NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260724_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)
=== ===== === ==== ==== === === === ====
Fri 07/24 12Z 0.28 2205  67  19   9 0.00
Fri 07/24 13Z 0.40 2306  67  19   9 0.00
Fri 07/24 14Z 0.93 2306  65  19   9 0.00
Fri 07/24 15Z 1.66 2406  62  20   9 0.00
Fri 07/24 16Z 2.29 2406  60  22  10 0.00
Fri 07/24 17Z 2.77 2505  59  24  10 0.00
Fri 07/24 18Z 2.04 2404  56  28  11 0.00
Fri 07/24 19Z 1.14 2402  55  33  11 0.00
Fri 07/24 20Z 0.70 2402  54  38  12 0.00
Fri 07/24 21Z 0.49 2202  54  42  12 0.00
Fri 07/24 22Z 0.22 2202  56  45  12 0.00
Fri 07/24 23Z 0.16 2202  57  47  12 0.00
Sat 07/25 00Z 0.18 2203  57  47  12 0.00
Sat 07/25 01Z 0.21 2303  57  43  12 0.00
Sat 07/25 02Z 0.20 2403  57  41  12 0.00
Sat 07/25 03Z 0.22 2403  59  42  12 0.00
Sat 07/25 04Z 0.19 2303  60  43  12 0.00
Sat 07/25 05Z 0.17 2402  60  45  12 0.00
Sat 07/25 06Z 0.12 2602  59  45  12 0.00
Sat 07/25 07Z 0.06 2200  59  43  12 0.00
Sat 07/25 08Z 0.04 1702  60  44  11 0.00
Sat 07/25 09Z 0.04 1703  59  42  11 0.00
Sat 07/25 10Z 0.10 1904  59  40  11 0.00
Sat 07/25 11Z 0.13 2004  60  38  11 0.00
Sat 07/25 12Z 0.19 2205  61  39  11 0.00
Sat 07/25 13Z 0.16 2204  64  38  11 0.00
Sat 07/25 14Z 0.14 2203  68  38  11 0.00
Sat 07/25 15Z 0.16 1902  71  37  11 0.00
Sat 07/25 16Z 0.25 1603  72  36  12 0.00
Sat 07/25 17Z 0.46 1503  72  33  12 0.00
Sat 07/25 18Z 0.61 1504  72  32  12 0.00
Sat 07/25 19Z 0.52 1604  72  30  13 0.00
Sat 07/25 20Z 0.87 1505  72  25  13 0.00
Sat 07/25 21Z 0.61 1506  72  23  13 0.00
Sat 07/25 22Z 0.13 1706  73  21  13 0.00
Sat 07/25 23Z 0.09 1708  75  18  13 0.00
Sun 07/26 00Z 0.09 1709  76  15  13 0.00
Sun 07/26 01Z 0.18 1810  77  12  12 0.00
Sun 07/26 02Z 0.26 1811  80   8  12 0.00
Sun 07/26 03Z 0.37 1910  83   8  12 0.00
Sun 07/26 04Z 0.39 2009  85   8  12 0.00
Sun 07/26 05Z 0.38 2108  85  10  11 0.00
Sun 07/26 06Z 0.43 2308  86  11  11 0.00
Sun 07/26 07Z 0.46 2308  85  12  11 0.00
Sun 07/26 08Z 0.43 2308  80  12  11 0.00
Sun 07/26 09Z 0.30 2306  76  13  11 0.00
Sun 07/26 10Z 0.30 2305  75  13  11 0.00
Sun 07/26 11Z 0.22 2204  76  14  11 0.00
Sun 07/26 12Z 0.14 2003  77  13  11 0.00
Sun 07/26 13Z 0.09 1804  78  12  11 0.00
Sun 07/26 14Z 0.13 1604  79  12  11 0.00
Sun 07/26 15Z 0.19 1704  81  12  11 0.00
Sun 07/26 16Z 0.25 1604  83  13  12 0.00
Sun 07/26 17Z 0.26 1803  84  15  12 0.00
Sun 07/26 18Z 0.53 1904  84  18  12 0.00
Sun 07/26 19Z 0.48 1804  83  23  12 0.00
Sun 07/26 20Z 0.26 1804  82  32  13 0.00
Sun 07/26 21Z 0.27 1804  81  41  13 0.00
Sun 07/26 22Z 0.08 1704  81  50  13 0.00
Sun 07/26 23Z 0.06 1704  83  55  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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