Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
251 PM EDT Mon Sep 16 2019
Valid 12Z Thu Sep 19 2019 - 12Z Mon Sep 23 2019
...Gulf of Mexico disturbance offers a Texas heavy rainfall
threat...
...Overview and Guidance Evaluation/Preferences...
The 00Z/06Z global model suite is in much better agreement with
the flow pattern coming off the Pacific and across the western
CONUS than recent days. There is great uncertainty among the
latest guidance in the Atlantic with Humberto and its interaction
with a trough which keeps off the CONUS. The NHC track is used for
Humberto with the Atlantic surface fronts and pressures conformed
to it.
Flow will be highlighted by an amplified upper trough that ejects
northeast out from The West and across the northern Plains through
Friday and sprawling/hot late summer east-central states upper
ridge into the weekend. The 00Z CMC/UKMET are slower with the
ejection. The WPC medium range product suite was primarily derived
from a composite blend of the 06Z GFS/GEFS, 00Z ECMWF/ECENS with
more deterministic guidance through Day 4 while Days 6 and 7 were
primarily means.
A general model blend works for the slow moving upper low over
east TX through Day 4.
...Weather Highlights/Threats...
A slow moving disturbance will have moved into east TX by
Wednesday night. This system offers a significant threat of
locally excessive rainfall dependent on track. The current track
brings it north up east TX where WPC QPF is focused. As pooled
tropical moisture lifts farther inland into east-central U.S.
convection later week into the weekend in advance of an
approaching surface front, especially over the east-central Plains
and Mid-MS Valley.
As the associated surface low with the western trough spreads onto
the northern Plains, expect an organized convective focus with
locally heavy downpours and potential for severe thunderstorms
Friday into Saturday. This focus this then shifts east to the
Great Lakes and east-central Plains/Mid-MS Valley/Midwest for the
weekend. Deepened moisture ahead of the cold front may support
some record high minimum temperatures Friday and Saturday over the
northern Plains and MN.
Strong ridging downstream over the east-central U.S. will cause
well-above average temperatures to spread east to the coast.
Northerly flow will lead to below normal temperatures midweek
along the Eastern Seaboard.
Jackson
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 portions of the Southern Plains, Thu-Fri, Sep
19-Sep 20.
- Heavy rain across portions of the Central Plains, the Lower
Mississippi Valley, the Southern
Plains, the Middle Mississippi Valley, the Great Lakes, and the
Ohio Valley, Sat-Sun, Sep 21-Sep 22.
- Heavy rain across portions of the Central Plains, the Upper
Mississippi Valley, and the Northern
Plains, Fri-Sat, Sep 20-Sep 21.
- Severe weather across portions of the Upper Mississippi Valley
and the Northern Plains, Fri, Sep
20.
- Flooding possible across portions of the Central Plains, the
Lower Mississippi Valley, the
Northern Plains, the Middle Mississippi Valley, the Upper
Mississippi Valley, and the Southern
Plains.
- Flooding occurring or imminent across portions of the Central
Plains, the Middle Mississippi
Valley, the Great Lakes, the Upper Mississippi Valley, and the
Northern Plains.
- Flooding likely across portions of the Central Plains, the
Middle Mississippi Valley, the Upper
Mississippi Valley, and the Northern Plains.
- Much below normal temperatures across portions of the Central
Great Basin, the Northern Rockies,
the Central Rockies, California, the Northern Great Basin, and the
Pacific Northwest, Thu-Sat, Sep
19-Sep 21.
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