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Excessive Rainfall Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0830Z Jul 19, 2018)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 AM EDT Thu Jul 19 2018

Day 1
Valid 12Z Thu Jul 19 2018 - 12Z Fri Jul 20 2018

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER EASTERN
PORTIONS OF THE NORTHERN PLAINS INTO THE UPPER MISSISSIPPI
VALLEY...

...Eastern portions of the Northern Plains into the Upper
Mississippi Valley...
There are no significant model mass field differences with the
Northern Plains closed low that is expected to push slowly
eastward Thursday morning from eastern portions of the Northern
Plains and into the Upper Mississippi Valley Thursday night into
early Friday.  There is strong model signal for heavy
precipitation potential in the vicinity of this upper center and
to its southeast in a region of defined upper difluence and above
average pw values from across eastern portions of the Northern
Plains into the Upper Mississippi Valley.  Changes to the previous
outlook for this period were minor with only a slight
southwestward extension of the slight risk area into far northeast
South Dakota and far southwest Minnesota and slight extension to
the slight risk area into northwest Illinois.  Both of these
changes were to cover the model spread with the max qpf axes. 
Slowest moving cells likely near and just to the north and
northwest of the mid to upper level center from far southeast ND
into far northeast SD...southwest to central Minnesota where
precipitation areas may pivot in the associated comma
head/deformation precipitation area.  Precipitation likely to be
more progressive to the southeast of the mid to upper level closed
low across Iowa into northern Illinois where greater instability
will counteract the expected more progressive motion of the precip
areas. 

...Central to Eastern Gulf Coast into the coastal Southeast...
A surface frontal boundary is expected to remain stationary this
period from the Lower Mississippi Valley eastward into the
Southeast.  Unstable air along and to the south of this
front..mu-cape values 1000-2000 j/kg will persist Thursday into
Thursday evening across the Central to Eastern Gulf coastal region
into the coastal Southeast.  This will support widespread
scattered convection in the axis of much above average pw
values...2 to 2.5 standard deviations above the mean.  Heavy to
isolated excessive rainfall amounts possible with slow moving
cells across these areas...with hourly rainfall rates of 2"+ per
hour possible.  Changes to the previous outlook were to extend the
marginal risk area farther westward into the central Gulf coastal
region from southern Georgia...the Florida Panhandle..southern
Alabama into far southern Mississippi.

...Southwest...
No significant changes made to the previous marginal risk area
extending across portions of the Southwest.  With the mid to upper
level ridge remaining in place this period across this area and
continued much above average pw values...additional widespread
scattered convection likely Thursday afternoon into Thursday
evening...especially along the high terrain from west-central New
Mexico westward along the Mogollon Rim of Arizona...into southern
Utah and southern Nevada.

Oravec



Day 2

The Day 2 outlook will be updated by 0830Z.


Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt