998
FXUS02 KWNH 280702
PREEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EDT Thu Aug 28 2025

Valid 12Z Sun Aug 31 2025 - 12Z Thu Sep 04 2025

...Heavy rain and flash flood potential in portions of Texas and
New Mexico this weekend...

...Overview...

Mean troughing over the East is expected to persist through the
medium range period with blocky ridging over the West. Weak
disturbances rotating through the upper ridge will interact with a
surface front to produce heavy rain threats across the
Great Plains and Southwest this weekend. A digging trough in the
East will support below average temperatures and heavy rain
potential across the Gulf Coast and Florida next week.


...Guidance/Predictability Assessment...

Models were generally agreeable during the medium range period. A
general model blend, consisting of equal parts Euro/GFS/CMC/UKMET,
was used on days on days 3 and 4. The weighting of the 18z GFS was
reduced in the day 5 blend, because it carries an outlier bubble
high over the Northeast/Quebec. The Euro/GEFS ensemble means are
introduced on day 5 and joined by the Canadian ensemble mean on day
6 through 7.

QPF-wise the GFS and UKMET have a more aggressive rainfall
footprint over parts of the Southern Plains and Lower Mississippi
on Sunday. The GFS has a more progressive system moving through the
Northern/Central Plains on Sunday-Monday, which is reflected in a
weaker and farther eastern placement of the maximum QPF on day 4.
Confidence is decreasing due to a waning signal for heavy rainfall
in the Southwest/Southern High Plains on day 5.


...Weather/Hazards Highlights...

A surface front draped from the Southern High Plains across the
Gulf Coast and through the Southeast will be the focus for heavy
rainfall beginning this weekend. A moist monsoonal environment
with embedded shortwave energy aloft could produce flash flooding
over portions of southern New Mexico and far western Texas this
Sunday (day 4), where a slight risk (at least 15% chance) of
excessive rainfall is in effect. This threat is supported by a
slight risk signal in our in house first guess field as well as the
1 year ARI being exceeded by the 24 hour grand ensemble mean.


The surface front drifts farther South into
the Gulf and West into central New Mexico on Monday (day 5), where
it may refocus monsoon storms. Another slight risk is in effect for
day 5 across parts of southern New Mexico and far western Texas. 1
Year ARI is exceeded over southern New Mexico on Monday as well.
Elsewhere a marginal risk area remains over the Northern/Central
Plains and Upper/Middle Mississippi Valley on days 4 and 5 due to a
somewhat progressive shortwave disturbance and weak surface low
pressure system propagating through the region. There`s an
increasing signal for heavy rainfall to develop over portions of
the Central/Southern Appalachians on Monday beneath a digging upper
trough in the East and approaching shortwave.

As the front slowly drifts south through the Florida Peninsula next
week, it may produce locally heavy rainfall in some areas.
Temperatures should remain below average beneath the Eastern U.S.
trough. A strong cold front will dive south through the Central
U.S. and bring well below average temperatures to the Plains and
Midwest by the middle of next week. Mean troughing in the Eastern
Pacific and persistent ridging in the Western U.S. should support
warm southerly flow into the West, resulting in above average
temperatures next week.


Kebede


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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