812
FXUS02 KWBC 060804
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
404 AM EDT Sat Jun 6 2026

Valid 12Z Tue Jun 09 2026 - 12Z Sat Jun 13 2026


...Significant heat wave will build over a large portion of the
central to eastern U.S. mid- to late next week...

...Severe weather and heavy rain threats possible in the northern
Rockies/Plains to Midwest...


...Overview...

The upper-level pattern at the start of the medium range period
Tuesday will consist of a trough over the West and mean ridging in
the south-central to eastern U.S., aside from a shortwave moving
through the Ohio Valley. While the shortwave provides forcing for
scattered thunderstorms in the Ohio Valley and vicinity, the larger
ridge will support broad areas of above normal temperatures/heat
indices as the first significant heat wave of the summer takes hold
in the central U.S. Tuesday-Wednesday, shifting/expanding into the
eastern U.S. later next week. Meanwhile, the western U.S. trough
should bring cooler, unsettled conditions to the Pacific Northwest
and northern Rockies, with precipitation lingering in Montana and
vicinity through much of the week. Ahead of the eastern edge of the
trough pushing a surface front and low pressure system east,
severe weather and localized flash flooding are possible Tuesday-
Wednesday across the north-central U.S., with some storms likely
for the Middle Mississippi Valley for later week.


...Guidance/Predictability Assessment...

Model guidance begins the forecast period in good agreement with
the primary features of the upper-level pattern described above. At
the surface, a strong surface low especially for June looks to
move from the northern High Plains early Tuesday, eastward on
Wednesday, and consolidating in south-central Canada by early
Thursday. The newest 00Z model suite is showing better consensus on
this low track. Meanwhile farther east, the broad ridge and the
embedded Ohio Valley shortwave seem adequately handled by a blend
of model guidance.

The most uncertain aspect of the pattern has been the evolution of
the trough that starts atop the West but lifts northeast through
next week. Previous runs of some guidance, including the 12/18Z GFS
and ECMWF, showed more troughing hanging back in the Northwest
into Thursday and Friday with more shortwaves coming through.
However, the 00Z models and ensembles are leaning away from this,
leading to higher heights in the Great Basin compared to previous
cycles. There are certainly still some shortwave differences
rounding the base of the trough, but at least the large scale is
somewhat more agreeable. By Friday into next Saturday, there is
some signal for a shortwave to drop into the Northwest, with the
AIFS and GFS keeping this separate from/west of the primary trough,
but the AIGFS/EC/CMC showing it just dropping into the western
side of the trough. Will have to see if models come to a better
consensus on this, as this affects sensible weather like
temperatures and QPF.

The WPC forecast was able to use a deterministic model blend
through Day 5 or so, with increasing proportions of the ensemble
means as the period progressed given the spread especially in the
northwestern to north-central U.S. with shortwaves there.


...Weather/Hazards Highlights...

The shortwave moving from the Ohio Valley eastward combined with
the hot, humid airmass in place from the broader ridge aloft will
lead to thunderstorms capable of heavy downpours and flash flooding
on Tuesday. A Marginal Risk stretches from Lower Michigan through
parts of the Ohio and Tennessee Valleys in the Day 4/Tue ERO.
Scattered thunderstorms are forecast to shift slightly east into
the Appalachians on Wednesday, but upper-level support should be
lessening. Convection could spark in much the same area of the
eastern third of the U.S. into later week. Florida can also expect
daily, diurnally driven thunderstorms as a surface front settles
there.

An unseasonably strong low pressure system is forecast to push
across the northern Plains Tuesday-Wednesday and into south-central
Canada by Thursday, ahead of the northwestern U.S. trough. Fronts
with the low will help focus convection and plentiful moisture,
instability, and shear will be in place. The Storm Prediction
Center is calling for risks of severe weather in the northern
Plains and Upper Midwest due to this potential. Meanwhile heavy
rainfall/flash flooding also looks to be a concern, and Marginal
Risks in the ERO are shown for this potential in the northern
Plains/Upper Midwest on Day 4/Tuesday, shifting somewhat east and
south on Day 5/Wednesday with the frontal boundary. More storms are
likely in parts of the Plains and Mississippi Valley into the
latter part of the week.

The upper trough in the West and multiple frontal passages will
bring cooler conditions and chances for scattered showers and
thunderstorms in the Pacific Northwest Tuesday-Wednesday. Then as
the trough sets up over the northern Rockies/Plains as the week
progresses, this should yield continued forcing for precipitation
there through much of next week. Moisture levels should be high but
instability should generally be lacking, preventing any
significant flooding threat. Some snow is possible in higher
elevations. Farther south, gusty winds under the upper trough and
very low relative humidity Tuesday could produce conditions
favorable for fire weather per SPC.

The amplifying upper-level ridge building over the central to
eastern U.S. is expected to bring the first significant heat of the
summer by mid- to late next week. The threat should gradually
shift from the central U.S. Tuesday and Wednesday towards the East
Coast by Friday and into next weekend. See WPC`s Key Messages for
more. Meanwhile, the upper trough over the western U.S. will lead
to some below average temperatures over the northwestern U.S.
eventually shifting into the northern High Plains and moderating.


Tate


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, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
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
https://www.wpc.ncep.noaa.gov/#page=ovw



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