Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
137 AM EDT Thu Aug 15 2019
Valid 12Z Sun Aug 18 2019 - 12Z Thu Aug 22 2019
...Guidance/Predictability Assessment and Weather
Highlights/Threats...
A stationary Southeast front lingers into early next week to pool
deep moisture. While a threat of locally heavy rainfall remains,
recent ECMWF runs in particular seem over zealous to spin-up and
track northward small scale convective systems with heavy QPF.
Guidance then overall agrees to build upper ridging over the
Southwest and U.S. southern tier that may support some daily
record high minimum/maximum temperatures. Meanwhile, an upper
trough will dig within northern stream flow off British Columbia
and the Pacific Northwest. A series of dynamic ejecting shortwaves
in this flow will progress downstream over southern Canada and the
U.S. northern tier to force wavy frontal systems down across the
north-central U.S., Midwest/Great Lakes, the Ohio Valley/Northeast
and Mid-Atlantic. Pooled moisture and instability will favors
periods of enhanced convection, with a cell training risk as the
fronts stall into the hot summer airmass underneath. Given
uncertainties and recent run-run continuity issues with
deterministic guidance, the WPC medium range product suite was
mainly derived from the GEFS/ECMWF ensemble means.
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