NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260806_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)
=== ===== === ==== ==== === === === ====
Thu 08/06 12Z 0.24 2707  85  54  16 0.00
Thu 08/06 13Z 0.22 2706  85  66  16 0.00
Thu 08/06 14Z 0.18 2605  85  77  16 0.00
Thu 08/06 15Z 0.15 2503  86  88  16 0.00
Thu 08/06 16Z 0.13 2402  87  89  16 0.00
Thu 08/06 17Z 0.24 2303  85  86  16 0.01
Thu 08/06 18Z 0.31 2204  83  85  17 0.01
Thu 08/06 19Z 0.26 2202  83  86  17 0.00
Thu 08/06 20Z 0.31 2503  86  87  17 0.01
Thu 08/06 21Z 0.18 2602  85  81  17 0.02
Thu 08/06 22Z 0.10 2102  84  76  17 0.00
Thu 08/06 23Z 0.11 2202  84  73  17 0.00
Fri 08/07 00Z 0.17 2204  85  72  17 0.00
Fri 08/07 01Z 0.31 2307  86  77  17 0.00
Fri 08/07 02Z 0.25 2406  85  70  17 0.00
Fri 08/07 03Z 0.23 2306  86  74  17 0.00
Fri 08/07 04Z 0.29 2408  91  73  17 0.00
Fri 08/07 05Z 0.28 2408  93  71  17 0.00
Fri 08/07 06Z 0.28 2508  92  71  17 0.02
Fri 08/07 07Z 0.24 2707  92  73  17 0.00
Fri 08/07 08Z 0.27 2808  94  77  16 0.01
Fri 08/07 09Z 0.21 2908  92  62  17 0.01
Fri 08/07 10Z 0.16 3108  89  68  16 0.00
Fri 08/07 11Z 0.14 3208  89  75  16 0.00
Fri 08/07 12Z 0.09 3207  86  60  16 0.00
Fri 08/07 13Z 0.09 3105  84  58  16 0.00
Fri 08/07 14Z 0.13 3005  80  63  16 0.00
Fri 08/07 15Z 0.15 3005  75  50  16 0.00
Fri 08/07 16Z 0.19 2905  75  48  16 0.00
Fri 08/07 17Z 0.29 2906  76  42  16 0.00
Fri 08/07 18Z 0.35 2906  77  33  16 0.00
Fri 08/07 19Z 0.37 2906  78  26  16 0.00
Fri 08/07 20Z 0.33 2907  79  20  17 0.00
Fri 08/07 21Z 0.28 2906  81  20  17 0.00
Fri 08/07 22Z 0.24 2806  81  12  17 0.00
Fri 08/07 23Z 0.22 2805  82  18  17 0.00
Sat 08/08 00Z 0.21 2806  83  27  17 0.00
Sat 08/08 01Z 0.18 2705  84  30  17 0.00
Sat 08/08 02Z 0.24 2606  85  33  17 0.00
Sat 08/08 03Z 0.22 2606  83  33  17 0.00
Sat 08/08 04Z 0.18 2505  82  37  17 0.00
Sat 08/08 05Z 0.17 2405  80  54  17 0.00
Sat 08/08 06Z 0.14 2305  80  75  17 0.00
Sat 08/08 07Z 0.18 2206  82  81  17 0.00
Sat 08/08 08Z 0.20 2207  82  76  17 0.00
Sat 08/08 09Z 0.18 2107  82  74  17 0.00
Sat 08/08 10Z 0.18 2107  82  75  16 0.00
Sat 08/08 11Z 0.16 2007  82  76  16 0.00
Sat 08/08 12Z 0.17 2008  82  73  16 0.00
Sat 08/08 13Z 0.18 2008  85  72  16 0.00
Sat 08/08 14Z 0.23 2108  92  77  16 0.00
Sat 08/08 15Z 0.26 2109  91  86  16 0.10
Sat 08/08 16Z 0.12 1908  81  84  16 0.16
Sat 08/08 17Z 0.15 1910  79  79  17 0.01
Sat 08/08 18Z 0.36 2012  83  71  16 0.00
Sat 08/08 19Z 0.74 2112  85  70  16 0.00
Sat 08/08 20Z 1.29 2013  86  75  16 0.00
Sat 08/08 21Z 1.21 2214  84  80  17 0.00
Sat 08/08 22Z 0.84 2214  88  68  17 0.05
Sat 08/08 23Z 0.70 2316  94  72  17 0.03

Run total areal avg QPF for the Central_Greens is: 0.44 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