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
Valley/Midwest.
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.
Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml