NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260801_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)
=== ===== === ==== ==== === === === ====
Sat 08/01 00Z 0.16 3208  83  72  14 0.00
Sat 08/01 01Z 0.12 3208  82  67  14 0.00
Sat 08/01 02Z 0.07 3309  80  60  14 0.00
Sat 08/01 03Z 0.02 3407  80  55  14 0.00
Sat 08/01 04Z 0.02 3504  79  53  14 0.00
Sat 08/01 05Z 0.05 3202  80  55  14 0.00
Sat 08/01 06Z 0.08 3002  80  57  14 0.00
Sat 08/01 07Z 0.13 2803  80  58  14 0.00
Sat 08/01 08Z 0.16 2804  80  62  14 0.00
Sat 08/01 09Z 0.16 2804  79  64  14 0.00
Sat 08/01 10Z 0.19 2705  79  63  13 0.00
Sat 08/01 11Z 0.19 2604  78  60  13 0.00
Sat 08/01 12Z 0.16 2603  77  56  13 0.00
Sat 08/01 13Z 0.19 2504  78  53  13 0.00
Sat 08/01 14Z 0.28 2405  79  46  13 0.00
Sat 08/01 15Z 0.59 2405  80  36  13 0.00
Sat 08/01 16Z 1.31 2404  79  27  14 0.00
Sat 08/01 17Z 1.94 2305  77  17  14 0.00
Sat 08/01 18Z 1.83 2205  76  16  14 0.00
Sat 08/01 19Z 0.78 2204  75  26  14 0.00
Sat 08/01 20Z 0.55 2004  74  39  15 0.00
Sat 08/01 21Z 0.20 1904  72  38  15 0.00
Sat 08/01 22Z 0.08 1804  75  32  15 0.00
Sat 08/01 23Z 0.11 1806  78  23  15 0.00
Sun 08/02 00Z 0.16 1807  81  14  15 0.00
Sun 08/02 01Z 0.22 1908  82  19  15 0.00
Sun 08/02 02Z 0.36 2010  85  23  14 0.00
Sun 08/02 03Z 0.38 2013  88  39  14 0.01
Sun 08/02 04Z 0.42 2017  91  55  15 0.01
Sun 08/02 05Z 0.51 2120  92  77  15 0.04
Sun 08/02 06Z 0.61 2222  94  81  15 0.02
Sun 08/02 07Z 0.67 2322  92  69  15 0.01
Sun 08/02 08Z 0.68 2321  92  66  14 0.00
Sun 08/02 09Z 0.67 2419  91  62  14 0.00
Sun 08/02 10Z 0.61 2417  90  51  14 0.00
Sun 08/02 11Z 0.54 2415  90  38  14 0.00
Sun 08/02 12Z 0.50 2314  91  39  14 0.00
Sun 08/02 13Z 0.45 2214  89  43  14 0.00
Sun 08/02 14Z 0.45 2213  88  52  14 0.00
Sun 08/02 15Z 0.40 2112  86  39  14 0.00
Sun 08/02 16Z 0.41 2012  87  38  14 0.00
Sun 08/02 17Z 0.71 2012  87  35  14 0.04
Sun 08/02 18Z 0.96 1913  86  33  14 0.03
Sun 08/02 19Z 0.44 1813  88  42  15 0.00
Sun 08/02 20Z 0.46 1814  90  54  15 0.00
Sun 08/02 21Z 0.33 1815  90  63  15 0.01
Sun 08/02 22Z 0.41 2018  89  60  15 0.05
Sun 08/02 23Z 0.45 2021  85  35  16 0.01
Mon 08/03 00Z 0.42 2021  81  32  16 0.00
Mon 08/03 01Z 0.45 2022  75  23  16 0.00
Mon 08/03 02Z 0.53 2026  72  25  15 0.00
Mon 08/03 03Z 0.58 2127  78  34  15 0.00
Mon 08/03 04Z 0.56 2127  77  51  15 0.00
Mon 08/03 05Z 0.54 2126  78  32  15 0.00
Mon 08/03 06Z 0.56 2125  77  36  15 0.00
Mon 08/03 07Z 0.52 2224  71  49  15 0.00
Mon 08/03 08Z 0.52 2223  69  41  15 0.00
Mon 08/03 09Z 0.53 2223  73  43  15 0.00
Mon 08/03 10Z 0.48 2221  76  54  15 0.00
Mon 08/03 11Z 0.47 2319  81  70  15 0.00

Run total areal avg QPF for the Central_Greens is: 0.23 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