Areas of Dangerous Heat and Heavy Rain with Possible Flooding into this Weekend

Hot temperatures and high humidity are forecast to continue across the mid-Mississippi Valley into this weekend with heat advisories in effect. Heavy to excessive rainfall occurring at times through Sunday could bring areas of flooding to parts of the upper Midwest, central Great Lakes, southern New England and Virginia/North Carolina tidewater region. Read More >

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FXZS60 NSTU 180115
AFDPPG

Area Forecast Discussion
National Weather Service Pago Pago AS
215 PM SST Thu Sep 17 2026

.Discussion...
A trough that brought over an inch of rain this morning continues
to linger across the area. Latest satellite loops show convection
associated with the trough gradually diminishing throughout the
day. This afternoon`s upper air sounding (RAOB 09/18 OOZ) also
shows a drying trend in the mid-levels. However, the sounding
still indicates a moist surface and an unstable profile, with
TOTL values near 44 supporting a slight chance for thunderstorms.
Although convection has diminished, numerous showers will persist
through Tuesday as the trough remains in the area. Additionally,
the trough is expected to weaken, briefly develop, and then
weaken again during this timeframe. However, the potential for
flash flooding is uncertain as instability models focus convection
westward. We will continue to monitor how things play out.

By Tuesday afternoon, the trough will finally diminish over the
area. Model data shows a ridge building from the southwest,
bringing a moderate east to southeast breeze with showers
embedded within the tradewind flow through the end of the forecast
period.

&&

.Marine...
Seas remain elevated as a south to southeast tradewind regime
lingers near the Samoa Islands, while a strong south swell
continues to move across coastal waters. Latest observations from
the PacIOOS buoys support this, with wave heights remaining near
6 to 8 feet and peak periods around 15 seconds. Model guidance
shows seas gradually diminishing later tonight as winds weaken
and the swell subsides. However, wave heights briefly increased to
near 8 feet in the past hour, likely due to nearby gusty winds.

The High Surf and Small Craft Advisories will likely continue
through tonight before conditions fall below advisory criteria on
Friday. Expect relatively calm seas through the weekend. However,
breezy conditions expected Monday will likely elevated seas once
again for the beginning of the new week. Another south swell is
also expected to increase wave heights early next week.

.PPG WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory
Small Craft Advisory

&&

$$

TM