NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260706_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)
=== ===== === ==== ==== === === === ====
Mon 07/06 06Z 0.30 1007  74  11  13 0.00
Mon 07/06 07Z 0.26 1208  79  13  13 0.00
Mon 07/06 08Z 0.18 1409  84  14  13 0.00
Mon 07/06 09Z 0.21 1310  84  17  13 0.00
Mon 07/06 10Z 0.22 1310  81  23  13 0.00
Mon 07/06 11Z 0.23 1311  79  28  13 0.00
Mon 07/06 12Z 0.23 1313  76  30  13 0.00
Mon 07/06 13Z 0.24 1314  72  27  13 0.00
Mon 07/06 14Z 0.29 1315  70  23  13 0.00
Mon 07/06 15Z 0.36 1216  73  19  12 0.00
Mon 07/06 16Z 0.46 1216  77  15  12 0.00
Mon 07/06 17Z 0.62 1318  81  16  11 0.00
Mon 07/06 18Z 1.04 1318  81  30  11 0.00
Mon 07/06 19Z 0.93 1317  81  45  11 0.00
Mon 07/06 20Z 0.57 1217  84  58  12 0.00
Mon 07/06 21Z 0.52 1217  80  58  12 0.00
Mon 07/06 22Z 0.59 1219  75  61  12 0.00
Mon 07/06 23Z 0.54 1220  74  64  12 0.00
Tue 07/07 00Z 0.47 1222  70  65  12 0.00
Tue 07/07 01Z 0.41 1222  72  65  13 0.00
Tue 07/07 02Z 0.38 1222  71  66  13 0.00
Tue 07/07 03Z 0.35 1221  74  69  14 0.00
Tue 07/07 04Z 0.35 1222  76  70  13 0.00
Tue 07/07 05Z 0.41 1224  79  64  13 0.01
Tue 07/07 06Z 0.41 1124  79  60  13 0.01
Tue 07/07 07Z 0.41 1225  81  61  13 0.03
Tue 07/07 08Z 0.43 1225  81  68  13 0.03
Tue 07/07 09Z 0.48 1125  83  70  12 0.04
Tue 07/07 10Z 0.47 1125  83  73  13 0.02
Tue 07/07 11Z 0.52 1127  85  78  13 0.02
Tue 07/07 12Z 0.52 1027  83  86  13 0.01
Tue 07/07 13Z 0.54 1027  88  85  12 0.01
Tue 07/07 14Z 0.56 1028  92  89  12 0.01
Tue 07/07 15Z 0.58 0927  93  87  12 0.01
Tue 07/07 16Z 0.59 0825  93  91  11 0.02
Tue 07/07 17Z 0.61 0825  91  91  11 0.02
Tue 07/07 18Z 0.61 0724  92  94  11 0.02
Tue 07/07 19Z 0.60 0724  92  95  11 0.04
Tue 07/07 20Z 0.62 0724  93  96  11 0.05
Tue 07/07 21Z 0.59 0723  91  95  11 0.06
Tue 07/07 22Z 0.56 0722  90  93  12 0.03
Tue 07/07 23Z 0.52 0621  87  95  12 0.03
Wed 07/08 00Z 0.50 0620  86  94  12 0.03
Wed 07/08 01Z 0.46 0619  85  89  12 0.04
Wed 07/08 02Z 0.43 0618  83  85  12 0.02
Wed 07/08 03Z 0.37 0516  80  91  12 0.01
Wed 07/08 04Z 0.33 0415  79  93  12 0.00
Wed 07/08 05Z 0.34 0317  75  94  12 0.00
Wed 07/08 06Z 0.30 0217  70  91  13 0.00
Wed 07/08 07Z 0.29 0217  65  87  13 0.00
Wed 07/08 08Z 0.17 0115  64  84  12 0.00
Wed 07/08 09Z 0.09 3515  63  74  12 0.00
Wed 07/08 10Z 0.05 3517  68  61  12 0.00
Wed 07/08 11Z 0.11 0017  73  34  12 0.00
Wed 07/08 12Z 0.10 0015  72  20  12 0.00
Wed 07/08 13Z 0.04 3513  72  12  12 0.00
Wed 07/08 14Z 0.03 3410  73   6  13 0.00
Wed 07/08 15Z 0.16 3312  78   4  12 0.00
Wed 07/08 16Z 0.26 3211  79   3  12 0.00
Wed 07/08 17Z 0.55 3211  79   3  13 0.00

Run total areal avg QPF for the Central_Greens is: 0.57 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