383
FXUS02 KWNH 110714
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
313 AM EDT Thu Sep 11 2025

Valid 12Z Sun Sep 14 2025 - 12Z Thu Sep 18 2025


...Overview...

It is still the case that upper troughing atop the Intermountain
West this weekend will support downstream moist southerly flow to
stream into the High Plains and cause some moderate to heavy rain.
This trough is forecast to slowly lift out early next week while
another trough reloads in the West to spread enhanced rain chances
from the Northwest/West to the Rockies/Plains. Troughing in the
East/Northeast may also get renewed early next week and bring some
Northeast rain, but this pattern and rain amounts are more
uncertain. A wavy and windy lingering front farther south across
the western Atlantic into next week could cause some heavy rain
along/offshore the coastal Carolinas. In between the renewing upper
troughs, the central U.S. should see above normal temperatures
with some areas well into the 90s underneath ridging aloft.

...Guidance/Predictability Assessment...

Models and ensembles agree on the general trough-ridge-trough
pattern over the lower 48 through much of the medium range period,
with more spread on energies serving to renew the troughs. Namely,
in the East/Northeast recent models have shown an upper low diving
south over Quebec this weekend and making it to the Northeast U.S.
by Monday. Non-NCEP models have tended to be farther west and
deeper with this upper low for most cycles over the past few days
compared to the GFS/GEFS runs, However, latest 00 UTC Non-NCEP
models have flip-flopped away from the deeper/slower closed low
solution. WPC has mainly been favoring an intermediate solution
more like the EC/CMC ensemble means, especially into the day 5-7
timeframe, thus deeper than the GFS/GEFS but not completely toward
the deterministic EC/CMC position for mass fields and for resultant
sensible weather like QPF well into next week. The latest 00 UTC
guidance trends may suggest an even less diggy solution despite a
favorable upstream position of an amplified upper ridge. Uncertain.

In the West, the first trough will pivot northeast through the
northern Plains by Monday while there is relatively more spread in
the trough incoming behind it. Will continue to monitor the timing
of this feature`s ejection east by midweek as models still show a
fair amount of variability and uncertainty to unpack. Accordingly,
favor a multi-model ensemble mean solution at these time frames.

...Weather/Hazards Highlights...

Rain and thunderstorms should focus over the northern Plains this
weekend ahead of the western trough and near a frontal system,
yielding a Marginal Risk in the Excessive Rainfall Outlook (ERO)
for Sunday for possible flooding concerns. Lighter rain may make
it into the Upper Midwest early next week. Meanwhile the next round
of troughing will push into the West this weekend and spread
another round of precipitation first to the Pacific Northwest and
possibly into the northern Great Basin and Rockies early next week.

A persistent and wavy frontal system over the Gulf and Florida
will linger just off/up the Eastern Seaboard well into next week.
This will provide a main focus for tropical moisture to pool to
fuel a elongated plume of enhanced wrapping rains. Scattered
showers could continue into next week over southern Florida behind
the main front, but with reduce post-frontal moisture levels
closer to normal. Farther north, models now show most moisture
along/just offshore the coastal Carolinas/Mid-Atlantic; expect
windy coastal/maritime flow and hazards to monitor. The coastal
boundary and any coastal low development may also play a role in
enhanced rainfall coming into the Northeast under the influnence of
an uncertain upper trough with another front. Some moderate QPF is
shown for the Interior Northeast Sunday, with modest instability
potentially enhancing rain rates, but held off on an ERO area given
uncertainties in the rain amounts and the overall pattern.

Slightly cooler than normal temperatures especially for highs are
likely across the western U.S. underneath periods of upper
troughing. But the upper ridge to the east will promote warm
temperatures across the central U.S., with greatest anomalies of
10-20 degrees above average in the Mississippi Valley with lesser
anomalies into the Plains and east into the Great Lakes, Ohio
Valley, and Southeast. Temperatures well in the 90s will be common
even up through parts of Iowa and Illinois into the weekend, but
becoming more suppressed to the South next week (though potentially
still remaining warmer than average into the Midwest, just with
lesser anomalies). A handful of record highs are possible across
the Mid-South. Meanwhile the East should generally see near normal
temperatures for mid-September.


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 (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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