NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260711_1800
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)
=== ===== === ==== ==== === === === ====
Sat 07/11 18Z 1.05 3409  69  22  11 0.00
Sat 07/11 19Z 0.52 3410  67  17  11 0.00
Sat 07/11 20Z 0.52 3510  67  12  11 0.00
Sat 07/11 21Z 0.61 3510  68  12  11 0.00
Sat 07/11 22Z 0.75 0010  69  10  11 0.00
Sat 07/11 23Z 0.74 0111  71   9  11 0.00
Sun 07/12 00Z 0.75 0212  72   9  11 0.00
Sun 07/12 01Z 0.88 0312  73   9  10 0.00
Sun 07/12 02Z 0.91 0413  73   9  10 0.00
Sun 07/12 03Z 0.91 0412  73   9  10 0.00
Sun 07/12 04Z 0.86 0512  72  11  10 0.00
Sun 07/12 05Z 0.69 0412  70  11  10 0.00
Sun 07/12 06Z 0.60 0411  69  13  10 0.00
Sun 07/12 07Z 0.55 0410  68  15  10 0.00
Sun 07/12 08Z 0.54 0410  68  16   9 0.00
Sun 07/12 09Z 0.49 0310  69  17   9 0.00
Sun 07/12 10Z 0.46 0310  69  17   9 0.00
Sun 07/12 11Z 0.47 0310  69  16   9 0.00
Sun 07/12 12Z 0.44 0309  67  13   9 0.00
Sun 07/12 13Z 0.49 0307  68  11   9 0.00
Sun 07/12 14Z 1.14 0206  71   9   9 0.00
Sun 07/12 15Z 1.43 0204  71   6  10 0.00
Sun 07/12 16Z 0.59 0004  71   5  10 0.00
Sun 07/12 17Z 0.24 3302  73   5  11 0.00
Sun 07/12 18Z 0.24 3302  75   8  11 0.00
Sun 07/12 19Z 0.14 3401  76   8  11 0.00
Sun 07/12 20Z 0.43 3002  77  10  11 0.00
Sun 07/12 21Z 0.42 3003  77  13  11 0.00
Sun 07/12 22Z 0.21 3103  73   7  12 0.00
Sun 07/12 23Z 0.16 3003  69   7  12 0.00
Mon 07/13 00Z 0.11 2601  65   7  12 0.00
Mon 07/13 01Z 0.19 2203  66   8  12 0.00
Mon 07/13 02Z 0.35 2205  68   6  12 0.00
Mon 07/13 03Z 0.56 2306  71   5  11 0.00
Mon 07/13 04Z 0.56 2307  72   6  11 0.00
Mon 07/13 05Z 0.61 2309  72   6  11 0.00
Mon 07/13 06Z 0.77 2411  73   7  11 0.00
Mon 07/13 07Z 0.91 2413  76   9  11 0.00
Mon 07/13 08Z 0.92 2514  73  10  11 0.00
Mon 07/13 09Z 0.95 2516  74  12  11 0.00
Mon 07/13 10Z 0.84 2516  72  16  11 0.00
Mon 07/13 11Z 0.76 2515  69  26  11 0.00
Mon 07/13 12Z 0.66 2515  66  41  11 0.00
Mon 07/13 13Z 0.61 2515  64  51  12 0.00
Mon 07/13 14Z 0.63 2514  62  55  12 0.00
Mon 07/13 15Z 0.57 2513  57  47  13 0.00
Mon 07/13 16Z 0.52 2513  52  51  14 0.00
Mon 07/13 17Z 0.53 2512  54  57  14 0.00
Mon 07/13 18Z 0.71 2512  66  65  14 0.00
Mon 07/13 19Z 0.78 2513  79  64  14 0.00
Mon 07/13 20Z 0.63 2515  82  55  14 0.00
Mon 07/13 21Z 0.68 2616  79  48  15 0.00
Mon 07/13 22Z 0.76 2618  79  50  15 0.00
Mon 07/13 23Z 0.81 2720  78  56  15 0.00
Tue 07/14 00Z 0.78 2721  72  55  16 0.00
Tue 07/14 01Z 0.78 2723  69  52  16 0.00
Tue 07/14 02Z 0.74 2724  65  54  17 0.00
Tue 07/14 03Z 0.70 2825  61  50  17 0.00
Tue 07/14 04Z 0.65 2825  55  48  17 0.00
Tue 07/14 05Z 0.53 2821  58  45  18 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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