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_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 07/26 06Z 0.15 2005  75  14  13 0.00
Sun 07/26 07Z 0.19 2105  76  13  13 0.00
Sun 07/26 08Z 0.21 2205  77  13  13 0.00
Sun 07/26 09Z 0.19 2304  78  12  12 0.00
Sun 07/26 10Z 0.14 2402  78  13  12 0.00
Sun 07/26 11Z 0.07 2500  78  12  12 0.00
Sun 07/26 12Z 0.07 1201  77  12  12 0.00
Sun 07/26 13Z 0.08 1101  77  11  12 0.00
Sun 07/26 14Z 0.24 1202  78  10  12 0.00
Sun 07/26 15Z 0.92 1104  80   8  13 0.00
Sun 07/26 16Z 1.33 1204  79   8  13 0.00
Sun 07/26 17Z 1.46 1305  79  13  13 0.00
Sun 07/26 18Z 1.78 1306  76  22  13 0.02
Sun 07/26 19Z 1.51 1407  75  26  13 0.01
Sun 07/26 20Z 1.06 1508  75  28  13 0.00
Sun 07/26 21Z 0.51 1607  75  30  13 0.00
Sun 07/26 22Z 0.18 1607  75  29  13 0.00
Sun 07/26 23Z 0.10 1607  74  25  13 0.00
Mon 07/27 00Z 0.08 1707  72  22  13 0.00
Mon 07/27 01Z 0.12 1807  72  20  13 0.00
Mon 07/27 02Z 0.16 1808  71  18  13 0.00
Mon 07/27 03Z 0.14 1808  71  17  13 0.00
Mon 07/27 04Z 0.12 1907  72  16  13 0.00
Mon 07/27 05Z 0.10 1906  74  14  13 0.00
Mon 07/27 06Z 0.27 2206  78  17  13 0.00
Mon 07/27 07Z 0.38 2307  80  30  12 0.00
Mon 07/27 08Z 0.40 2309  84  50  12 0.01
Mon 07/27 09Z 0.31 2307  84  62  12 0.01
Mon 07/27 10Z 0.18 2106  82  65  12 0.00
Mon 07/27 11Z 0.16 2006  82  69  12 0.00
Mon 07/27 12Z 0.16 2007  83  69  12 0.00
Mon 07/27 13Z 0.16 2006  88  74  12 0.00
Mon 07/27 14Z 0.14 2006  90  72  12 0.00
Mon 07/27 15Z 0.17 1906  90  69  12 0.00
Mon 07/27 16Z 0.22 2005  90  66  13 0.00
Mon 07/27 17Z 0.40 2005  90  66  13 0.00
Mon 07/27 18Z 0.47 2005  89  66  13 0.00
Mon 07/27 19Z 0.49 2005  88  63  13 0.00
Mon 07/27 20Z 0.29 1804  88  65  14 0.00
Mon 07/27 21Z 0.26 1806  88  64  14 0.01
Mon 07/27 22Z 0.13 1706  89  64  14 0.01
Mon 07/27 23Z 0.08 1708  90  65  14 0.02
Tue 07/28 00Z 0.12 1809  89  61  14 0.02
Tue 07/28 01Z 0.11 1812  89  58  14 0.01
Tue 07/28 02Z 0.13 1812  90  63  14 0.01
Tue 07/28 03Z 0.10 1811  90  65  13 0.02
Tue 07/28 04Z 0.13 1910  92  72  13 0.02
Tue 07/28 05Z 0.18 2010  95  77  13 0.01
Tue 07/28 06Z 0.25 2111  96  76  13 0.03
Tue 07/28 07Z 0.24 2111  96  73  13 0.04
Tue 07/28 08Z 0.19 2010  95  72  13 0.02
Tue 07/28 09Z 0.17 2009  93  76  14 0.01
Tue 07/28 10Z 0.10 1909  92  81  14 0.00
Tue 07/28 11Z 0.07 1809  92  81  14 0.00
Tue 07/28 12Z 0.04 1709  94  79  13 0.00
Tue 07/28 13Z 0.02 1708  96  77  13 0.00
Tue 07/28 14Z 0.03 1610  97  76  13 0.01
Tue 07/28 16Z 0.05 1710  98  77  13 0.01
Tue 07/28 17Z 0.05 1610  98  75  13 0.01

Run total areal avg QPF for the Central_Greens is: 0.31 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