NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260726_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)
=== ===== === ==== ==== === === === ====
Sun 07/26 12Z 0.10 2402  79  13  12 0.00
Sun 07/26 13Z 0.06 2101  79  10  12 0.00
Sun 07/26 14Z 0.06 1501  80   8  12 0.00
Sun 07/26 15Z 0.16 1402  83  10  12 0.01
Sun 07/26 16Z 0.35 1403  85  23  12 0.05
Sun 07/26 17Z 0.51 1503  84  35  13 0.08
Sun 07/26 18Z 0.25 1504  83  43  13 0.07
Sun 07/26 19Z 0.23 1505  80  43  13 0.02
Sun 07/26 20Z 0.17 1505  78  42  13 0.00
Sun 07/26 21Z 0.20 1605  79  43  13 0.00
Sun 07/26 22Z 0.10 1606  81  44  13 0.00
Sun 07/26 23Z 0.08 1607  83  38  13 0.01
Mon 07/27 00Z 0.08 1708  84  35  13 0.01
Mon 07/27 01Z 0.14 1808  84  36  13 0.00
Mon 07/27 02Z 0.15 1907  84  36  13 0.00
Mon 07/27 03Z 0.19 2007  82  37  13 0.00
Mon 07/27 04Z 0.22 2108  81  38  13 0.00
Mon 07/27 05Z 0.20 2107  80  36  13 0.00
Mon 07/27 06Z 0.25 2207  81  42  13 0.00
Mon 07/27 07Z 0.27 2307  82  51  13 0.00
Mon 07/27 08Z 0.27 2407  86  57  12 0.00
Mon 07/27 09Z 0.14 2205  85  54  13 0.00
Mon 07/27 10Z 0.15 2105  86  58  12 0.00
Mon 07/27 11Z 0.18 2206  89  67  12 0.00
Mon 07/27 12Z 0.23 2307  91  73  12 0.00
Mon 07/27 13Z 0.20 2306  92  71  12 0.00
Mon 07/27 14Z 0.16 2305  91  68  12 0.00
Mon 07/27 15Z 0.14 2303  89  62  12 0.00
Mon 07/27 16Z 0.18 2303  88  58  13 0.00
Mon 07/27 17Z 0.25 2203  88  55  13 0.00
Mon 07/27 18Z 0.37 2202  86  53  13 0.00
Mon 07/27 19Z 0.41 2003  84  54  14 0.00
Mon 07/27 20Z 0.42 2003  82  59  14 0.00
Mon 07/27 21Z 0.31 2003  81  62  14 0.00
Mon 07/27 22Z 0.31 2104  82  70  14 0.00
Mon 07/27 23Z 0.33 2304  85  71  14 0.00
Tue 07/28 00Z 0.23 2204  90  73  14 0.00
Tue 07/28 01Z 0.22 2106  90  75  14 0.00
Tue 07/28 02Z 0.23 2107  91  79  13 0.00
Tue 07/28 03Z 0.26 2108  92  84  13 0.01
Tue 07/28 04Z 0.26 2109  91  85  13 0.01
Tue 07/28 05Z 0.29 2110  88  82  13 0.00
Tue 07/28 06Z 0.33 2112  92  79  13 0.00
Tue 07/28 07Z 0.34 2113  95  80  13 0.00
Tue 07/28 08Z 0.36 2214  95  81  13 0.01
Tue 07/28 09Z 0.30 2212  95  80  14 0.01
Tue 07/28 10Z 0.23 2110  94  79  14 0.01
Tue 07/28 11Z 0.26 2210  95  75  13 0.01
Tue 07/28 12Z 0.23 2109  95  74  13 0.01
Tue 07/28 13Z 0.16 2008  94  71  13 0.00
Tue 07/28 14Z 0.06 1807  94  67  14 0.00
Tue 07/28 15Z 0.03 1709  96  67  13 0.00
Tue 07/28 16Z 0.04 1609  97  67  13 0.01
Tue 07/28 17Z 0.09 1609  96  67  14 0.02
Tue 07/28 18Z 0.06 1711  93  68  14 0.12
Tue 07/28 19Z 0.08 1609  94  67  14 0.05
Tue 07/28 20Z 0.06 1610  94  69  14 0.05
Tue 07/28 21Z 0.07 1612  92  72  14 0.13
Tue 07/28 22Z 0.20 1914  93  82  14 0.25
Tue 07/28 23Z 0.24 2015  84  76  14 0.24

Run total areal avg QPF for the Central_Greens is: 1.19 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