WPC Medium Range Archive
Medium Range Products Valid On:
(Day 7 PMDEPD: Valid 05/23/2022 to 05/27/2022)
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
536 PM EDT Fri May 20 2022
Valid 12Z Mon May 23 2022 - 12Z Fri May 27 2022
...Heavy Rainfall/Runoff and Strong Thunderstorm Threat from the
Southern Plains and Lower Mississippi/Tennessee Valleys to the
Ohio Valley and Great Lakes early-mid next week...
...Weather Pattern Overview...
A lead front is forecast to push across the South and East into
Monday to end the protracted heat wave over the South and also
usher in a cooler and more comfortable airmass over much of the
eastern U.S. after a sweltering weekend. Meanwhile, a rather
active weather pattern is expected to develop across the
continental U.S. going into next week, as multiple waves of low
pressure develop along a resurgent frontal boundary from the
Plains to the Great Lakes. This will be in response to a building
upper level trough over the High Plains and this main system will
slowly move eastward through next week. This offers a widespread
threat for heavy rainfall/convection and local runoff issues as
moisture and instability focus ahead/over the well organized and
wavy system. The experimental WPC Day 4/5 excessive rainfall
outlook has a "slight" risk from the southern Plains to the lower
Mississippi Valley, with activity spreading up through the Midwest
and eventually across the East. Meanwhile, a warming pattern over
the West by early-mid next week may be partially supplanted late
week as Pacific upper troughing works a front inland with modest
precipitation across the Northwest in an otherwise mainly dry week
west of the Rockies.
Forecast spread has decreased significantly with the latest model
runs whose mid-larger scale flow evolutions are now much better
clustered with the ensemble means days 3-7. While local convective
rainfall focus remains much less settled through medium range time
scales, guidance offers fairly consistent and uniform regional
areas of threat. The WPC medium range product suite was primarily
derived from a composite blend of the 06 UTC GFS and 00 UTC
ECMWF/UKMET/Canadian and the 13 UTC National Blend of Models (NBM)
days 3-5 (Monday-Wednesday) before enough uncertainty is
introduced to gravitate more toward the 06 UTC GEFS mean and 00
UTC ECMWF ensemble mean along with the best matched GFS/ECMWF and
NBM for better local detail consistent with predictability. This
general plan maintains good WPC product continuity and seems in
line with latest overall 12 UTC models and ensembles despite local
convective focus differences along with some lingering run to run
system timing/amplitude differences.
...Sensible Weather/Threat Highlights...
Temperatures behind the cold front exiting the East Coast next
week should return to near seasonal levels after a potentially
record setting early season heatwave. Low pressure forming along
the trailing front as it meanders near the Southeast Coast may
continue a moderate to heavy rainfall threat into Monday as well
for the southern Appalachians/Mid-Atlantic and Southeast.
The next system developing over the south-central U.S. into
early-mid next week is expected to become the main weather
headline of this forecast period. There will likely be widespread
convection and heavy rainfall from the southern Plains to the Ohio
Valley with moist return flow into another slow moving and wavy
frontal system. There is the potential for flash flooding with the
slower moving storms within a very moist and unstable atmosphere.
The potential exists for additional heavy rain as the system
translates eastward into mid-later next week.
The western-central U.S. trough should keep temperatures below
normal across Rockies and Plains through at least Tuesday. Much of
the Western U.S. should remain mainly dry through the middle of
next week as upper ridging builds over the region and warmer
temperatures expand across the region, with the exception of some
showers entering the Northwest into Friday. This may lead to an
excessive heat episode over interior California and the Desert
Southwest next week, with lead transient system warming across the
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
- Heavy rain across portions of the Central Plains, the
Middle/Lower Mississippi Valley, the
Tennessee Valley, the Upper Great Lakes, the Southern
Appalachians, the Southeast, the Southern
Plains, and the Ohio Valley, Mon-Wed, May 23-May 25.
- Heavy rain across portions of the Southeast, the southern
Mid-Atlantic, the Central/Southern
Appalachians, and the Tennessee Valley, Mon, May 23.
- Heavy rain across portions of the Central/Southern Appalachians,
the Mid-Atlantic, the Southern
Appalachians, and the Ohio Valley, Thu, May 26.
- Flooding possible across portions of the Middle Mississippi
- Flooding occurring or imminent across portions of the Upper
Mississippi Valley, and the Northern
- Flooding likely across portions of the Northern Plains.
- Excessive heat across portions of the Central Great Basin,
California, and the Southwest,
Mon-Fri, May 23-May 27.
- Excessive heat across portions of California, Mon-Wed, May
- Excessive heat across portions of California, Mon-Thu, May
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, winter weather outlook probabilities and heat indices are