NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260605_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)
=== ===== === ==== ==== === === === ====
Fri 06/05 00Z 0.83 2813  46  19  14 0.00
Fri 06/05 01Z 0.81 2916  46  18  14 0.00
Fri 06/05 02Z 0.75 2918  45  19  14 0.00
Fri 06/05 03Z 0.68 3019  41  18  13 0.00
Fri 06/05 04Z 0.56 3018  41  16  13 0.00
Fri 06/05 05Z 0.47 3018  47  16  13 0.00
Fri 06/05 06Z 0.44 3118  57  16  13 0.00
Fri 06/05 07Z 0.46 3118  60  13  13 0.00
Fri 06/05 08Z 0.40 3118  56   8  13 0.00
Fri 06/05 09Z 0.37 3116  51   5  13 0.00
Fri 06/05 10Z 0.34 3114  49   5  13 0.00
Fri 06/05 11Z 0.33 3113  48   5  13 0.00
Fri 06/05 12Z 0.31 3112  47   7  13 0.00
Fri 06/05 13Z 0.29 3010  46  11  13 0.00
Fri 06/05 14Z 0.30 3008  46  15  13 0.00
Fri 06/05 15Z 0.56 2907  48  19  13 0.00
Fri 06/05 16Z 2.03 2807  49  20  13 0.00
Fri 06/05 17Z 3.32 2807  49  21  13 0.00
Fri 06/05 18Z 4.26 2707  49  25  13 0.00
Fri 06/05 19Z 4.24 2707  53  31  14 0.00
Fri 06/05 20Z 4.18 2607  59  34  14 0.00
Fri 06/05 21Z 3.41 2508  61  30  14 0.00
Fri 06/05 22Z 1.32 2509  60  25  14 0.00
Fri 06/05 23Z 0.88 2610  57  12  14 0.00
Sat 06/06 00Z 0.90 2610  56   7  14 0.00
Sat 06/06 01Z 0.84 2611  59   7  14 0.00
Sat 06/06 02Z 0.85 2512  65  15  14 0.00
Sat 06/06 03Z 0.85 2512  65  15  14 0.00
Sat 06/06 04Z 0.85 2413  63   8  14 0.00
Sat 06/06 05Z 0.93 2415  61  23  14 0.00
Sat 06/06 06Z 1.15 2317  63  32  14 0.00
Sat 06/06 07Z 1.17 2318  67  33  13 0.00
Sat 06/06 08Z 1.10 2221  69  50  13 0.00
Sat 06/06 09Z 0.98 2221  69  45  13 0.00
Sat 06/06 10Z 0.86 2220  70  46  13 0.00
Sat 06/06 11Z 0.86 2321  74  42  13 0.00
Sat 06/06 12Z 0.86 2320  77  39  13 0.00
Sat 06/06 13Z 0.95 2220  78  70  13 0.00
Sat 06/06 14Z 1.59 2221  82  86  13 0.00
Sat 06/06 15Z 1.88 2123  83  93  13 0.00
Sat 06/06 16Z 4.01 2225  84  95  13 0.01
Sat 06/06 17Z 1.06 2327  95  73  13 0.03
Sat 06/06 18Z 1.21 2326  95  73  14 0.02
Sat 06/06 19Z 1.28 2431  98  69  14 0.09
Sat 06/06 20Z 1.27 2629  96  54  14 0.03
Sat 06/06 21Z 1.18 2625  95  64  13 0.02
Sat 06/06 22Z 1.05 2723  93  69  13 0.01
Sat 06/06 23Z 0.90 2722  90  67  13 0.01
Sun 06/07 00Z 0.84 2722  89  77  14 0.00
Sun 06/07 01Z 0.84 2722  90  86  13 0.00
Sun 06/07 02Z 0.77 2720  94  84  13 0.01
Sun 06/07 03Z 0.70 2821  92  73  13 0.01
Sun 06/07 04Z 0.67 2821  92  59  13 0.00
Sun 06/07 05Z 0.62 2820  92  51  12 0.01
Sun 06/07 06Z 0.54 2919  93  37  12 0.01
Sun 06/07 07Z 0.49 2919  94  36  12 0.01
Sun 06/07 08Z 0.46 3019  95  45  12 0.01
Sun 06/07 09Z 0.50 3019  97  52  11 0.02
Sun 06/07 10Z 0.48 3019  96  56  10 0.02
Sun 06/07 11Z 0.45 3019  96  60  10 0.02

Run total areal avg QPF for the Central_Greens is: 0.34 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