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Extended Forecast Discussion
(Caution: Version displayed is not the latest version. - Issued 0655Z Sep 18, 2019)
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Wed Sep 18 2019

Valid 12Z Sat Sep 21 2019 - 12Z Wed Sep 25 2019

...Imelda moisture offers a East-Central Plains to Midwest Heavy
Rainfall Threat...

...Overview and Guidance Evaluation/Preferences...
Models and ensembles offer a reasonably similar medium range flow
evolution in a pattern with above average forecast confidence. The
WPC medium range product suite was primarily derived from a
composite blend of fairly well clustered guidance from the
GFS/ECMWF/UKMET/Canadian, GEFS/ECMWF ensemble means and the
National Blend of Models. This maintains excellent WPC continuity.

...Weather Highlights/Threats...
Deep tropical moisture with the remains of Imelda will offer a
significant threat of locally excessive rainfall into the weekend.
Expected inland lifting/entrainment into the flow with approaching
mid-latitude upper trough energy from the West and surface front
proximity will likely then focus heavy convection/runoff issues
with cell training from the east-central Plains to the Mid-MS

Meanwhile, an aforementioned upper trough will lift northeastward
from the unsettled and cooled West/Rockies to the north-central
U.S. This will support an organized convective focus with locally
heavy downpours and a severe thunderstorm risk into Saturday as
per SPC. Deepened lead moisture may also support some record high
minimum temperatures.

Upstream, upper low/trough energies will reload back into an again
unsettled West/Southwest Sunday into next week with an initial
precipitation swath over the Northwest then Great Basin. There is
guidance uncertainty, but monsoonal rainfall/convection then into
the Southwest/Southern Rockies may be enhanced early next week by
an influx of tropical moisture well downstream of current Tropical
Storm Lorena.

Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at: