National Weather Service United States Department of Commerce

Freezing Rain Expected Today across New York and Grand Isle County in Vermont. Flooding Remains Possible Through Thursday.

Temperatures across northern New York and Grand Isle County in Vermont will drop below freezing today as rain moves into the region. A glaze up to a tenth of an inch of freezing rain will be possible through this afternoon; locally higher near Massena, New York. Flooding remains possible through Thursday due to snow melt, ice jams, and widespread rainfall today and Thursday. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260311_0600
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)
=== ===== === ==== ==== === === === ====
Wed 03/11 06Z 0.05 2302  81  98   8 0.00
Wed 03/11 07Z 0.03 1704  86  98   8 0.01
Wed 03/11 08Z 0.03 1609  83  95   9 0.01
Wed 03/11 09Z 0.04 1616  80  96   9 0.00
Wed 03/11 10Z 0.08 1523  84  88   9 0.01
Wed 03/11 11Z 0.07 1629  85  74   9 0.00
Wed 03/11 12Z 0.06 1631  87  73   9 0.00
Wed 03/11 14Z 0.04 1732  84  89   9 0.03
Wed 03/11 15Z 0.08 1735  85  90   9 0.01
Wed 03/11 16Z 0.17 1833  92  92  10 0.01
Wed 03/11 17Z 0.20 1932  91  77  11 0.01
Wed 03/11 18Z 0.24 1933  91  50  11 0.01
Wed 03/11 19Z 0.23 1934  87  52  12 0.00
Wed 03/11 20Z 0.25 1936  85  44  12 0.00
Wed 03/11 21Z 0.28 1940  86  23  12 0.00
Wed 03/11 22Z 0.34 1942  89  35  12 0.00
Wed 03/11 23Z 0.35 1942  91  81  11 0.00
Thu 03/12 00Z 0.40 2044  90  86  12 0.01
Thu 03/12 01Z 0.51 2044  89  93  13 0.00
Thu 03/12 02Z 0.59 2143  92  86  12 0.00
Thu 03/12 03Z 0.72 2142  96  77  11 0.00
Thu 03/12 04Z 0.78 2144  98  84  12 0.00
Thu 03/12 05Z 0.99 2144  96  81  11 0.01
Thu 03/12 06Z 0.90 2235  98  72  11 0.06
Thu 03/12 07Z 1.21 2333  98  64   9 0.05
Thu 03/12 08Z 1.24 2530  98  75   7 0.07
Thu 03/12 09Z 0.90 2530  95  83   5 0.06
Thu 03/12 10Z 0.80 2630  94  80   1 0.04
Thu 03/12 11Z 0.85 2629  95  95  -2 0.03
Thu 03/12 12Z 0.76 2729  92  94  -4 0.04
Thu 03/12 13Z 0.87 2728  90  69  -6 0.03
Thu 03/12 14Z 0.86 2827  89  30  -8 0.01
Thu 03/12 15Z 1.09 2825  89  16 -10 0.00
Thu 03/12 16Z 2.66 2826  88   7 -11 0.00
Thu 03/12 17Z 5.60 2925  86   2 -11 0.00
Thu 03/12 18Z 5.86 2924  84   5 -11 0.00
Thu 03/12 19Z 4.98 2924  81   9 -11 0.00
Thu 03/12 20Z 2.98 3023  80  10 -11 0.00
Thu 03/12 21Z 1.24 3022  80  15 -11 0.00
Thu 03/12 22Z 1.10 3021  80  22 -11 0.00
Thu 03/12 23Z 0.94 3020  81  30 -11 0.00
Fri 03/13 00Z 1.02 3021  83  38 -11 0.00
Fri 03/13 01Z 1.37 2921  85  47 -11 0.00
Fri 03/13 02Z 1.43 2923  88  52 -12 0.00
Fri 03/13 03Z 1.50 2923  91  53 -12 0.00
Fri 03/13 04Z 1.53 2923  92  56 -12 0.00
Fri 03/13 05Z 1.01 3023  92  59 -12 0.00
Fri 03/13 06Z 0.82 3021  92  57 -12 0.00
Fri 03/13 07Z 0.82 2920  94  56 -12 0.00
Fri 03/13 08Z 0.72 2917  93  45 -12 0.00
Fri 03/13 09Z 0.63 2816  92  30 -12 0.00
Fri 03/13 10Z 0.65 2716  92  20 -12 0.00
Fri 03/13 11Z 0.52 2714  91  10 -11 0.00
Fri 03/13 12Z 0.29 2509  84   5 -10 0.00
Fri 03/13 13Z 0.25 2309  78   6 -10 0.00
Fri 03/13 14Z 0.20 2109  69   6  -9 0.00
Fri 03/13 15Z 0.16 1911  59   8  -9 0.00
Fri 03/13 16Z 0.19 1814  55  24  -9 0.00
Fri 03/13 17Z 0.87 1816  57  54  -9 0.00

Run total areal avg QPF for the Central_Greens is: 0.51 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