Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
334 PM EDT Fri Sep 13 2019

Valid 12Z Mon Sep 16 2019 - 12Z Fri Sep 20 2019

...Potential Tropical Cyclone NINE to exit away from the Southeast
next week...

...Overview and Guidance Evaluation/Preferences...

Troughing in the West and ridging in the Midwest/East will be
favored next week per the latest ensemble guidance. There remains
uncertainty in the track/evolution of Potential Tropical Cyclone
NINE just off the Southeast coast, but the models favor a track
offshore after Monday at this point (see the latest information
from the National Hurricane Center). In the Pacific, a larger
amount of uncertainty at longer wavelengths suggests an increased
weight toward the ensemble means by later next week, given
significant run-to-run differences in most deterministic runs.
Though a consensus blend sufficed to start, the 00Z/06Z GFS and
Canadian departed from the ensemble consensus around Wednesday
while the 00Z ECMWF appeared too aggressive out of the Gulf of
Alaska around Thursday. With the 00Z GEFS mean likely too deep
with central Pacific troughing and downstream ridging in the Pac
NW, opted to rely on an ensemble blend of the 06Z GEFS mean, 00Z
NAEFS mean, and 00Z ECMWF ensemble mean by next Friday that
favored some troughing in the interior West as ridging moves into
the Northeast/Atlantic Canada.


...Weather Highlights/Threats...

Per the latest NHC track, "NINE" is forecast to bring some
rain/wind to coastal areas of FL/GA/SC/NC before it turns eastward
out to sea.

With strong ridging in the central states, well-above average
temperatures are expected next week from the High Plains/Upper
Midwest into the Great Lakes region. Daytime max temperatures well
into the 80s will be about 10-15F above average and overnight lows
in the 60s to near 70F will be about 15-20F above average. Some
locations may set record highs and/or record high minimums for the
day. A frontal boundary will bring in cooler weather (back to near
seasonal levels) and some generally light/modest rain fall midweek
to the area.

In the Pacific Northwest, a surface front and subsequent upper
trough will bring a widespread chance of rain (some very high
elevation snow) to the region early in the week, spreading through
the northern/central Rockies before exiting onto the Plains. This
may help tap some subtropical moisture out of Mexico on southwest
flow aloft across the Southwest/Four Corners states early in the
week before rainfall chances decrease.

In the western Gulf of Mexico, a trough/wave associated with an
upper low favors a chance of rainfall, potentially locally heavy,
over southeastern/coastal Texas next week. Weak steering aloft may
allow this area of rain to persist through the medium range
forecast as some models show several inches of rainfall over the
5-day period.


Fracasso


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

Hazards:
- Heavy rain across northwestern Oregon, Wed, Sep 18.
- Flooding possible across portions of the northern and central
Plains, the Great Lakes, and the
upper Mississippi Valley.
- Flooding occurring or imminent across portions of the northern
and central Plains, as well as the
upper Mississippi Valley.
- Flooding likely across portions of the northern and central
Plains, as well as the upper
Mississippi Valley.
- Much above normal temperatures across much of the northern
Plains into portions of the northern
Rockies, central Plains, and into the upper Midwest, Mon-Tue, Sep
16-Sep 17.
- Much below normal temperatures across portions of northern
California, southern Oregon, into
northwestern Nevada, Mon-Tue, Sep 16-Sep 17.


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