National Weather Service United States Department of Commerce

Light freezing rain and freezing drizzle expected across portions of north central and northeastern Vermont tonight

Areas of light freezing rain and patchy freezing drizzle are expected tonight across portions of north central and northeastern Vermont. Up to a tenth of an inch of ice accumulation is possible which may lead to slick travel. Precipitation will change to areas of light rain or rain showers after 700 am Saturday as temperatures climb above freezing. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260306_1800
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 03/06 18Z 0.05 1511  93  63  -1 0.00
Fri 03/06 19Z 0.05 1512  92  61  -1 0.00
Fri 03/06 20Z 0.03 1613  90  58   0 0.00
Fri 03/06 21Z 0.02 1714  90  49   0 0.00
Fri 03/06 22Z 0.03 1716  90  28   0 0.00
Fri 03/06 23Z 0.08 1819  93  11   0 0.00
Sat 03/07 00Z 0.13 1821  94  11   0 0.00
Sat 03/07 01Z 0.19 1923  96  17   0 0.00
Sat 03/07 02Z 0.23 1926  97  38   0 0.01
Sat 03/07 03Z 0.24 1928  96  53   1 0.01
Sat 03/07 04Z 0.25 1927  96  59   2 0.01
Sat 03/07 05Z 0.25 2027  97  31   3 0.01
Sat 03/07 06Z 0.28 2027  97  23   3 0.01
Sat 03/07 07Z 0.28 2027  96  23   4 0.01
Sat 03/07 08Z 0.28 2028  95  62   5 0.00
Sat 03/07 09Z 0.31 2030  96  93   5 0.01
Sat 03/07 10Z 0.36 2133  96  90   7 0.01
Sat 03/07 11Z 0.39 2134  97  83   8 0.02
Sat 03/07 12Z 0.45 2236  97  68   9 0.02
Sat 03/07 13Z 0.52 2337  97  79   9 0.04
Sat 03/07 14Z 0.57 2338  98  67  10 0.03
Sat 03/07 15Z 0.56 2436  97  71  10 0.03
Sat 03/07 16Z 0.53 2333  96  61  10 0.03
Sat 03/07 17Z 0.56 2434  97  69  10 0.03
Sat 03/07 18Z 0.60 2435  95  79  10 0.04
Sat 03/07 19Z 0.59 2334  93  66  11 0.02
Sat 03/07 20Z 0.62 2335  96  62  11 0.01
Sat 03/07 21Z 0.63 2337  95  67  11 0.01
Sat 03/07 22Z 0.63 2338  95  66  12 0.01
Sat 03/07 23Z 0.66 2340  91  56  12 0.01
Sun 03/08 00Z 0.71 2342  94  45  12 0.01
Sun 03/08 01Z 0.75 2443  91  59  12 0.01
Sun 03/08 02Z 0.78 2445  90  80  12 0.01
Sun 03/08 03Z 0.84 2446  93  75  11 0.01
Sun 03/08 04Z 0.87 2444  96  88  10 0.03
Sun 03/08 05Z 0.89 2443  96  93  10 0.08
Sun 03/08 06Z 0.88 2542  95  83  10 0.04
Sun 03/08 07Z 0.86 2539  96  54   9 0.02
Sun 03/08 08Z 0.82 2537  94  52   9 0.02
Sun 03/08 09Z 0.82 2536  95  43   8 0.02
Sun 03/08 11Z 0.82 2533  93  14   7 0.02
Sun 03/08 12Z 0.97 2534  95   8   5 0.02
Sun 03/08 13Z 1.10 2534  94  10   4 0.02
Sun 03/08 14Z 1.24 2536  95  15   3 0.01
Sun 03/08 15Z 1.39 2636  95  45   1 0.02
Sun 03/08 16Z 1.24 2730  94  43   0 0.02
Sun 03/08 17Z 1.08 2730  93   4   0 0.02
Sun 03/08 18Z 1.20 2730  95   1  -1 0.01
Sun 03/08 19Z 1.31 2726  95   3  -1 0.00
Sun 03/08 20Z 1.27 2726  93   2  -2 0.00
Sun 03/08 21Z 0.98 2628  85   6  -1 0.00
Sun 03/08 22Z 0.76 2629  72  13   0 0.00
Sun 03/08 23Z 0.72 2632  62  45   0 0.00
Mon 03/09 00Z 0.73 2635  56  63   1 0.00
Mon 03/09 01Z 0.78 2637  54  63   1 0.00
Mon 03/09 02Z 0.82 2639  54  58   2 0.00
Mon 03/09 03Z 0.87 2640  59  45   2 0.00
Mon 03/09 04Z 0.91 2640  58  34   2 0.00
Mon 03/09 05Z 0.87 2739  58  29   2 0.00

Run total areal avg QPF for the Central_Greens is: 0.77 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