970
FXUS02 KWBC 190700
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Jun 19 2025

Valid 12Z Sun Jun 22 2025 - 12Z Thu Jun 26 2025

...First significant and extremely dangerous heat wave of the
season expected for the central Plains, Midwest, and Mid-
Atlantic/Northeast this weekend into next week...

...Multi-day heavy rain threat with potential for flash flooding
across the central Plains/Upper Midwest as well as the southern
Rockies/High Plains next week...


...General Overview...

A significant and extremely dangerous heat wave is expected to
start the Summer across much of the central/eastern U.S. this
weekend through at least the middle of next week under a strong
upper-level ridge. A deep upper trough is forecast to work its way
across the Northwest, eventually emerging into the northern U.S.,
where a rather deep cyclone is forecast to develop this weekend.
Multiple frontal waves appear to follow as they develop and track
northeast through the central/northern Plains along a slow-moving
front by early next week leading to multiple days of heavy
rainfall and embedded severe weather. Influx of tropical moisture
into the Southern Rockies/High Plains will also bring a heavy
rainfall threat next week.


...Guidance/Predictability Assessment...

Guidance has remained in above average agreement on the overall
larger-scale pattern through the medium range period as an
amplifying upper-level ridge over the central/eastern U.S. and
upper-level trough over the western U.S. take hold this weekend and
through the middle of next week. Most of the uncertainty early in
the period has revolved around deep-cyclone development over the
Plains as the upper-level trough makes little to no progression and
upper- level energies rounding the trough bring at least a couple
rounds of cyclogenesis. The latest 12Z/18Z guidance continues to
come into better agreement regarding the details of this deep
cyclone and lead frontal system development later this weekend,
with the main low expected to lift northeastward into Canada while
the trailing frontal boundary makes slow progression through the
Midwest and central/northern Plains as the upper-level pattern
remains stagnant through the middle of next week. Not surprisingly
there are some differences with regards to the specifics, which
will impact the potential areal coverage of heavy rainfall
expected. However, the guidance is clustered well overall through
at least Tuesday.

Later in the period mid- to late next week (Wednesday-Thursday),
some larger differences begin to appear with regards to how long
and how strong the upper-high over the Southeast holds on (which
will impact the duration and intensity of the heat wave) and the
evolution of the last in a series of upper-energies progressing
eastward with the upper-trough. The latest 12Z ECMWF maintains a
stronger, broader upper-ridge keeping the wave track more northward
through Thursday, while the CMC brings an upper-wave eastward over
the central Plains/Midwest helping to suppress portions of the
ridge, and several of the last few runs of the GFS bring an
energetic disturbance into the Southeast along the southside of the
ridge. The ensemble means and AI guidance suggest a compromise
solution with the upper- wave a bit stronger than in the ECMWF
guidance but weaker than in the CMC.

The updated WPC forecast begins with a composite blend of the
deterministic guidance given above average agreement/clustering on
most of the pattern with only a few smaller-scale differences.
Contributions from the ECens and GEFS means are added during the
middle to late period, increasing from 20% to 55% of the blend, as
greater differences with respect to the evolution of the upper-
ridge/upper-trough overall, and specifically with regards to the
Plains/Midwest, increases.

...Weather/Hazards Highlights...

A major synoptic pattern change is in store this weekend and into
next week as an upper-level ridge amplifies over the
central/eastern U.S. and precipitation chances focus along the
periphery. A leading frontal system ahead of a deep- upper trough
over the western U.S. will become quasi-stationary northwest of the
ridge through the Midwest southwest through the central Plains.
Embedded energies in the upper flow with accompanying frontal waves
to follow look to trigger widespread convection in vicinity of the
boundary Monday-Thursday. Anomalously high moisture (2+ standard
deviations above the mean) will lead to multiple days of heavy
rainfall and flash flood potential, with a Slight Risk ERO
introduced for day 5 (Monday) centered on the Middle Missouri
Valley, and a broader Marginal Risk from the Upper Midwest
southwest through the central Plains. Some severe weather will be
possible as well. To the southwest, an influx of moisture from
Mexico, connected at least in part to tropical cyclone Erick in the
eastern Pacific, is forecast to bring an increasing chance of
enhanced rainfall into west Texas and the southern high
Plains/Rockies later this weekend and especially into Monday-
Wednesday as PWATs rise upwards of 2.5-3 standard deviations above
the mean. For this reason, portions of the southern Rockies/High
Plains have been included in a day 5 (Monday) Marginal Risk.
Elsewhere, daily showers and thunderstorms are also expected in
vicinity of the Gulf Coast as disturbances round the south side of
the ridge. Precipitation chances (including some very high
elevation snow) will linger through Monday for the northern Rockies
under the influence of the deep upper-trough.

The first significant heat wave of the season is expected to be
expanding in coverage from the central Plains/Midwest/Great Lakes
into the Ohio Valley/Mid-Atlantic/Northeast on Sunday thanks to an
anomalous upper-level high building overhead. Heat will intensify
for portions of the interior South as well. Widespread Major to
Extreme Heat Risk (levels 3 and 4/4) is forecast, indicating an
intensity and duration of heat that is extremely dangerous to
anyone without adequate cooling or hydration. Heat indices are
forecast to climb into the 100-110 degree range, with 110-115
possible for portions of the Upper Ohio Valley and eastern
Carolinas/southern Mid- Atlantic. In addition, muggy overnight lows
in the mid- to upper 70s will bring little overnight relief from
the heat. Numerous daily record high and minimum temperatures are
possible. Some locations from the central Plains into the Upper
Midwest will see some relief Monday-Tuesday as a cold front moves
into the region, and the focus for the most intense heat shifts
from the Midwest/Great Lakes into the Ohio Valley and Mid-Atlantic.
Highs will be cooler and below average by as much as 10-20 degrees
across portions of the Pacific Northwest, Great Basin, and
northern Rockies/High Plains this weekend with a deep-upper level
trough overhead. Temperatures will moderate closer to average
through early/mid next week.

Putnam


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 forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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
https://www.wpc.ncep.noaa.gov/#page=ovw


















































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