Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1150 AM EDT Sat Sep 07 2019
Valid 12Z Tue Sep 10 2019 - 12Z Sat Sep 14 2019
...Record heat to continue for the Lower Mississippi Valley/Gulf
Coast next week...
...Overview and Guidance Evaluation/Preferences...
The synoptic pattern across the CONUS at the beginning of the
medium range period (Wednesday) is expected to feature an
anomalously strong ridge over the southeast U.S. while troughing
deepens in the west. As this trough advances toward the northern
Plains mid to late week, the southeast ridge weakens and is
shunted to mainly the Gulf Coast region. The northern Plains
shortwave will deepen considerably by Thursday-Friday and force an
area of low pressure and associated frontal system across the
Upper Midwest and Great Lakes regions. Finally, as upper flow
consolidates by mid to late next week, models show some consensus
that another shortwave should dig toward the Pacific Northwest by
next Friday, with an associated surface frontal system pressing
inland, reaching the Great Basin/Rockies by Saturday.
For this forecast cycle, the 00Z ECMWF, 06Z GFS, and 00Z CMC/UKMET
were used as a starting point for Day 3, with the greatest weight
placed on the ECMWF and GFS solutions. For Day 4 onward, the CMC
and UKMET solutions were increasingly out of consistency with
continuity and the ensemble means and therefore were not included.
The preference was for a general blend of the 00Z ECMWF/ECENS and
06Z GFS/GEFS, gradually increasing the weight of the ensemble
means toward Day 6-7 although the deterministic ECMWF and GFS did
offer some utility through Day 7 and was incorporated in the model
blend.
...Weather Highlights/Threats...
Through the medium range period, heavy rainfall potential will be
focused across the northern tier of the US, from portions of
eastern Montana eastward through the northern Plains, Upper
Midwest, and Great Lakes as a series of low pressure systems track
through the area. Another area of heavy rainfall may accompany a
cold frontal passage across the central Plains on Day 5-6
(Thur-Fri).
The other weather headline will the continuation of much above
normal temperatures across the southeast U.S. High temperatures
are forecast to be 5 to 15 degrees F above average much of next
week from the Gulf Coast region through the Tennessee, lower Ohio
Valley, and Southeast.
Taylor
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