Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1200 PM EDT Tue Jul 16 2019
Valid 12Z Fri Jul 19 2019 - 12Z Tue Jul 23 2019
...Guidance/Predictability Assessment...
The WPC medium range product suite was prmarily derived from a
blend of the 06 UTC GEFS mean, 00 UTC NAEFS/ECMWF ensemble means,
and WPC continuity.
Latest guidance still depicts a fair amount of uncertainty through
the extended period; therefore, followed suite to the previous
forecast and utilized a compromise of the NAEFS and ECWMF ensemble
means. Again, the ECMWF and GEFS mean clustered reasonably well
with this preferred solution that offers a fairly well established
larger scale pattern with much less certainty with embedded
smaller scale impulses and local convective focus.
...Overview and Weather Highlights/Threats...
There is a significant threat for dangerously hot and humid
conditions later this week/weekend into early next week within an
expansive sector of the nation. Later week hot upper ridging will
encompass much of the Southwest and south-central portions of the
Rockies and central and eastern U.S. By early next week, upper
ridging/heat is expected to build up through the west-central
states and begin to moderate downstream into the east-central U.S.
with upper trough amplification.
Some locations may tie or set new daily high minimum records. Heat
indices will be around 105 to 115F, which may lead to some future
issuance of heat advisories.
Overtop, a quasi-zonal mean flow pattern develops over the
northern-tier of the U.S. late week and for the weekend. A
prolonged series of impulses/trough energies will pass over
southern Canada and through the U.S. northern tier states with
uncertain individual system amplitudes and timings. Showers and
thunderstorms capable of producing locally heavy convection/MCS
activity will sporadically develop and propagate within a wavy
frontal/baroclinic zone across the north-central states,
Midwest/Great Lakes and Northeast/Mid-Atlantic. Multiple rounds of
rain/high rain rates may lead to locally excessive rainfall as the
moisture and instability pools along the slow moving and wavy main
frontal boundary. Although the model spread for QPF is not as high
as previous cycles, it still lower confidence on where and when
the highest amounts occur. Guidance continues to suggest the max
QPF occurs over the Upper Mississippi Valley and Great Lakes this
weekend that spreads into the east-central states early next week
with flow amplification.
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