
Extreme heat continues across the Southwest as temperatures may top 120 degrees. The heat may expand across the West and south-central U.S. into the middle of the month. Severe thunderstorms capable of severe wind gusts and large hail will be the primary hazards today across the northern Plains into the upper Midwest. Rainfall could be locally heavy across the Eastern U.S. today. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260803_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)
=== ===== === ==== ==== === === === ====
Mon 08/03 12Z 0.20 1817 97 93 15 0.00
Mon 08/03 13Z 0.26 1917 99 88 15 0.02
Mon 08/03 14Z 0.36 2018 99 76 15 0.01
Mon 08/03 15Z 0.46 2018 98 72 15 0.01
Mon 08/03 16Z 0.44 1918 98 64 16 0.01
Mon 08/03 17Z 0.51 2019 96 75 16 0.02
Mon 08/03 18Z 0.51 2118 97 93 16 0.21
Mon 08/03 19Z 0.77 2320 94 78 15 0.26
Mon 08/03 20Z 0.93 2420 92 35 14 0.00
Mon 08/03 21Z 1.26 2522 92 53 13 0.01
Mon 08/03 22Z 0.88 2623 97 75 13 0.03
Mon 08/03 23Z 0.77 2928 98 85 12 0.10
Tue 08/04 00Z 0.75 3032 98 95 10 0.11
Tue 08/04 01Z 0.63 3133 94 70 10 0.04
Tue 08/04 02Z 0.71 3134 88 19 10 0.00
Tue 08/04 03Z 0.56 3231 81 8 10 0.00
Tue 08/04 04Z 0.55 3229 81 10 10 0.00
Tue 08/04 05Z 0.66 3126 88 5 10 0.00
Tue 08/04 06Z 0.71 3026 87 4 10 0.00
Tue 08/04 07Z 0.69 3024 82 4 10 0.00
Tue 08/04 08Z 0.65 3022 78 5 11 0.00
Tue 08/04 09Z 0.61 3022 71 3 11 0.00
Tue 08/04 10Z 0.56 3023 63 3 12 0.00
Tue 08/04 11Z 0.52 3022 57 2 12 0.00
Tue 08/04 12Z 0.49 3021 54 1 13 0.00
Tue 08/04 13Z 0.45 3021 52 1 13 0.00
Tue 08/04 14Z 0.40 3019 50 2 14 0.00
Tue 08/04 15Z 0.36 3016 46 2 14 0.00
Tue 08/04 16Z 0.32 3014 44 1 14 0.00
Tue 08/04 17Z 0.30 2911 46 1 15 0.00
Tue 08/04 18Z 0.30 2809 50 1 15 0.00
Tue 08/04 19Z 0.28 2807 50 2 15 0.00
Tue 08/04 20Z 0.27 2707 51 3 15 0.00
Tue 08/04 21Z 0.24 2606 52 4 16 0.00
Tue 08/04 22Z 0.19 2605 53 5 16 0.00
Tue 08/04 23Z 0.15 2504 52 6 16 0.00
Wed 08/05 00Z 0.12 2204 50 7 16 0.00
Wed 08/05 01Z 0.17 2207 48 9 16 0.00
Wed 08/05 02Z 0.21 2208 43 11 17 0.00
Wed 08/05 03Z 0.19 2209 39 12 17 0.00
Wed 08/05 04Z 0.21 2309 37 12 17 0.00
Wed 08/05 05Z 0.22 2309 36 11 18 0.00
Wed 08/05 06Z 0.21 2409 35 8 18 0.00
Wed 08/05 07Z 0.22 2409 37 4 17 0.00
Wed 08/05 08Z 0.22 2509 41 2 17 0.00
Wed 08/05 09Z 0.22 2509 43 1 17 0.00
Wed 08/05 10Z 0.21 2508 44 2 16 0.00
Wed 08/05 11Z 0.21 2508 46 2 16 0.00
Wed 08/05 12Z 0.22 2408 46 1 16 0.00
Wed 08/05 13Z 0.25 2409 47 1 16 0.00
Wed 08/05 14Z 0.26 2409 46 1 16 0.00
Wed 08/05 15Z 0.29 2409 51 1 15 0.00
Wed 08/05 16Z 0.27 2308 54 2 15 0.00
Wed 08/05 17Z 0.24 2208 50 4 16 0.00
Wed 08/05 18Z 0.27 2210 49 10 16 0.00
Wed 08/05 19Z 0.30 2211 51 15 16 0.00
Wed 08/05 20Z 0.32 2112 53 30 16 0.00
Wed 08/05 21Z 0.32 2112 50 38 17 0.00
Wed 08/05 22Z 0.34 2212 45 41 17 0.00
Wed 08/05 23Z 0.36 2213 45 37 17 0.00
Run total areal avg QPF for the Central_Greens is: 0.83 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