NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260726_0000
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 07/26 00Z 0.07 1707  71  42  14 0.00
Sun 07/26 01Z 0.06 1608  73  32  13 0.00
Sun 07/26 02Z 0.06 1611  76  23  13 0.00
Sun 07/26 03Z 0.09 1712  77  20  13 0.00
Sun 07/26 04Z 0.19 1911  77  19  13 0.00
Sun 07/26 05Z 0.22 2008  80  18  13 0.00
Sun 07/26 06Z 0.21 2106  81  16  12 0.00
Sun 07/26 07Z 0.19 2105  82  15  12 0.00
Sun 07/26 08Z 0.17 2105  84  18  12 0.00
Sun 07/26 09Z 0.16 2205  85  22  12 0.00
Sun 07/26 10Z 0.15 2304  84  24  12 0.00
Sun 07/26 11Z 0.11 2202  82  24  12 0.00
Sun 07/26 12Z 0.08 2301  80  22  12 0.00
Sun 07/26 13Z 0.04 1501  79  17  12 0.00
Sun 07/26 14Z 0.04 1601  82  17  12 0.00
Sun 07/26 15Z 0.19 1402  85  18  12 0.00
Sun 07/26 16Z 0.49 1303  86  26  12 0.02
Sun 07/26 17Z 0.79 1304  84  40  12 0.03
Sun 07/26 18Z 0.93 1405  79  44  13 0.02
Sun 07/26 19Z 0.68 1505  77  45  13 0.00
Sun 07/26 20Z 0.52 1505  78  45  13 0.00
Sun 07/26 21Z 0.25 1605  78  45  13 0.00
Sun 07/26 22Z 0.08 1606  78  39  13 0.00
Sun 07/26 23Z 0.08 1707  77  30  13 0.00
Mon 07/27 00Z 0.11 1808  78  26  13 0.00
Mon 07/27 01Z 0.16 1808  79  25  13 0.00
Mon 07/27 02Z 0.27 2008  80  25  12 0.00
Mon 07/27 03Z 0.30 2108  82  26  12 0.00
Mon 07/27 04Z 0.26 2107  81  25  12 0.00
Mon 07/27 05Z 0.27 2207  80  27  12 0.00
Mon 07/27 06Z 0.25 2406  81  29  12 0.00
Mon 07/27 07Z 0.17 2404  82  31  13 0.00
Mon 07/27 08Z 0.17 2404  84  32  12 0.00
Mon 07/27 09Z 0.16 2304  85  33  12 0.00
Mon 07/27 10Z 0.13 2303  86  34  12 0.00
Mon 07/27 11Z 0.15 2303  87  35  12 0.00
Mon 07/27 12Z 0.14 2303  88  35  12 0.00
Mon 07/27 13Z 0.13 2302  88  35  12 0.00
Mon 07/27 14Z 0.11 2002  87  39  12 0.00
Mon 07/27 15Z 0.11 1602  87  44  12 0.00
Mon 07/27 16Z 0.19 1603  88  50  13 0.00
Mon 07/27 17Z 0.27 1804  87  59  13 0.02
Mon 07/27 18Z 0.63 1904  84  64  13 0.01
Mon 07/27 19Z 0.52 1905  83  62  13 0.00
Mon 07/27 20Z 0.54 1906  82  57  14 0.00
Mon 07/27 21Z 0.43 1906  81  53  14 0.00
Mon 07/27 22Z 0.29 1906  82  50  14 0.00
Mon 07/27 23Z 0.17 1807  83  54  14 0.00
Tue 07/28 00Z 0.15 1808  85  56  14 0.00
Tue 07/28 01Z 0.16 1809  87  59  14 0.00
Tue 07/28 02Z 0.22 1911  89  64  13 0.00
Tue 07/28 03Z 0.22 1912  91  63  13 0.00
Tue 07/28 04Z 0.25 1913  93  63  13 0.00
Tue 07/28 05Z 0.26 1913  94  64  13 0.00
Tue 07/28 06Z 0.27 2014  95  66  13 0.00
Tue 07/28 07Z 0.24 2014  95  67  13 0.00
Tue 07/28 08Z 0.19 1913  94  61  14 0.00
Tue 07/28 09Z 0.17 1912  94  63  14 0.00
Tue 07/28 10Z 0.15 1912  95  70  13 0.00
Tue 07/28 11Z 0.07 1812  96  66  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.10 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