Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
240 AM EDT Wed Jul 17 2019
Valid 12Z Sat Jul 20 2019 - 12Z Wed Jul 24 2019
...Widespread Excessive Heat Threat...
...Heat Wave Threat...
...Overview and Weather Highlights/Threats...
A large portion of the country will be rather hot and humid this
coming week, which bolsters an increasing threat for excessive
heat. By early next week, upper ridging/heat is expected to build
up through the west-central states and begin to gradually moderate
downstream down into the east-central U.S. with upper trough
amplification and southward sagging of a main northern tier states
frontal zone. Numerous locations will likely reach, or set new
daily high minimum records and some maximum temperature records.
With high humidity and persistent heat indices of 105 to 115F+,
there may be some issuance of heat advisories. This heat wave may
become problematic for those working or recreating outdoors,
individuals sensitive to heat, especially the elderly and animals.
Areas north of the ridging will be stuck in a quasi-zonal mean
flow pattern, with a series of impulses/trough energies that will
track through southern Canada and into the northern tier of the
U.S. The specifics for each system continues to be uncertain.
However, this pattern will be favorable for developing showers and
thunderstorms that will be capable of producing locally heavy
convection/MCS activity- sporadically propagating within a wavy
frontal/baroclinic zone across the north-central states,
Midwest/Great Lakes and Northeast/Mid-Atlantic. Locally excessive
rainfall may result from the multiple rounds of rain/high rain
rates. 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. Also expect renewed monsoonal convection over the
Southwest and southern Rockies later period with flow transition.
...Guidance/Predictability Assessment...
Uncertainty on individual features in respect to timing, location
and strength continues; therefore persisted in utilizing ensemble
means for a starting point. The WPC medium range product suite was
mainly derived from a blend of the reasonably compatible 00Z GEFS
mean and 12Z NAEFS/ECMWF ensemble means.
Campbell
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