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Excessive Rainfall and Potential Tropical Cyclone in the South; Severe Thunderstorms in the Midwest

Excessive rainfall may produce locally considerable flash flooding over parts of the northwestern Gulf Coast, lower Mississippi River Valley, and Deep South through Thursday. Potential Tropical Cyclone One is forecast to become a tropical storm (Arthur) as it moves along or just off the northwestern Gulf coast through Wednesday. An outbreak of severe weather is forecast in the Midwest Wednesday. Read More >

Subject: NAM3 EXPERIMENTAL Froude Number for the Central_Greens

Model run: BTV_GRID_D2D_NAM3_20260617_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)
=== ===== === ==== ==== === === === ====
Wed 06/17 00Z 0.50 2409  76  73   9 0.00
Wed 06/17 01Z 0.57 2410  73  68   9 0.00
Wed 06/17 02Z 0.62 2411  73  61   9 0.00
Wed 06/17 03Z 0.64 2411  76  48   9 0.00
Wed 06/17 04Z 0.56 2310  76  47   9 0.00
Wed 06/17 05Z 0.54 2311  76  50   9 0.00
Wed 06/17 06Z 0.54 2311  77  56   9 0.00
Wed 06/17 07Z 0.52 2311  76  58   9 0.00
Wed 06/17 08Z 0.48 2211  76  60   9 0.00
Wed 06/17 09Z 0.46 2212  76  62   9 0.00
Wed 06/17 10Z 0.41 2212  74  61   9 0.00
Wed 06/17 11Z 0.37 2112  74  58   9 0.00
Wed 06/17 12Z 0.35 2111  75  58   9 0.00
Wed 06/17 13Z 0.44 2110  74  60   9 0.00
Wed 06/17 14Z 1.39 2008  74  60   9 0.00
Wed 06/17 15Z 3.22 2108  73  64   9 0.00
Wed 06/17 16Z 3.75 2110  74  57   9 0.01
Wed 06/17 17Z 3.68 2110  70  53  10 0.01
Wed 06/17 18Z 1.64 1809  68  63  10 0.00
Wed 06/17 19Z 1.51 1809  70  74  11 0.00
Wed 06/17 20Z 1.98 2010  69  86  11 0.00
Wed 06/17 21Z 0.45 1808  71  76  11 0.01
Wed 06/17 22Z 0.14 1810  70  71  11 0.00
Wed 06/17 23Z 0.16 1811  72  68  11 0.00
Thu 06/18 00Z 0.27 1814  74  62  11 0.00
Thu 06/18 01Z 0.26 1815  75  52  11 0.00
Thu 06/18 02Z 0.39 1918  75  53  11 0.00
Thu 06/18 03Z 0.54 1921  76  55  11 0.00
Thu 06/18 04Z 0.56 1924  82  63  11 0.00
Thu 06/18 05Z 0.45 1925  81  72  11 0.00
Thu 06/18 06Z 0.49 2025  86  56  11 0.00
Thu 06/18 07Z 0.59 2027  89  56  11 0.00
Thu 06/18 08Z 0.51 2027  90  56  11 0.01
Thu 06/18 09Z 0.46 2027  94  92  11 0.05
Thu 06/18 10Z 0.37 1926  91  89  12 0.05
Thu 06/18 11Z 0.25 1832  90  69  12 0.00
Thu 06/18 12Z 0.19 1836  90  95  13 0.01
Thu 06/18 13Z 0.32 1840  89  98  13 0.01
Thu 06/18 14Z 0.31 1841  85  96  13 0.07
Thu 06/18 15Z 0.29 1842  96  96  13 0.07
Thu 06/18 16Z 0.30 1842  98  94  13 0.15
Thu 06/18 17Z 0.45 1937  98  93  13 0.17
Thu 06/18 18Z 0.48 1933  98  85  14 0.06
Thu 06/18 19Z 0.56 2031  98  79  14 0.04
Thu 06/18 20Z 0.61 2028  97  58  14 0.04
Thu 06/18 21Z 0.91 2224  95  84  14 0.16
Thu 06/18 22Z 0.82 2526  85  77  12 0.18
Thu 06/18 23Z 0.76 2624  88  78  12 0.01
Fri 06/19 00Z 0.80 2524  87  50  12 0.00
Fri 06/19 01Z 0.96 2526  91  50  11 0.00
Fri 06/19 02Z 1.06 2427  95  58  11 0.01
Fri 06/19 03Z 1.20 2528  96  62  10 0.01
Fri 06/19 04Z 1.23 2529  96  83   9 0.03
Fri 06/19 05Z 1.21 2530  97  92   9 0.05
Fri 06/19 06Z 1.41 2630  96  74   8 0.05
Fri 06/19 07Z 1.19 2631  94  65   7 0.01
Fri 06/19 08Z 0.97 2632  91  67   8 0.00
Fri 06/19 09Z 0.90 2732  91  61   9 0.01
Fri 06/19 10Z 0.86 2732  93  56   9 0.01
Fri 06/19 11Z 0.85 2731  92  56   9 0.01

Run total areal avg QPF for the Central_Greens is: 1.30 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