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Winter Weather Advisory in Effect for Eastern Vermont 7 PM Tonight Through 10 AM Friday

A Winter Weather Advisory is in effect from 7 PM tonight to 10 AM Friday for portions of eastern Vermont. Freezing rain is expected in these areas, especially above 1000 feet elevation. Slick travel conditions are possible, so be sure to slow down and use caution if traveling this evening into Friday morning. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260403_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)
=== ===== === ==== ==== === === === ====
Fri 04/03 00Z 0.07 1521  97  99   2 0.00
Fri 04/03 01Z 0.06 1623  96  92   3 0.03
Fri 04/03 02Z 0.03 1725  97  82   3 0.02
Fri 04/03 03Z 0.08 1728  97  77   3 0.02
Fri 04/03 04Z 0.14 1829  97  79   5 0.01
Fri 04/03 05Z 0.19 1930  97  74   6 0.01
Fri 04/03 06Z 0.23 1931  97  77   7 0.01
Fri 04/03 07Z 0.26 2031  97  83   8 0.01
Fri 04/03 08Z 0.30 2032  97  86   9 0.01
Fri 04/03 09Z 0.37 2136  97  94  10 0.02
Fri 04/03 10Z 0.39 2135  97  92  10 0.09
Fri 04/03 11Z 0.46 2237  97  93  10 0.06
Fri 04/03 12Z 0.54 2239  98  87  10 0.06
Fri 04/03 13Z 0.56 2337  97  91  10 0.04
Fri 04/03 14Z 0.57 2436  93  92  10 0.04
Fri 04/03 15Z 0.60 2335  95  95  10 0.03
Fri 04/03 16Z 0.68 2437  95  86  10 0.06
Fri 04/03 17Z 0.72 2438  93  84  10 0.00
Fri 04/03 18Z 0.76 2537  94  72  11 0.00
Fri 04/03 19Z 0.80 2536  94  67  11 0.00
Fri 04/03 20Z 0.86 2535  91  58  11 0.00
Fri 04/03 21Z 0.99 2535  91  48  10 0.00
Fri 04/03 22Z 1.03 2535  90  38  10 0.00
Fri 04/03 23Z 1.14 2438  94  21  10 0.00
Sat 04/04 00Z 1.24 2541  95  21  10 0.00
Sat 04/04 01Z 1.20 2541  97  16   9 0.01
Sat 04/04 02Z 1.27 2540  98  16   9 0.02
Sat 04/04 03Z 1.39 2640  97  14   8 0.04
Sat 04/04 04Z 1.40 2637  94  14   7 0.03
Sat 04/04 05Z 1.26 2735  91  13   6 0.02
Sat 04/04 06Z 0.85 2831  87  12   5 0.01
Sat 04/04 07Z 0.60 2928  88  10   4 0.01
Sat 04/04 08Z 0.45 2926  88  14   3 0.00
Sat 04/04 09Z 0.33 3024  90  15   2 0.01
Sat 04/04 10Z 0.22 3121  88  23   2 0.01
Sat 04/04 11Z 0.12 3218  84  29   3 0.00
Sat 04/04 12Z 0.06 3314  82  28   3 0.00
Sat 04/04 13Z 0.04 3509  81  30   4 0.00
Sat 04/04 14Z 0.05 0105  82  35   4 0.00
Sat 04/04 15Z 0.05 0702  81  38   5 0.00
Sat 04/04 16Z 0.05 1304  82  35   4 0.00
Sat 04/04 17Z 0.04 1506  82  32   4 0.00
Sat 04/04 18Z 0.06 1509  81  32   4 0.00
Sat 04/04 19Z 0.10 1512  80  38   4 0.00
Sat 04/04 20Z 0.13 1516  83  33   4 0.00
Sat 04/04 21Z 0.07 1620  85  51   5 0.00
Sat 04/04 22Z 0.05 1622  84  91   6 0.00
Sat 04/04 23Z 0.03 1624  89  94   5 0.01
Sun 04/05 00Z 0.04 1626  94  85   6 0.01
Sun 04/05 01Z 0.04 1627  94  85   7 0.01
Sun 04/05 02Z 0.04 1728  95  87   8 0.01
Sun 04/05 03Z 0.04 1730  97  91   8 0.02
Sun 04/05 04Z 0.06 1733  97  95   7 0.04
Sun 04/05 05Z 0.09 1736  97  91   8 0.10
Sun 04/05 06Z 0.11 1838  97  86   8 0.05
Sun 04/05 07Z 0.14 1838  97  86   9 0.03
Sun 04/05 08Z 0.16 1837  97  92  10 0.02
Sun 04/05 09Z 0.18 1838  96  90  10 0.02
Sun 04/05 10Z 0.22 1938  97  83  10 0.02
Sun 04/05 11Z 0.28 2037  97  64  10 0.02

Run total areal avg QPF for the Central_Greens is: 1.04 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