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Additional Severe Weather Concerns for the Center of the Nation; Heat Builds for the West; Critical Fire Weather for Alaska

Active hazardous weather continues for the center of the nation with more severe thunderstorms and heavy rainfall today. Heat will linger across the southern Plains, then expand westward early in the week. The combination of heat and dry conditions will fuel fire weather concerns for the Four Corners region and across interior Alaska. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260621_0600
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 06/21 06Z 0.43 2912  87  77   8 0.00
Sun 06/21 07Z 0.44 2914  88  74   8 0.00
Sun 06/21 08Z 0.47 2915  92  77   8 0.00
Sun 06/21 09Z 0.48 2917  95  86   7 0.01
Sun 06/21 10Z 0.44 2916  95  95   7 0.01
Sun 06/21 11Z 0.45 2917  93  79   7 0.00
Sun 06/21 12Z 0.49 2917  93  77   7 0.00
Sun 06/21 13Z 0.49 2916  91  78   7 0.00
Sun 06/21 14Z 0.46 2915  91  80   8 0.00
Sun 06/21 15Z 0.51 3015  93  85   7 0.00
Sun 06/21 16Z 0.49 3115  95  90   7 0.01
Sun 06/21 17Z 0.58 3114  95  90   8 0.01
Sun 06/21 18Z 0.51 3213  92  89   8 0.00
Sun 06/21 19Z 0.42 3114  88  90   8 0.03
Sun 06/21 20Z 0.59 3113  80  75   9 0.05
Sun 06/21 21Z 0.78 3012  80  74   9 0.00
Sun 06/21 22Z 0.58 3012  82  66   9 0.00
Sun 06/21 23Z 0.57 2912  87  67   9 0.00
Mon 06/22 00Z 0.55 2914  88  76   9 0.02
Mon 06/22 01Z 0.46 3013  89  72   9 0.06
Mon 06/22 02Z 0.35 3113  87  66   9 0.00
Mon 06/22 03Z 0.28 3113  86  60   9 0.00
Mon 06/22 04Z 0.27 3112  88  60   9 0.00
Mon 06/22 05Z 0.21 3111  87  46   9 0.00
Mon 06/22 06Z 0.16 3210  82  31  10 0.00
Mon 06/22 07Z 0.16 3209  82  31   9 0.00
Mon 06/22 08Z 0.15 3107  81  31   9 0.00
Mon 06/22 09Z 0.18 2905  82  31   9 0.00
Mon 06/22 10Z 0.21 2805  81  33   9 0.00
Mon 06/22 11Z 0.24 2706  79  32   9 0.00
Mon 06/22 12Z 0.17 2804  77  28   9 0.00
Mon 06/22 13Z 0.05 2701  74  25   9 0.00
Mon 06/22 14Z 0.03 1702  78  23   9 0.00
Mon 06/22 15Z 0.09 1805  81  25   9 0.00
Mon 06/22 16Z 0.41 1908  82  47   9 0.00
Mon 06/22 17Z 0.16 1810  76  90   9 0.01
Mon 06/22 18Z 0.22 1911  84  94   8 0.03
Mon 06/22 19Z 0.11 1511  89  95   8 0.06
Mon 06/22 20Z 0.23 1418  89  99   8 0.06
Mon 06/22 21Z 0.33 1422  89  99   9 0.04
Mon 06/22 22Z 0.39 1429  96  99   9 0.09
Mon 06/22 23Z 0.37 1434  97  99  11 0.13
Tue 06/23 00Z 0.24 1535  98  98  12 0.13
Tue 06/23 01Z 0.19 1633  96  91  12 0.34
Tue 06/23 02Z 0.22 1832  95  90  13 0.17
Tue 06/23 03Z 0.28 1930  97  89  13 0.21
Tue 06/23 04Z 0.33 1930  98  93  13 0.17
Tue 06/23 05Z 0.38 2030  99  91  14 0.13
Tue 06/23 06Z 0.46 2028  99  93  14 0.28
Tue 06/23 07Z 0.44 2124 100  95  13 0.19
Tue 06/23 08Z 0.45 2220  99  86  13 0.14
Tue 06/23 09Z 0.44 2417  99  95  12 0.06
Tue 06/23 10Z 0.35 2817  98  86  12 0.04
Tue 06/23 11Z 0.34 3021  97  61  11 0.02
Tue 06/23 12Z 0.34 3125  96  44   9 0.02
Tue 06/23 13Z 0.35 3228  94  26   9 0.02
Tue 06/23 14Z 0.34 3227  92  24   9 0.01
Tue 06/23 15Z 0.41 3225  94  21   8 0.01
Tue 06/23 16Z 0.55 3123  95  23   8 0.01
Tue 06/23 17Z 0.63 3121  93  19   8 0.01

Run total areal avg QPF for the Central_Greens is: 2.58 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