NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260704_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)
=== ===== === ==== ==== === === === ====
Sat 07/04 18Z 1.93 3012  92  70  15 0.00
Sat 07/04 19Z 1.09 3115  89  65  15 0.12
Sat 07/04 20Z 0.68 3112  84  62  15 0.03
Sat 07/04 21Z 0.35 3212  85  71  15 0.01
Sat 07/04 22Z 0.25 3314  83  66  14 0.01
Sat 07/04 23Z 0.17 3314  79  59  14 0.00
Sun 07/05 00Z 0.10 3413  77  50  14 0.00
Sun 07/05 01Z 0.06 3514  71  42  14 0.00
Sun 07/05 02Z 0.06 3513  67  31  13 0.00
Sun 07/05 03Z 0.12 0013  63  27  13 0.00
Sun 07/05 04Z 0.16 0112  60  22  13 0.00
Sun 07/05 05Z 0.19 0111  59  23  13 0.00
Sun 07/05 06Z 0.21 0109  58  23  13 0.00
Sun 07/05 07Z 0.28 0309  56  17  13 0.00
Sun 07/05 08Z 0.31 0309  56  13  12 0.00
Sun 07/05 09Z 0.35 0408  58   6  12 0.00
Sun 07/05 10Z 0.31 0408  59   3  12 0.00
Sun 07/05 11Z 0.29 0407  62   2  12 0.00
Sun 07/05 12Z 0.30 0407  64   2  11 0.00
Sun 07/05 13Z 0.41 0405  68   2  11 0.00
Sun 07/05 14Z 1.05 0503  72   3  11 0.00
Sun 07/05 15Z 0.65 0201  73   3  11 0.00
Sun 07/05 16Z 0.43 0002  75   3  11 0.00
Sun 07/05 17Z 0.38 0003  76   4  12 0.00
Sun 07/05 18Z 0.25 3503  76   6  12 0.00
Sun 07/05 19Z 0.21 3503  76   6  12 0.00
Sun 07/05 20Z 0.26 3504  77   4  12 0.00
Sun 07/05 21Z 0.38 0004  78   3  12 0.00
Sun 07/05 22Z 0.44 0204  77   3  12 0.00
Sun 07/05 23Z 0.51 0305  75   2  12 0.00
Mon 07/06 00Z 0.47 0406  73   3  12 0.00
Mon 07/06 01Z 0.60 0508  72   3  12 0.00
Mon 07/06 02Z 0.70 0609  73   3  12 0.00
Mon 07/06 03Z 0.69 0710  70   3  12 0.00
Mon 07/06 04Z 0.68 0812  68   3  12 0.00
Mon 07/06 05Z 0.61 1012  69   4  12 0.00
Mon 07/06 06Z 0.49 1214  77   4  12 0.00
Mon 07/06 07Z 0.31 1315  80   4  11 0.00
Mon 07/06 08Z 0.28 1415  78   3  11 0.00
Mon 07/06 09Z 0.28 1416  79   3  11 0.00
Mon 07/06 10Z 0.31 1417  80   3  11 0.00
Mon 07/06 11Z 0.29 1417  80   3  11 0.00
Mon 07/06 12Z 0.28 1418  79   3  10 0.00
Mon 07/06 13Z 0.30 1419  79   3  10 0.00
Mon 07/06 14Z 0.35 1318  79   3  10 0.00
Mon 07/06 15Z 0.36 1317  80   4  10 0.00
Mon 07/06 16Z 0.39 1217  80   7  10 0.00
Mon 07/06 17Z 0.44 1216  81  13  10 0.00
Mon 07/06 18Z 0.51 1214  83  17  10 0.00
Mon 07/06 19Z 0.56 1213  86  23  10 0.00
Mon 07/06 20Z 0.62 1214  90  23  10 0.00
Mon 07/06 21Z 0.51 1214  92  29  10 0.00
Mon 07/06 22Z 0.41 1214  92  32  10 0.00
Mon 07/06 23Z 0.35 1214  91  33  10 0.00
Tue 07/07 00Z 0.34 1215  88  30  10 0.00
Tue 07/07 01Z 0.34 1115  86  31  11 0.00
Tue 07/07 02Z 0.36 1116  85  38  11 0.00
Tue 07/07 03Z 0.40 1117  79  47  11 0.00
Tue 07/07 04Z 0.38 1118  67  52  11 0.00
Tue 07/07 05Z 0.37 1118  58  55  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.17 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