Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
248 AM EDT Fri Jul 23 2021
Valid 12Z Mon Jul 26 2021 - 12Z Fri Jul 30 2021
...Heatwave with some Record Temperatures for the North-Central
U.S...
...Overview with Weather Highlights/Hazards...
Hot upper ridging will consolidate and strengthen over the
north-central Rockies/Plains next week. The heatwave offers some
records/triple digit temperatures. Flow over the ridge will feed
into a Great Lakes/Northeast mean trough aloft. Moisture and
instability pooling along a wavy frontal zone and upper
difluence/jet will intermittently fuel scattered heavy convection
and downpours out from the Northern Plains, Midwest and the
Northeast through the Mid-Atlantic.
Meanwhile, an upper low drifting offshore into the Pacific and the
strengthening/consolidation of the Rockies-Plains upper ridge next
week should act to spread moisture to the north and west out from
from the Southwest. Activity to extend into California, the Great
Basin, and northward over the Rockies should be less intense than
a mainly short term focusing Arizona event.
Guidance also suggests that a surface trough with one or more
embedded lows off the Southeast coast lingering into early-mid
next week offer modest development potential. NHC will monitor.
...Guidance/Predictability Evaluation...
The WPC medium range product suite was primarily derived from best
clustered guidance from the 18 UTC GFS and 12 UTC ECMWF/UKMET days
3-5 (Mon-Wed) along with 01 UTC National Blend of Models. The
ECMWF seems to remain the best clustered model with the GEFS/ECMWF
ensemble means into days 6/7 in a period of gradually growing
forecast spread, but still above normal average predictability
beyond smaller scales. 00 UTC models remain in line with the most
variance still with periodic energy amplitude feeding into the
Great Lakes/Northeast upper trough.
Schichtel
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook 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