
A Winter Weather Advisory is in effect from 1 PM today to 5 AM Tuesday for lake effect snow in southern St. Lawrence County. Total snow accumulations between 2 and 5 inches are expected. Plan on slippery road conditions. Strong winds will cause blowing snow and further reduce visibilities. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260119_1200
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 01/19 12Z 0.31 2408 89 65 -14 0.00
Mon 01/19 13Z 0.41 2410 91 63 -14 0.00
Mon 01/19 14Z 0.59 2313 91 66 -14 0.00
Mon 01/19 15Z 0.61 2313 86 74 -14 0.00
Mon 01/19 16Z 0.96 2315 83 67 -14 0.00
Mon 01/19 17Z 3.74 2316 81 64 -15 0.00
Mon 01/19 18Z 5.68 2317 79 72 -15 0.00
Mon 01/19 19Z 2.73 2317 83 78 -14 0.00
Mon 01/19 20Z 5.06 2319 87 79 -15 0.00
Mon 01/19 21Z 1.91 2323 90 73 -14 0.00
Mon 01/19 22Z 2.26 2426 89 65 -14 0.01
Mon 01/19 23Z 1.98 2426 89 45 -14 0.00
Tue 01/20 00Z 1.95 2427 85 36 -15 0.00
Tue 01/20 01Z 1.93 2429 79 40 -15 0.00
Tue 01/20 02Z 2.61 2431 86 55 -15 0.00
Tue 01/20 03Z 7.75 2432 78 51 -16 0.00
Tue 01/20 04Z 3.11 2431 77 46 -17 0.00
Tue 01/20 05Z 1.84 2430 78 48 -17 0.00
Tue 01/20 06Z 1.72 2533 85 50 -17 0.00
Tue 01/20 07Z 1.32 2631 84 50 -17 0.00
Tue 01/20 08Z 1.19 2629 85 48 -17 0.00
Tue 01/20 09Z 1.37 2628 88 44 -18 0.00
Tue 01/20 10Z 1.72 2627 90 42 -18 0.00
Tue 01/20 11Z 2.57 2626 88 39 -19 0.00
Tue 01/20 12Z 2.91 2625 82 38 -20 0.00
Tue 01/20 13Z 2.63 2724 79 40 -20 0.01
Tue 01/20 14Z 4.77 2722 78 43 -21 0.00
Tue 01/20 15Z 7.54 2719 78 49 -21 0.00
Tue 01/20 16Z 9.89 2618 78 61 -21 0.00
Tue 01/20 17Z 11.26 2617 78 66 -21 0.00
Tue 01/20 18Z 11.42 2518 79 67 -21 0.00
Tue 01/20 19Z 11.17 2519 79 65 -21 0.00
Tue 01/20 20Z 12.43 2521 73 68 -20 0.00
Tue 01/20 21Z 10.66 2622 74 59 -21 0.00
Tue 01/20 22Z 6.67 2623 76 47 -21 0.00
Tue 01/20 23Z 4.87 2624 79 48 -21 0.00
Wed 01/21 00Z 3.50 2626 76 49 -21 0.00
Wed 01/21 01Z 2.45 2628 78 47 -21 0.00
Wed 01/21 02Z 1.69 2629 79 45 -21 0.00
Wed 01/21 03Z 1.29 2728 78 46 -21 0.00
Wed 01/21 04Z 1.13 2627 81 46 -20 0.00
Wed 01/21 05Z 1.01 2728 82 45 -20 0.00
Wed 01/21 06Z 0.96 2728 83 45 -20 0.00
Wed 01/21 07Z 0.85 2626 84 41 -20 0.00
Wed 01/21 08Z 0.76 2625 84 35 -19 0.00
Wed 01/21 09Z 0.83 2527 86 22 -19 0.00
Wed 01/21 10Z 0.72 2527 77 11 -18 0.00
Wed 01/21 11Z 0.64 2527 65 11 -17 0.00
Wed 01/21 12Z 0.64 2528 60 11 -16 0.00
Wed 01/21 13Z 0.62 2528 55 15 -15 0.00
Wed 01/21 14Z 0.59 2527 51 26 -14 0.00
Wed 01/21 15Z 0.49 2523 47 30 -14 0.00
Wed 01/21 16Z 0.44 2321 46 90 -13 0.00
Wed 01/21 17Z 0.40 2221 42 88 -13 0.00
Wed 01/21 18Z 0.40 2122 36 92 -13 0.00
Wed 01/21 19Z 0.45 2026 36 91 -13 0.00
Wed 01/21 20Z 0.39 2027 49 86 -11 0.00
Wed 01/21 21Z 0.32 1928 41 74 -10 0.00
Wed 01/21 22Z 0.32 1932 40 83 -9 0.00
Wed 01/21 23Z 0.35 1936 38 89 -8 0.00
Run total areal avg QPF for the Central_Greens is: 0.02 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