Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260705_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)
=== ===== === ==== ==== === === === ====
Sun 07/05 18Z 0.64 2901 69 23 13 0.00
Sun 07/05 19Z 0.38 3301 67 22 14 0.00
Sun 07/05 20Z 0.23 3502 68 21 14 0.00
Sun 07/05 21Z 0.44 0202 70 22 14 0.00
Sun 07/05 22Z 0.52 0402 73 18 14 0.00
Sun 07/05 23Z 0.48 0504 75 17 13 0.00
Mon 07/06 00Z 0.50 0706 75 17 13 0.00
Mon 07/06 01Z 0.58 0808 73 15 13 0.00
Mon 07/06 02Z 0.62 0909 72 11 13 0.00
Mon 07/06 03Z 0.56 1010 76 9 13 0.00
Mon 07/06 04Z 0.44 1110 82 8 13 0.00
Mon 07/06 05Z 0.31 1211 87 10 13 0.00
Mon 07/06 06Z 0.26 1312 88 15 13 0.00
Mon 07/06 07Z 0.28 1313 89 19 13 0.00
Mon 07/06 08Z 0.26 1313 90 21 13 0.00
Mon 07/06 09Z 0.28 1314 93 23 12 0.00
Mon 07/06 10Z 0.34 1317 93 19 12 0.01
Mon 07/06 11Z 0.36 1319 78 12 12 0.01
Mon 07/06 12Z 0.39 1220 72 8 12 0.00
Mon 07/06 13Z 0.36 1220 64 15 12 0.00
Mon 07/06 14Z 0.33 1320 64 17 12 0.00
Mon 07/06 15Z 0.32 1318 67 12 12 0.00
Mon 07/06 16Z 0.38 1217 68 7 11 0.00
Mon 07/06 17Z 0.47 1217 69 5 11 0.00
Mon 07/06 18Z 0.63 1217 71 7 11 0.00
Mon 07/06 19Z 1.26 1217 75 11 10 0.00
Mon 07/06 20Z 1.48 1217 76 14 10 0.00
Mon 07/06 21Z 1.11 1118 73 16 11 0.00
Mon 07/06 22Z 0.74 1118 73 23 11 0.00
Mon 07/06 23Z 0.64 1119 72 26 11 0.00
Tue 07/07 00Z 0.52 1221 64 35 12 0.00
Tue 07/07 01Z 0.44 1221 63 44 12 0.00
Tue 07/07 02Z 0.38 1220 64 56 13 0.00
Tue 07/07 03Z 0.35 1220 65 59 13 0.00
Tue 07/07 04Z 0.32 1220 68 62 13 0.00
Tue 07/07 05Z 0.29 1219 73 57 13 0.00
Tue 07/07 06Z 0.28 1217 76 50 13 0.00
Tue 07/07 07Z 0.28 1217 78 45 13 0.00
Tue 07/07 08Z 0.28 1217 80 41 13 0.00
Tue 07/07 09Z 0.28 1217 78 38 13 0.00
Tue 07/07 10Z 0.30 1117 73 40 13 0.00
Tue 07/07 11Z 0.34 1117 72 43 13 0.00
Tue 07/07 12Z 0.37 1019 72 41 13 0.00
Tue 07/07 13Z 0.38 1019 72 38 13 0.00
Tue 07/07 14Z 0.40 1019 75 38 13 0.00
Tue 07/07 15Z 0.40 1017 78 39 13 0.00
Tue 07/07 16Z 0.44 1015 81 40 12 0.00
Tue 07/07 17Z 0.49 1014 81 36 12 0.00
Tue 07/07 18Z 0.64 1013 81 36 11 0.00
Tue 07/07 19Z 1.01 0912 82 32 11 0.00
Tue 07/07 20Z 0.97 1012 83 28 11 0.00
Tue 07/07 21Z 0.59 1013 82 21 12 0.00
Tue 07/07 22Z 0.38 1012 83 16 12 0.00
Tue 07/07 23Z 0.33 0911 82 16 12 0.00
Wed 07/08 00Z 0.29 0911 79 17 13 0.00
Wed 07/08 01Z 0.29 0811 77 18 13 0.00
Wed 07/08 02Z 0.25 0810 75 20 13 0.00
Wed 07/08 03Z 0.20 0908 75 22 13 0.00
Wed 07/08 04Z 0.17 0806 75 21 13 0.00
Wed 07/08 05Z 0.13 0705 74 19 13 0.00
Run total areal avg QPF for the Central_Greens is: 0.02 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