587
FXUS02 KWBC 091802
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
202 PM EDT Sat May 9 2026

Valid 12Z Tue May 12 2026 - 12Z Sat May 16 2026


...Guidance/Predictability Assessment...

The latest guidance remains reasonably well clustered with the
larger scale pattern through most of next week, highlighted by a
building/warming ridge over the West, troughing over the East, and
shortwaves dropping from the Northern Plains/Great Lakes to
reinforce troughing in the East. A guidance composite continues to
offer a solid forecast basis in this time frame.

The greatest source of uncertainty continues to surround the
upstream evolution and timing of a main shortwave/closed low that
digs over the eastern Pacific before eventually advancing inland
over the Northwest/West. Initial 00/06Z guidance seemed to be split
between the faster UKMET/CMC and the slower GFS, with the EC and
EC-AIFS in between. The latest 12Z CMC and UKMET are now much
closer to consensus for Days 3 and 4, with solutions diverging
significantly for Days 5, 6, and 7. For the latter half of the
period, the 12Z CMC interestingly enough is now the slowest piece
of guidance, with the EC and EC-AIFS in between the faster UKMET
and slower GFS. Given the uncertainty and run-to-run changes
between some guidance members, continued to lean heavily on the EC
and GEFS ensemble means with the remaining deterministic solutions
favoring the EC, EC-AIFS, and GFS.

...Weather/Hazards Highlights...

An eastern Canadian closed upper-level low will continue to help
support a mean longwave trough down into the eastern U.S. This
pattern will support a persistent cyclonic circulation aloft,
allowing multiple shortwave energies to approach the base of the
mean trough from upstream. Impulses will lead to the progression of
wavy frontal systems, bringing periods of showers and
thunderstorms through the eastern half of the country next week. By
mid to late week, each system eventually works downstream to the
Atlantic to spawn moderate coastal cyclogenesis with wrapping
moisture feeds before lifting up/off the East Coast.

Upstream, an eastern Pacific closed low will advance inland
sometime mid to late next week, focusing organized light to
moderate precipitation across portions of the northern Great Basin,
Pacific Northwest, and northern Rockies. A developing downstream
surface low and frontal boundary will form over the Northern Tier,
bringing chances for showers and thunderstorms across the northern
Plains into the Upper Midwest, and then the Great Lakes/East. Deep
boundary layer mixing may bring some gusty winds across the Rockies
and Plains with system passage.

Temperatures across the eastern half of the U.S. will remain near
to below normal through most of next week. Meanwhile, a ridging
pattern will keep well above normal temperatures in place across
much of the western U.S., with pre-frontal warmth spreading
eastward into the central U.S. mid to late week. Several high
temperature records are likely to be tied or broken through the
period.


Schichtel/Miller


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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