
A Flood Watch has been issued until 8 AM Monday for most of northern and central Vermont, outside of Grand Isle County, for heavy rain. Rainfall between 1 to 2 inches, with locally up to 3 inches, will be possible through this evening and overnight as a cold front moves through. Flash Flooding will be possible if areas receive multiple rounds of showers and thunderstorms. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260614_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)
=== ===== === ==== ==== === === === ====
Sun 06/14 12Z 0.55 2418 73 34 14 0.00
Sun 06/14 13Z 0.63 2318 73 42 14 0.00
Sun 06/14 14Z 0.83 2319 75 43 14 0.00
Sun 06/14 15Z 2.12 2219 78 35 14 0.00
Sun 06/14 16Z 6.30 2119 80 50 14 0.00
Sun 06/14 17Z 7.72 2121 78 60 15 0.00
Sun 06/14 18Z 4.05 2122 72 52 15 0.01
Sun 06/14 19Z 3.80 2122 71 43 16 0.01
Sun 06/14 20Z 4.61 2317 83 74 15 0.05
Sun 06/14 21Z 0.64 2317 89 86 14 0.05
Sun 06/14 22Z 0.51 2415 94 92 13 0.30
Sun 06/14 23Z 0.31 2116 90 80 14 0.08
Mon 06/15 00Z 0.42 2022 86 87 14 0.01
Mon 06/15 01Z 0.43 2027 84 87 15 0.01
Mon 06/15 02Z 0.33 1927 92 96 15 0.10
Mon 06/15 03Z 0.48 2123 95 85 14 0.44
Mon 06/15 04Z 0.53 2222 94 81 14 0.23
Mon 06/15 05Z 0.60 2419 97 89 13 0.03
Mon 06/15 06Z 0.55 2718 97 92 11 0.07
Mon 06/15 07Z 0.30 2812 91 89 12 0.05
Mon 06/15 08Z 0.37 2814 93 88 11 0.01
Mon 06/15 09Z 0.35 2914 93 82 10 0.00
Mon 06/15 10Z 0.39 2915 94 92 9 0.00
Mon 06/15 11Z 0.38 2915 92 84 9 0.01
Mon 06/15 12Z 0.34 3015 87 60 9 0.00
Mon 06/15 13Z 0.37 3015 83 18 8 0.00
Mon 06/15 14Z 0.43 3015 81 7 8 0.00
Mon 06/15 15Z 0.63 3014 83 15 7 0.00
Mon 06/15 16Z 1.87 3013 87 28 7 0.00
Mon 06/15 17Z 2.42 3014 89 22 7 0.01
Mon 06/15 18Z 2.42 3014 88 13 7 0.00
Mon 06/15 19Z 2.95 3113 85 11 7 0.00
Mon 06/15 20Z 3.35 3113 86 16 7 0.00
Mon 06/15 21Z 2.93 3114 85 19 7 0.00
Mon 06/15 22Z 2.50 3014 85 17 6 0.00
Mon 06/15 23Z 1.13 3015 88 15 6 0.00
Tue 06/16 00Z 0.86 3018 89 15 6 0.00
Tue 06/16 01Z 0.80 3020 90 12 5 0.00
Tue 06/16 02Z 0.66 3020 95 6 5 0.00
Tue 06/16 03Z 0.57 3020 95 3 5 0.01
Tue 06/16 04Z 0.49 3121 96 2 5 0.01
Tue 06/16 05Z 0.41 3120 96 1 4 0.00
Tue 06/16 06Z 0.38 3120 97 4 4 0.01
Tue 06/16 07Z 0.39 3120 97 3 4 0.01
Tue 06/16 08Z 0.36 3219 96 4 4 0.01
Tue 06/16 09Z 0.28 3218 93 6 4 0.01
Tue 06/16 10Z 0.22 3216 91 16 5 0.00
Tue 06/16 11Z 0.21 3114 89 33 5 0.00
Tue 06/16 12Z 0.19 3112 86 43 5 0.00
Tue 06/16 13Z 0.18 3110 82 30 6 0.00
Tue 06/16 14Z 0.18 3009 77 30 6 0.00
Tue 06/16 15Z 0.22 2908 69 30 6 0.00
Tue 06/16 16Z 0.23 3007 60 29 7 0.00
Tue 06/16 17Z 0.60 2906 56 28 7 0.00
Tue 06/16 18Z 1.17 2805 55 32 8 0.00
Tue 06/16 19Z 1.48 2605 54 31 8 0.00
Tue 06/16 20Z 1.59 2506 58 25 9 0.00
Tue 06/16 21Z 1.35 2406 63 13 9 0.00
Tue 06/16 22Z 0.90 2306 66 14 9 0.00
Tue 06/16 23Z 0.42 2207 67 17 9 0.00
Run total areal avg QPF for the Central_Greens is: 1.53 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