National Weather Service United States Department of Commerce

Winter Headlines in effect 10 AM today through 10 AM Saturday with heaviest snow in eastern foothills of the Adirondacks and south-central Vermont.

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

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260220_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 02/20 18Z 0.09 1515  82  87  -1 0.00
Fri 02/20 19Z 0.17 1419  90  92   0 0.02
Fri 02/20 20Z 0.19 1421  95  95  -1 0.06
Fri 02/20 21Z 0.21 1321  96  97  -1 0.10
Sat 02/21 00Z 0.36 1223  96  99  -3 0.10
Sat 02/21 01Z 0.34 1321  96  93  -4 0.13
Sat 02/21 02Z 0.29 1317  96  95  -5 0.17
Sat 02/21 03Z 0.22 1415  95  92  -6 0.12
Sat 02/21 04Z 0.14 1513  95  89  -6 0.12
Sat 02/21 05Z 0.06 1610  96  90  -6 0.06
Sat 02/21 06Z 0.05 1708  96  91  -7 0.03
Sat 02/21 07Z 0.06 1806  96  91  -7 0.03
Sat 02/21 08Z 0.12 2006  96  94  -7 0.03
Sat 02/21 09Z 0.21 2106  97  94  -7 0.02
Sat 02/21 10Z 0.26 2407  99  93  -7 0.02
Sat 02/21 11Z 0.26 2707  99  91  -7 0.02
Sat 02/21 12Z 0.24 2907  99  89  -7 0.02
Sat 02/21 13Z 0.21 3007  99  89  -7 0.02
Sat 02/21 14Z 0.19 3107  99  88  -7 0.02
Sat 02/21 15Z 0.12 3207  98  85  -7 0.01
Sat 02/21 16Z 0.08 3305  98  81  -8 0.01
Sat 02/21 17Z 0.07 3405  98  76  -8 0.00
Sat 02/21 18Z 0.07 3504  98  72  -8 0.00
Sat 02/21 19Z 0.07 3504  97  70  -8 0.00
Sat 02/21 20Z 0.05 3505  95  63  -8 0.00
Sat 02/21 21Z 0.05 0005  93  58  -8 0.00
Sat 02/21 22Z 0.08 0105  91  54  -8 0.00
Sat 02/21 23Z 0.14 0306  87  53  -8 0.00
Sun 02/22 00Z 0.17 0407  79  53  -8 0.00
Sun 02/22 01Z 0.18 0507  68  43  -8 0.00
Sun 02/22 02Z 0.19 0707  65  34  -8 0.00
Sun 02/22 03Z 0.17 0906  67  28  -8 0.00
Sun 02/22 04Z 0.16 1007  64  25  -8 0.00
Sun 02/22 05Z 0.16 1108  56  24  -8 0.00
Sun 02/22 06Z 0.15 1209  54  26  -7 0.00
Sun 02/22 07Z 0.15 1311  55  28  -7 0.00
Sun 02/22 08Z 0.14 1412  54  29  -7 0.00
Sun 02/22 09Z 0.14 1312  52  29  -7 0.00
Sun 02/22 10Z 0.16 1312  50  29  -7 0.00
Sun 02/22 11Z 0.20 1213  53  27  -7 0.00
Sun 02/22 12Z 0.22 1214  57  25  -7 0.00
Sun 02/22 13Z 0.26 1215  60  23  -7 0.00
Sun 02/22 14Z 0.23 1316  63  29  -7 0.00
Sun 02/22 15Z 0.23 1316  65  35  -8 0.00
Sun 02/22 16Z 0.29 1215  64  34  -7 0.00
Sun 02/22 17Z 0.32 1216  65  33  -7 0.00
Sun 02/22 18Z 0.36 1216  68  37  -8 0.00
Sun 02/22 19Z 0.41 1216  74  37  -8 0.00
Sun 02/22 20Z 0.46 1215  78  35  -8 0.00
Sun 02/22 21Z 0.48 1115  80  33  -8 0.00
Sun 02/22 22Z 0.47 1115  78  32  -8 0.00
Sun 02/22 23Z 0.47 1016  71  32  -7 0.00
Mon 02/23 00Z 0.49 0917  67  39  -8 0.00
Mon 02/23 01Z 0.50 0918  67  45  -8 0.00
Mon 02/23 02Z 0.49 0920  60  35  -7 0.00
Mon 02/23 03Z 0.49 0922  52  38  -7 0.00
Mon 02/23 04Z 0.52 0924  48  35  -7 0.00
Mon 02/23 05Z 0.55 0825  47  38  -7 0.00

Run total areal avg QPF for the Central_Greens is: 1.11 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