NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260817_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)
=== ===== === ==== ==== === === === ====
Mon 08/17 00Z 0.61 2020  95  98  12 0.00
Mon 08/17 01Z 0.58 2023  97  96  12 0.01
Mon 08/17 02Z 0.54 2025  94  98  12 0.01
Mon 08/17 03Z 0.51 2027  91  96  12 0.00
Mon 08/17 04Z 0.55 2028  95  91  13 0.00
Mon 08/17 05Z 0.61 2130  97  87  13 0.01
Mon 08/17 06Z 0.60 2130  98  86  13 0.02
Mon 08/17 07Z 0.56 2127  98  91  13 0.02
Mon 08/17 08Z 0.54 2225  98  92  14 0.02
Mon 08/17 09Z 0.51 2223  98  90  14 0.02
Mon 08/17 10Z 0.50 2322  98  90  14 0.02
Mon 08/17 11Z 0.44 2319  98  89  14 0.02
Mon 08/17 12Z 0.40 2317  98  90  14 0.02
Mon 08/17 13Z 0.39 2316  98  90  14 0.02
Mon 08/17 14Z 0.39 2415  98  89  14 0.02
Mon 08/17 15Z 0.39 2414  98  83  15 0.02
Mon 08/17 16Z 0.36 2511  98  76  15 0.01
Mon 08/17 17Z 0.32 2609  98  73  15 0.00
Mon 08/17 18Z 0.26 2706  98  72  14 0.00
Mon 08/17 19Z 0.23 2705  97  78  14 0.00
Mon 08/17 20Z 0.18 2703  97  78  14 0.01
Mon 08/17 21Z 0.18 2803  97  74  15 0.03
Mon 08/17 22Z 0.19 3006  97  54  15 0.08
Mon 08/17 23Z 0.14 3206  95  39  15 0.07
Tue 08/18 00Z 0.08 3408  92  34  15 0.02
Tue 08/18 01Z 0.04 3510  89  43  15 0.01
Tue 08/18 02Z 0.02 3511  88  56  14 0.00
Tue 08/18 03Z 0.03 3510  87  51  14 0.00
Tue 08/18 04Z 0.03 3509  85  43  14 0.00
Tue 08/18 05Z 0.06 0008  82  24  14 0.00
Tue 08/18 06Z 0.04 0006  81  14  14 0.00
Tue 08/18 07Z 0.05 0006  80  10  14 0.00
Tue 08/18 08Z 0.05 0005  80   7  14 0.00
Tue 08/18 09Z 0.04 0005  80   5  14 0.00
Tue 08/18 10Z 0.04 3504  79   4  13 0.00
Tue 08/18 11Z 0.04 3405  76   3  13 0.00
Tue 08/18 12Z 0.03 3405  73   3  13 0.00
Tue 08/18 13Z 0.03 3506  73   2  13 0.00
Tue 08/18 14Z 0.04 3506  74   2  13 0.00
Tue 08/18 15Z 0.03 3504  78   2  12 0.00
Tue 08/18 16Z 0.03 3403  82   2  12 0.00
Tue 08/18 17Z 0.04 3403  85   2  12 0.00
Tue 08/18 18Z 0.11 3204  86   2  12 0.01
Tue 08/18 19Z 0.12 3204  85   2  12 0.01
Tue 08/18 20Z 0.11 3205  83   2  12 0.00
Tue 08/18 21Z 0.13 3105  81   2  12 0.00
Tue 08/18 22Z 0.12 3105  77   2  12 0.00
Tue 08/18 23Z 0.07 3205  72   2  12 0.00
Wed 08/19 00Z 0.18 3007  70   3  12 0.00
Wed 08/19 01Z 0.11 3206  68   4  12 0.00
Wed 08/19 02Z 0.12 3106  71   4  12 0.00
Wed 08/19 03Z 0.17 3006  78   3  11 0.00
Wed 08/19 04Z 0.18 2906  83   3  11 0.00
Wed 08/19 05Z 0.16 2806  80   4  12 0.00
Wed 08/19 06Z 0.17 2907  79   6  12 0.00
Wed 08/19 07Z 0.15 2906  76  10  12 0.00
Wed 08/19 08Z 0.13 2805  76  13  11 0.00
Wed 08/19 09Z 0.18 2806  79  14  11 0.00
Wed 08/19 10Z 0.15 2806  76  16  11 0.00
Wed 08/19 11Z 0.13 2705  75  15  11 0.00

Run total areal avg QPF for the Central_Greens is: 0.48 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