Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
219 AM EDT Fri Aug 09 2019
Valid 12Z Mon Aug 12 2019 - 12Z Fri Aug 16 2019
...Guidance/Predictability Assessment and Weather
Highlights/Threats...
Models and ensembles agree in showing general zonal upper flow
over the northern tier of the lower 48 states early next week.
There is a trend towards amplification mid-later next week with
development of troughs/height falls to push convection focusing
surface frontal passages through an unsettled Northwest and
Northeast, with height rises in between over the north-central
U.S. and the re-emergence of a hot southern Plains closed upper
high. This seems reasonable. However, the models continue to offer
significant embedded system timing differences Monday to Friday,
albeit with some favorable forecast clustering showing decent
shortwave trough/height falls progression from the northern
Rockies Monday eastward over the Midwest/Great Lakes to the
Northeast into midweek. This seems likely to drive a lead/wavy
surface frontal system and the best convective rainfall potential
focus/threat southward across the central and eastern states this
period, eventually working later week into the southern
Plains/South/Southeast. The South and Southeast ahead of this
front will remain quite hot through much of the period beneath
upper ridging, especially over the southern Plains under the
closed upper high. Pre-frontal maximum and minimum temperatures
are forecast to be 5 to 10+ deg above normal. This would result in
a threat for widespread record high minimum temperatures in the
quite moist and hot summer airmass.
The WPC medium range product suite was primarily derived from a
broad composite blend of the National Blend of Models with the
latest GFS/ECMWF and GEFS/NAEFS/ECMWF ensemble means Monday before
transitioning Tuesday to mainly just the ensemble means Wednesday
to Friday.
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