Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
428 PM EDT Fri Aug 09 2019
Valid 12Z Mon Aug 12 2019 - 12Z Fri Aug 16 2019
...Overview and Guidance/Predictability Assessment...
Generally quasi-zonal flow is expected to prevail early next week
across the CONUS, with embedded shortwaves tracking through and
some indication of troughing along the West Coast. This trough is
least amplified in the EC solutions. By midweek, more amplified
flow begins rebuilding as a deeper trough pushes into the
Northwest and ridging centered in the Southern Plains is expected
to strengthen by Thu/Fri. This would likely lead to troughing
downstream in the eastern U.S. Model guidance, particularly the
GEFS and EC means, are in pretty good alignment with the pattern,
so a multi-model blend was able to be used early on. The 00Z CMC
by day 5/Wed pushes more energy into the eastern U.S. trough,
deepening it more than other guidance into day 6/7. On the other
hand, the GFS deterministic runs, particularly the 06Z run,
flatten out that trough. Thus, the ECMWF and GEFS means made up
the bulk of the forecast later in the period. Overall not many
changes were needed to the overnight fronts/pressures forecast.
...Weather Highlights/Threats...
Widespread rain and thunderstorms are expected around a low
pressure system from the Northern Plains into the Upper Midwest
and Ohio Valley early in the workweek ahead of a shortwave. Gulf
moisture flowing into the vicinity of that front as it pushes into
the Southeast will lead to scattered showers and thunderstorms
there. Temperature-wise, above average temperatures are forecast
in the southern tier underneath the upper high, leading to the
likelihood of excessive heat and widespread record high minimum
temperatures. Meanwhile the northwestern and north-central CONUS
will generally have below average high temperatures.
Tate
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 Middle Mississippi Valley, the
Great Lakes, the Upper
Mississippi Valley, and the Northern Plains, Mon, Aug 12.
- Heavy rain across portions of the Southeast, Thu, Aug 15.
- Heavy rain across portions of the Great Lakes, the Central
Appalachians, and the Ohio Valley,
Tue, Aug 13.
- Flooding occurring or imminent across portions of the Central
Plains, the Southern Plains, and
the Northern Plains.
- Flooding likely across portions of the Central Plains, the
Middle Mississippi Valley, and the
Northern Plains.
- Excessive heat across portions of the Lower/Middle Mississippi
Valley, the Tennessee/Ohio Valley,
the Southeast, and the Southern Plains, Mon-Wed, Aug 12-Aug 14.
- Excessive heat across portions of Southern Texas, Mon-Fri, Aug
12-Aug 16.
- Excessive heat across portions of the Central Plains and the
Middle Mississippi Valley, Mon, Aug
12.
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