801
FXUS02 KWNH 280702
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
201 AM EST Fri Feb 28 2025

Valid 12Z Mon Mar 03 2025 - 12Z Fri Mar 07 2025


...Severe weather and heavy rain potential likely to focus in
Lower/Middle Mississippi Valley and Mid-South on Tuesday and
perhaps the East on Wednesday...


...Overview...

The upper pattern will be progressive through the extended period
as noted with a pair of troughs tracking across the nation. After
troughing exits the East a southern stream cutoff low over the
southern High Plains on Sunday is projected to lift toward the
north and east prior to becoming absorbed within the larger scale
flow over the south-central states. An upstream, deep trough/closed
low will advance into the West Sunday/Monday while spreading modest
precipitation and winds across the region. As this system emerges,
reasonably deep low pressure system will form over the Central
Plains by Tuesday and track northeast Wednesday-Thursday. Locations
ahead of the approaching cold front will be primed for severe
thunderstorms and heavy rainfall that could led to areas of
flooding across the south-central into east-central U.S. peaking
on Tuesday, with some perhaps continuing into Wednesday in the
East. Another amplified trough approaches the West Coast next
Thursday.


...Guidance/Predictability Assessment...

In general the model and ensemble guidance continues to be in
fairly good agreement, particularly with the southern Rockies/High
Plains small southern stream low getting absorbed and the trough
moving from the eastern Pacific into the West. There are some
smaller scale differences among the guidance that may impact the
sensible weather and location/amounts of QPF however, the use of a
multi-model blend provided a decent start. The 12Z ECMWF, 18Z/00Z
GFS, and 12Z CMC along with the GEFS mean and Ecmwf ensemble
maintained good clustering for the mid- late medium range period
as it shifts into the Plains and beyond and causes a surface low to
develop and track northeast.

There is greater uncertainty with the upper trough that is forecast
to advance through the western states by mid-late week shows.
Although the ECMWF runs continue to be slightly on the faster side
of the envelope the weighting tipped in its favor, especially since
the ensemble members supported a combination of slower and faster
solutions that created a proxy middle ground. WPC maintained
continuity by utilizing a heavier inclusion of the ensemble means
for Days 6 and 7 to reduce some of the noise across the West.


...Weather/Hazards Highlights...

The trough coming into the western U.S. early next week will also
lead to some precipitation spreading across the West Coast into the
Great Basin and Rockies, with lower elevation rain and higher
elevation snow as well as gusty winds. Precipitation totals are
expected to be limited as the moisture influx into the region will
be modest. As this feature exits into the central U.S. Gulf
moisture will be drawn northward to fuel more widespread and heavy
rains from the southern to eastern U.S. The latest guidance
continues to signal the heaviest rainfall accumulations to set up
from the Lower/Middle Mississippi Valley to Southeast and
Tennessee/Ohio Valleys on Tuesday. Some areas have wet antecedent
soil conditions, which would exacerbate flood potential. Severe
weather is also a notable threat over the south-central states per
SPC. WPC has introduced a Marginal Risk for excessive rainfall for
portions of the Lower/Middle Mississippi Valley into western
portions of the Tennessee Valley. Precipitation should overspread
the East on Wednesday, and SPC continues to show severe potential
in the Southeast to southern Mid-Atlantic. Areas of heavy rainfall
become even more uncertain with placement at that time, but may
become problematic in terms of flooding if heavy rain falls on
snow- covered areas of the Northeast, per the National Water
Center. Northwest of the low track, it may be cold enough to
support snow across the north- central Plains into the Great Lakes,
but totals are uncertain. Gusty winds are also possible depending
on how deep the surface low gets. Another round of moderate rain
and elevation snow should move into California Wednesday-Thursday
with the next upper trough.

Much above normal temperatures over the Rockies and Plains states
on Sunday will gradually progress eastward with time and moderate.
The greatest anomalies, 15 to 25 degrees above normal, will be
across the northern Plains through Monday. Temperatures across much
of the East will be considerably colder than normal on Sunday, but
should moderate back to normal Monday-Tuesday, and warmer than
normal Wednesday. By next Thursday, much of the country may be near
or within a few degrees of normal.


Campbell/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 (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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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