Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Tue Sep 17 2019
Valid 12Z Fri Sep 20 2019 - 12Z Tue Sep 24 2019
...Gulf of Mexico disturbance offers a Texas to Midwest heavy
rainfall threat...
...Overview and Guidance Evaluation/Preferences...
Models and ensembles again offer a reasonably similar and
amplified larger scale pattern over the lower 48 and vicinity for
much of the upcoming medium range period. Forecast spread and
uncertainty for even mid-scale embedded features remains mostly
improved, bolstering overall forecast confidence to above normal
levels. The WPC medium range product suite was primarily derived
from a composite blend of the latest and fairly well clustered
GFS/ECMWF, GEFS/ECMWF ensemble means and the National Blend of
Models.
...Weather Highlights/Threats...
A slow moving disturbance is expected to reach TX by midweek. This
system offers a significant threat of locally excessive rainfall.
Deep tropical moisture will fuel a heavy rainfall/runoff threat
across eastern TX into Fri. Expected northward lifting and
entrainment into the flow with approaching mid-latitude upper
trough energy from the West and surface front proximity will
likely then focus heavy weekend convection/runoff issues with cell
training from the east-central Plains to the Mid-MS
Valley/Midwest.
Overtop, the aforementioned and amplified upper trough will lift
northeastward from the unsettled and cooled West/Rockies to the
north-central U.S. This supports an organized convective focus
with locally heavy downpours and severe thunderstorms risk Friday
into Saturday as per SPC. Deepened lead moisture may also support
some record high minimum temperatures. Guidance is now in better
agreement in showing the reloading of upper trough energies back
into an again unsettled West Sunday/Monday with widespread
precipitation over the Northwest shifting across the north-central
Great Basin/Rockies, reaching the Plains earlu next week.
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