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Dangerous Cold Continues Tonight

A Cold Weather Advisory is in in effect across the entire region through 10AM Monday. Wind chills of 20 to 30 below zero are expected, especially tomorrow morning. The risk of frostbite and hypothermia will be elevated, especially for vulnerable populations. Use extra caution and dress appropriately if you plan to be outdoors. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260208_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)
=== ===== === ==== ==== === === === ====
Sun 02/08 18Z 0.03 3422  71  23 -17 0.00
Sun 02/08 19Z 0.04 3425  68  27 -16 0.00
Sun 02/08 20Z 0.05 3427  68  40 -15 0.00
Sun 02/08 21Z 0.06 3428  63  52 -14 0.00
Sun 02/08 22Z 0.06 3428  61  57 -14 0.00
Sun 02/08 23Z 0.05 3429  59  58 -13 0.00
Mon 02/09 00Z 0.03 3430  56  56 -13 0.00
Mon 02/09 01Z 0.03 3431  54  53 -12 0.00
Mon 02/09 02Z 0.02 3430  57  40 -12 0.00
Mon 02/09 03Z 0.04 3429  61  35 -12 0.00
Mon 02/09 04Z 0.07 3428  62  34 -12 0.00
Mon 02/09 05Z 0.09 3328  64  36 -12 0.00
Mon 02/09 06Z 0.11 3329  65  33 -12 0.00
Mon 02/09 07Z 0.12 3331  64  31 -12 0.00
Mon 02/09 08Z 0.13 3332  66  29 -12 0.00
Mon 02/09 09Z 0.12 3333  64  27 -12 0.00
Mon 02/09 10Z 0.11 3333  62  23 -12 0.00
Mon 02/09 11Z 0.10 3334  59  18 -12 0.00
Mon 02/09 12Z 0.08 3434  56  13 -12 0.00
Mon 02/09 13Z 0.07 3434  53  11 -12 0.00
Mon 02/09 14Z 0.07 3432  51  12 -11 0.00
Mon 02/09 15Z 0.07 3431  49  23 -11 0.00
Mon 02/09 16Z 0.06 3429  49  49 -11 0.00
Mon 02/09 17Z 0.08 3428  48  58 -11 0.00
Mon 02/09 18Z 0.11 3327  47  75 -11 0.00
Mon 02/09 19Z 0.11 3325  46  66 -11 0.00
Mon 02/09 20Z 0.11 3324  40  46 -10 0.00
Mon 02/09 21Z 0.13 3324  36  43  -9 0.00
Mon 02/09 22Z 0.12 3324  33  47  -8 0.00
Mon 02/09 23Z 0.10 3324  30  55  -8 0.00
Tue 02/10 00Z 0.12 3324  33  53  -8 0.00
Tue 02/10 01Z 0.10 3323  31  55  -8 0.00
Tue 02/10 02Z 0.09 3322  29  60  -8 0.00
Tue 02/10 03Z 0.08 3321  30  68  -8 0.00
Tue 02/10 04Z 0.08 3320  34  74  -8 0.00
Tue 02/10 05Z 0.09 3319  37  86  -8 0.00
Tue 02/10 07Z 0.08 3316  40  82  -8 0.00
Tue 02/10 08Z 0.09 3314  40  77  -7 0.00
Tue 02/10 09Z 0.10 3212  36  75  -8 0.00
Tue 02/10 10Z 0.10 3210  36  72  -8 0.00
Tue 02/10 11Z 0.13 3008  37  73  -8 0.00
Tue 02/10 12Z 0.11 2906  45  64  -7 0.00
Tue 02/10 13Z 0.11 2705  51  60  -7 0.00
Tue 02/10 14Z 0.13 2505  57  58  -7 0.00
Tue 02/10 15Z 0.11 2205  64  57  -7 0.00
Tue 02/10 16Z 0.11 2106  65  58  -7 0.00
Tue 02/10 17Z 0.12 2009  61  61  -6 0.00
Tue 02/10 18Z 0.14 1911  51  60  -6 0.00
Tue 02/10 19Z 0.13 1913  44  62  -6 0.00
Tue 02/10 20Z 0.10 1814  47  89  -6 0.00
Tue 02/10 21Z 0.18 1915  56  93  -7 0.00
Tue 02/10 22Z 0.04 1716  91  97  -8 0.00
Tue 02/10 23Z 0.07 1720  93  94  -6 0.02
Wed 02/11 00Z 0.16 1822  94  93  -7 0.06
Wed 02/11 01Z 0.32 1921  94  96  -9 0.06
Wed 02/11 02Z 0.41 2119  95  95  -9 0.05
Wed 02/11 03Z 0.47 2218  96  95  -8 0.05
Wed 02/11 04Z 0.47 2317  97  89  -8 0.04

Run total areal avg QPF for the Central_Greens is: 0.28 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