NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260609_1200
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)
=== ===== === ==== ==== === === === ====
Tue 06/09 12Z 0.27 2810  70   2  12 0.00
Tue 06/09 13Z 0.27 2810  71   2  12 0.00
Tue 06/09 14Z 0.25 2808  72   1  11 0.00
Tue 06/09 15Z 0.29 2805  71   0  11 0.00
Tue 06/09 16Z 0.49 2704  67   0  12 0.00
Tue 06/09 17Z 0.89 2605  64   0  12 0.00
Tue 06/09 18Z 1.19 2606  68   0  13 0.00
Tue 06/09 19Z 1.22 2607  78   0  13 0.00
Tue 06/09 20Z 1.10 2508  82   0  13 0.00
Tue 06/09 21Z 0.84 2508  83   1  13 0.00
Tue 06/09 22Z 0.91 2512  86   1  13 0.00
Tue 06/09 23Z 0.69 2515  88   1  14 0.00
Wed 06/10 00Z 0.61 2516  91   1  14 0.00
Wed 06/10 01Z 0.57 2616  90   2  14 0.01
Wed 06/10 02Z 0.54 2717  89   1  14 0.01
Wed 06/10 03Z 0.50 2716  87   2  15 0.02
Wed 06/10 04Z 0.45 2814  88   2  14 0.01
Wed 06/10 05Z 0.45 2815  87   4  14 0.01
Wed 06/10 06Z 0.42 2814  89   4  14 0.01
Wed 06/10 07Z 0.31 2811  88   4  15 0.01
Wed 06/10 08Z 0.29 2810  87  14  14 0.01
Wed 06/10 09Z 0.27 2809  85  28  15 0.01
Wed 06/10 10Z 0.27 2709  85  58  15 0.01
Wed 06/10 11Z 0.28 2709  86  66  15 0.00
Wed 06/10 12Z 0.28 2509  89  83  15 0.00
Wed 06/10 13Z 0.24 2308  88  90  15 0.00
Wed 06/10 14Z 0.25 2208  87  93  15 0.00
Wed 06/10 15Z 0.23 2208  87  92  15 0.01
Wed 06/10 16Z 0.26 2209  92  95  15 0.01
Wed 06/10 17Z 0.20 2108  91  91  15 0.02
Wed 06/10 18Z 0.20 2109  89  93  15 0.01
Wed 06/10 19Z 0.17 2008  87  92  15 0.01
Wed 06/10 20Z 0.13 1908  86  89  16 0.00
Wed 06/10 21Z 0.08 1808  88  93  16 0.00
Wed 06/10 22Z 0.03 1708  91  92  16 0.00
Wed 06/10 23Z 0.03 1709  93  92  16 0.00
Thu 06/11 00Z 0.03 1710  95  93  16 0.00
Thu 06/11 01Z 0.07 1811  94  92  16 0.00
Thu 06/11 02Z 0.11 1811  94  92  16 0.00
Thu 06/11 03Z 0.14 1912  94  89  15 0.08
Thu 06/11 04Z 0.19 2012  91  89  15 0.18
Thu 06/11 05Z 0.19 2010  91  88  15 0.07
Thu 06/11 06Z 0.15 2107  89  86  15 0.03
Thu 06/11 07Z 0.12 2106  90  88  15 0.01
Thu 06/11 08Z 0.08 2004  94  88  15 0.01
Thu 06/11 09Z 0.03 1804  97  90  15 0.02
Thu 06/11 10Z 0.02 1603  98  90  15 0.01
Thu 06/11 11Z 0.04 1503  98  86  15 0.01
Thu 06/11 12Z 0.03 1503  98  81  15 0.00
Thu 06/11 13Z 0.04 2002  98  89  15 0.00
Thu 06/11 14Z 0.02 1701  98  86  15 0.00
Thu 06/11 15Z 0.05 1302  97  81  15 0.00
Thu 06/11 16Z 0.07 1102  96  78  15 0.00
Thu 06/11 17Z 0.04 1502  94  74  15 0.00
Thu 06/11 18Z 0.04 1501  94  76  15 0.00
Thu 06/11 19Z 0.06 1402  93  77  16 0.02
Thu 06/11 20Z 0.13 1302  92  77  16 0.05
Thu 06/11 21Z 0.04 1702  92  78  16 0.04
Thu 06/11 22Z 0.05 1802  92  82  16 0.04
Thu 06/11 23Z 0.05 1802  92  81  16 0.05

Run total areal avg QPF for the Central_Greens is: 0.79 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