174
FXUS02 KWBC 100730
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
330 AM EDT Sun May 10 2026

Valid 12Z Wed May 13 2026 - 12Z Sun May 17 2026


...Guidance/Predictability Assessment...

Guidance remains reasonably clustered with the larger scale upper
pattern into mid-late week, highlighted by a West-Central U.S.
warming ridge, troughing over the East, and shortwaves dropping
from the Northern Plains/Great Lakes to reinforce East troughing.
The greatest source of uncertainty continues to surround the
upstream evolution and timing of a main closed low from the
eastern Pacific that should meanwhile advance inland over the West
and then downstream, leading a subsequent trailing shortwave series
within increasingly zonal flow over the lower 48 into next
weekend. Given the uncertainty and run-to-run changes in guidance
without resolve through this forecast period, continued to lean
heavily on albeit less than ideally compatible GEFS/ECMWF/Canadian
ensemble mean in an effort for best feasible product continuity.

...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. into
mid-late week. 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 to bring periods of
showers/thunderstorms through the eastern third of the country
mid-late week. System progression to the Atlantic will also look
to spawn moderate coastal cyclogenesis with wrapping moisture/rains
lifting up/off the East Coast, lending into a maritime threat.

Upstream, an eastern Pacific closed low is with much uncertainty
slated to advance inland sometime mid-late week to focus organized
light to moderate precipitation most likely across portions of the
northern Great Basin, Pacific Northwest, and northern Rockies. A
developing downstream surface low and frontal boundary will form
down from the Northern Tier, bringing chances for showers and
thunderstorms from the north-central U.S. to the Great Lakes/East.
Farther upstream system energies will subseuently work inland into
the West and downstream over the lower 48 with uncertain
timing and weather focus in increasingly zonal flow aloft.

Temperatures for the eastern third of the U.S. will be near to
below normal into mid-late week before moderating into next weekend
with main upper trough ejection into the Atlantic. Meanwhile, a
slowly eastward shifting upper ridge will gradually spread well
above normal temperatures out from the West to the Rockies and
Central U.S. that may produce several high temperature records.


Schichtel


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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