Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260705_0600
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 06Z 0.05 0004 59 0 13 0.00
Sun 07/05 07Z 0.05 3503 59 0 13 0.00
Sun 07/05 08Z 0.06 3504 60 1 13 0.00
Sun 07/05 09Z 0.08 0103 61 1 13 0.00
Sun 07/05 10Z 0.11 0103 62 1 12 0.00
Sun 07/05 11Z 0.16 0303 63 2 12 0.00
Sun 07/05 12Z 0.10 0501 64 5 12 0.00
Sun 07/05 13Z 0.10 1700 64 8 12 0.00
Sun 07/05 14Z 0.28 2101 67 9 12 0.00
Sun 07/05 15Z 0.46 2002 68 11 12 0.00
Sun 07/05 16Z 0.56 2002 68 14 13 0.00
Sun 07/05 17Z 0.77 2202 68 18 13 0.00
Sun 07/05 18Z 0.65 2402 67 23 13 0.00
Sun 07/05 19Z 0.47 2602 67 27 13 0.00
Sun 07/05 20Z 0.23 2901 67 31 13 0.00
Sun 07/05 21Z 0.11 3301 67 31 14 0.00
Sun 07/05 22Z 0.13 3502 69 24 14 0.00
Sun 07/05 23Z 0.16 0103 71 18 13 0.00
Mon 07/06 00Z 0.24 0205 73 15 13 0.01
Mon 07/06 01Z 0.38 0406 75 11 13 0.00
Mon 07/06 02Z 0.46 0608 80 10 12 0.00
Mon 07/06 03Z 0.44 0809 85 8 12 0.00
Mon 07/06 04Z 0.34 1008 86 11 12 0.00
Mon 07/06 05Z 0.30 1107 83 7 12 0.00
Mon 07/06 06Z 0.29 1107 81 6 12 0.00
Mon 07/06 07Z 0.30 1108 80 8 12 0.00
Mon 07/06 08Z 0.27 1310 79 10 12 0.00
Mon 07/06 09Z 0.25 1412 77 11 12 0.00
Mon 07/06 10Z 0.24 1414 75 10 11 0.00
Mon 07/06 11Z 0.28 1316 69 9 11 0.00
Mon 07/06 12Z 0.26 1315 68 10 12 0.00
Mon 07/06 13Z 0.28 1215 67 12 12 0.00
Mon 07/06 14Z 0.31 1315 72 11 11 0.00
Mon 07/06 15Z 0.35 1313 80 9 11 0.00
Mon 07/06 16Z 0.46 1313 86 9 10 0.00
Mon 07/06 17Z 0.42 1313 86 14 10 0.00
Mon 07/06 18Z 0.51 1314 85 15 10 0.00
Mon 07/06 19Z 0.67 1315 83 16 10 0.00
Mon 07/06 20Z 1.04 1215 85 19 10 0.00
Mon 07/06 21Z 1.03 1217 83 23 10 0.00
Mon 07/06 22Z 0.81 1217 82 27 11 0.00
Mon 07/06 23Z 0.65 1219 84 32 10 0.00
Tue 07/07 00Z 0.60 1222 80 38 10 0.00
Tue 07/07 01Z 0.48 1222 72 41 11 0.00
Tue 07/07 02Z 0.41 1223 65 40 12 0.00
Tue 07/07 03Z 0.40 1223 63 47 12 0.00
Tue 07/07 04Z 0.39 1224 63 54 12 0.00
Tue 07/07 05Z 0.38 1223 64 60 12 0.00
Tue 07/07 06Z 0.38 1222 63 56 12 0.00
Tue 07/07 07Z 0.36 1222 62 54 13 0.00
Tue 07/07 08Z 0.37 1222 61 52 13 0.00
Tue 07/07 09Z 0.38 1222 62 52 13 0.00
Tue 07/07 10Z 0.39 1122 63 47 13 0.00
Tue 07/07 11Z 0.39 1122 67 51 12 0.00
Tue 07/07 12Z 0.38 1121 69 56 12 0.00
Tue 07/07 13Z 0.41 1122 73 57 12 0.00
Tue 07/07 14Z 0.43 1120 77 64 11 0.00
Tue 07/07 15Z 0.46 1118 78 67 11 0.00
Tue 07/07 16Z 0.48 1015 79 66 11 0.00
Tue 07/07 17Z 0.54 1012 80 68 11 0.00
Run total areal avg QPF for the Central_Greens is: 0.01 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