NAM3 EXPERIMENTAL Froude Number for the Central Green Mountains

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260521_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)
=== ===== === ==== ==== === === === ====
Thu 05/21 12Z 0.12 3313  75   3   2 0.00
Thu 05/21 13Z 0.16 3213  72   2   2 0.00
Thu 05/21 14Z 0.20 3213  69   2   1 0.00
Thu 05/21 15Z 0.22 3213  63   2   1 0.00
Thu 05/21 16Z 0.40 3312  57   3   1 0.00
Thu 05/21 17Z 0.72 3313  51   3   1 0.00
Thu 05/21 18Z 0.75 3314  45   4   1 0.00
Thu 05/21 19Z 0.72 3214  44   4   1 0.00
Thu 05/21 20Z 0.72 3212  49   4   1 0.00
Thu 05/21 21Z 0.70 3212  55   4   1 0.00
Thu 05/21 22Z 0.42 3313  56   4   1 0.00
Thu 05/21 23Z 0.17 3313  58   3   1 0.00
Fri 05/22 00Z 0.11 3414  58   3   1 0.00
Fri 05/22 01Z 0.04 3415  57   2   1 0.00
Fri 05/22 02Z 0.03 3515  55   2   1 0.00
Fri 05/22 03Z 0.05 3516  53   2   1 0.00
Fri 05/22 04Z 0.05 3514  53   2   0 0.00
Fri 05/22 05Z 0.08 3513  51   2   1 0.00
Fri 05/22 06Z 0.13 0013  52   3   0 0.00
Fri 05/22 07Z 0.15 0111  52   3   0 0.00
Fri 05/22 08Z 0.18 0110  54   3   0 0.00
Fri 05/22 09Z 0.21 0210  53   3   0 0.00
Fri 05/22 10Z 0.18 0211  49   3   0 0.00
Fri 05/22 11Z 0.21 0212  44   3   0 0.00
Fri 05/22 12Z 0.19 0212  40   3   0 0.00
Fri 05/22 13Z 0.16 0210  37   4   1 0.00
Fri 05/22 14Z 0.19 0208  36   4   1 0.00
Fri 05/22 15Z 0.32 0306  37   5   0 0.00
Fri 05/22 16Z 0.60 0304  37   8   1 0.00
Fri 05/22 17Z 0.53 0103  38   9   1 0.00
Fri 05/22 18Z 0.63 0103  39  12   2 0.00
Fri 05/22 19Z 0.65 0203  41  14   3 0.00
Fri 05/22 20Z 0.37 0003  43  15   3 0.00
Fri 05/22 21Z 0.32 0103  44  16   4 0.00
Fri 05/22 22Z 0.22 0103  44  19   4 0.00
Fri 05/22 23Z 0.07 0002  43  19   4 0.00
Sat 05/23 00Z 0.09 0202  41  19   4 0.00
Sat 05/23 01Z 0.12 0303  39  21   4 0.00
Sat 05/23 02Z 0.19 0504  37  22   4 0.00
Sat 05/23 03Z 0.21 0604  35  25   4 0.00
Sat 05/23 04Z 0.25 0605  36  25   4 0.00
Sat 05/23 05Z 0.29 0606  38  18   4 0.00
Sat 05/23 06Z 0.36 0707  40  11   4 0.00
Sat 05/23 07Z 0.45 0709  41   7   4 0.00
Sat 05/23 08Z 0.50 0710  43   5   3 0.00
Sat 05/23 09Z 0.54 0711  44   4   3 0.00
Sat 05/23 10Z 0.55 0812  45   4   3 0.00
Sat 05/23 11Z 0.52 0912  44   4   3 0.00
Sat 05/23 12Z 0.48 1013  45   5   3 0.00
Sat 05/23 13Z 0.43 1113  46   5   4 0.00
Sat 05/23 14Z 0.41 1111  48   5   3 0.00
Sat 05/23 15Z 0.58 1210  52   5   3 0.00
Sat 05/23 16Z 1.30 1209  56   5   3 0.00
Sat 05/23 17Z 1.65 1208  56   5   4 0.00
Sat 05/23 18Z 1.75 1307  57   4   4 0.00
Sat 05/23 19Z 1.49 1308  59   4   4 0.00
Sat 05/23 20Z 1.26 1408  62   4   5 0.00
Sat 05/23 21Z 1.06 1409  65   4   5 0.00
Sat 05/23 22Z 0.81 1410  69   3   4 0.00
Sat 05/23 23Z 0.53 1411  70   3   4 0.00

Run total areal avg QPF for the Central_Greens is: 0.00 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