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Severe Weather and Flooding Threats for the Central U.S.; Fire Weather Concerns for the Western U.S.

Severe weather and flooding threats continue for portions of the central U.S., with impactful flash flooding possible from southern Kansas to southwestern Missouri. Extremely Critical fire weather conditions will develop across the Great Basin and Southwest on Friday, with dry and windy conditions through the weekend. Dangerous heat will increase across the southern and central U.S. this weekend. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the greens

Model run: BTV_GRID_D2D_NAM3_20260626_0000
Using the MB925 to MB850 layer.
Assumes greens are orthogonal to 270 degree winds.

925-850 mb Layer Average Wind/RH. Avg QPF over the greens.
Date   Time        Wind RH% 700 850T QPF
Day mm/dd hhZ Frd# DDFF (%) RH% (C) (in)
=== ===== === ==== ==== === === === ====
Fri 06/26 00Z 0.53 2213  77  91  10 0.00
Fri 06/26 01Z 0.42 2212  75  93  10 0.00
Fri 06/26 02Z 0.27 2012  75  97  10 0.01
Fri 06/26 03Z 0.11 1813  81  99  10 0.01
Fri 06/26 04Z 0.12 1716  84  99  10 0.02
Fri 06/26 05Z 0.11 1718  89  97  10 0.05
Fri 06/26 06Z 0.09 1721  93  96  10 0.11
Fri 06/26 07Z 0.08 1723  94  97  10 0.11
Fri 06/26 08Z 0.08 1723  90  94  10 0.06
Fri 06/26 09Z 0.09 1825  92  92  10 0.05
Fri 06/26 10Z 0.06 1822  92  86  10 0.01
Fri 06/26 11Z 0.16 1919  94  85  10 0.00
Fri 06/26 12Z 0.22 2018  95  75  10 0.00
Fri 06/26 13Z 0.24 2016  96  75  10 0.01
Fri 06/26 14Z 0.26 2115  97  68  10 0.01
Fri 06/26 15Z 0.31 2213  98  70  10 0.01
Fri 06/26 16Z 0.34 2212  98  67  10 0.01
Fri 06/26 17Z 0.38 2312  96  60  11 0.05
Fri 06/26 18Z 0.40 2309  95  58  11 0.07
Fri 06/26 19Z 0.47 2308  93  67  11 0.07
Fri 06/26 20Z 0.83 2309  93  84  11 0.16
Fri 06/26 21Z 0.65 2611  90  83  11 0.19
Fri 06/26 22Z 0.43 3014  87  81  11 0.11
Fri 06/26 23Z 0.32 3113  86  67  11 0.03
Sat 06/27 00Z 0.36 3011  89  64  11 0.00
Sat 06/27 01Z 0.40 2912  92  52  11 0.00
Sat 06/27 02Z 0.40 2913  93  49  11 0.01
Sat 06/27 03Z 0.36 3012  93  48  10 0.01
Sat 06/27 04Z 0.30 3011  93  44  10 0.01
Sat 06/27 05Z 0.29 3112  92  44  10 0.01
Sat 06/27 06Z 0.24 3211  91  48  10 0.01
Sat 06/27 07Z 0.19 3211  89  55  10 0.01
Sat 06/27 08Z 0.16 3210  87  53  10 0.01
Sat 06/27 09Z 0.16 3210  86  57  10 0.00
Sat 06/27 10Z 0.18 3210  85  55  10 0.00
Sat 06/27 11Z 0.18 3210  85  52  10 0.00
Sat 06/27 12Z 0.17 3210  85  49  10 0.00
Sat 06/27 13Z 0.18 3211  86  47  10 0.00
Sat 06/27 14Z 0.18 3209  88  43  10 0.00
Sat 06/27 15Z 0.18 3207  90  43  10 0.00
Sat 06/27 16Z 0.19 3206  88  42  10 0.00
Sat 06/27 17Z 0.32 3105  87  42  10 0.00
Sat 06/27 18Z 0.33 3104  86  45  11 0.01
Sat 06/27 19Z 0.35 3104  84  46  11 0.01
Sat 06/27 20Z 0.33 3204  82  45  11 0.01
Sat 06/27 21Z 0.12 3302  80  44  11 0.00
Sat 06/27 22Z 0.08 3202  81  48  11 0.01
Sat 06/27 23Z 0.09 3203  80  55  11 0.01
Sun 06/28 00Z 0.04 3403  79  57  12 0.01
Sun 06/28 01Z 0.04 3503  78  58  11 0.01
Sun 06/28 02Z 0.04 3403  77  57  12 0.00
Sun 06/28 03Z 0.04 3403  77  56  11 0.00
Sun 06/28 04Z 0.04 3503  79  54  11 0.00
Sun 06/28 05Z 0.05 3403  79  52  11 0.00
Sun 06/28 06Z 0.04 3403  79  50  11 0.00
Sun 06/28 07Z 0.04 3303  78  49  11 0.00
Sun 06/28 08Z 0.07 3203  78  49  11 0.00
Sun 06/28 09Z 0.06 3305  77  47  11 0.00
Sun 06/28 10Z 0.04 3406  76  44  11 0.00
Sun 06/28 11Z 0.04 3406  75  43  11 0.00

Run total areal avg QPF for the greens is: 1.29 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