
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_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 08/03 18Z 0.77 2321 98 95 15 0.00
Mon 08/03 19Z 0.94 2524 98 91 14 0.07
Mon 08/03 20Z 1.03 2625 98 87 13 0.05
Mon 08/03 21Z 0.99 2726 98 91 12 0.06
Mon 08/03 22Z 0.91 2925 97 77 12 0.02
Mon 08/03 23Z 0.88 3027 97 63 11 0.02
Tue 08/04 00Z 0.78 3027 98 39 11 0.02
Tue 08/04 01Z 0.63 3128 95 52 10 0.02
Tue 08/04 02Z 0.37 3230 84 46 11 0.00
Tue 08/04 03Z 0.35 3229 77 23 11 0.00
Tue 08/04 04Z 0.58 3126 86 13 10 0.00
Tue 08/04 05Z 0.74 3026 83 3 10 0.00
Tue 08/04 06Z 0.73 2924 80 3 11 0.00
Tue 08/04 07Z 0.77 2924 74 4 11 0.00
Tue 08/04 08Z 0.74 2924 68 3 12 0.00
Tue 08/04 09Z 0.78 3025 66 2 12 0.00
Tue 08/04 10Z 0.77 3026 64 2 12 0.00
Tue 08/04 11Z 0.64 3025 59 2 12 0.00
Tue 08/04 12Z 0.54 3024 55 2 13 0.00
Tue 08/04 13Z 0.46 3022 53 2 13 0.00
Tue 08/04 14Z 0.43 3018 52 2 13 0.00
Tue 08/04 15Z 0.42 2914 52 2 13 0.00
Tue 08/04 16Z 0.41 2912 53 2 13 0.00
Tue 08/04 17Z 0.41 2809 56 2 13 0.00
Tue 08/04 18Z 0.46 2609 60 2 14 0.00
Tue 08/04 19Z 0.58 2608 62 2 14 0.00
Tue 08/04 20Z 0.55 2607 62 3 14 0.00
Tue 08/04 21Z 0.34 2606 61 3 15 0.00
Tue 08/04 22Z 0.25 2506 59 4 15 0.00
Tue 08/04 23Z 0.18 2505 54 4 16 0.00
Wed 08/05 00Z 0.16 2405 49 5 17 0.00
Wed 08/05 01Z 0.15 2305 46 6 17 0.00
Wed 08/05 02Z 0.18 2207 45 7 17 0.00
Wed 08/05 03Z 0.16 2207 44 8 17 0.00
Wed 08/05 04Z 0.16 2207 41 8 17 0.00
Wed 08/05 05Z 0.14 2206 37 8 17 0.00
Wed 08/05 06Z 0.15 2306 37 7 17 0.00
Wed 08/05 07Z 0.15 2406 38 6 17 0.00
Wed 08/05 08Z 0.15 2505 40 6 17 0.00
Wed 08/05 09Z 0.15 2505 43 6 16 0.00
Wed 08/05 10Z 0.16 2505 47 7 16 0.00
Wed 08/05 11Z 0.13 2504 45 7 16 0.00
Wed 08/05 12Z 0.13 2604 46 8 16 0.00
Wed 08/05 13Z 0.15 2605 51 9 15 0.00
Wed 08/05 14Z 0.16 2605 56 8 15 0.00
Wed 08/05 15Z 0.14 2304 57 6 15 0.00
Wed 08/05 16Z 0.15 2204 58 4 15 0.00
Wed 08/05 17Z 0.28 2206 59 2 15 0.00
Wed 08/05 18Z 0.43 2106 56 1 16 0.00
Wed 08/05 19Z 0.46 2208 51 1 16 0.00
Wed 08/05 20Z 0.33 2209 45 1 17 0.00
Wed 08/05 21Z 0.34 2309 44 2 17 0.00
Wed 08/05 22Z 0.38 2310 51 5 17 0.00
Wed 08/05 23Z 0.40 2411 59 12 17 0.00
Thu 08/06 00Z 0.40 2411 64 21 17 0.00
Thu 08/06 01Z 0.38 2410 67 26 17 0.00
Thu 08/06 02Z 0.34 2410 71 34 17 0.00
Thu 08/06 03Z 0.33 2410 73 49 17 0.00
Thu 08/06 04Z 0.32 2310 75 63 17 0.00
Thu 08/06 05Z 0.29 2311 77 73 17 0.00
Run total areal avg QPF for the Central_Greens is: 0.26 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