri 06/26 15Z 0.35 2212 98 66 10 0.01
Fri 06/26 16Z 0.38 2410 98 64 10 0.01
Fri 06/26 17Z 0.44 2509 97 62 10 0.01
Fri 06/26 18Z 0.45 2608 96 58 11 0.01
Fri 06/26 19Z 0.45 2607 94 63 11 0.02
Fri 06/26 20Z 0.42 2607 93 66 11 0.12
Fri 06/26 21Z 0.43 2809 91 68 11 0.11
Fri 06/26 22Z 0.46 2812 92 68 11 0.11
Fri 06/26 23Z 0.41 2912 90 61 11 0.04
Sat 06/27 00Z 0.43 2912 91 53 11 0.01
Sat 06/27 01Z 0.41 2913 93 52 11 0.00
Sat 06/27 02Z 0.30 3010 92 47 11 0.01
Sat 06/27 03Z 0.30 2910 92 46 11 0.00
Sat 06/27 04Z 0.27 2909 93 48 11 0.01
Sat 06/27 05Z 0.26 3009 94 49 11 0.01
Sat 06/27 06Z 0.23 2908 92 51 11 0.00
Sat 06/27 07Z 0.21 3008 91 53 11 0.00
Sat 06/27 08Z 0.18 3007 92 54 11 0.00
Sat 06/27 09Z 0.16 3106 94 53 10 0.00
Sat 06/27 10Z 0.13 3105 93 55 10 0.00
Sat 06/27 11Z 0.07 3304 92 54 10 0.00
Sat 06/27 12Z 0.03 3503 91 53 10 0.00
Sat 06/27 13Z 0.05 3402 91 55 10 0.00
Sat 06/27 14Z 0.03 3301 91 57 10 0.00
Sat 06/27 15Z 0.04 3001 92 56 10 0.01
Sat 06/27 16Z 0.04 2900 93 56 11 0.02
Sat 06/27 17Z 0.06 2700 93 59 11 0.03
Sat 06/27 18Z 0.07 3001 93 58 11 0.04
Sat 06/27 19Z 0.06 3201 92 55 11 0.02
Sat 06/27 20Z 0.05 3502 91 52 11 0.02
Sat 06/27 21Z 0.05 3502 91 51 11 0.03
Sat 06/27 22Z 0.05 3502 91 52 11 0.03
Sat 06/27 23Z 0.06 0002 91 51 12 0.02
Sun 06/28 00Z 0.08 0303 91 50 12 0.02
Sun 06/28 01Z 0.07 0203 91 51 11 0.01
Sun 06/28 02Z 0.09 0303 91 52 11 0.01
Sun 06/28 03Z 0.10 0304 91 55 11 0.00
Sun 06/28 04Z 0.07 0204 91 56 11 0.00
Sun 06/28 05Z 0.06 0105 91 59 11 0.00
Run total areal avg QPF for the greens is: 1.38 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