Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Sat Jun 18 2022
Valid 12Z Tue Jun 21 2022 - 12Z Sat Jun 25 2022
...Expansive area of heat to shift from the Midwest into the South
next week...
...Overview and Guidance/Predictability Evaluation...
The overall pattern during the medium range period features a
persistant and very warm upper level ridge expanding across the
Southern U.S. as weak and progressive systems ride overtop through
the northern tier. The guidance constinues to show reasonably good
agreement on the large scale pattern through the period, though
with some lingering differences in the details and timing of
individual systems. Recent runs of the deterministic models have
trended faster with an amplified trough off the Northeast early
next week, which would allow for more ridge building and warmth
across the Mid-Atlantic states. But the ensemble means are still
slower suggesting a fair bit of uncertainty still with regards to
temperatures across the region next week. Elsewhere, the most
notable difference is the CMC seems to break down the western edge
of the ridge too fast allowing for a more amplified and faster
shortwave into the Northwest and moving into the northern Plains
late next week. Meanwhile, the ECMWF and GFS have consistently
suggested a farther westward expansion of the southern ridge and
thus the shortwave axis tends to linger more over the
Northwest/western Canada into next weekend, which has more support
from the ensemble means. The WPC blend for tonight favored the
deterministic models early on, and increasing the ensemble means
late period (in place of the CMC).
...Sensible Weather/Threat Highlights...
The biggest weather hazard during the medium range period will be
a dome of heat and anomalous warmth across much of the eastern
half of the country next week. The greatest anomalies (generally
10-15+ above normal) will shift from the Midwest on Tuesday into
the South Wednesday-Friday, meaning high temperatures in the mid
to upper 90s and low 100s likely and little relief overnight as
low temperatures hover in the mid to upper 70s. Widespread record
high max and min temperatures are likely in many places.
Northward streaming anomalous moisture west of the ridge will
bring an unusually early monsoon type pattern to parts of the Four
Corners states and vicinity, mainly early in the week, supporting
an increase in coverage and intensity of rainfall across the
region with at least local flood and flash flood threats. By mid
week, there are still mixed signals over how much rainfall the
interaction of this moisture with the western front advancing into
the Plains will produce. However, the potential for some
training/repeat activity may have to be monitored as models
continue to show this Plains front becoming aligned west-east
along the southern edge of the westerlies by Wednesday-Thursday.
Farther east, an area of showers and thunderstorms may push across
the Great Lakes and possibly into the Northeast ahead of an
advancing warm front, with some activity possibly on the heavy
side earlier in the period.
Santorelli
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, experimental excessive rainfall
outlook, 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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml