National Weather Service United States Department of Commerce

Cold Weather Advisory in Effect for Portions of Northern New York Tonight

A Cold Weather Advisory is in effect from 1 AM to 8 AM Monday for portions of northern New York. Very cold temperatures temperatures and/or wind chills as low as 15 to 25 below zero are expected. The dangerously cold wind chills as low as 15 to 25 below zero could cause frostbite on exposed skin in as little as 30 minutes. Wear appropriate clothing, a hat, and gloves. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260302_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)
=== ===== === ==== ==== === === === ====
Mon 03/02 00Z 0.41 3016  66  35 -17 0.00
Mon 03/02 01Z 0.42 3120  63  32 -18 0.00
Mon 03/02 02Z 0.37 3121  57  24 -18 0.00
Mon 03/02 03Z 0.30 3120  51  15 -18 0.00
Mon 03/02 04Z 0.25 3220  48  10 -19 0.00
Mon 03/02 05Z 0.22 3220  47   8 -19 0.00
Mon 03/02 06Z 0.19 3218  46   6 -19 0.00
Mon 03/02 07Z 0.19 3217  44   4 -19 0.00
Mon 03/02 08Z 0.18 3115  44   5 -19 0.00
Mon 03/02 09Z 0.19 3115  43   7 -19 0.00
Mon 03/02 10Z 0.21 3115  41  10 -19 0.00
Mon 03/02 11Z 0.23 3015  40  12 -19 0.00
Mon 03/02 12Z 0.25 3014  40  16 -19 0.00
Mon 03/02 13Z 0.27 2914  42  19 -19 0.00
Mon 03/02 14Z 0.27 2913  43  24 -19 0.00
Mon 03/02 15Z 0.29 2913  44  23 -18 0.00
Mon 03/02 16Z 0.30 2913  42  19 -18 0.00
Mon 03/02 17Z 0.31 2912  38  15 -17 0.00
Mon 03/02 18Z 0.32 2912  37  16 -17 0.00
Mon 03/02 19Z 0.33 2911  39  24 -16 0.00
Mon 03/02 20Z 0.33 2810  43  33 -16 0.00
Mon 03/02 21Z 0.32 2710  46  38 -15 0.00
Mon 03/02 22Z 0.31 2610  47  33 -14 0.00
Mon 03/02 23Z 0.33 2612  46  31 -13 0.00
Tue 03/03 00Z 0.31 2513  44  36 -12 0.00
Tue 03/03 01Z 0.34 2514  43  41 -11 0.00
Tue 03/03 02Z 0.35 2516  38  51 -10 0.00
Tue 03/03 03Z 0.41 2520  33  60  -9 0.00
Tue 03/03 04Z 0.45 2522  30  67  -8 0.00
Tue 03/03 05Z 0.47 2523  34  75  -8 0.00
Tue 03/03 06Z 0.47 2523  31  69  -7 0.00
Tue 03/03 07Z 0.46 2523  33  60  -6 0.00
Tue 03/03 08Z 0.43 2522  34  53  -5 0.00
Tue 03/03 09Z 0.41 2421  34  51  -5 0.00
Tue 03/03 10Z 0.40 2421  31  52  -4 0.00
Tue 03/03 11Z 0.39 2321  28  49  -4 0.00
Tue 03/03 12Z 0.38 2320  27  45  -3 0.00
Tue 03/03 13Z 0.38 2321  30  43  -3 0.00
Tue 03/03 14Z 0.39 2323  38  38  -2 0.00
Tue 03/03 15Z 0.38 2324  48  35  -2 0.00
Tue 03/03 16Z 0.41 2324  58  34  -2 0.00
Tue 03/03 17Z 0.43 2325  68  30  -2 0.01
Tue 03/03 18Z 0.45 2324  78  26  -2 0.01
Tue 03/03 19Z 0.48 2324  89  23  -3 0.01
Tue 03/03 20Z 0.50 2324  96  30  -3 0.01
Tue 03/03 21Z 0.48 2323  97  58  -3 0.02
Tue 03/03 22Z 0.47 2323  97  81  -3 0.03
Tue 03/03 23Z 0.41 2221  97  88  -2 0.03
Wed 03/04 00Z 0.43 2221  97  87  -2 0.03
Wed 03/04 01Z 0.47 2222  98  89  -3 0.03
Wed 03/04 02Z 0.51 2321  98  96  -3 0.04
Wed 03/04 03Z 0.51 2419  98  97  -3 0.03
Wed 03/04 04Z 0.45 2517  98  95  -3 0.02
Wed 03/04 05Z 0.43 2616  98  85  -3 0.02
Wed 03/04 06Z 0.32 2814  96  84  -2 0.01
Wed 03/04 07Z 0.20 3012  92  58  -1 0.00
Wed 03/04 08Z 0.13 3111  84  33   0 0.00
Wed 03/04 09Z 0.12 3111  72  24   0 0.00
Wed 03/04 10Z 0.16 3113  64  26   0 0.00
Wed 03/04 11Z 0.15 3113  60  21   0 0.00

Run total areal avg QPF for the Central_Greens is: 0.30 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