551
FXUS02 KWBC 020529
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
129 AM EDT Sat May 2 2026

Valid 12Z Tue May 05 2026 - 12Z Sat May 09 2026


...Overview...

A synoptic scale upper-level low meandering over central to
southeastern Canada will support amplified troughing across
central/eastern U.S., reinforcing cool and unsettled conditions
through the period. Meanwhile, a Pacific trough/closed low will
move inland across the Southwest early in the period before
ejecting into the Plains, which may bring mixed precipitation for
the Front Range by midweek. The system will merge with the
northern stream by late week, bringing chances for cyclogenesis
over the Northeast. The cold front moving southward across eastern
U.S. will bring heavy rainfall across the Mississippi Valley,
Ohio/Tennessee Valley, and Southeast.


...Guidance/Predictability Assessment...

The models continue to show good agreement on maintaining a broad
trough across Central/Eastern U.S. and a Pacific system moving into
western U.S. The deterministic models show some slight differences
amongst the shortwave energies embedded at the base of the low
over southeast Canada by Day 5. For the feature over Western U.S.,
models begin to show noticeable discrepancies with timing and
structure for the overall large- scale pattern after Day 5. The
ensemble means compensate for some of these differences,
especially for the GFS where run- to-run variability continues for
the southwest energy ejecting eastward. In addition, CMC/CMC means
continue to show a slower progression for the Southwest trough
after Day 5, which can affect sensible weather. Therefore, the WPC
forecast utilized as multi- model blend amongst the
CMC/ECMWF/GFS/UKMET and EC-AIFS through day 5, with incorporating
more weight towards the ensemble means for the remainder of the
period.


...Weather/Hazards Highlights...

As the upper-level low continues to meander over central to
southeastern Canada through the medium-range period, bringing a
series of shortwave rotating around the mean trough. This will
support multiple frontal passages and waves of precipitation
across Central/Eastern U.S. The associated cold air behind the
front and cyclonic flow will bring below seasonal temperatures
across North/Central Plains into much of eastern U.S. bringing
concern for frost/freeze conditions from the Upper Midwest. Ahead
of the cold front, expect showers and thunderstorms across Upper
Midwest/Mississippi Valley, Ohio/Tennessee Valley, Great Lakes and
Northeast on Tuesday, with gusty winds across from the Southern
Plains to the Ohio Valley and into the Northeast.

As the front slowly moves southward and interacts with warm Gulf
moisture, showers and thunderstorms will expand into the lower
Mississippi Valley, Mid- Atlantic and Southeast by Wednesday. With
the combination of upper- level forcing and organized thunderstorms
producing heavy rainfall along the front, localized flooding may
be possible across mid/lower Mississippi Valley into Ohio/Tennessee
Valley Wed- Thu. This flood threat is represented by the Marginal
Risk on Day 4/Tuesday ERO. On Thursday, the front becomes semi-
stationary, allowing for an influx of moisture along the boundary
over Southeast and Tennessee Valley, supporting locally heavy
rainfall. With flooding concerns over the area, a Marginal Risk has
been introduced for Day 5/Wednesday ERO for parts of the
Ohio/Tennessee Valley, lower Mississippi Valley, and Southeast.

As cold air pushes into Northern U.S., there is a slight chance
for some mixed precipitation over some isolated higher- elevation
areas/northern areas near the U.S. Canada border, but impacts will
be minimal. In addition, colder air behind the upper low ejecting
from the Southwest U.S. will also bring below normal temperatures
into California, and Southwest, where temperatures will drop 10-15
degrees below average into midweek before moderating to above
normal late next week.

Over the western U.S., the Pacific upper low/trough will move into
the Southwest early in the period, then gradually ejects into the
Plains by late week. This will bring sufficient moisture and
instability to support widespread low elevation showers and
possible thunderstorms, as well as some high elevation snow across
parts of California and Great Basin. The cold front associated
with the leading edge of the cold air intrusion into the High
Plains will drop into the Rockies/Plains on Tuesday, expanding the
chance for showers and thunderstorms, with a chance for mix
precipitation across the Front Range of Colorado to southern
Wyoming through Wednesday. Over the Pacific Northwest, a ridge will
push inland, bringing a warming trend. As the ridge continues to
move eastward, above normal temperatures will return across much of
western U.S. later next week.


Oudit


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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