Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
239 PM EDT Thu Aug 15 2019
Valid 12Z Sun Aug 18 2019 - 12Z Thu Aug 22 2019
...Guidance/Predictability Assessment and Weather
Highlights/Threats...
Flow becomes rather zonal over the CONUS Sunday as low pressure
lifts toward Hudson Bay. The movement of this eastern Canadian low
and a western Canadian low that persists over northern coastal BC
into the middle of next week are the main weather makers over
North America with ridging building again over the southwest
CONUS. The 00Z/06Z GFS and 00Z ECMWF are in good agreement into
Day 6/Wednesday before the operational 00Z ECMWF ejects the
western Canadian low into the Canadian Prairies which by 22/12Z is
10 degrees longitude east of the 00Z ECENS mean trough axis which
is 10 degrees east of the 06Z GEFS trough axis. The trough over
the eastern CONUS will send cold fronts into pooled moisture and
instability causing convective thunderstorms, though no particular
areas of heavy rain stand out at this time. Above normal
temperatures will persist across the southern CONUS through Days
3-7 with abnormal warmth in the northeast continuing into
Wednesday until the next cold front pushes through. The WPC medium
range product suite was mainly derived from the 06Z GFS/00Z ECMWF
through Day 5, then heavier toward the 06Z GEFS/00Z ECENS means.
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:
- Flooding possible across portions of the Central Plains and the
Middle Mississippi Valley.
- Flooding occurring or imminent across portions of the Northern
Plains.
- Excessive heat across portions of the Southwest, Tue-Thu, Aug
20-Aug 22.
- Excessive heat across portions of the Southern Plains into the
Lower Mississippi Valley, Sun-Mon, Aug 18-Aug 19.
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