NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260805_0600
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)
=== ===== === ==== ==== === === === ====
Wed 08/05 06Z 0.28 2710  67  35  17 0.00
Wed 08/05 07Z 0.27 2710  68  37  17 0.00
Wed 08/05 08Z 0.27 2709  69  38  16 0.00
Wed 08/05 09Z 0.28 2810  69  37  16 0.00
Wed 08/05 10Z 0.26 2809  69  36  16 0.00
Wed 08/05 11Z 0.22 2808  68  33  15 0.00
Wed 08/05 12Z 0.16 2906  67  30  16 0.00
Wed 08/05 13Z 0.11 2804  65  27  16 0.00
Wed 08/05 14Z 0.11 2503  66  23  16 0.00
Wed 08/05 15Z 0.12 2303  68  18  15 0.00
Wed 08/05 16Z 0.19 2204  69  10  15 0.00
Wed 08/05 17Z 0.43 2205  66   4  15 0.00
Wed 08/05 18Z 0.55 2206  62   2  16 0.00
Wed 08/05 19Z 0.59 2106  58   1  16 0.00
Wed 08/05 20Z 0.46 2106  56   1  16 0.00
Wed 08/05 21Z 0.37 2207  54   9  17 0.00
Wed 08/05 22Z 0.34 2208  55  27  17 0.00
Wed 08/05 23Z 0.34 2209  57  46  17 0.00
Thu 08/06 00Z 0.39 2309  62  58  16 0.00
Thu 08/06 01Z 0.42 2410  68  63  16 0.00
Thu 08/06 02Z 0.43 2410  71  73  16 0.00
Thu 08/06 03Z 0.39 2311  74  77  16 0.00
Thu 08/06 04Z 0.35 2211  78  74  16 0.00
Thu 08/06 05Z 0.34 2212  78  83  16 0.00
Thu 08/06 06Z 0.33 2212  77  89  16 0.00
Thu 08/06 07Z 0.34 2212  77  93  16 0.00
Thu 08/06 08Z 0.31 2211  75  92  16 0.00
Thu 08/06 09Z 0.27 2110  74  91  16 0.00
Thu 08/06 10Z 0.22 2009  76  94  16 0.00
Thu 08/06 11Z 0.15 1909  79  90  17 0.00
Thu 08/06 12Z 0.18 2010  85  92  16 0.00
Thu 08/06 13Z 0.16 2010  88  92  16 0.00
Thu 08/06 14Z 0.19 2010  91  88  16 0.00
Thu 08/06 15Z 0.21 2110  93  85  16 0.00
Thu 08/06 16Z 0.24 2110  95  85  17 0.01
Thu 08/06 17Z 0.33 2112  98  88  16 0.00
Thu 08/06 18Z 0.35 2212  99  88  17 0.01
Thu 08/06 19Z 0.33 2211  97  82  17 0.01
Thu 08/06 20Z 0.42 2311  95  78  17 0.00
Thu 08/06 21Z 0.33 2308  95  77  17 0.00
Thu 08/06 22Z 0.34 2408  95  80  17 0.01
Thu 08/06 23Z 0.32 2608  94  77  17 0.00
Fri 08/07 00Z 0.28 2607  95  74  17 0.01
Fri 08/07 01Z 0.22 2606  91  69  17 0.01
Fri 08/07 02Z 0.23 2607  89  69  18 0.01
Fri 08/07 03Z 0.25 2708  84  68  18 0.00
Fri 08/07 04Z 0.26 2808  86  67  18 0.00
Fri 08/07 05Z 0.29 2810  85  66  17 0.00
Fri 08/07 06Z 0.27 2910  88  62  17 0.00
Fri 08/07 07Z 0.26 2909  90  53  17 0.00
Fri 08/07 08Z 0.23 3009  93  37  17 0.00
Fri 08/07 09Z 0.17 3007  93  37  17 0.00
Fri 08/07 10Z 0.13 3106  91  37  17 0.00
Fri 08/07 11Z 0.14 3107  92  37  17 0.00
Fri 08/07 12Z 0.12 3006  91  33  17 0.00
Fri 08/07 13Z 0.12 3005  90  55  17 0.00
Fri 08/07 14Z 0.14 2805  87  54  17 0.00
Fri 08/07 15Z 0.16 2705  85  49  17 0.00
Fri 08/07 16Z 0.17 2705  82  55  17 0.00
Fri 08/07 17Z 0.21 2706  80  60  17 0.00

Run total areal avg QPF for the Central_Greens is: 0.07 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