National Weather Service United States Department of Commerce

Winter Storm Warnings in effect for Essex County in New York, and the southern Greens of Vermont, with Winter Weather Advisories elsewhere from 10 AM Friday through 10 AM Saturday

A warm front will approach Friday afternoon. A brief wintry mix or rain in warmer valleys is possible before a quick transition into moderate to heavy snow takes place during the Friday evening commute. 1-1.5 inch per hour snowfall rates are likely in northeastern New York and much of Vermont. Difficult travel is likely Friday Evening. Light snow will continue Friday night into Saturday. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260219_1200
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Thu 02/19 12Z 0.06 0702  48  23  -6 0.00
Thu 02/19 13Z 0.06 0702  43  15  -5 0.00
Thu 02/19 14Z 0.05 0702  42   9  -5 0.00
Thu 02/19 15Z 0.04 0901  41   6  -5 0.00
Thu 02/19 16Z 0.04 1302  42   6  -5 0.00
Thu 02/19 17Z 0.02 1802  44   7  -5 0.00
Thu 02/19 18Z 0.04 1603  43  11  -4 0.00
Thu 02/19 19Z 0.02 1704  45  17  -4 0.00
Thu 02/19 20Z 0.04 1904  49  25  -4 0.00
Thu 02/19 21Z 0.07 2004  52  36  -4 0.00
Thu 02/19 22Z 0.05 2003  52  42  -4 0.00
Thu 02/19 23Z 0.05 2103  53  38  -4 0.00
Fri 02/20 00Z 0.03 2002  54  35  -4 0.00
Fri 02/20 01Z 0.04 1904  56  30  -4 0.00
Fri 02/20 03Z 0.10 2007  68  26  -4 0.00
Fri 02/20 04Z 0.15 2108  73  32  -4 0.00
Fri 02/20 05Z 0.15 2108  78  28  -4 0.00
Fri 02/20 06Z 0.15 2108  81  22  -4 0.00
Fri 02/20 07Z 0.11 2107  81  17  -3 0.00
Fri 02/20 08Z 0.09 2106  81  19  -3 0.00
Fri 02/20 09Z 0.07 2105  80  16  -3 0.00
Fri 02/20 10Z 0.02 1903  77  19  -2 0.00
Fri 02/20 11Z 0.03 1603  75  24  -1 0.00
Fri 02/20 12Z 0.05 1505  74  25  -2 0.00
Fri 02/20 13Z 0.06 1507  74  23  -2 0.00
Fri 02/20 14Z 0.07 1509  75  24  -2 0.00
Fri 02/20 15Z 0.07 1609  75  28  -2 0.00
Fri 02/20 16Z 0.05 1611  74  33  -2 0.00
Fri 02/20 17Z 0.04 1711  73  34  -2 0.00
Fri 02/20 18Z 0.06 1611  70  32  -1 0.00
Fri 02/20 19Z 0.10 1512  65  45   0 0.00
Fri 02/20 20Z 0.13 1513  62  62   0 0.00
Fri 02/20 21Z 0.20 1415  61  76   0 0.00
Fri 02/20 22Z 0.26 1318  69  87   0 0.00
Fri 02/20 23Z 0.29 1320  73  94  -1 0.00
Sat 02/21 00Z 0.31 1321  83  95  -2 0.01
Sat 02/21 01Z 0.33 1322  92  97  -3 0.04
Sat 02/21 02Z 0.29 1320  95  97  -3 0.07
Sat 02/21 03Z 0.27 1319  96  97  -3 0.08
Sat 02/21 04Z 0.27 1317  95  98  -4 0.06
Sat 02/21 05Z 0.26 1415  95  98  -5 0.09
Sat 02/21 06Z 0.22 1413  95  97  -6 0.05
Sat 02/21 07Z 0.17 1511  95  95  -6 0.03
Sat 02/21 08Z 0.10 1610  95  93  -7 0.02
Sat 02/21 09Z 0.05 1709  95  92  -7 0.02
Sat 02/21 10Z 0.05 1807  95  92  -7 0.02
Sat 02/21 11Z 0.06 1906  95  93  -8 0.01
Sat 02/21 12Z 0.07 1906  95  91  -8 0.01
Sat 02/21 13Z 0.05 1905  96  89  -8 0.01
Sat 02/21 14Z 0.05 1904  97  89  -8 0.02
Sat 02/21 15Z 0.06 1903  97  90  -8 0.01
Sat 02/21 16Z 0.07 2003  97  92  -8 0.01
Sat 02/21 17Z 0.07 2102  97  91  -8 0.01
Sat 02/21 18Z 0.06 2201  97  88  -8 0.01
Sat 02/21 19Z 0.06 1700  97  86  -8 0.00
Sat 02/21 20Z 0.06 1000  97  86  -8 0.00
Sat 02/21 21Z 0.08 1001  97  88  -8 0.00
Sat 02/21 22Z 0.11 1003  96  89  -8 0.00
Sat 02/21 23Z 0.17 1004  94  90  -8 0.00

Run total areal avg QPF for the greens is: 0.58 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