Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
221 AM EDT Sat Jul 11 2020
Valid 12Z Tue Jul 14 2020 - 12Z Sat Jul 18 2020
...Toasty in Texas next week...
...Overview and Guidance/Predictability Assessment...
Classic summertime upper high will meander over the southern
Plains and lower Mississippi Valley with an extension toward the
East Coast next Tue-Sat. Models/ensembles show excellent agreement
in the lower latitudes with a weakness off California in between
another upper high well offshore. Jet stream will be relegated to
along the U.S./Canadian border with an increasingly zonal flow,
lowering predictability in shortwave timing. Lead-in pattern will
feature one closed upper low over Saskatchewan/Manitoba that is
forecast to slowly drift northeastward toward Hudson Bay. A second
upper low over southern Quebec/northern New England will move into
Atlantic Canada by Thursday. The frontal system attached to each
upper low will progress from west to east and generally lift
northward in time as height rise across the mid-latitudes. A
consensus blend sufficed for much of the period, though the 12Z
Canadian departed most from the ensemble majority with the flow
out of the northeast Pacific by midweek, and was discounted.
Otherwise, trended toward a blend of the GFS/ECMWF and their
ensemble means by the start of next weekend with an expansive area
> 588dam heights.
...Weather Pattern/Hazard Highlights...
A potent cold front will push through the Upper Midwest/Great
Lakes Tue-Wed with a chance of showers/thunderstorms and locally
heavy rain. The unsettled weather will continue along and to the
south of the boundary (Plains/Corn Belt/Midwest) but with overall
modest rainfall amounts. Generally dry conditions are expected
elsewhere over the CONUS except Florida which will see afternoons
showers/storms.
Temperatures near and above record highs are likely over parts of
the Southwest and across much of Texas on Tuesday with widespread
100+ readings. Above normal temperatures are likely from the
Rockies to the East Coast much of next week with the largest
anomalies over Texas (5-10 deg above normal but 10-15 deg above
normal Tue). Widespread mid-90s to low 100s are likely with higher
heat indices from Oklahoma eastward to the Southeast. A few hotter
days are likely for the Northeast/Mid-Atlantic into the upper 80s
to mid 90s. Overnight temperatures may only fall into the mid 70s
to near 80 in urban areas under the influence of the upper high.
Fracasso
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