020
FXUS02 KWNH 080716
PREEPD

Preliminary Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
315 AM EDT Fri May 8 2026

Valid 12Z Mon May 11 2026 - 12Z Fri May 15 2026


...General Overview...

It generally remains the case that an amplified mean flow pattern
will persist through much of the period, tied to a closed low
anchored over eastern Canada. This will bring deep cyclonic flow
and shortwave energies ejecting into central/eastern U.S. and the
western Atlantic to support a series of wavy frontal passages,
which will bring showers and thunderstorms along the boundaries. As
the primary cold front moves southeastward, below normal
temperatures will spread into eastern U.S. through Tuesday. A
strengthening ridge across the western U.S. will bring well above
normal temperatures that will gradually move into the Central U.S.
by midweek. Additional troughing, with much more uncertainty, may
move into the West by the end of the period.

...Guidance/Predictability Assessment...

Recent guidance solutions aloft remain reasonably well clustered
with the larger scale pattern develolpment and maintainance through
early-mid next week as highlighted by a building ridge over the
West, troughing over the East, and shortwaves dropping from the
Northern Plains into the Great Lakes to reinforce the trough in the
East. A model composite offers a solid forecast basis for this that
seems well supported by ensembles. The greatest source of
uncertainty still surrounds the well upstream evolution and timing
of a shortwave that drops south and eastward from near Alaska into
the northeast Pacific and possibly eventually into the West.
Recent ECMWF/Canadian guidance brings the bulk of energy inland.
The GFS and GEFS members continue to keep this system well
offshore, with less breakdown of the ridge over the West. The new
00 UTC guidance tonight does not provide much additional clarity.
Given lingering unresolved uncertainty, latest WPC surface progs
and sensible weather grids tried to best maintain continuity by
bringing decent energy inland, but holding some stream separted
troughing offshore as per a mainly ECMWF/NAEFS ensemble mean blend.

...Weather/Hazards Highlights...

The closed upper-level low over eastern Canada will continue to
support a mean longwave trough extending into the eastern U.S.
through the period. This pattern will bring a mature and persistent
cyclonic circulation aloft and multiple shortwave energies
ejecting along the base of the mean trough. Each impulse will
support the progression of a wavy cold front that sweeps through
the eastern half of the country early next week, leading into
moderate coastal low genesis. The frontal passage will bring
widespread showers and thunderstorms across portions of the Great
Lakes, Lower Mississippi Valley/Southern Plains, Ohio Valley into
the Northeast and Mid- Atlantic, with locally heavy rainfall
possible along the boundary then up the coast through Monday.

As the primary cold front moves closer to the East Coast, much of
the Plains and Mississippi Valley will see a short-lived drying
trend by Monday with the front clearing the East Coast by Tuesday.
Farther west, another frontal boundary begins to form over the
Northern Tier as a potential clipper system, bringing chances for
showers and thunderstorms across the northern Plains into the Upper
Midwest, and eventually the Great Lakes and Northeast. In
addition, deep boundary layer mixing may bring somewhat gusty winds
across the Rockies and Plains through the period. System
progression to the western Atlantic may also support renewed
moderate coastal low genesis and inland wrapping rains/unsettled
weather Wednesday into Thursday. Meanwhile, the possible mid-later
trough/system ejection into/across the Northwest/West may spread
some generally light and terrain induced precipitation as well.

Temperatures will continue to trend below average across the
eastern U.S., as the primary cold front pushes southeastward
through Monday. Across the western U.S., a ridging pattern will
bring well above normal highs through midweek, and will push
eastward into central U.S. by Tuesday. Record tying/breaking highs
will expand from California into Southern Plains on Tuesday. Some
of the high temperatures across portions of central California
Valleys and Desert Southwest will reach Moderate to Major HeatRisk
levels into Monday/Tuesday. Moderate to major, and even spotty
extreme, HeatRisk is also possible this weekend into early next
week for parts of south Florida, and given continued drought and
low humidities, may pose an increased fire weather risk as well.

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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