
A winter weather advisory is in effect from 1 pm Monday to 1 pm Tuesday for lake effect snow in southern St Lawrence County in northern New York. Total snow accumulations between 3 and 6 inches, especially south and east of Route 11. There may be isolated higher amounts. Read More >
Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens
Model run: BTV_GRID_D2D_NAM3_20260119_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 01/19 00Z 0.06 2600 82 82 -10 0.00
Mon 01/19 01Z 0.10 2903 81 90 -10 0.00
Mon 01/19 02Z 0.10 3104 79 89 -10 0.00
Mon 01/19 03Z 0.08 3104 79 90 -10 0.00
Mon 01/19 04Z 0.06 3404 83 92 -11 0.00
Mon 01/19 05Z 0.08 3505 88 92 -11 0.00
Mon 01/19 06Z 0.08 3505 93 93 -12 0.00
Mon 01/19 07Z 0.08 3403 95 91 -12 0.00
Mon 01/19 08Z 0.08 3102 95 89 -12 0.00
Mon 01/19 09Z 0.11 2702 94 87 -12 0.00
Mon 01/19 10Z 0.11 2603 94 78 -12 0.00
Mon 01/19 11Z 0.24 2506 94 78 -13 0.00
Mon 01/19 12Z 0.34 2508 93 63 -13 0.01
Mon 01/19 13Z 0.33 2408 91 42 -13 0.00
Mon 01/19 14Z 0.34 2309 92 43 -13 0.00
Mon 01/19 15Z 0.47 2211 91 67 -13 0.00
Mon 01/19 16Z 0.96 2214 89 85 -14 0.00
Mon 01/19 17Z 2.24 2215 78 71 -14 0.00
Mon 01/19 18Z 1.71 2315 71 67 -14 0.00
Mon 01/19 19Z 2.24 2315 74 71 -14 0.00
Mon 01/19 20Z 4.31 2217 79 76 -14 0.00
Mon 01/19 21Z 1.79 2220 85 73 -14 0.00
Mon 01/19 22Z 1.35 2324 93 55 -14 0.01
Mon 01/19 23Z 2.13 2326 92 46 -14 0.01
Tue 01/20 00Z 1.95 2428 91 36 -14 0.00
Tue 01/20 01Z 1.75 2427 81 42 -14 0.00
Tue 01/20 02Z 1.71 2329 86 69 -14 0.00
Tue 01/20 03Z 9.70 2531 87 66 -16 0.01
Tue 01/20 04Z 4.52 2530 78 50 -17 0.00
Tue 01/20 05Z 1.72 2432 75 54 -17 0.00
Tue 01/20 06Z 1.80 2534 82 57 -17 0.00
Tue 01/20 07Z 1.51 2533 84 57 -17 0.00
Tue 01/20 08Z 1.66 2532 86 56 -18 0.00
Tue 01/20 09Z 1.38 2530 82 47 -18 0.00
Tue 01/20 10Z 1.43 2530 82 35 -19 0.00
Tue 01/20 11Z 1.62 2628 84 33 -19 0.00
Tue 01/20 12Z 1.60 2625 84 36 -20 0.00
Tue 01/20 13Z 1.68 2624 85 39 -20 0.00
Tue 01/20 14Z 5.26 2623 84 45 -21 0.00
Tue 01/20 15Z 7.52 2620 83 56 -21 0.00
Tue 01/20 16Z 11.38 2619 83 71 -21 0.00
Tue 01/20 17Z 12.02 2519 81 72 -21 0.00
Tue 01/20 18Z 11.21 2519 80 69 -21 0.00
Tue 01/20 19Z 11.56 2520 77 68 -20 0.00
Tue 01/20 20Z 13.64 2623 72 67 -21 0.00
Tue 01/20 21Z 9.34 2623 75 64 -21 0.00
Tue 01/20 22Z 6.42 2625 76 43 -21 0.00
Tue 01/20 23Z 3.90 2626 79 42 -21 0.00
Wed 01/21 00Z 5.32 2628 79 44 -21 0.00
Wed 01/21 01Z 1.74 2728 74 47 -21 0.00
Wed 01/21 03Z 1.23 2628 76 46 -20 0.00
Wed 01/21 04Z 1.13 2628 77 47 -20 0.00
Wed 01/21 05Z 1.06 2628 80 43 -20 0.00
Wed 01/21 06Z 0.99 2628 85 49 -20 0.00
Wed 01/21 07Z 0.89 2627 86 37 -19 0.00
Wed 01/21 08Z 0.81 2527 84 19 -19 0.00
Wed 01/21 09Z 0.81 2528 82 10 -18 0.00
Wed 01/21 10Z 0.78 2529 76 15 -18 0.00
Wed 01/21 11Z 0.69 2527 71 25 -17 0.00
Run total areal avg QPF for the Central_Greens is: 0.04 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