846
FXUS02 KWBC 171847
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 PM EDT Sun Aug 17 2025

Valid 12Z Wed Aug 20 2025 - 12Z Sun Aug 24 2025

...Dangerous Hurricane Erin pass offshore this week to bring high
waves and rip current threats for much of the East Coast...


...Overview...

A Four Corners subtropical ridge will remain in place through much
of the medium range period for midweek into next weekend, with
upper troughing favored downstream over the East, which is expected
to keep Hurricane Erin on a track offshore the Eastern Seaboard. A
shortwave moving over Canada will help to reinforce troughing over
the East next weekend, while weaker shortwaves periodically move
into the Northwest and ride the top of the upper ridge to fire some
thunderstorms over the north-central states. Heat threats across
the Intermountain West and especially the Southwest will build
through the period, while rainfall focuses mainly across the South
and East along with monsoonal activity over the Southwest/Rockies.

...Guidance/Predictability Assessment...

The mid-large scale flow pattern continues to show above average
agreement and predictability through the upcoming medium range
period. Early on into midweek, the greatest differences involve
the speed of Erin as it tracks offshore the East Coast. Guidance
shows a lot of uncertainty in this evolution, but continue to favor
a track curving away from the coast. Please consult NHC products
for the latest information on the track and intensity forecasts for
Hurricane Erin. Of the 00/06 UTC guidance suite, the 00 UTC
ECMWF/Canadian and ECMWF/Canadian ensembles seemed to best fit the
latest track for Erin from the National Hurricane Center. A favored
composite also seems to provide a solid forecast basis for much of
the rest of the nation, generally in line with the National Blend
of Models and WPC product continuity.

...Weather/Hazards Highlights...

An NHC forecast track offshore the East Coast by powerful Hurricane
Erin will bring high waves and an increased and multi-day threat
for rip currents along much of the East Coast this week to monitor.

A frontal boundary dropping southward through the Southern tier
will be the focus for heavy rainfall much of next week, aided by
above normal PW values and instability. A broad Marginal Risk on
the Day 4/Wednesday Excessive Rainfall Outlook is highlighted from
the Southern Plains to the central Appalachians, with a southerly
shift over the South for Day 5/Thursday. Opted to shift/confine
the Day 5 ERO southward given frontal trends in that direction on
the backside of Erin, especially over a refreshed Eastern
Seaboard. The front will continue to sag into the Southeast and
weaken with time with increased convection continuing from the
Southern Plains to the Southeast later in the week. Moisture may
lift northward towards the Mid-Atlantic and Northeast with time
next weekend ahead of another approaching trough.

Surges of moisture into the Southwest under the base of the Four
Corners ridge combined with diurnal heating may trigger storms
capable of producing heavier rainfall over more sensitive areas
(steep terrain, in/around burn scars, dry washes/arroyos, urban
areas). A Marginal Risk ERO continues to be depicted for both Days
4/5 valid for Wednesday/Thursday. Moisutre and favorable flow may
spread actitity over the central Rockies/Plains into next weekend.

Significant heat across the Midwest during the short range period
will moderate by mid next week, but heat threats will increase
across much of the interior West and Southwest. Major to localized
extreme HeatRisk is likely by late week and next weekend across
much of the Southwest with daytime temperatures exceeding 110F in
some locations.

Santorelli/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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