NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260807_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 08/07 00Z 0.24 2206  87  86  17 0.00
Fri 08/07 01Z 0.35 2508  92  85  17 0.03
Fri 08/07 02Z 0.36 2510  92  83  17 0.25
Fri 08/07 03Z 0.32 2609  90  88  17 0.08
Fri 08/07 04Z 0.34 2611  88  85  17 0.01
Fri 08/07 05Z 0.34 2812  88  88  17 0.01
Fri 08/07 06Z 0.28 2911  86  89  17 0.00
Fri 08/07 07Z 0.24 3012  86  87  17 0.00
Fri 08/07 08Z 0.21 3111  85  83  16 0.00
Fri 08/07 09Z 0.17 3109  81  72  16 0.00
Fri 08/07 10Z 0.19 3009  78  64  16 0.00
Fri 08/07 11Z 0.17 3108  74  59  16 0.00
Fri 08/07 12Z 0.16 3108  73  61  16 0.00
Fri 08/07 13Z 0.14 3107  76  66  16 0.00
Fri 08/07 14Z 0.10 3206  79  77  15 0.00
Fri 08/07 15Z 0.11 3205  81  72  15 0.00
Fri 08/07 16Z 0.07 3304  82  63  15 0.00
Fri 08/07 17Z 0.08 3203  82  58  16 0.00
Fri 08/07 18Z 0.14 2903  82  51  16 0.00
Fri 08/07 19Z 0.17 2803  80  48  16 0.01
Fri 08/07 20Z 0.34 2804  79  46  16 0.00
Fri 08/07 21Z 0.32 2703  79  49  17 0.00
Fri 08/07 22Z 0.20 2603  78  47  17 0.00
Fri 08/07 23Z 0.16 2703  77  34  17 0.00
Sat 08/08 00Z 0.17 2504  75  39  17 0.00
Sat 08/08 01Z 0.20 2404  75  41  17 0.00
Sat 08/08 02Z 0.21 2405  76  40  17 0.00
Sat 08/08 03Z 0.24 2306  79  39  17 0.00
Sat 08/08 04Z 0.21 2206  81  38  16 0.00
Sat 08/08 05Z 0.16 2304  82  37  17 0.00
Sat 08/08 06Z 0.14 2503  82  44  16 0.00
Sat 08/08 07Z 0.14 2303  84  56  16 0.00
Sat 08/08 08Z 0.12 2103  85  65  16 0.00
Sat 08/08 09Z 0.02 1703  82  82  16 0.00
Sat 08/08 10Z 0.05 1902  83  89  16 0.00
Sat 08/08 11Z 0.02 1602  81  86  16 0.00
Sat 08/08 12Z 0.02 1704  82  84  16 0.00
Sat 08/08 13Z 0.03 1705  84  87  16 0.00
Sat 08/08 14Z 0.04 1706  86  84  16 0.00
Sat 08/08 15Z 0.19 1807  89  88  16 0.00
Sat 08/08 16Z 0.34 1908  89  83  16 0.02
Sat 08/08 17Z 0.44 2110  89  71  16 0.03
Sat 08/08 18Z 0.81 2110  89  66  16 0.00
Sat 08/08 19Z 1.02 2111  89  63  17 0.00
Sat 08/08 20Z 1.00 2214  88  73  17 0.00
Sat 08/08 21Z 0.68 2314  88  64  17 0.00
Sat 08/08 22Z 0.61 2314  89  77  17 0.05
Sat 08/08 23Z 0.61 2416  92  77  16 0.05
Sun 08/09 00Z 0.53 2515  91  74  17 0.03
Sun 08/09 01Z 0.50 2614  90  67  17 0.13
Sun 08/09 02Z 0.51 2715  87  67  17 0.01
Sun 08/09 03Z 0.45 2713  91  70  16 0.00
Sun 08/09 04Z 0.37 2811  91  71  16 0.00
Sun 08/09 05Z 0.41 2612  91  69  16 0.00
Sun 08/09 06Z 0.45 2614  92  53  16 0.00
Sun 08/09 07Z 0.49 2515  91  34  16 0.00
Sun 08/09 08Z 0.59 2618  94  41  16 0.01
Sun 08/09 09Z 0.62 2620  94  34  16 0.01
Sun 08/09 10Z 0.58 2620  90  45  16 0.01
Sun 08/09 11Z 0.53 2619  90  60  16 0.00

Run total areal avg QPF for the Central_Greens is: 0.74 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