Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jul 04 2024 21:18:58

AWUS01 KWNH 042118
FFGMPD
WIZ000-MNZ000-IAZ000-050300-

Mesoscale Precipitation Discussion 0557
NWS Weather Prediction Center College Park MD
518 PM EDT Thu Jul 04 2024

Areas affected...Southeastern MN...Northeastern IA...Southern
WI...

Concerning...Heavy rainfall...Flash flooding possible

Valid 042120Z - 050300Z

SUMMARY...Solid moisture flux and instability to support 1.5-2"/hr
rates and localized 2-3" with potential repeating cells in the
vicinity of the warm front and recently saturated soils suggests
an incident or two of flash flooding may be possible through
evening.

DISCUSSION...GOES-WV suite depicts strong dynamic environment with
a strong closed/occluding low across Southern MN slowly drifting
eastward.  Visible imagery and 21z surface analysis clearly shows
a warm front draped eastward across SE MN and S WI with scattered
thunderstorms developing along it in WI; wile advancing strong
cold front with 15-20kts of westerly CAA is providing strong
convergence for broader overall thunderstorms in proximity of the
triple point near KJYG and southward along the front across
north-central IA.   Strong diffluence in left exit of 90+kt 3H jet
rounding the based of the deeper low along with strong DPVA ahead
of the mid-level wave will further deepen the low and
strengthen/back low level flow in the warm sector while
strengthening moisture flux into the developing cells.   Deep
layer moisture is a bit limited with 1.3-1.5" total PWats and
surface Tds in the mid to upper 60s suggest rainfall
production/efficiency will be much less than what has been
experienced over the last few weeks; that have saturated the upper
soil profiles which remain between 60-75% per NASA SPoRT LIS
0-40cm product.

Pooled instability along/south of the warm frontal zone remains
modest with 1000-1500 J/kg.  Though with stronger convergence
thunderstorm updrafts are starting to cool below -50C and expand
in coverage.  Rates of 1-1.5"/hr will become more common with some
isolated 1.75" for any slower, rotating cells that may
isallobarically enhance moisture flux convergence into the
updrafts...mainly in proximity to the warm front.   Cell motion is
likely to diminish overall totals given 30-40kts of mean steering
flow; again with exception of slowed rotating cells which may be
in the 20-25kt range per Bunkers right moving vectors.  FFG values
are lowered due to saturated soils at 1-1.5"/hr and 1.5-2"/3hrs;
so it is likely more critical for cells to be repeating or
training along/in proximity to the warm front to generate those
spots of 2-3" that are possible to result in flash flooding
conditions.  So, best potential will reside across SE MN, far NE
IA into S WI this evening.=20

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4lFpIdJLfHU8IiyeanWIiDD1IEjV9W7EN2kK6FQVzmrJOgCZCCVKXNrrBPVnxfNVLjss=
d6d2BVnFlZz8lVm6Eq1MzXo$  for graphic product...

ATTN...WFO...ARX...DMX...DVN...GRB...MKX...MPX...

ATTN...RFC...NCRFC...NWC...

LAT...LON   44779329 44719138 44609026 44468938 44278855=20
            43898777 43338777 42638795 42528877 42538962=20
            42569119 42519220 42639361 42949414 43899355=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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